Documentation/DocBook/v4l/controls.xml

   1   <section id="control">
   2     <title>User Controls</title>
   3
   4     <para>Devices typically have a number of user-settable controls
   5 such as brightness, saturation and so on, which would be presented to
   6 the user on a graphical user interface. But, different devices
   7 will have different controls available, and furthermore, the range of
   8 possible values, and the default value will vary from device to
   9 device. The control ioctls provide the information and a mechanism to
  10 create a nice user interface for these controls that will work
  11 correctly with any device.</para>
  12
  13     <para>All controls are accessed using an ID value. V4L2 defines
  14 several IDs for specific purposes. Drivers can also implement their
  15 own custom controls using <constant>V4L2_CID_PRIVATE_BASE</constant>
  16 and higher values. The pre-defined control IDs have the prefix
  17 <constant>V4L2_CID_</constant>, and are listed in <xref
  18 linkend="control-id" />. The ID is used when querying the attributes of
  19 a control, and when getting or setting the current value.</para>
  20
  21     <para>Generally applications should present controls to the user
  22 without assumptions about their purpose. Each control comes with a
  23 name string the user is supposed to understand. When the purpose is
  24 non-intuitive the driver writer should provide a user manual, a user
  25 interface plug-in or a driver specific panel application. Predefined
  26 IDs were introduced to change a few controls programmatically, for
  27 example to mute a device during a channel switch.</para>
  28
  29     <para>Drivers may enumerate different controls after switching
  30 the current video input or output, tuner or modulator, or audio input
  31 or output. Different in the sense of other bounds, another default and
  32 current value, step size or other menu items. A control with a certain
  33 <emphasis>custom</emphasis> ID can also change name and
  34 type.<footnote>
  35         <para>It will be more convenient for applications if drivers
  36 make use of the <constant>V4L2_CTRL_FLAG_DISABLED</constant> flag, but
  37 that was never required.</para>
  38       </footnote> Control values are stored globally, they do not
  39 change when switching except to stay within the reported bounds. They
  40 also do not change &eg; when the device is opened or closed, when the
  41 tuner radio frequency is changed or generally never without
  42 application request. Since V4L2 specifies no event mechanism, panel
  43 applications intended to cooperate with other panel applications (be
  44 they built into a larger application, as a TV viewer) may need to
  45 regularly poll control values to update their user
  46 interface.<footnote>
  47         <para>Applications could call an ioctl to request events.
  48 After another process called &VIDIOC-S-CTRL; or another ioctl changing
  49 shared properties the &func-select; function would indicate
  50 readability until any ioctl (querying the properties) is
  51 called.</para>
  52       </footnote></para>
  53
  54     <table pgwide="1" frame="none" id="control-id">
  55       <title>Control IDs</title>
  56       <tgroup cols="3">
  57         &cs-def;
  58         <thead>
  59           <row>
  60             <entry>ID</entry>
  61             <entry>Type</entry>
  62             <entry>Description</entry>
  63           </row>
  64         </thead>
  65         <tbody valign="top">
  66           <row>
  67             <entry><constant>V4L2_CID_BASE</constant></entry>
  68             <entry></entry>
  69             <entry>First predefined ID, equal to
  70 <constant>V4L2_CID_BRIGHTNESS</constant>.</entry>
  71           </row>
  72           <row>
  73             <entry><constant>V4L2_CID_USER_BASE</constant></entry>
  74             <entry></entry>
  75             <entry>Synonym of <constant>V4L2_CID_BASE</constant>.</entry>
  76           </row>
  77           <row>
  78             <entry><constant>V4L2_CID_BRIGHTNESS</constant></entry>
  79             <entry>integer</entry>
  80             <entry>Picture brightness, or more precisely, the black
  81 level.</entry>
  82           </row>
  83           <row>
  84             <entry><constant>V4L2_CID_CONTRAST</constant></entry>
  85             <entry>integer</entry>
  86             <entry>Picture contrast or luma gain.</entry>
  87           </row>
  88           <row>
  89             <entry><constant>V4L2_CID_SATURATION</constant></entry>
  90             <entry>integer</entry>
  91             <entry>Picture color saturation or chroma gain.</entry>
  92           </row>
  93           <row>
  94             <entry><constant>V4L2_CID_HUE</constant></entry>
  95             <entry>integer</entry>
  96             <entry>Hue or color balance.</entry>
  97           </row>
  98           <row>
  99             <entry><constant>V4L2_CID_AUDIO_VOLUME</constant></entry>
 100             <entry>integer</entry>
 101             <entry>Overall audio volume. Note some drivers also
 102 provide an OSS or ALSA mixer interface.</entry>
 103           </row>
 104           <row>
 105             <entry><constant>V4L2_CID_AUDIO_BALANCE</constant></entry>
 106             <entry>integer</entry>
 107             <entry>Audio stereo balance. Minimum corresponds to all
 108 the way left, maximum to right.</entry>
 109           </row>
 110           <row>
 111             <entry><constant>V4L2_CID_AUDIO_BASS</constant></entry>
 112             <entry>integer</entry>
 113             <entry>Audio bass adjustment.</entry>
 114           </row>
 115           <row>
 116             <entry><constant>V4L2_CID_AUDIO_TREBLE</constant></entry>
 117             <entry>integer</entry>
 118             <entry>Audio treble adjustment.</entry>
 119           </row>
 120           <row>
 121             <entry><constant>V4L2_CID_AUDIO_MUTE</constant></entry>
 122             <entry>boolean</entry>
 123             <entry>Mute audio, &ie; set the volume to zero, however
 124 without affecting <constant>V4L2_CID_AUDIO_VOLUME</constant>. Like
 125 ALSA drivers, V4L2 drivers must mute at load time to avoid excessive
 126 noise. Actually the entire device should be reset to a low power
 127 consumption state.</entry>
 128           </row>
 129           <row>
 130             <entry><constant>V4L2_CID_AUDIO_LOUDNESS</constant></entry>
 131             <entry>boolean</entry>
 132             <entry>Loudness mode (bass boost).</entry>
 133           </row>
 134           <row>
 135             <entry><constant>V4L2_CID_BLACK_LEVEL</constant></entry>
 136             <entry>integer</entry>
 137             <entry>Another name for brightness (not a synonym of
 138 <constant>V4L2_CID_BRIGHTNESS</constant>). This control is deprecated
 139 and should not be used in new drivers and applications.</entry>
 140           </row>
 141           <row>
 142             <entry><constant>V4L2_CID_AUTO_WHITE_BALANCE</constant></entry>
 143             <entry>boolean</entry>
 144             <entry>Automatic white balance (cameras).</entry>
 145           </row>
 146           <row>
 147             <entry><constant>V4L2_CID_DO_WHITE_BALANCE</constant></entry>
 148             <entry>button</entry>
 149             <entry>This is an action control. When set (the value is
 150 ignored), the device will do a white balance and then hold the current
 151 setting. Contrast this with the boolean
 152 <constant>V4L2_CID_AUTO_WHITE_BALANCE</constant>, which, when
 153 activated, keeps adjusting the white balance.</entry>
 154           </row>
 155           <row>
 156             <entry><constant>V4L2_CID_RED_BALANCE</constant></entry>
 157             <entry>integer</entry>
 158             <entry>Red chroma balance.</entry>
 159           </row>
 160           <row>
 161             <entry><constant>V4L2_CID_BLUE_BALANCE</constant></entry>
 162             <entry>integer</entry>
 163             <entry>Blue chroma balance.</entry>
 164           </row>
 165           <row>
 166             <entry><constant>V4L2_CID_GAMMA</constant></entry>
 167             <entry>integer</entry>
 168             <entry>Gamma adjust.</entry>
 169           </row>
 170           <row>
 171             <entry><constant>V4L2_CID_WHITENESS</constant></entry>
 172             <entry>integer</entry>
 173             <entry>Whiteness for grey-scale devices. This is a synonym
 174 for <constant>V4L2_CID_GAMMA</constant>. This control is deprecated
 175 and should not be used in new drivers and applications.</entry>
 176           </row>
 177           <row>
 178             <entry><constant>V4L2_CID_EXPOSURE</constant></entry>
 179             <entry>integer</entry>
 180             <entry>Exposure (cameras). [Unit?]</entry>
 181           </row>
 182           <row>
 183             <entry><constant>V4L2_CID_AUTOGAIN</constant></entry>
 184             <entry>boolean</entry>
 185             <entry>Automatic gain/exposure control.</entry>
 186           </row>
 187           <row>
 188             <entry><constant>V4L2_CID_GAIN</constant></entry>
 189             <entry>integer</entry>
 190             <entry>Gain control.</entry>
 191           </row>
 192           <row>
 193             <entry><constant>V4L2_CID_HFLIP</constant></entry>
 194             <entry>boolean</entry>
 195             <entry>Mirror the picture horizontally.</entry>
 196           </row>
 197           <row>
 198             <entry><constant>V4L2_CID_VFLIP</constant></entry>
 199             <entry>boolean</entry>
 200             <entry>Mirror the picture vertically.</entry>
 201           </row>
 202         <row>
 203           <entry><constant>V4L2_CID_HCENTER_DEPRECATED</constant> (formerly <constant>V4L2_CID_HCENTER</constant>)</entry>
 204             <entry>integer</entry>
 205             <entry>Horizontal image centering. This control is
 206 deprecated. New drivers and applications should use the <link
 207 linkend="camera-controls">Camera class controls</link>
 208 <constant>V4L2_CID_PAN_ABSOLUTE</constant>,
 209 <constant>V4L2_CID_PAN_RELATIVE</constant> and
 210 <constant>V4L2_CID_PAN_RESET</constant> instead.</entry>
 211           </row>
 212           <row>
 213             <entry><constant>V4L2_CID_VCENTER_DEPRECATED</constant>
 214             (formerly <constant>V4L2_CID_VCENTER</constant>)</entry>
 215             <entry>integer</entry>
 216             <entry>Vertical image centering. Centering is intended to
 217 <emphasis>physically</emphasis> adjust cameras. For image cropping see
 218 <xref linkend="crop" />, for clipping <xref linkend="overlay" />. This
 219 control is deprecated. New drivers and applications should use the
 220 <link linkend="camera-controls">Camera class controls</link>
 221 <constant>V4L2_CID_TILT_ABSOLUTE</constant>,
 222 <constant>V4L2_CID_TILT_RELATIVE</constant> and
 223 <constant>V4L2_CID_TILT_RESET</constant> instead.</entry>
 224           </row>
 225           <row id="v4l2-power-line-frequency">
 226             <entry><constant>V4L2_CID_POWER_LINE_FREQUENCY</constant></entry>
 227             <entry>enum</entry>
 228             <entry>Enables a power line frequency filter to avoid
 229 flicker. Possible values for <constant>enum v4l2_power_line_frequency</constant> are:
 230 <constant>V4L2_CID_POWER_LINE_FREQUENCY_DISABLED</constant> (0),
 231 <constant>V4L2_CID_POWER_LINE_FREQUENCY_50HZ</constant> (1) and
 232 <constant>V4L2_CID_POWER_LINE_FREQUENCY_60HZ</constant> (2).</entry>
 233           </row>
 234           <row>
 235             <entry><constant>V4L2_CID_HUE_AUTO</constant></entry>
 236             <entry>boolean</entry>
 237             <entry>Enables automatic hue control by the device. The
 238 effect of setting <constant>V4L2_CID_HUE</constant> while automatic
 239 hue control is enabled is undefined, drivers should ignore such
 240 request.</entry>
 241           </row>
 242           <row>
 243             <entry><constant>V4L2_CID_WHITE_BALANCE_TEMPERATURE</constant></entry>
 244             <entry>integer</entry>
 245             <entry>This control specifies the white balance settings
 246 as a color temperature in Kelvin. A driver should have a minimum of
 247 2800 (incandescent) to 6500 (daylight). For more information about
 248 color temperature see <ulink
 249 url="http://en.wikipedia.org/wiki/Color_temperature">Wikipedia</ulink>.</entry>
 250           </row>
 251           <row>
 252             <entry><constant>V4L2_CID_SHARPNESS</constant></entry>
 253             <entry>integer</entry>
 254             <entry>Adjusts the sharpness filters in a camera. The
 255 minimum value disables the filters, higher values give a sharper
 256 picture.</entry>
 257           </row>
 258           <row>
 259             <entry><constant>V4L2_CID_BACKLIGHT_COMPENSATION</constant></entry>
 260             <entry>integer</entry>
 261             <entry>Adjusts the backlight compensation in a camera. The
 262 minimum value disables backlight compensation.</entry>
 263           </row>
 264           <row>
 265             <entry><constant>V4L2_CID_CHROMA_AGC</constant></entry>
 266             <entry>boolean</entry>
 267             <entry>Chroma automatic gain control.</entry>
 268           </row>
 269           <row>
 270             <entry><constant>V4L2_CID_COLOR_KILLER</constant></entry>
 271             <entry>boolean</entry>
 272             <entry>Enable the color killer (&ie; force a black &amp; white image in case of a weak video signal).</entry>
 273           </row>
 274           <row id="v4l2-colorfx">
 275             <entry><constant>V4L2_CID_COLORFX</constant></entry>
 276             <entry>enum</entry>
 277             <entry>Selects a color effect. Possible values for
 278 <constant>enum v4l2_colorfx</constant> are:
 279 <constant>V4L2_COLORFX_NONE</constant> (0),
 280 <constant>V4L2_COLORFX_BW</constant> (1) and
 281 <constant>V4L2_COLORFX_SEPIA</constant> (2).</entry>
 282           </row>
 283           <row>
 284             <entry><constant>V4L2_CID_LASTP1</constant></entry>
 285             <entry></entry>
 286             <entry>End of the predefined control IDs (currently
 287 <constant>V4L2_CID_COLORFX</constant> + 1).</entry>
 288           </row>
 289           <row>
 290             <entry><constant>V4L2_CID_PRIVATE_BASE</constant></entry>
 291             <entry></entry>
 292             <entry>ID of the first custom (driver specific) control.
