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Diffstat (limited to 'Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml')
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diff --git a/Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml b/Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml new file mode 100644 index 000000000000..74b87f6e480a --- /dev/null +++ b/Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml @@ -0,0 +1,256 @@ +<refentry id="vidioc-decoder-cmd"> + <refmeta> + <refentrytitle>ioctl VIDIOC_DECODER_CMD, VIDIOC_TRY_DECODER_CMD</refentrytitle> + &manvol; + </refmeta> + + <refnamediv> + <refname>VIDIOC_DECODER_CMD</refname> + <refname>VIDIOC_TRY_DECODER_CMD</refname> + <refpurpose>Execute an decoder command</refpurpose> + </refnamediv> + + <refsynopsisdiv> + <funcsynopsis> + <funcprototype> + <funcdef>int <function>ioctl</function></funcdef> + <paramdef>int <parameter>fd</parameter></paramdef> + <paramdef>int <parameter>request</parameter></paramdef> + <paramdef>struct v4l2_decoder_cmd *<parameter>argp</parameter></paramdef> + </funcprototype> + </funcsynopsis> + </refsynopsisdiv> + + <refsect1> + <title>Arguments</title> + + <variablelist> + <varlistentry> + <term><parameter>fd</parameter></term> + <listitem> + <para>&fd;</para> + </listitem> + </varlistentry> + <varlistentry> + <term><parameter>request</parameter></term> + <listitem> + <para>VIDIOC_DECODER_CMD, VIDIOC_TRY_DECODER_CMD</para> + </listitem> + </varlistentry> + <varlistentry> + <term><parameter>argp</parameter></term> + <listitem> + <para></para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> + + <refsect1> + <title>Description</title> + + <note> + <title>Experimental</title> + + <para>This is an <link linkend="experimental">experimental</link> +interface and may change in the future.</para> + </note> + + <para>These ioctls control an audio/video (usually MPEG-) decoder. +<constant>VIDIOC_DECODER_CMD</constant> sends a command to the +decoder, <constant>VIDIOC_TRY_DECODER_CMD</constant> can be used to +try a command without actually executing it. To send a command applications +must initialize all fields of a &v4l2-decoder-cmd; and call +<constant>VIDIOC_DECODER_CMD</constant> or <constant>VIDIOC_TRY_DECODER_CMD</constant> +with a pointer to this structure.</para> + + <para>The <structfield>cmd</structfield> field must contain the +command code. Some commands use the <structfield>flags</structfield> field for +additional information. +</para> + + <para>A <function>write</function>() or &VIDIOC-STREAMON; call sends an implicit +START command to the decoder if it has not been started yet. +</para> + + <para>A <function>close</function>() or &VIDIOC-STREAMOFF; call of a streaming +file descriptor sends an implicit immediate STOP command to the decoder, and all +buffered data is discarded.</para> + + <para>These ioctls are optional, not all drivers may support +them. They were introduced in Linux 3.3.</para> + + <table pgwide="1" frame="none" id="v4l2-decoder-cmd"> + <title>struct <structname>v4l2_decoder_cmd</structname></title> + <tgroup cols="5"> + &cs-str; + <tbody valign="top"> + <row> + <entry>__u32</entry> + <entry><structfield>cmd</structfield></entry> + <entry></entry> + <entry></entry> + <entry>The decoder command, see <xref linkend="decoder-cmds" />.</entry> + </row> + <row> + <entry>__u32</entry> + <entry><structfield>flags</structfield></entry> + <entry></entry> + <entry></entry> + <entry>Flags to go with the command. If no flags are defined for +this command, drivers and applications must set this field to zero.</entry> + </row> + <row> + <entry>union</entry> + <entry>(anonymous)</entry> + <entry></entry> + <entry></entry> + <entry></entry> + </row> + <row> + <entry></entry> + <entry>struct</entry> + <entry><structfield>start</structfield></entry> + <entry></entry> + <entry>Structure containing additional data for the +<constant>V4L2_DEC_CMD_START</constant> command.