Documentation/DocBook/media/v4l/vidioc-g-jpegcomp.xml

   1 <refentry id="vidioc-g-jpegcomp">
   2   <refmeta>
   3     <refentrytitle>ioctl VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP</refentrytitle>
   4     &manvol;
   5   </refmeta>
   6
   7   <refnamediv>
   8     <refname>VIDIOC_G_JPEGCOMP</refname>
   9     <refname>VIDIOC_S_JPEGCOMP</refname>
  10     <refpurpose></refpurpose>
  11   </refnamediv>
  12
  13   <refsynopsisdiv>
  14     <funcsynopsis>
  15       <funcprototype>
  16         <funcdef>int <function>ioctl</function></funcdef>
  17         <paramdef>int <parameter>fd</parameter></paramdef>
  18         <paramdef>int <parameter>request</parameter></paramdef>
  19         <paramdef>v4l2_jpegcompression *<parameter>argp</parameter></paramdef>
  20       </funcprototype>
  21     </funcsynopsis>
  22     <funcsynopsis>
  23       <funcprototype>
  24         <funcdef>int <function>ioctl</function></funcdef>
  25         <paramdef>int <parameter>fd</parameter></paramdef>
  26         <paramdef>int <parameter>request</parameter></paramdef>
  27         <paramdef>const v4l2_jpegcompression *<parameter>argp</parameter></paramdef>
  28       </funcprototype>
  29     </funcsynopsis>
  30   </refsynopsisdiv>
  31
  32   <refsect1>
  33     <title>Arguments</title>
  34
  35     <variablelist>
  36       <varlistentry>
  37         <term><parameter>fd</parameter></term>
  38         <listitem>
  39           <para>&fd;</para>
  40         </listitem>
  41       </varlistentry>
  42       <varlistentry>
  43         <term><parameter>request</parameter></term>
  44         <listitem>
  45           <para>VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP</para>
  46         </listitem>
  47       </varlistentry>
  48       <varlistentry>
  49         <term><parameter>argp</parameter></term>
  50         <listitem>
  51           <para></para>
  52         </listitem>
  53       </varlistentry>
  54     </variablelist>
  55   </refsect1>
  56
  57   <refsect1>
  58     <title>Description</title>
  59
  60     <para>These ioctls are <emphasis role="bold">deprecated</emphasis>.
  61     New drivers and applications should use <link linkend="jpeg-controls">
  62     JPEG class controls</link> for image quality and JPEG markers control.
  63     </para>
  64
  65     <para>[to do]</para>
  66
  67     <para>Ronald Bultje elaborates:</para>
  68
  69     <!-- See video4linux-list@redhat.com on 16 Oct 2002, subject
  70 "Re: [V4L] Re: v4l2 api / Zoran v4l2_jpegcompression" -->
  71
  72     <para>APP is some application-specific information. The
  73 application can set it itself, and it'll be stored in the JPEG-encoded
  74 fields (eg; interlacing information for in an AVI or so). COM is the
  75 same, but it's comments, like 'encoded by me' or so.</para>
  76
  77     <para>jpeg_markers describes whether the huffman tables,
  78 quantization tables and the restart interval information (all
  79 JPEG-specific stuff) should be stored in the JPEG-encoded fields.
  80 These define how the JPEG field is encoded. If you omit them,
  81 applications assume you've used standard encoding. You usually do want
  82 to add them.</para>
  83
  84     <!-- NB VIDIOC_S_JPEGCOMP is w/o. -->
  85
  86     <table pgwide="1" frame="none" id="v4l2-jpegcompression">
  87       <title>struct <structname>v4l2_jpegcompression</structname></title>
  88       <tgroup cols="3">
  89         &cs-str;
  90         <tbody valign="top">
  91           <row>
  92             <entry>int</entry>
  93             <entry><structfield>quality</structfield></entry>
  94             <entry>Deprecated. If <link linkend="jpeg-quality-control"><constant>
  95             V4L2_CID_JPEG_COMPRESSION_QUALITY</constant></link> control is exposed
  96             by a driver applications should use it instead and ignore this field.
  97             </entry>
  98           </row>
  99           <row>
 100             <entry>int</entry>
 101             <entry><structfield>APPn</structfield></entry>
 102             <entry></entry>
 103           </row>
 104           <row>
 105             <entry>int</entry>
 106             <entry><structfield>APP_len</structfield></entry>
 107             <entry></entry>
 108           </row>
 109           <row>
 110             <entry>char</entry>
 111             <entry><structfield>APP_data</structfield>[60]</entry>
 112             <entry></entry>
 113           </row>
 114           <row>
 115             <entry>int</entry>
 116             <entry><structfield>COM_len</structfield></entry>
 117             <entry></entry>
 118           </row>
 119           <row>
 120             <entry>char</entry>
 121             <entry><structfield>COM_data</structfield>[60]</entry>
 122             <entry></entry>
 123           </row>
 124           <row>
 125             <entry>__u32</entry>
 126             <entry><structfield>jpeg_markers</structfield></entry>
 127             <entry>See <xref linkend="jpeg-markers"/>. Deprecated.
 128             If <link linkend="jpeg-active-marker-control"><constant>
 129             V4L2_CID_JPEG_ACTIVE_MARKER</constant></link> control
 130             is exposed by a driver applications should use it instead
 131             and ignore this field.</entry>
 132           </row>
 133         </tbody>
 134       </tgroup>
 135     </table>
 136
 137     <table pgwide="1" frame="none" id="jpeg-markers">
 138       <title>JPEG Markers Flags</title>
 139       <tgroup cols="3">
 140         &cs-def;
 141         <tbody valign="top">
 142           <row>
 143             <entry><constant>V4L2_JPEG_MARKER_DHT</constant></entry>
 144             <entry>(1&lt;&lt;3)</entry>
 145             <entry>Define Huffman Tables</entry>
 146           </row>
 147           <row>
 148             <entry><constant>V4L2_JPEG_MARKER_DQT</constant></entry>
 149             <entry>(1&lt;&lt;4)</entry>
 150             <entry>Define Quantization Tables</entry>
 151           </row>
 152           <row>
 153             <entry><constant>V4L2_JPEG_MARKER_DRI</constant></entry>
 154             <entry>(1&lt;&lt;5)</entry>
 155             <entry>Define Restart Interval</entry>
 156           </row>
 157           <row>
 158             <entry><constant>V4L2_JPEG_MARKER_COM</constant></entry>
 159             <entry>(1&lt;&lt;6)</entry>
 160             <entry>Comment segment</entry>
 161           </row>
 162           <row>
 163             <entry><constant>V4L2_JPEG_MARKER_APP</constant></entry>
 164             <entry>(1&lt;&lt;7)</entry>
 165             <entry>App segment, driver will always use APP0</entry>
 166           </row>
 167         </tbody>
 168       </tgroup>
 169     </table>
 170   </refsect1>
 171
 172   <refsect1>
 173     &return-value;
 174   </refsect1>
 175 </refentry>