 293 Applications depending on particular custom controls should check the
 294 driver name and version, see <xref linkend="querycap" />.</entry>
 295           </row>
 296         </tbody>
 297       </tgroup>
 298     </table>
 299
 300     <para>Applications can enumerate the available controls with the
 301 &VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls, get and set a
 302 control value with the &VIDIOC-G-CTRL; and &VIDIOC-S-CTRL; ioctls.
 303 Drivers must implement <constant>VIDIOC_QUERYCTRL</constant>,
 304 <constant>VIDIOC_G_CTRL</constant> and
 305 <constant>VIDIOC_S_CTRL</constant> when the device has one or more
 306 controls, <constant>VIDIOC_QUERYMENU</constant> when it has one or
 307 more menu type controls.</para>
 308
 309     <example>
 310       <title>Enumerating all controls</title>
 311
 312       <programlisting>
 313 &v4l2-queryctrl; queryctrl;
 314 &v4l2-querymenu; querymenu;
 315
 316 static void
 317 enumerate_menu (void)
 318 {
 319         printf ("  Menu items:\n");
 320
 321         memset (&amp;querymenu, 0, sizeof (querymenu));
 322         querymenu.id = queryctrl.id;
 323
 324         for (querymenu.index = queryctrl.minimum;
 325              querymenu.index &lt;= queryctrl.maximum;
 326               querymenu.index++) {
 327                 if (0 == ioctl (fd, &VIDIOC-QUERYMENU;, &amp;querymenu)) {
 328                         printf ("  %s\n", querymenu.name);
 329                 } else {
 330                         perror ("VIDIOC_QUERYMENU");
 331                         exit (EXIT_FAILURE);
 332                 }
 333         }
 334 }
 335
 336 memset (&amp;queryctrl, 0, sizeof (queryctrl));
 337
 338 for (queryctrl.id = V4L2_CID_BASE;
 339      queryctrl.id &lt; V4L2_CID_LASTP1;
 340      queryctrl.id++) {
 341         if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;queryctrl)) {
 342                 if (queryctrl.flags &amp; V4L2_CTRL_FLAG_DISABLED)
 343                         continue;
 344
 345                 printf ("Control %s\n", queryctrl.name);
 346
 347                 if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
 348                         enumerate_menu ();
 349         } else {
 350                 if (errno == EINVAL)
 351                         continue;
 352
 353                 perror ("VIDIOC_QUERYCTRL");
 354                 exit (EXIT_FAILURE);
 355         }
 356 }
 357
 358 for (queryctrl.id = V4L2_CID_PRIVATE_BASE;;
 359      queryctrl.id++) {
 360         if (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;queryctrl)) {
 361                 if (queryctrl.flags &amp; V4L2_CTRL_FLAG_DISABLED)
 362                         continue;
 363
 364                 printf ("Control %s\n", queryctrl.name);
 365
 366                 if (queryctrl.type == V4L2_CTRL_TYPE_MENU)
 367                         enumerate_menu ();
 368         } else {
 369                 if (errno == EINVAL)
 370                         break;
 371
 372                 perror ("VIDIOC_QUERYCTRL");
 373                 exit (EXIT_FAILURE);
 374         }
 375 }
 376 </programlisting>
 377     </example>
 378
 379     <example>
 380       <title>Changing controls</title>
 381
 382       <programlisting>
 383 &v4l2-queryctrl; queryctrl;
 384 &v4l2-control; control;
 385
 386 memset (&amp;queryctrl, 0, sizeof (queryctrl));
 387 queryctrl.id = V4L2_CID_BRIGHTNESS;
 388
 389 if (-1 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;queryctrl)) {
 390         if (errno != EINVAL) {
 391                 perror ("VIDIOC_QUERYCTRL");
 392                 exit (EXIT_FAILURE);
 393         } else {
 394                 printf ("V4L2_CID_BRIGHTNESS is not supported\n");
 395         }
 396 } else if (queryctrl.flags &amp; V4L2_CTRL_FLAG_DISABLED) {
 397         printf ("V4L2_CID_BRIGHTNESS is not supported\n");
 398 } else {
 399         memset (&amp;control, 0, sizeof (control));
 400         control.id = V4L2_CID_BRIGHTNESS;
 401         control.value = queryctrl.default_value;
 402
 403         if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &amp;control)) {
 404                 perror ("VIDIOC_S_CTRL");
 405                 exit (EXIT_FAILURE);
 406         }
 407 }
 408
 409 memset (&amp;control, 0, sizeof (control));
 410 control.id = V4L2_CID_CONTRAST;
 411
 412 if (0 == ioctl (fd, &VIDIOC-G-CTRL;, &amp;control)) {
 413         control.value += 1;
 414
 415         /* The driver may clamp the value or return ERANGE, ignored here */
 416
 417         if (-1 == ioctl (fd, &VIDIOC-S-CTRL;, &amp;control)
 418             &amp;&amp; errno != ERANGE) {
 419                 perror ("VIDIOC_S_CTRL");
 420                 exit (EXIT_FAILURE);
 421         }
 422 /* Ignore if V4L2_CID_CONTRAST is unsupported */
 423 } else if (errno != EINVAL) {
 424         perror ("VIDIOC_G_CTRL");
 425         exit (EXIT_FAILURE);
 426 }
 427
 428 control.id = V4L2_CID_AUDIO_MUTE;
 429 control.value = TRUE; /* silence */
 430
 431 /* Errors ignored */
 432 ioctl (fd, VIDIOC_S_CTRL, &amp;control);
 433 </programlisting>
 434     </example>
 435   </section>
 436
 437   <section id="extended-controls">
 438     <title>Extended Controls</title>
 439
 440     <section>
 441       <title>Introduction</title>
 442
 443       <para>The control mechanism as originally designed was meant
 444 to be used for user settings (brightness, saturation, etc). However,
 445 it turned out to be a very useful model for implementing more
 446 complicated driver APIs where each driver implements only a subset of
 447 a larger API.</para>
 448
 449       <para>The MPEG encoding API was the driving force behind
 450 designing and implementing this extended control mechanism: the MPEG
 451 standard is quite large and the currently supported hardware MPEG
 452 encoders each only implement a subset of this standard. Further more,
 453 many parameters relating to how the video is encoded into an MPEG
 454 stream are specific to the MPEG encoding chip since the MPEG standard
 455 only defines the format of the resulting MPEG stream, not how the
 456 video is actually encoded into that format.</para>
 457
 458       <para>Unfortunately, the original control API lacked some
 459 features needed for these new uses and so it was extended into the
 460 (not terribly originally named) extended control API.</para>
 461
 462       <para>Even though the MPEG encoding API was the first effort
 463 to use the Extended Control API, nowadays there are also other classes
 464 of Extended Controls, such as Camera Controls and FM Transmitter Controls.
