![Mauro Carvalho Chehab](/assets/img/avatar_default.png)
The V4L and DVB API's are there for a long time. however, up to now, no efforts were done to merge them to kernel DocBook. This patch adds the current versions of the specs as an unique compendium. Signed-off-by: Mauro Carvalho Chehab <mchehab@redhat.com>
181 lines
4.7 KiB
XML
181 lines
4.7 KiB
XML
<refentry id="vidioc-g-jpegcomp">
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<refmeta>
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<refentrytitle>ioctl VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP</refentrytitle>
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&manvol;
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</refmeta>
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<refnamediv>
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<refname>VIDIOC_G_JPEGCOMP</refname>
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<refname>VIDIOC_S_JPEGCOMP</refname>
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<refpurpose></refpurpose>
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</refnamediv>
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<refsynopsisdiv>
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<funcsynopsis>
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<funcprototype>
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<funcdef>int <function>ioctl</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>request</parameter></paramdef>
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<paramdef>v4l2_jpegcompression *<parameter>argp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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<funcsynopsis>
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<funcprototype>
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<funcdef>int <function>ioctl</function></funcdef>
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<paramdef>int <parameter>fd</parameter></paramdef>
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<paramdef>int <parameter>request</parameter></paramdef>
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<paramdef>const v4l2_jpegcompression *<parameter>argp</parameter></paramdef>
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</funcprototype>
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</funcsynopsis>
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</refsynopsisdiv>
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<refsect1>
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<title>Arguments</title>
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<variablelist>
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<varlistentry>
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<term><parameter>fd</parameter></term>
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<listitem>
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<para>&fd;</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>request</parameter></term>
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<listitem>
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<para>VIDIOC_G_JPEGCOMP, VIDIOC_S_JPEGCOMP</para>
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</listitem>
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</varlistentry>
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<varlistentry>
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<term><parameter>argp</parameter></term>
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<listitem>
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<para></para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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<refsect1>
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<title>Description</title>
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<para>[to do]</para>
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<para>Ronald Bultje elaborates:</para>
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<!-- See video4linux-list@redhat.com on 16 Oct 2002, subject
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"Re: [V4L] Re: v4l2 api / Zoran v4l2_jpegcompression" -->
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<para>APP is some application-specific information. The
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application can set it itself, and it'll be stored in the JPEG-encoded
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fields (eg; interlacing information for in an AVI or so). COM is the
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same, but it's comments, like 'encoded by me' or so.</para>
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<para>jpeg_markers describes whether the huffman tables,
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quantization tables and the restart interval information (all
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JPEG-specific stuff) should be stored in the JPEG-encoded fields.
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These define how the JPEG field is encoded. If you omit them,
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applications assume you've used standard encoding. You usually do want
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to add them.</para>
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<!-- NB VIDIOC_S_JPEGCOMP is w/o. -->
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<table pgwide="1" frame="none" id="v4l2-jpegcompression">
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<title>struct <structname>v4l2_jpegcompression</structname></title>
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<tgroup cols="3">
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&cs-str;
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<tbody valign="top">
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<row>
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<entry>int</entry>
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<entry><structfield>quality</structfield></entry>
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<entry></entry>
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</row>
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<row>
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<entry>int</entry>
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<entry><structfield>APPn</structfield></entry>
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<entry></entry>
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</row>
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<row>
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<entry>int</entry>
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<entry><structfield>APP_len</structfield></entry>
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<entry></entry>
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</row>
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<row>
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<entry>char</entry>
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<entry><structfield>APP_data</structfield>[60]</entry>
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<entry></entry>
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</row>
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<row>
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<entry>int</entry>
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<entry><structfield>COM_len</structfield></entry>
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<entry></entry>
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</row>
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<row>
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<entry>char</entry>
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<entry><structfield>COM_data</structfield>[60]</entry>
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<entry></entry>
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</row>
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<row>
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<entry>__u32</entry>
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<entry><structfield>jpeg_markers</structfield></entry>
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<entry>See <xref linkend="jpeg-markers" />.</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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<table pgwide="1" frame="none" id="jpeg-markers">
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<title>JPEG Markers Flags</title>
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<tgroup cols="3">
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&cs-def;
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<tbody valign="top">
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<row>
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<entry><constant>V4L2_JPEG_MARKER_DHT</constant></entry>
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<entry>(1<<3)</entry>
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<entry>Define Huffman Tables</entry>
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</row>
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<row>
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<entry><constant>V4L2_JPEG_MARKER_DQT</constant></entry>
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<entry>(1<<4)</entry>
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<entry>Define Quantization Tables</entry>
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</row>
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<row>
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<entry><constant>V4L2_JPEG_MARKER_DRI</constant></entry>
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<entry>(1<<5)</entry>
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<entry>Define Restart Interval</entry>
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</row>
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<row>
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<entry><constant>V4L2_JPEG_MARKER_COM</constant></entry>
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<entry>(1<<6)</entry>
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<entry>Comment segment</entry>
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</row>
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<row>
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<entry><constant>V4L2_JPEG_MARKER_APP</constant></entry>
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<entry>(1<<7)</entry>
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<entry>App segment, driver will always use APP0</entry>
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</row>
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</tbody>
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</tgroup>
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</table>
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</refsect1>
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<refsect1>
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&return-value;
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<variablelist>
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<varlistentry>
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<term><errorcode>EINVAL</errorcode></term>
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<listitem>
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<para>This ioctl is not supported.</para>
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</listitem>
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</varlistentry>
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</variablelist>
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</refsect1>
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</refentry>
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<!--
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Local Variables:
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mode: sgml
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sgml-parent-document: "v4l2.sgml"
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indent-tabs-mode: nil
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End:
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-->
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