</entry> + </row> + <row> + <entry></entry> + <entry></entry> + <entry>__s32</entry> + <entry><structfield>speed</structfield></entry> + <entry>Playback speed and direction. The playback speed is defined as +<structfield>speed</structfield>/1000 of the normal speed. So 1000 is normal playback. +Negative numbers denote reverse playback, so -1000 does reverse playback at normal +speed. Speeds -1, 0 and 1 have special meanings: speed 0 is shorthand for 1000 +(normal playback). A speed of 1 steps just one frame forward, a speed of -1 steps +just one frame back. + </entry> + </row> + <row> + <entry></entry> + <entry></entry> + <entry>__u32</entry> + <entry><structfield>format</structfield></entry> + <entry>Format restrictions. This field is set by the driver, not the +application. Possible values are <constant>V4L2_DEC_START_FMT_NONE</constant> if +there are no format restrictions or <constant>V4L2_DEC_START_FMT_GOP</constant> +if the decoder operates on full GOPs (<wordasword>Group Of Pictures</wordasword>). +This is usually the case for reverse playback: the decoder needs full GOPs, which +it can then play in reverse order. So to implement reverse playback the application +must feed the decoder the last GOP in the video file, then the GOP before that, etc. etc. + </entry> + </row> + <row> + <entry></entry> + <entry>struct</entry> + <entry><structfield>stop</structfield></entry> + <entry></entry> + <entry>Structure containing additional data for the +<constant>V4L2_DEC_CMD_STOP</constant> command.</entry> + </row> + <row> + <entry></entry> + <entry></entry> + <entry>__u64</entry> + <entry><structfield>pts</structfield></entry> + <entry>Stop playback at this <structfield>pts</structfield> or immediately +if the playback is already past that timestamp. Leave to 0 if you want to stop after the +last frame was decoded. + </entry> + </row> + <row> + <entry></entry> + <entry>struct</entry> + <entry><structfield>raw</structfield></entry> + <entry></entry> + <entry></entry> + </row> + <row> + <entry></entry> + <entry></entry> + <entry>__u32</entry> + <entry><structfield>data</structfield>[16]</entry> + <entry>Reserved for future extensions. Drivers and +applications must set the array to zero.</entry> + </row> + </tbody> + </tgroup> + </table> + + <table pgwide="1" frame="none" id="decoder-cmds"> + <title>Decoder Commands</title> + <tgroup cols="3"> + &cs-def; + <tbody valign="top"> + <row> + <entry><constant>V4L2_DEC_CMD_START</constant></entry> + <entry>0</entry> + <entry>Start the decoder. When the decoder is already +running or paused, this command will just change the playback speed. +That means that calling <constant>V4L2_DEC_CMD_START</constant> when +the decoder was paused will <emphasis>not</emphasis> resume the decoder. +You have to explicitly call <constant>V4L2_DEC_CMD_RESUME</constant> for that. +This command has one flag: +<constant>V4L2_DEC_CMD_START_MUTE_AUDIO</constant>. If set, then audio will +be muted when playing back at a non-standard speed. + </entry> + </row> + <row> + <entry><constant>V4L2_DEC_CMD_STOP</constant></entry> + <entry>1</entry> + <entry>Stop the decoder. When the decoder is already stopped, +this command does nothing. This command has two flags: +if <constant>V4L2_DEC_CMD_STOP_TO_BLACK</constant> is set, then the decoder will +set the picture to black after it stopped decoding. Otherwise the last image will +repeat. If <constant>V4L2_DEC_CMD_STOP_IMMEDIATELY</constant> is set, then the decoder +stops immediately (ignoring the <structfield>pts</structfield> value), otherwise it +will keep decoding until timestamp >= pts or until the last of the pending data from +its internal buffers was decoded. +</entry> + </row> + <row> + <entry><constant>V4L2_DEC_CMD_PAUSE</constant></entry> + <entry>2</entry> + <entry>Pause the decoder. When the decoder has not been +started yet, the driver will return an &EPERM;. When the decoder is +already paused, this command does nothing. This command has one flag: +if <constant>V4L2_DEC_CMD_PAUSE_TO_BLACK</constant> is set, then set the +decoder output to black when paused. +</entry> + </row> + <row> + <entry><constant>V4L2_DEC_CMD_RESUME</constant></entry> + <entry>3</entry> + <entry>Resume decoding after a PAUSE command. When the +decoder has not been started yet, the driver will return an &EPERM;. +When the decoder is already running, this command does nothing. No +flags are defined for this command.</entry> + </row> + </tbody> + </tgroup> + </table> + + </refsect1> + + <refsect1> + &return-value; + + <variablelist> + <varlistentry> + <term><errorcode>EINVAL</errorcode></term> + <listitem> + <para>The <structfield>cmd</structfield> field is invalid.</para> + </listitem> + </varlistentry> + <varlistentry> + <term><errorcode>EPERM</errorcode></term> + <listitem> + <para>The application sent a PAUSE or RESUME command when +the decoder was not running.</para> + </listitem> + </varlistentry> + </variablelist> + </refsect1> +</refentry> |