 465 The Extended Controls API as well as all Extended Controls classes are
 466 described in the following text.</para>
 467     </section>
 468
 469     <section>
 470       <title>The Extended Control API</title>
 471
 472       <para>Three new ioctls are available: &VIDIOC-G-EXT-CTRLS;,
 473 &VIDIOC-S-EXT-CTRLS; and &VIDIOC-TRY-EXT-CTRLS;. These ioctls act on
 474 arrays of controls (as opposed to the &VIDIOC-G-CTRL; and
 475 &VIDIOC-S-CTRL; ioctls that act on a single control). This is needed
 476 since it is often required to atomically change several controls at
 477 once.</para>
 478
 479       <para>Each of the new ioctls expects a pointer to a
 480 &v4l2-ext-controls;. This structure contains a pointer to the control
 481 array, a count of the number of controls in that array and a control
 482 class. Control classes are used to group similar controls into a
 483 single class. For example, control class
 484 <constant>V4L2_CTRL_CLASS_USER</constant> contains all user controls
 485 (&ie; all controls that can also be set using the old
 486 <constant>VIDIOC_S_CTRL</constant> ioctl). Control class
 487 <constant>V4L2_CTRL_CLASS_MPEG</constant> contains all controls
 488 relating to MPEG encoding, etc.</para>
 489
 490       <para>All controls in the control array must belong to the
 491 specified control class. An error is returned if this is not the
 492 case.</para>
 493
 494       <para>It is also possible to use an empty control array (count
 495 == 0) to check whether the specified control class is
 496 supported.</para>
 497
 498       <para>The control array is a &v4l2-ext-control; array. The
 499 <structname>v4l2_ext_control</structname> structure is very similar to
 500 &v4l2-control;, except for the fact that it also allows for 64-bit
 501 values and pointers to be passed.</para>
 502
 503       <para>It is important to realize that due to the flexibility of
 504 controls it is necessary to check whether the control you want to set
 505 actually is supported in the driver and what the valid range of values
 506 is. So use the &VIDIOC-QUERYCTRL; and &VIDIOC-QUERYMENU; ioctls to
 507 check this. Also note that it is possible that some of the menu
 508 indices in a control of type <constant>V4L2_CTRL_TYPE_MENU</constant>
 509 may not be supported (<constant>VIDIOC_QUERYMENU</constant> will
 510 return an error). A good example is the list of supported MPEG audio
 511 bitrates. Some drivers only support one or two bitrates, others
 512 support a wider range.</para>
 513     </section>
 514
 515     <section>
 516       <title>Enumerating Extended Controls</title>
 517
 518       <para>The recommended way to enumerate over the extended
 519 controls is by using &VIDIOC-QUERYCTRL; in combination with the
 520 <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> flag:</para>
 521
 522       <informalexample>
 523         <programlisting>
 524 &v4l2-queryctrl; qctrl;
 525
 526 qctrl.id = V4L2_CTRL_FLAG_NEXT_CTRL;
 527 while (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;qctrl)) {
 528         /* ... */
 529         qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
 530 }
 531 </programlisting>
 532       </informalexample>
 533
 534       <para>The initial control ID is set to 0 ORed with the
 535 <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant> flag. The
 536 <constant>VIDIOC_QUERYCTRL</constant> ioctl will return the first
 537 control with a higher ID than the specified one. When no such controls
 538 are found an error is returned.</para>
 539
 540       <para>If you want to get all controls within a specific control
 541 class, then you can set the initial
 542 <structfield>qctrl.id</structfield> value to the control class and add
 543 an extra check to break out of the loop when a control of another
 544 control class is found:</para>
 545
 546       <informalexample>
 547         <programlisting>
 548 qctrl.id = V4L2_CTRL_CLASS_MPEG | V4L2_CTRL_FLAG_NEXT_CTRL;
 549 while (0 == ioctl (fd, &VIDIOC-QUERYCTRL;, &amp;qctrl)) {
 550         if (V4L2_CTRL_ID2CLASS (qctrl.id) != V4L2_CTRL_CLASS_MPEG)
 551                 break;
 552                 /* ... */
 553                 qctrl.id |= V4L2_CTRL_FLAG_NEXT_CTRL;
 554         }
 555 </programlisting>
 556       </informalexample>
 557
 558       <para>The 32-bit <structfield>qctrl.id</structfield> value is
 559 subdivided into three bit ranges: the top 4 bits are reserved for
 560 flags (&eg; <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant>) and are not
 561 actually part of the ID. The remaining 28 bits form the control ID, of
 562 which the most significant 12 bits define the control class and the
 563 least significant 16 bits identify the control within the control
 564 class. It is guaranteed that these last 16 bits are always non-zero
 565 for controls. The range of 0x1000 and up are reserved for
 566 driver-specific controls. The macro
 567 <constant>V4L2_CTRL_ID2CLASS(id)</constant> returns the control class
 568 ID based on a control ID.</para>
 569
 570       <para>If the driver does not support extended controls, then
 571 <constant>VIDIOC_QUERYCTRL</constant> will fail when used in
 572 combination with <constant>V4L2_CTRL_FLAG_NEXT_CTRL</constant>. In
 573 that case the old method of enumerating control should be used (see
 574 1.8). But if it is supported, then it is guaranteed to enumerate over
 575 all controls, including driver-private controls.</para>
 576     </section>
 577
 578     <section>
 579       <title>Creating Control Panels</title>
 580
 581       <para>It is possible to create control panels for a graphical
 582 user interface where the user can select the various controls.
 583 Basically you will have to iterate over all controls using the method
 584 described above. Each control class starts with a control of type
 585 <constant>V4L2_CTRL_TYPE_CTRL_CLASS</constant>.
 586 <constant>VIDIOC_QUERYCTRL</constant> will return the name of this
 587 control class which can be used as the title of a tab page within a
 588 control panel.</para>
 589
 590       <para>The flags field of &v4l2-queryctrl; also contains hints on
 591 the behavior of the control. See the &VIDIOC-QUERYCTRL; documentation
 592 for more details.</para>
 593     </section>
 594
 595     <section id="mpeg-controls">
 596       <title>MPEG Control Reference</title>
 597
 598       <para>Below all controls within the MPEG control class are
 599 described. First the generic controls, then controls specific for
 600 certain hardware.</para>
 601
 602       <section>
 603         <title>Generic MPEG Controls</title>
 604
 605         <table pgwide="1" frame="none" id="mpeg-control-id">
 606           <title>MPEG Control IDs</title>
 607           <tgroup cols="4">
 608             <colspec colname="c1" colwidth="1*" />
 609             <colspec colname="c2" colwidth="6*" />
 610             <colspec colname="c3" colwidth="2*" />
 611             <colspec colname="c4" colwidth="6*" />
 612             <spanspec namest="c1" nameend="c2" spanname="id" />
 613             <spanspec namest="c2" nameend="c4" spanname="descr" />
 614             <thead>
 615               <row>
 616                 <entry spanname="id" align="left">ID</entry>
 617                 <entry align="left">Type</entry>
 618               </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
 619               </row>
 620             </thead>
 621             <tbody valign="top">
 622               <row><entry></entry></row>
 623               <row>
 624                 <entry spanname="id"><constant>V4L2_CID_MPEG_CLASS</constant>&nbsp;</entry>
 625                 <entry>class</entry>
 626               </row><row><entry spanname="descr">The MPEG class
 627 descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
 628 description of this control class. This description can be used as the
 629 caption of a Tab page in a GUI, for example.</entry>
 630               </row>
 631               <row><entry></entry></row>
 632               <row id="v4l2-mpeg-stream-type">
 633                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_TYPE</constant>&nbsp;</entry>
 634                 <entry>enum&nbsp;v4l2_mpeg_stream_type</entry>
 635               </row><row><entry spanname="descr">The MPEG-1, -2 or -4
 636 output stream type. One cannot assume anything here. Each hardware
 637 MPEG encoder tends to support different subsets of the available MPEG
 638 stream types. The currently defined stream types are:</entry>
 639               </row>
 640               <row>
 641                 <entrytbl spanname="descr" cols="2">
 642                   <tbody valign="top">
 643                     <row>
 644                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_PS</constant>&nbsp;</entry>
 645                       <entry>MPEG-2 program stream</entry>
 646                     </row>
 647                     <row>
 648                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_TS</constant>&nbsp;</entry>
 649                       <entry>MPEG-2 transport stream</entry>
 650                     </row>
 651                     <row>
 652                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG1_SS</constant>&nbsp;</entry>
 653                       <entry>MPEG-1 system stream</entry>
 654                     </row>
 655                     <row>
 656                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_DVD</constant>&nbsp;</entry>
 657                       <entry>MPEG-2 DVD-compatible stream</entry>
 658                     </row>
 659                     <row>
 660                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG1_VCD</constant>&nbsp;</entry>
 661                       <entry>MPEG-1 VCD-compatible stream</entry>
 662                     </row>
 663                     <row>
 664                       <entry><constant>V4L2_MPEG_STREAM_TYPE_MPEG2_SVCD</constant>&nbsp;</entry>
 665                       <entry>MPEG-2 SVCD-compatible stream</entry>
 666                     </row>
 667                   </tbody>
 668                 </entrytbl>
 669               </row>
 670               <row><entry></entry></row>
 671               <row>
 672                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_PMT</constant>&nbsp;</entry>
 673                 <entry>integer</entry>
 674               </row><row><entry spanname="descr">Program Map Table
 675 Packet ID for the MPEG transport stream (default 16)</entry>
 676               </row>
 677               <row><entry></entry></row>
 678               <row>
 679                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_AUDIO</constant>&nbsp;</entry>
 680                 <entry>integer</entry>
 681               </row><row><entry spanname="descr">Audio Packet ID for
 682 the MPEG transport stream (default 256)</entry>
 683               </row>
 684               <row><entry></entry></row>
 685               <row>
 686                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_VIDEO</constant>&nbsp;</entry>
 687                 <entry>integer</entry>
 688               </row><row><entry spanname="descr">Video Packet ID for
 689 the MPEG transport stream (default 260)</entry>
 690               </row>
 691               <row><entry></entry></row>
 692               <row>
 693                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PID_PCR</constant>&nbsp;</entry>
 694                 <entry>integer</entry>
 695               </row><row><entry spanname="descr">Packet ID for the
 696 MPEG transport stream carrying PCR fields (default 259)</entry>
 697               </row>
 698               <row><entry></entry></row>
 699               <row>
 700                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PES_ID_AUDIO</constant>&nbsp;</entry>
 701                 <entry>integer</entry>
 702               </row><row><entry spanname="descr">Audio ID for MPEG
 703 PES</entry>
 704               </row>
 705               <row><entry></entry></row>
 706               <row>
 707                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_PES_ID_VIDEO</constant>&nbsp;</entry>
 708                 <entry>integer</entry>
 709               </row><row><entry spanname="descr">Video ID for MPEG
 710 PES</entry>
 711               </row>
 712               <row><entry></entry></row>
 713               <row id="v4l2-mpeg-stream-vbi-fmt">
 714                 <entry spanname="id"><constant>V4L2_CID_MPEG_STREAM_VBI_FMT</constant>&nbsp;</entry>
 715                 <entry>enum&nbsp;v4l2_mpeg_stream_vbi_fmt</entry>
 716               </row><row><entry spanname="descr">Some cards can embed
 717 VBI data (&eg; Closed Caption, Teletext) into the MPEG stream. This
 718 control selects whether VBI data should be embedded, and if so, what
 719 embedding method should be used. The list of possible VBI formats
 720 depends on the driver. The currently defined VBI format types
 721 are:</entry>
 722               </row>
 723               <row>
 724                 <entrytbl spanname="descr" cols="2">
 725                   <tbody valign="top">
 726                     <row>
 727                       <entry><constant>V4L2_MPEG_STREAM_VBI_FMT_NONE</constant>&nbsp;</entry>
 728                       <entry>No VBI in the MPEG stream</entry>
 729                     </row>
 730                     <row>
 731                       <entry><constant>V4L2_MPEG_STREAM_VBI_FMT_IVTV</constant>&nbsp;</entry>
 732                       <entry>VBI in private packets, IVTV format (documented
 733 in the kernel sources in the file <filename>Documentation/video4linux/cx2341x/README.vbi</filename>)</entry>
 734                     </row>
 735                   </tbody>
 736                 </entrytbl>
 737               </row>
 738               <row><entry></entry></row>
 739               <row id="v4l2-mpeg-audio-sampling-freq">
 740                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_SAMPLING_FREQ</constant>&nbsp;</entry>
 741                 <entry>enum&nbsp;v4l2_mpeg_audio_sampling_freq</entry>
 742               </row><row><entry spanname="descr">MPEG Audio sampling
 743 frequency. Possible values are:</entry>
 744               </row>
 745               <row>
 746                 <entrytbl spanname="descr" cols="2">
 747                   <tbody valign="top">
 748                     <row>
 749                       <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_44100</constant>&nbsp;</entry>
 750                       <entry>44.1 kHz</entry>
 751                     </row>
 752                     <row>
 753                       <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_48000</constant>&nbsp;</entry>
 754                       <entry>48 kHz</entry>
 755                     </row>
 756                     <row>
 757                       <entry><constant>V4L2_MPEG_AUDIO_SAMPLING_FREQ_32000</constant>&nbsp;</entry>
 758                       <entry>32 kHz</entry>
 759                     </row>
 760                   </tbody>
 761                 </entrytbl>
 762               </row>
 763               <row><entry></entry></row>
 764               <row id="v4l2-mpeg-audio-encoding">
 765                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_ENCODING</constant>&nbsp;</entry>
 766                 <entry>enum&nbsp;v4l2_mpeg_audio_encoding</entry>
 767               </row><row><entry spanname="descr">MPEG Audio encoding.
