| <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> |