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Commit 6b4f1252 authored by Hans Verkuil's avatar Hans Verkuil Committed by Mauro Carvalho Chehab
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[media] v4l spec: document VIDIOC_(TRY_)DECODER_CMD 

Signed-off-by: default avatarHans Verkuil <hans.verkuil@cisco.com>
Signed-off-by: default avatarMauro Carvalho Chehab <mchehab@redhat.com>
parent a45c0ad5
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Documentation/DocBook/media/v4l/v4l2.xml
View file @ 6b4f1252
......@@ -480,6 +480,7 @@ and discussions on the V4L mailing list.</revremark>
&sub-cropcap;
&sub-dbg-g-chip-ident;
&sub-dbg-g-register;
&sub-decoder-cmd;
&sub-dqevent;
&sub-encoder-cmd;
&sub-enumaudio;
......
Documentation/DocBook/media/v4l/vidioc-decoder-cmd.xml 0 → 100644
View file @ 6b4f1252
<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>__u32</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>
Documentation/DocBook/media/v4l/vidioc-encoder-cmd.xml
View file @ 6b4f1252
......@@ -74,15 +74,16 @@ only used by the STOP command and contains one bit: If the
encoding will continue until the end of the current <wordasword>Group
Of Pictures</wordasword>, otherwise it will stop immediately.</para>
<para>A <function>read</function>() call sends a START command to
the encoder if it has not been started yet. After a STOP command,
<para>A <function>read</function>() or &VIDIOC-STREAMON; call sends an implicit
START command to the encoder if it has not been started yet. After a STOP command,
<function>read</function>() calls will read the remaining data
buffered by the driver. When the buffer is empty,
<function>read</function>() will return zero and the next
<function>read</function>() call will restart the encoder.</para>
<para>A <function>close</function>() call sends an immediate STOP
to the encoder, and all buffered data is discarded.</para>
<para>A <function>close</function>() or &VIDIOC-STREAMOFF; call of a streaming
file descriptor sends an implicit immediate STOP to the encoder, and all buffered
data is discarded.</para>
<para>These ioctls are optional, not all drivers may support
them. They were introduced in Linux 2.6.21.</para>
......
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