 768 Possible values are:</entry>
 769               </row>
 770               <row>
 771                 <entrytbl spanname="descr" cols="2">
 772                   <tbody valign="top">
 773                     <row>
 774                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_1</constant>&nbsp;</entry>
 775                       <entry>MPEG-1/2 Layer I encoding</entry>
 776                     </row>
 777                     <row>
 778                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_2</constant>&nbsp;</entry>
 779                       <entry>MPEG-1/2 Layer II encoding</entry>
 780                     </row>
 781                     <row>
 782                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_LAYER_3</constant>&nbsp;</entry>
 783                       <entry>MPEG-1/2 Layer III encoding</entry>
 784                     </row>
 785                     <row>
 786                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_AAC</constant>&nbsp;</entry>
 787                       <entry>MPEG-2/4 AAC (Advanced Audio Coding)</entry>
 788                     </row>
 789                     <row>
 790                       <entry><constant>V4L2_MPEG_AUDIO_ENCODING_AC3</constant>&nbsp;</entry>
 791                       <entry>AC-3 aka ATSC A/52 encoding</entry>
 792                     </row>
 793                   </tbody>
 794                 </entrytbl>
 795               </row>
 796               <row><entry></entry></row>
 797               <row id="v4l2-mpeg-audio-l1-bitrate">
 798                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L1_BITRATE</constant>&nbsp;</entry>
 799                 <entry>enum&nbsp;v4l2_mpeg_audio_l1_bitrate</entry>
 800               </row><row><entry spanname="descr">MPEG-1/2 Layer I bitrate.
 801 Possible values are:</entry>
 802               </row>
 803               <row>
 804                 <entrytbl spanname="descr" cols="2">
 805                   <tbody valign="top">
 806                     <row>
 807                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_32K</constant>&nbsp;</entry>
 808                       <entry>32 kbit/s</entry></row>
 809                     <row>
 810                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_64K</constant>&nbsp;</entry>
 811                       <entry>64 kbit/s</entry>
 812                     </row>
 813                     <row>
 814                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_96K</constant>&nbsp;</entry>
 815                       <entry>96 kbit/s</entry>
 816                     </row>
 817                     <row>
 818                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_128K</constant>&nbsp;</entry>
 819                       <entry>128 kbit/s</entry>
 820                     </row>
 821                     <row>
 822                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_160K</constant>&nbsp;</entry>
 823                       <entry>160 kbit/s</entry>
 824                     </row>
 825                     <row>
 826                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_192K</constant>&nbsp;</entry>
 827                       <entry>192 kbit/s</entry>
 828                     </row>
 829                     <row>
 830                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_224K</constant>&nbsp;</entry>
 831                       <entry>224 kbit/s</entry>
 832                     </row>
 833                     <row>
 834                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_256K</constant>&nbsp;</entry>
 835                       <entry>256 kbit/s</entry>
 836                     </row>
 837                     <row>
 838                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_288K</constant>&nbsp;</entry>
 839                       <entry>288 kbit/s</entry>
 840                     </row>
 841                     <row>
 842                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_320K</constant>&nbsp;</entry>
 843                       <entry>320 kbit/s</entry>
 844                     </row>
 845                     <row>
 846                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_352K</constant>&nbsp;</entry>
 847                       <entry>352 kbit/s</entry>
 848                     </row>
 849                     <row>
 850                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_384K</constant>&nbsp;</entry>
 851                       <entry>384 kbit/s</entry>
 852                     </row>
 853                     <row>
 854                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_416K</constant>&nbsp;</entry>
 855                       <entry>416 kbit/s</entry>
 856                     </row>
 857                     <row>
 858                       <entry><constant>V4L2_MPEG_AUDIO_L1_BITRATE_448K</constant>&nbsp;</entry>
 859                       <entry>448 kbit/s</entry>
 860                     </row>
 861                   </tbody>
 862                 </entrytbl>
 863               </row>
 864               <row><entry></entry></row>
 865               <row id="v4l2-mpeg-audio-l2-bitrate">
 866                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L2_BITRATE</constant>&nbsp;</entry>
 867                 <entry>enum&nbsp;v4l2_mpeg_audio_l2_bitrate</entry>
 868               </row><row><entry spanname="descr">MPEG-1/2 Layer II bitrate.
 869 Possible values are:</entry>
 870               </row>
 871               <row>
 872                 <entrytbl spanname="descr" cols="2">
 873                   <tbody valign="top">
 874                     <row>
 875                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_32K</constant>&nbsp;</entry>
 876                       <entry>32 kbit/s</entry>
 877                     </row>
 878                     <row>
 879                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_48K</constant>&nbsp;</entry>
 880                       <entry>48 kbit/s</entry>
 881                     </row>
 882                     <row>
 883                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_56K</constant>&nbsp;</entry>
 884                       <entry>56 kbit/s</entry>
 885                     </row>
 886                     <row>
 887                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_64K</constant>&nbsp;</entry>
 888                       <entry>64 kbit/s</entry>
 889                     </row>
 890                     <row>
 891                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_80K</constant>&nbsp;</entry>
 892                       <entry>80 kbit/s</entry>
 893                     </row>
 894                     <row>
 895                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_96K</constant>&nbsp;</entry>
 896                       <entry>96 kbit/s</entry>
 897                     </row>
 898                     <row>
 899                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_112K</constant>&nbsp;</entry>
 900                       <entry>112 kbit/s</entry>
 901                     </row>
 902                     <row>
 903                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_128K</constant>&nbsp;</entry>
 904                       <entry>128 kbit/s</entry>
 905                     </row>
 906                     <row>
 907                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_160K</constant>&nbsp;</entry>
 908                       <entry>160 kbit/s</entry>
 909                     </row>
 910                     <row>
 911                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_192K</constant>&nbsp;</entry>
 912                       <entry>192 kbit/s</entry>
 913                     </row>
 914                     <row>
 915                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_224K</constant>&nbsp;</entry>
 916                       <entry>224 kbit/s</entry>
 917                     </row>
 918                     <row>
 919                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_256K</constant>&nbsp;</entry>
 920                       <entry>256 kbit/s</entry>
 921                     </row>
 922                     <row>
 923                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_320K</constant>&nbsp;</entry>
 924                       <entry>320 kbit/s</entry>
 925                     </row>
 926                     <row>
 927                       <entry><constant>V4L2_MPEG_AUDIO_L2_BITRATE_384K</constant>&nbsp;</entry>
 928                       <entry>384 kbit/s</entry>
 929                     </row>
 930                   </tbody>
 931                 </entrytbl>
 932               </row>
 933               <row><entry></entry></row>
 934               <row id="v4l2-mpeg-audio-l3-bitrate">
 935                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_L3_BITRATE</constant>&nbsp;</entry>
 936                 <entry>enum&nbsp;v4l2_mpeg_audio_l3_bitrate</entry>
 937               </row><row><entry spanname="descr">MPEG-1/2 Layer III bitrate.
 938 Possible values are:</entry>
 939               </row>
 940               <row>
 941                 <entrytbl spanname="descr" cols="2">
 942                   <tbody valign="top">
 943                     <row>
 944                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_32K</constant>&nbsp;</entry>
 945                       <entry>32 kbit/s</entry>
 946                     </row>
 947                     <row>
 948                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_40K</constant>&nbsp;</entry>
 949                       <entry>40 kbit/s</entry>
 950                     </row>
 951                     <row>
 952                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_48K</constant>&nbsp;</entry>
 953                       <entry>48 kbit/s</entry>
 954                     </row>
 955                     <row>
 956                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_56K</constant>&nbsp;</entry>
 957                       <entry>56 kbit/s</entry>
 958                     </row>
 959                     <row>
 960                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_64K</constant>&nbsp;</entry>
 961                       <entry>64 kbit/s</entry>
 962                     </row>
 963                     <row>
 964                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_80K</constant>&nbsp;</entry>
 965                       <entry>80 kbit/s</entry>
 966                     </row>
 967                     <row>
 968                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_96K</constant>&nbsp;</entry>
 969                       <entry>96 kbit/s</entry>
 970                     </row>
 971                     <row>
 972                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_112K</constant>&nbsp;</entry>
 973                       <entry>112 kbit/s</entry>
 974                     </row>
 975                     <row>
 976                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_128K</constant>&nbsp;</entry>
 977                       <entry>128 kbit/s</entry>
 978                     </row>
 979                     <row>
 980                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_160K</constant>&nbsp;</entry>
 981                       <entry>160 kbit/s</entry>
 982                     </row>
 983                     <row>
 984                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_192K</constant>&nbsp;</entry>
 985                       <entry>192 kbit/s</entry>
 986                     </row>
 987                     <row>
 988                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_224K</constant>&nbsp;</entry>
 989                       <entry>224 kbit/s</entry>
 990                     </row>
 991                     <row>
 992                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_256K</constant>&nbsp;</entry>
 993                       <entry>256 kbit/s</entry>
 994                     </row>
 995                     <row>
 996                       <entry><constant>V4L2_MPEG_AUDIO_L3_BITRATE_320K</constant>&nbsp;</entry>
 997                       <entry>320 kbit/s</entry>
 998                     </row>
 999                   </tbody>
1000                 </entrytbl>
1001               </row>
1002               <row><entry></entry></row>
1003               <row>
1004                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_AAC_BITRATE</constant>&nbsp;</entry>
1005                 <entry>integer</entry>
1006               </row><row><entry spanname="descr">AAC bitrate in bits per second.</entry>
1007               </row>
1008               <row><entry></entry></row>
1009               <row id="v4l2-mpeg-audio-ac3-bitrate">
1010                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_AC3_BITRATE</constant>&nbsp;</entry>
1011                 <entry>enum&nbsp;v4l2_mpeg_audio_ac3_bitrate</entry>
1012               </row><row><entry spanname="descr">AC-3 bitrate.
1013 Possible values are:</entry>
1014               </row>
1015               <row>
1016                 <entrytbl spanname="descr" cols="2">
1017                   <tbody valign="top">
1018                     <row>
1019                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_32K</constant>&nbsp;</entry>
1020                       <entry>32 kbit/s</entry>
1021                     </row>
1022                     <row>
1023                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_40K</constant>&nbsp;</entry>
1024                       <entry>40 kbit/s</entry>
1025                     </row>
1026                     <row>
1027                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_48K</constant>&nbsp;</entry>
1028                       <entry>48 kbit/s</entry>
1029                     </row>
1030                     <row>
1031                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_56K</constant>&nbsp;</entry>
1032                       <entry>56 kbit/s</entry>
1033                     </row>
1034                     <row>
1035                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_64K</constant>&nbsp;</entry>
1036                       <entry>64 kbit/s</entry>
1037                     </row>
1038                     <row>
1039                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_80K</constant>&nbsp;</entry>
1040                       <entry>80 kbit/s</entry>
1041                     </row>
1042                     <row>
1043                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_96K</constant>&nbsp;</entry>
1044                       <entry>96 kbit/s</entry>
1045                     </row>
1046                     <row>
1047                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_112K</constant>&nbsp;</entry>
1048                       <entry>112 kbit/s</entry>
1049                     </row>
1050                     <row>
1051                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_128K</constant>&nbsp;</entry>
1052                       <entry>128 kbit/s</entry>
1053                     </row>
1054                     <row>
1055                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_160K</constant>&nbsp;</entry>
1056                       <entry>160 kbit/s</entry>
1057                     </row>
1058                     <row>
1059                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_192K</constant>&nbsp;</entry>
1060                       <entry>192 kbit/s</entry>
1061                     </row>
1062                     <row>
1063                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_224K</constant>&nbsp;</entry>
1064                       <entry>224 kbit/s</entry>
1065                     </row>
1066                     <row>
1067                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_256K</constant>&nbsp;</entry>
1068                       <entry>256 kbit/s</entry>
1069                     </row>
1070                     <row>
1071                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_320K</constant>&nbsp;</entry>
1072                       <entry>320 kbit/s</entry>
1073                     </row>
1074                     <row>
1075                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_384K</constant>&nbsp;</entry>
1076                       <entry>384 kbit/s</entry>
1077                     </row>
1078                     <row>
1079                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_448K</constant>&nbsp;</entry>
1080                       <entry>448 kbit/s</entry>
1081                     </row>
1082                     <row>
1083                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_512K</constant>&nbsp;</entry>
1084                       <entry>512 kbit/s</entry>
1085                     </row>
1086                     <row>
1087                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_576K</constant>&nbsp;</entry>
1088                       <entry>576 kbit/s</entry>
1089                     </row>
1090                     <row>
1091                       <entry><constant>V4L2_MPEG_AUDIO_AC3_BITRATE_640K</constant>&nbsp;</entry>
1092                       <entry>640 kbit/s</entry>
1093                     </row>
1094                   </tbody>
1095                 </entrytbl>
1096               </row>
1097               <row><entry></entry></row>
1098               <row id="v4l2-mpeg-audio-mode">
1099                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MODE</constant>&nbsp;</entry>
1100                 <entry>enum&nbsp;v4l2_mpeg_audio_mode</entry>
1101               </row><row><entry spanname="descr">MPEG Audio mode.
1102 Possible values are:</entry>
1103               </row>
1104               <row>
1105                 <entrytbl spanname="descr" cols="2">
1106                   <tbody valign="top">
1107                     <row>
1108                       <entry><constant>V4L2_MPEG_AUDIO_MODE_STEREO</constant>&nbsp;</entry>
1109                       <entry>Stereo</entry>
1110                     </row>
1111                     <row>
1112                       <entry><constant>V4L2_MPEG_AUDIO_MODE_JOINT_STEREO</constant>&nbsp;</entry>
1113                       <entry>Joint Stereo</entry>
1114                     </row>
1115                     <row>
1116                       <entry><constant>V4L2_MPEG_AUDIO_MODE_DUAL</constant>&nbsp;</entry>
1117                       <entry>Bilingual</entry>
1118                     </row>
1119                     <row>
1120                       <entry><constant>V4L2_MPEG_AUDIO_MODE_MONO</constant>&nbsp;</entry>
1121                       <entry>Mono</entry>
1122                     </row>
1123                   </tbody>
1124                 </entrytbl>
1125               </row>
1126               <row><entry></entry></row>
1127               <row id="v4l2-mpeg-audio-mode-extension">
1128                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MODE_EXTENSION</constant>&nbsp;</entry>
1129                 <entry>enum&nbsp;v4l2_mpeg_audio_mode_extension</entry>
1130               </row><row><entry spanname="descr">Joint Stereo
1131 audio mode extension. In Layer I and II they indicate which subbands
1132 are in intensity stereo. All other subbands are coded in stereo. Layer
1133 III is not (yet) supported. Possible values
1134 are:</entry>
1135               </row>
1136               <row>
1137                 <entrytbl spanname="descr" cols="2">
1138                   <tbody valign="top">
1139                     <row>
1140                       <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_4</constant>&nbsp;</entry>
1141                       <entry>Subbands 4-31 in intensity stereo</entry>
1142                     </row>
1143                     <row>
1144                       <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_8</constant>&nbsp;</entry>
1145                       <entry>Subbands 8-31 in intensity stereo</entry>
1146                     </row>
1147                     <row>
1148                       <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_12</constant>&nbsp;</entry>
1149                       <entry>Subbands 12-31 in intensity stereo</entry>
1150                     </row>
1151                     <row>
1152                       <entry><constant>V4L2_MPEG_AUDIO_MODE_EXTENSION_BOUND_16</constant>&nbsp;</entry>
1153                       <entry>Subbands 16-31 in intensity stereo</entry>
1154                     </row>
1155                   </tbody>
1156                 </entrytbl>
1157               </row>
1158               <row><entry></entry></row>
1159               <row id="v4l2-mpeg-audio-emphasis">
1160                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_EMPHASIS</constant>&nbsp;</entry>
1161                 <entry>enum&nbsp;v4l2_mpeg_audio_emphasis</entry>
1162               </row><row><entry spanname="descr">Audio Emphasis.
1163 Possible values are:</entry>
1164               </row>
1165               <row>
1166                 <entrytbl spanname="descr" cols="2">
1167                   <tbody valign="top">
1168                     <row>
1169                       <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_NONE</constant>&nbsp;</entry>
1170                       <entry>None</entry>
1171                     </row>
1172                     <row>
1173                       <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_50_DIV_15_uS</constant>&nbsp;</entry>
1174                       <entry>50/15 microsecond emphasis</entry>
1175                     </row>
1176                     <row>
1177                       <entry><constant>V4L2_MPEG_AUDIO_EMPHASIS_CCITT_J17</constant>&nbsp;</entry>
1178                       <entry>CCITT J.17</entry>
1179                     </row>
1180                   </tbody>
1181                 </entrytbl>
1182               </row>
1183               <row><entry></entry></row>
1184               <row id="v4l2-mpeg-audio-crc">
1185                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_CRC</constant>&nbsp;</entry>
1186                 <entry>enum&nbsp;v4l2_mpeg_audio_crc</entry>
1187               </row><row><entry spanname="descr">CRC method. Possible
1188 values are:</entry>
1189               </row>
1190               <row>
1191                 <entrytbl spanname="descr" cols="2">
1192                   <tbody valign="top">
1193                     <row>
1194                       <entry><constant>V4L2_MPEG_AUDIO_CRC_NONE</constant>&nbsp;</entry>
1195                       <entry>None</entry>
1196                     </row>
1197                     <row>
1198                       <entry><constant>V4L2_MPEG_AUDIO_CRC_CRC16</constant>&nbsp;</entry>
1199                       <entry>16 bit parity check</entry>
1200                     </row>
1201                   </tbody>
1202                 </entrytbl>
1203               </row>
1204               <row><entry></entry></row>
1205               <row>
1206                 <entry spanname="id"><constant>V4L2_CID_MPEG_AUDIO_MUTE</constant>&nbsp;</entry>
1207                 <entry>boolean</entry>
1208               </row><row><entry spanname="descr">Mutes the audio when
1209 capturing. This is not done by muting audio hardware, which can still
1210 produce a slight hiss, but in the encoder itself, guaranteeing a fixed
1211 and reproducable audio bitstream. 0 = unmuted, 1 = muted.</entry>
1212               </row>
1213               <row><entry></entry></row>
1214               <row id="v4l2-mpeg-video-encoding">
1215                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_ENCODING</constant>&nbsp;</entry>
1216                 <entry>enum&nbsp;v4l2_mpeg_video_encoding</entry>
1217               </row><row><entry spanname="descr">MPEG Video encoding
1218 method. Possible values are:</entry>
1219               </row>
1220               <row>
1221                 <entrytbl spanname="descr" cols="2">
1222                   <tbody valign="top">
1223                     <row>
1224                       <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_1</constant>&nbsp;</entry>
1225                       <entry>MPEG-1 Video encoding</entry>
1226                     </row>
1227                     <row>
1228                       <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_2</constant>&nbsp;</entry>
1229                       <entry>MPEG-2 Video encoding</entry>
1230                     </row>
1231                     <row>
1232                       <entry><constant>V4L2_MPEG_VIDEO_ENCODING_MPEG_4_AVC</constant>&nbsp;</entry>
1233                       <entry>MPEG-4 AVC (H.264) Video encoding</entry>
1234                     </row>
1235                   </tbody>
1236                 </entrytbl>
1237               </row>
1238               <row><entry></entry></row>
1239               <row id="v4l2-mpeg-video-aspect">
1240                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_ASPECT</constant>&nbsp;</entry>
1241                 <entry>enum&nbsp;v4l2_mpeg_video_aspect</entry>
1242               </row><row><entry spanname="descr">Video aspect.
1243 Possible values are:</entry>
1244               </row>
1245               <row>
1246                 <entrytbl spanname="descr" cols="2">
1247                   <tbody valign="top">
1248                     <row>
1249                       <entry><constant>V4L2_MPEG_VIDEO_ASPECT_1x1</constant>&nbsp;</entry>
1250                     </row>
1251                     <row>
1252                       <entry><constant>V4L2_MPEG_VIDEO_ASPECT_4x3</constant>&nbsp;</entry>
1253                     </row>
1254                     <row>
1255                       <entry><constant>V4L2_MPEG_VIDEO_ASPECT_16x9</constant>&nbsp;</entry>
1256                     </row>
1257                     <row>
1258                       <entry><constant>V4L2_MPEG_VIDEO_ASPECT_221x100</constant>&nbsp;</entry>
1259                     </row>
1260                   </tbody>
1261                 </entrytbl>
1262               </row>
1263               <row><entry></entry></row>
1264               <row>
1265                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_B_FRAMES</constant>&nbsp;</entry>
1266                 <entry>integer</entry>
1267               </row><row><entry spanname="descr">Number of B-Frames
1268 (default 2)</entry>
1269               </row>
1270               <row><entry></entry></row>
1271               <row>
1272                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_GOP_SIZE</constant>&nbsp;</entry>
1273                 <entry>integer</entry>
1274               </row><row><entry spanname="descr">GOP size (default
1275 12)</entry>
1276               </row>
1277               <row><entry></entry></row>
1278               <row>
1279                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_GOP_CLOSURE</constant>&nbsp;</entry>
1280                 <entry>boolean</entry>
1281               </row><row><entry spanname="descr">GOP closure (default
1282 1)</entry>
1283               </row>
1284               <row><entry></entry></row>
1285               <row>
1286                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_PULLDOWN</constant>&nbsp;</entry>
1287                 <entry>boolean</entry>
1288               </row><row><entry spanname="descr">Enable 3:2 pulldown
1289 (default 0)</entry>
1290               </row>
1291               <row><entry></entry></row>
1292               <row id="v4l2-mpeg-video-bitrate-mode">
1293                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE_MODE</constant>&nbsp;</entry>
1294                 <entry>enum&nbsp;v4l2_mpeg_video_bitrate_mode</entry>
1295               </row><row><entry spanname="descr">Video bitrate mode.
1296 Possible values are:</entry>
1297               </row>
1298               <row>
1299                 <entrytbl spanname="descr" cols="2">
1300                   <tbody valign="top">
1301                     <row>
1302                       <entry><constant>V4L2_MPEG_VIDEO_BITRATE_MODE_VBR</constant>&nbsp;</entry>
1303                       <entry>Variable bitrate</entry>
1304                     </row>
1305                     <row>
1306                       <entry><constant>V4L2_MPEG_VIDEO_BITRATE_MODE_CBR</constant>&nbsp;</entry>
1307                       <entry>Constant bitrate</entry>
1308                     </row>
1309                   </tbody>
1310                 </entrytbl>
1311               </row>
1312               <row><entry></entry></row>
1313               <row>
1314                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE</constant>&nbsp;</entry>
1315                 <entry>integer</entry>
1316               </row><row><entry spanname="descr">Video bitrate in bits
1317 per second.</entry>
1318               </row>
1319               <row><entry></entry></row>
1320               <row>
1321                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_BITRATE_PEAK</constant>&nbsp;</entry>
1322                 <entry>integer</entry>
1323               </row><row><entry spanname="descr">Peak video bitrate in
1324 bits per second. Must be larger or equal to the average video bitrate.
1325 It is ignored if the video bitrate mode is set to constant
1326 bitrate.</entry>
1327               </row>
1328               <row><entry></entry></row>
1329               <row>
1330                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_TEMPORAL_DECIMATION</constant>&nbsp;</entry>
1331                 <entry>integer</entry>
1332               </row><row><entry spanname="descr">For every captured
1333 frame, skip this many subsequent frames (default 0).</entry>
1334               </row>
1335               <row><entry></entry></row>
1336               <row>
1337                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_MUTE</constant>&nbsp;</entry>
1338                 <entry>boolean</entry>
1339               </row>
1340               <row><entry spanname="descr">"Mutes" the video to a
1341 fixed color when capturing. This is useful for testing, to produce a
1342 fixed video bitstream. 0 = unmuted, 1 = muted.</entry>
1343               </row>
1344               <row><entry></entry></row>
1345               <row>
1346                 <entry spanname="id"><constant>V4L2_CID_MPEG_VIDEO_MUTE_YUV</constant>&nbsp;</entry>
1347                 <entry>integer</entry>
1348               </row><row><entry spanname="descr">Sets the "mute" color
1349 of the video. The supplied 32-bit integer is interpreted as follows (bit
1350 0 = least significant bit):</entry>
1351               </row>
1352               <row>
1353                 <entrytbl spanname="descr" cols="2">
1354                   <tbody valign="top">
1355                     <row>
1356                       <entry>Bit 0:7</entry>
1357                       <entry>V chrominance information</entry>
1358                     </row>
1359                     <row>
1360                       <entry>Bit 8:15</entry>
1361                       <entry>U chrominance information</entry>
1362                     </row>
1363                     <row>
1364                       <entry>Bit 16:23</entry>
1365                       <entry>Y luminance information</entry>
1366                     </row>
1367                     <row>
1368                       <entry>Bit 24:31</entry>
1369                       <entry>Must be zero.</entry>
1370                     </row>
1371                   </tbody>
1372                 </entrytbl>
1373               </row>
1374             </tbody>
1375           </tgroup>
1376         </table>
1377       </section>
1378
1379       <section>
1380         <title>CX2341x MPEG Controls</title>
1381
1382         <para>The following MPEG class controls deal with MPEG
1383 encoding settings that are specific to the Conexant CX23415 and
1384 CX23416 MPEG encoding chips.</para>
1385
1386         <table pgwide="1" frame="none" id="cx2341x-control-id">
1387           <title>CX2341x Control IDs</title>
1388           <tgroup cols="4">
1389             <colspec colname="c1" colwidth="1*" />
1390             <colspec colname="c2" colwidth="6*" />
1391             <colspec colname="c3" colwidth="2*" />
1392             <colspec colname="c4" colwidth="6*" />
1393             <spanspec namest="c1" nameend="c2" spanname="id" />
1394             <spanspec namest="c2" nameend="c4" spanname="descr" />
1395             <thead>
1396               <row>
1397                 <entry spanname="id" align="left">ID</entry>
1398                 <entry align="left">Type</entry>
1399               </row><row><entry spanname="descr" align="left">Description</entry>
1400               </row>
1401             </thead>
1402             <tbody valign="top">
1403               <row><entry></entry></row>
1404               <row id="v4l2-mpeg-cx2341x-video-spatial-filter-mode">
1405                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE</constant>&nbsp;</entry>
1406                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_spatial_filter_mode</entry>
1407               </row><row><entry spanname="descr">Sets the Spatial
1408 Filter mode (default <constant>MANUAL</constant>). Possible values
1409 are:</entry>
1410               </row>
1411               <row>
1412                 <entrytbl spanname="descr" cols="2">
1413                   <tbody valign="top">
1414                     <row>
1415                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_MANUAL</constant>&nbsp;</entry>
1416                       <entry>Choose the filter manually</entry>
1417                     </row>
1418                     <row>
1419                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_SPATIAL_FILTER_MODE_AUTO</constant>&nbsp;</entry>
1420                       <entry>Choose the filter automatically</entry>
1421                     </row>
1422                   </tbody>
1423                 </entrytbl>
1424               </row>
1425               <row><entry></entry></row>
1426               <row>
1427                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_SPATIAL_FILTER</constant>&nbsp;</entry>
1428                 <entry>integer&nbsp;(0-15)</entry>
1429               </row><row><entry spanname="descr">The setting for the
1430 Spatial Filter. 0 = off, 15 = maximum. (Default is 0.)</entry>
1431               </row>
1432               <row><entry></entry></row>
1433               <row id="luma-spatial-filter-type">
1434                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE</constant>&nbsp;</entry>
1435                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_luma_spatial_filter_type</entry>
1436               </row><row><entry spanname="descr">Select the algorithm
1437 to use for the Luma Spatial Filter (default
1438 <constant>1D_HOR</constant>). Possible values:</entry>
1439               </row>
1440               <row>
1441                 <entrytbl spanname="descr" cols="2">
1442                   <tbody valign="top">
1443                     <row>
1444                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_OFF</constant>&nbsp;</entry>
1445                       <entry>No filter</entry>
1446                     </row>
1447                     <row>
1448                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_HOR</constant>&nbsp;</entry>
1449                       <entry>One-dimensional horizontal</entry>
1450                     </row>
1451                     <row>
1452                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_1D_VERT</constant>&nbsp;</entry>
1453                       <entry>One-dimensional vertical</entry>
1454                     </row>
1455                     <row>
1456                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_HV_SEPARABLE</constant>&nbsp;</entry>
1457                       <entry>Two-dimensional separable</entry>
1458                     </row>
1459                     <row>
1460                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_LUMA_SPATIAL_FILTER_TYPE_2D_SYM_NON_SEPARABLE</constant>&nbsp;</entry>
1461                       <entry>Two-dimensional symmetrical
1462 non-separable</entry>
1463                     </row>
1464                   </tbody>
1465                 </entrytbl>
1466               </row>
1467               <row><entry></entry></row>
1468               <row id="chroma-spatial-filter-type">
1469                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE</constant>&nbsp;</entry>
1470                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_chroma_spatial_filter_type</entry>
1471               </row><row><entry spanname="descr">Select the algorithm
1472 for the Chroma Spatial Filter (default <constant>1D_HOR</constant>).
1473 Possible values are:</entry>
1474               </row>
1475               <row>
1476                 <entrytbl spanname="descr" cols="2">
1477                   <tbody valign="top">
1478                     <row>
1479                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_OFF</constant>&nbsp;</entry>
1480                       <entry>No filter</entry>
1481                     </row>
1482                     <row>
1483                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_CHROMA_SPATIAL_FILTER_TYPE_1D_HOR</constant>&nbsp;</entry>
1484                       <entry>One-dimensional horizontal</entry>
1485                     </row>
1486                   </tbody>
1487                 </entrytbl>
1488               </row>
1489               <row><entry></entry></row>
1490               <row id="v4l2-mpeg-cx2341x-video-temporal-filter-mode">
1491                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE</constant>&nbsp;</entry>
1492                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_temporal_filter_mode</entry>
1493               </row><row><entry spanname="descr">Sets the Temporal
1494 Filter mode (default <constant>MANUAL</constant>). Possible values
1495 are:</entry>
1496               </row>
1497               <row>
1498                 <entrytbl spanname="descr" cols="2">
1499                   <tbody valign="top">
1500                     <row>
1501                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_MANUAL</constant>&nbsp;</entry>
1502                       <entry>Choose the filter manually</entry>
1503                     </row>
1504                     <row>
1505                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER_MODE_AUTO</constant>&nbsp;</entry>
1506                       <entry>Choose the filter automatically</entry>
1507                     </row>
1508                   </tbody>
1509                 </entrytbl>
1510               </row>
1511               <row><entry></entry></row>
1512               <row>
1513                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_TEMPORAL_FILTER</constant>&nbsp;</entry>
1514                 <entry>integer&nbsp;(0-31)</entry>
1515               </row><row><entry spanname="descr">The setting for the
1516 Temporal Filter. 0 = off, 31 = maximum. (Default is 8 for full-scale
1517 capturing and 0 for scaled capturing.)</entry>
1518               </row>
1519               <row><entry></entry></row>
1520               <row id="v4l2-mpeg-cx2341x-video-median-filter-type">
1521                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE</constant>&nbsp;</entry>
1522                 <entry>enum&nbsp;v4l2_mpeg_cx2341x_video_median_filter_type</entry>
1523               </row><row><entry spanname="descr">Median Filter Type
1524 (default <constant>OFF</constant>). Possible values are:</entry>
1525               </row>
1526               <row>
1527                 <entrytbl spanname="descr" cols="2">
1528                   <tbody valign="top">
1529                     <row>
1530                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_OFF</constant>&nbsp;</entry>
1531                       <entry>No filter</entry>
1532                     </row>
1533                     <row>
1534                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR</constant>&nbsp;</entry>
1535                       <entry>Horizontal filter</entry>
1536                     </row>
1537                     <row>
1538                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_VERT</constant>&nbsp;</entry>
1539                       <entry>Vertical filter</entry>
1540                     </row>
1541                     <row>
1542                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_HOR_VERT</constant>&nbsp;</entry>
1543                       <entry>Horizontal and vertical filter</entry>
1544                     </row>
1545                     <row>
1546                       <entry><constant>V4L2_MPEG_CX2341X_VIDEO_MEDIAN_FILTER_TYPE_DIAG</constant>&nbsp;</entry>
1547                       <entry>Diagonal filter</entry>
1548                     </row>
1549                   </tbody>
1550                 </entrytbl>
1551               </row>
1552               <row><entry></entry></row>
1553               <row>
1554                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_BOTTOM</constant>&nbsp;</entry>
1555                 <entry>integer&nbsp;(0-255)</entry>
1556               </row><row><entry spanname="descr">Threshold above which
1557 the luminance median filter is enabled (default 0)</entry>
1558               </row>
1559               <row><entry></entry></row>
1560               <row>
1561                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_LUMA_MEDIAN_FILTER_TOP</constant>&nbsp;</entry>
1562                 <entry>integer&nbsp;(0-255)</entry>
1563               </row><row><entry spanname="descr">Threshold below which
1564 the luminance median filter is enabled (default 255)</entry>
1565               </row>
1566               <row><entry></entry></row>
1567               <row>
1568                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_BOTTOM</constant>&nbsp;</entry>
1569                 <entry>integer&nbsp;(0-255)</entry>
1570               </row><row><entry spanname="descr">Threshold above which
1571 the chroma median filter is enabled (default 0)</entry>
1572               </row>
1573               <row><entry></entry></row>
1574               <row>
1575                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_VIDEO_CHROMA_MEDIAN_FILTER_TOP</constant>&nbsp;</entry>
1576                 <entry>integer&nbsp;(0-255)</entry>
1577               </row><row><entry spanname="descr">Threshold below which
1578 the chroma median filter is enabled (default 255)</entry>
1579               </row>
1580               <row><entry></entry></row>
1581               <row>
1582                 <entry spanname="id"><constant>V4L2_CID_MPEG_CX2341X_STREAM_INSERT_NAV_PACKETS</constant>&nbsp;</entry>
1583                 <entry>boolean</entry>
1584               </row>
1585               <row><entry spanname="descr">The CX2341X MPEG encoder
1586 can insert one empty MPEG-2 PES packet into the stream between every
1587 four video frames. The packet size is 2048 bytes, including the
1588 packet_start_code_prefix and stream_id fields. The stream_id is 0xBF
1589 (private stream 2). The payload consists of 0x00 bytes, to be filled
1590 in by the application. 0 = do not insert, 1 = insert packets.</entry>
1591               </row>
1592             </tbody>
1593           </tgroup>
1594         </table>
1595       </section>
1596     </section>
1597
1598     <section id="camera-controls">
1599       <title>Camera Control Reference</title>
1600
1601       <para>The Camera class includes controls for mechanical (or
1602 equivalent digital) features of a device such as controllable lenses
1603 or sensors.</para>
1604
1605     <table pgwide="1" frame="none" id="camera-control-id">
1606       <title>Camera Control IDs</title>
1607       <tgroup cols="4">
1608         <colspec colname="c1" colwidth="1*" />
1609         <colspec colname="c2" colwidth="6*" />
1610         <colspec colname="c3" colwidth="2*" />
1611         <colspec colname="c4" colwidth="6*" />
1612         <spanspec namest="c1" nameend="c2" spanname="id" />
1613         <spanspec namest="c2" nameend="c4" spanname="descr" />
1614         <thead>
1615           <row>
1616             <entry spanname="id" align="left">ID</entry>
1617             <entry align="left">Type</entry>
1618           </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
1619           </row>
1620         </thead>
1621         <tbody valign="top">
1622           <row><entry></entry></row>
1623           <row>
1624             <entry spanname="id"><constant>V4L2_CID_CAMERA_CLASS</constant>&nbsp;</entry>
1625             <entry>class</entry>
1626           </row><row><entry spanname="descr">The Camera class
1627 descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
1628 description of this control class.</entry>
1629           </row>
1630           <row><entry></entry></row>
1631
1632           <row id="v4l2-exposure-auto-type">
1633             <entry spanname="id"><constant>V4L2_CID_EXPOSURE_AUTO</constant>&nbsp;</entry>
1634             <entry>enum&nbsp;v4l2_exposure_auto_type</entry>
1635           </row><row><entry spanname="descr">Enables automatic
1636 adjustments of the exposure time and/or iris aperture. The effect of
1637 manual changes of the exposure time or iris aperture while these
1638 features are enabled is undefined, drivers should ignore such
1639 requests. Possible values are:</entry>
1640           </row>
1641           <row>
1642             <entrytbl spanname="descr" cols="2">
1643               <tbody valign="top">
1644                 <row>
1645                   <entry><constant>V4L2_EXPOSURE_AUTO</constant>&nbsp;</entry>
1646                       <entry>Automatic exposure time, automatic iris
1647 aperture.</entry>
1648                 </row>
1649                 <row>
1650                   <entry><constant>V4L2_EXPOSURE_MANUAL</constant>&nbsp;</entry>
1651                   <entry>Manual exposure time, manual iris.</entry>
1652                 </row>
1653                 <row>
1654                   <entry><constant>V4L2_EXPOSURE_SHUTTER_PRIORITY</constant>&nbsp;</entry>
1655                   <entry>Manual exposure time, auto iris.</entry>
1656                 </row>
1657                 <row>
1658                   <entry><constant>V4L2_EXPOSURE_APERTURE_PRIORITY</constant>&nbsp;</entry>
1659                   <entry>Auto exposure time, manual iris.</entry>
1660                 </row>
1661               </tbody>
1662             </entrytbl>
1663           </row>
1664           <row><entry></entry></row>
1665
1666           <row>
1667             <entry spanname="id"><constant>V4L2_CID_EXPOSURE_ABSOLUTE</constant>&nbsp;</entry>
1668             <entry>integer</entry>
1669           </row><row><entry spanname="descr">Determines the exposure
1670 time of the camera sensor. The exposure time is limited by the frame
1671 interval. Drivers should interpret the values as 100 &micro;s units,
1672 where the value 1 stands for 1/10000th of a second, 10000 for 1 second
1673 and 100000 for 10 seconds.</entry>
1674           </row>
1675           <row><entry></entry></row>
1676
1677           <row>
1678             <entry spanname="id"><constant>V4L2_CID_EXPOSURE_AUTO_PRIORITY</constant>&nbsp;</entry>
1679             <entry>boolean</entry>
1680           </row><row><entry spanname="descr">When
1681 <constant>V4L2_CID_EXPOSURE_AUTO</constant> is set to
1682 <constant>AUTO</constant> or <constant>APERTURE_PRIORITY</constant>,
1683 this control determines if the device may dynamically vary the frame
1684 rate. By default this feature is disabled (0) and the frame rate must
1685 remain constant.</entry>
1686           </row>
1687           <row><entry></entry></row>
1688
1689           <row>
1690             <entry spanname="id"><constant>V4L2_CID_PAN_RELATIVE</constant>&nbsp;</entry>
1691             <entry>integer</entry>
1692           </row><row><entry spanname="descr">This control turns the
1693 camera horizontally by the specified amount. The unit is undefined. A
1694 positive value moves the camera to the right (clockwise when viewed
1695 from above), a negative value to the left. A value of zero does not
1696 cause motion. This is a write-only control.</entry>
1697           </row>
1698           <row><entry></entry></row>
1699
1700           <row>
1701             <entry spanname="id"><constant>V4L2_CID_TILT_RELATIVE</constant>&nbsp;</entry>
1702             <entry>integer</entry>
1703           </row><row><entry spanname="descr">This control turns the
1704 camera vertically by the specified amount. The unit is undefined. A
1705 positive value moves the camera up, a negative value down. A value of
1706 zero does not cause motion. This is a write-only control.</entry>
1707           </row>
1708           <row><entry></entry></row>
1709
1710           <row>
1711             <entry spanname="id"><constant>V4L2_CID_PAN_RESET</constant>&nbsp;</entry>
1712             <entry>button</entry>
1713           </row><row><entry spanname="descr">When this control is set,
1714 the camera moves horizontally to the default position.</entry>
1715           </row>
1716           <row><entry></entry></row>
1717
1718           <row>
1719             <entry spanname="id"><constant>V4L2_CID_TILT_RESET</constant>&nbsp;</entry>
1720             <entry>button</entry>
1721           </row><row><entry spanname="descr">When this control is set,
1722 the camera moves vertically to the default position.</entry>
1723           </row>
1724           <row><entry></entry></row>
1725
1726           <row>
1727             <entry spanname="id"><constant>V4L2_CID_PAN_ABSOLUTE</constant>&nbsp;</entry>
1728             <entry>integer</entry>
1729           </row><row><entry spanname="descr">This control
1730 turns the camera horizontally to the specified position. Positive
1731 values move the camera to the right (clockwise when viewed from above),
1732 negative values to the left. Drivers should interpret the values as arc
1733 seconds, with valid values between -180 * 3600 and +180 * 3600
1734 inclusive.</entry>
1735           </row>
1736           <row><entry></entry></row>
1737
1738           <row>
1739             <entry spanname="id"><constant>V4L2_CID_TILT_ABSOLUTE</constant>&nbsp;</entry>
1740             <entry>integer</entry>
1741           </row><row><entry spanname="descr">This control
1742 turns the camera vertically to the specified position. Positive values
1743 move the camera up, negative values down. Drivers should interpret the
1744 values as arc seconds, with valid values between -180 * 3600 and +180
1745 * 3600 inclusive.</entry>
1746           </row>
1747           <row><entry></entry></row>
1748
1749           <row>
1750             <entry spanname="id"><constant>V4L2_CID_FOCUS_ABSOLUTE</constant>&nbsp;</entry>
1751             <entry>integer</entry>
1752           </row><row><entry spanname="descr">This control sets the
1753 focal point of the camera to the specified position. The unit is
1754 undefined. Positive values set the focus closer to the camera,
1755 negative values towards infinity.</entry>
1756           </row>
1757           <row><entry></entry></row>
1758
1759           <row>
1760             <entry spanname="id"><constant>V4L2_CID_FOCUS_RELATIVE</constant>&nbsp;</entry>
1761             <entry>integer</entry>
1762           </row><row><entry spanname="descr">This control moves the
1763 focal point of the camera by the specified amount. The unit is
1764 undefined. Positive values move the focus closer to the camera,
1765 negative values towards infinity. This is a write-only control.</entry>
1766           </row>
1767           <row><entry></entry></row>
1768
1769           <row>
1770             <entry spanname="id"><constant>V4L2_CID_FOCUS_AUTO</constant>&nbsp;</entry>
1771             <entry>boolean</entry>
1772           </row><row><entry spanname="descr">Enables automatic focus
1773 adjustments. The effect of manual focus adjustments while this feature
1774 is enabled is undefined, drivers should ignore such requests.</entry>
1775           </row>
1776           <row><entry></entry></row>
1777
1778           <row>
1779             <entry spanname="id"><constant>V4L2_CID_ZOOM_ABSOLUTE</constant>&nbsp;</entry>
1780             <entry>integer</entry>
1781           </row><row><entry spanname="descr">Specify the objective lens
1782 focal length as an absolute value. The zoom unit is driver-specific and its
1783 value should be a positive integer.</entry>
1784           </row>
1785           <row><entry></entry></row>
1786
1787           <row>
1788             <entry spanname="id"><constant>V4L2_CID_ZOOM_RELATIVE</constant>&nbsp;</entry>
1789             <entry>integer</entry>
1790           </row><row><entry spanname="descr">Specify the objective lens
1791 focal length relatively to the current value. Positive values move the zoom
1792 lens group towards the telephoto direction, negative values towards the
1793 wide-angle direction. The zoom unit is driver-specific. This is a write-only control.</entry>
1794           </row>
1795           <row><entry></entry></row>
1796
1797           <row>
1798             <entry spanname="id"><constant>V4L2_CID_ZOOM_CONTINUOUS</constant>&nbsp;</entry>
1799             <entry>integer</entry>
1800           </row><row><entry spanname="descr">Move the objective lens group
1801 at the specified speed until it reaches physical device limits or until an
1802 explicit request to stop the movement. A positive value moves the zoom lens
1803 group towards the telephoto direction. A value of zero stops the zoom lens
1804 group movement. A negative value moves the zoom lens group towards the
1805 wide-angle direction. The zoom speed unit is driver-specific.</entry>
1806           </row>
1807           <row><entry></entry></row>
1808
1809           <row>
1810             <entry spanname="id"><constant>V4L2_CID_PRIVACY</constant>&nbsp;</entry>
1811             <entry>boolean</entry>
1812           </row><row><entry spanname="descr">Prevent video from being acquired
1813 by the camera. When this control is set to <constant>TRUE</constant> (1), no
1814 image can be captured by the camera. Common means to enforce privacy are
1815 mechanical obturation of the sensor and firmware image processing, but the
1816 device is not restricted to these methods. Devices that implement the privacy
1817 control must support read access and may support write access.</entry>
1818           </row>
1819
1820           <row>
1821             <entry spanname="id"><constant>V4L2_CID_BAND_STOP_FILTER</constant>&nbsp;</entry>
1822             <entry>integer</entry>
1823           </row><row><entry spanname="descr">Switch the band-stop filter of a
1824 camera sensor on or off, or specify its strength. Such band-stop filters can
1825 be used, for example, to filter out the fluorescent light component.</entry>
1826           </row>
1827           <row><entry></entry></row>
1828         </tbody>
1829       </tgroup>
1830     </table>
1831   </section>
1832
1833     <section id="fm-tx-controls">
1834       <title>FM Transmitter Control Reference</title>
1835
1836       <para>The FM Transmitter (FM_TX) class includes controls for common features of
1837 FM transmissions capable devices. Currently this class includes parameters for audio
1838 compression, pilot tone generation, audio deviation limiter, RDS transmission and
1839 tuning power features.</para>
1840
1841       <table pgwide="1" frame="none" id="fm-tx-control-id">
1842       <title>FM_TX Control IDs</title>
1843
1844       <tgroup cols="4">
1845         <colspec colname="c1" colwidth="1*" />
1846         <colspec colname="c2" colwidth="6*" />
1847         <colspec colname="c3" colwidth="2*" />
1848         <colspec colname="c4" colwidth="6*" />
1849         <spanspec namest="c1" nameend="c2" spanname="id" />
1850         <spanspec namest="c2" nameend="c4" spanname="descr" />
1851         <thead>
1852           <row>
1853             <entry spanname="id" align="left">ID</entry>
1854             <entry align="left">Type</entry>
1855           </row><row rowsep="1"><entry spanname="descr" align="left">Description</entry>
1856           </row>
1857         </thead>
1858         <tbody valign="top">
1859           <row><entry></entry></row>
1860           <row>
1861             <entry spanname="id"><constant>V4L2_CID_FM_TX_CLASS</constant>&nbsp;</entry>
1862             <entry>class</entry>
1863           </row><row><entry spanname="descr">The FM_TX class
1864 descriptor. Calling &VIDIOC-QUERYCTRL; for this control will return a
1865 description of this control class.</entry>
1866           </row>
1867           <row>
1868             <entry spanname="id"><constant>V4L2_CID_RDS_TX_DEVIATION</constant>&nbsp;</entry>
1869             <entry>integer</entry>
1870           </row>
1871           <row><entry spanname="descr">Configures RDS signal frequency deviation level in Hz.
1872 The range and step are driver-specific.</entry>
1873           </row>
1874           <row>
1875             <entry spanname="id"><constant>V4L2_CID_RDS_TX_PI</constant>&nbsp;</entry>
1876             <entry>integer</entry>
1877           </row>
1878           <row><entry spanname="descr">Sets the RDS Programme Identification field
1879 for transmission.</entry>
1880           </row>
1881           <row>
1882             <entry spanname="id"><constant>V4L2_CID_RDS_TX_PTY</constant>&nbsp;</entry>
1883             <entry>integer</entry>
1884           </row>
1885           <row><entry spanname="descr">Sets the RDS Programme Type field for transmission.
1886 This encodes up to 31 pre-defined programme types.</entry>
1887           </row>
1888           <row>
1889             <entry spanname="id"><constant>V4L2_CID_RDS_TX_PS_NAME</constant>&nbsp;</entry>
1890             <entry>string</entry>
1891           </row>
1892           <row><entry spanname="descr">Sets the Programme Service name (PS_NAME) for transmission.
1893 It is intended for static display on a receiver. It is the primary aid to listeners in programme service
1894 identification and selection.  In Annex E of <xref linkend="en50067" />, the RDS specification,
1895 there is a full description of the correct character encoding for Programme Service name strings.
1896 Also from RDS specification, PS is usually a single eight character text. However, it is also possible
1897 to find receivers which can scroll strings sized as 8 x N characters. So, this control must be configured
1898 with steps of 8 characters. The result is it must always contain a string with size multiple of 8.</entry>
1899           </row>
1900           <row>
1901             <entry spanname="id"><constant>V4L2_CID_RDS_TX_RADIO_TEXT</constant>&nbsp;</entry>
1902             <entry>string</entry>
1903           </row>
1904           <row><entry spanname="descr">Sets the Radio Text info for transmission. It is a textual description of
1905 what is being broadcasted. RDS Radio Text can be applied when broadcaster wishes to transmit longer PS names,
1906 programme-related information or any other text. In these cases, RadioText should be used in addition to
1907 <constant>V4L2_CID_RDS_TX_PS_NAME</constant>. The encoding for Radio Text strings is also fully described
1908 in Annex E of <xref linkend="en50067" />. The length of Radio Text strings depends on which RDS Block is being
1909 used to transmit it, either 32 (2A block) or 64 (2B block).  However, it is also possible
1910 to find receivers which can scroll strings sized as 32 x N or 64 x N characters. So, this control must be configured
1911 with steps of 32 or 64 characters. The result is it must always contain a string with size multiple of 32 or 64. </entry>
1912           </row>
1913           <row>
1914             <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_ENABLED</constant>&nbsp;</entry>
1915             <entry>boolean</entry>
1916           </row>
1917           <row><entry spanname="descr">Enables or disables the audio deviation limiter feature.
1918 The limiter is useful when trying to maximize the audio volume, minimize receiver-generated
1919 distortion and prevent overmodulation.
1920 </entry>
1921           </row>
1922           <row>
1923             <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_RELEASE_TIME</constant>&nbsp;</entry>
1924             <entry>integer</entry>
1925           </row>
1926           <row><entry spanname="descr">Sets the audio deviation limiter feature release time.
1927 Unit is in useconds. Step and range are driver-specific.</entry>
1928           </row>
1929           <row>
1930             <entry spanname="id"><constant>V4L2_CID_AUDIO_LIMITER_DEVIATION</constant>&nbsp;</entry>
1931             <entry>integer</entry>
1932           </row>
1933           <row><entry spanname="descr">Configures audio frequency deviation level in Hz.
1934 The range and step are driver-specific.</entry>
1935           </row>
1936           <row>
1937             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_ENABLED</constant>&nbsp;</entry>
1938             <entry>boolean</entry>
1939           </row>
1940           <row><entry spanname="descr">Enables or disables the audio compression feature.
1941 This feature amplifies signals below the threshold by a fixed gain and compresses audio
1942 signals above the threshold by the ratio of Threshold/(Gain + Threshold).</entry>
1943           </row>
1944           <row>
1945             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_GAIN</constant>&nbsp;</entry>
1946             <entry>integer</entry>
1947           </row>
1948           <row><entry spanname="descr">Sets the gain for audio compression feature. It is
1949 a dB value. The range and step are driver-specific.</entry>
1950           </row>
1951           <row>
1952             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_THRESHOLD</constant>&nbsp;</entry>
1953             <entry>integer</entry>
1954           </row>
1955           <row><entry spanname="descr">Sets the threshold level for audio compression freature.
1956 It is a dB value. The range and step are driver-specific.</entry>
1957           </row>
1958           <row>
1959             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_ATTACK_TIME</constant>&nbsp;</entry>
1960             <entry>integer</entry>
1961           </row>
1962           <row><entry spanname="descr">Sets the attack time for audio compression feature.
1963 It is a useconds value. The range and step are driver-specific.</entry>
1964           </row>
1965           <row>
1966             <entry spanname="id"><constant>V4L2_CID_AUDIO_COMPRESSION_RELEASE_TIME</constant>&nbsp;</entry>
1967             <entry>integer</entry>
1968           </row>
1969           <row><entry spanname="descr">Sets the release time for audio compression feature.
1970 It is a useconds value. The range and step are driver-specific.</entry>
1971           </row>
1972           <row>
1973             <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_ENABLED</constant>&nbsp;</entry>
1974             <entry>boolean</entry>
1975           </row>
1976           <row><entry spanname="descr">Enables or disables the pilot tone generation feature.</entry>
1977           </row>
1978           <row>
1979             <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_DEVIATION</constant>&nbsp;</entry>
1980             <entry>integer</entry>
1981           </row>
1982           <row><entry spanname="descr">Configures pilot tone frequency deviation level. Unit is
1983 in Hz. The range and step are driver-specific.</entry>
1984           </row>
1985           <row>
1986             <entry spanname="id"><constant>V4L2_CID_PILOT_TONE_FREQUENCY</constant>&nbsp;</entry>
1987             <entry>integer</entry>
1988           </row>
1989           <row><entry spanname="descr">Configures pilot tone frequency value. Unit is
1990 in Hz. The range and step are driver-specific.</entry>
1991           </row>
1992           <row>
1993             <entry spanname="id"><constant>V4L2_CID_TUNE_PREEMPHASIS</constant>&nbsp;</entry>
1994             <entry>integer</entry>
1995           </row>
1996           <row id="v4l2-preemphasis"><entry spanname="descr">Configures the pre-emphasis value for broadcasting.
1997 A pre-emphasis filter is applied to the broadcast to accentuate the high audio frequencies.
1998 Depending on the region, a time constant of either 50 or 75 useconds is used. The enum&nbsp;v4l2_preemphasis
1999 defines possible values for pre-emphasis. Here they are:</entry>
2000         </row><row>
2001         <entrytbl spanname="descr" cols="2">
2002                   <tbody valign="top">
2003                     <row>
2004                       <entry><constant>V4L2_PREEMPHASIS_DISABLED</constant>&nbsp;</entry>
2005                       <entry>No pre-emphasis is applied.</entry>
2006                     </row>
2007                     <row>
2008                       <entry><constant>V4L2_PREEMPHASIS_50_uS</constant>&nbsp;</entry>
2009                       <entry>A pre-emphasis of 50 uS is used.</entry>
2010                     </row>
2011                     <row>
2012                       <entry><constant>V4L2_PREEMPHASIS_75_uS</constant>&nbsp;</entry>
2013                       <entry>A pre-emphasis of 75 uS is used.</entry>
2014                     </row>
2015                   </tbody>
2016                 </entrytbl>
2017
2018           </row>
2019           <row>
2020             <entry spanname="id"><constant>V4L2_CID_TUNE_POWER_LEVEL</constant>&nbsp;</entry>
2021             <entry>integer</entry>
2022           </row>
2023           <row><entry spanname="descr">Sets the output power level for signal transmission.
2024 Unit is in dBuV. Range and step are driver-specific.</entry>
2025           </row>
2026           <row>
2027             <entry spanname="id"><constant>V4L2_CID_TUNE_ANTENNA_CAPACITOR</constant>&nbsp;</entry>
2028             <entry>integer</entry>
2029           </row>
2030           <row><entry spanname="descr">This selects the value of antenna tuning capacitor
2031 manually or automatically if set to zero. Unit, range and step are driver-specific.</entry>
2032           </row>
2033           <row><entry></entry></row>
2034         </tbody>
2035       </tgroup>
2036       </table>
2037
2038 <para>For more details about RDS specification, refer to
2039 <xref linkend="en50067" /> document, from CENELEC.</para>
2040     </section>
2041 </section>
2042
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