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Diffstat (limited to 'Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst')
| -rw-r--r-- | Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst | 325 |
1 files changed, 132 insertions, 193 deletions
diff --git a/Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst b/Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst index 2a36e91b57b9..85c916b0ce07 100644 --- a/Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst +++ b/Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst @@ -15,7 +15,12 @@ VIDIOC_DECODER_CMD - VIDIOC_TRY_DECODER_CMD - Execute an decoder command Synopsis ======== -.. cpp:function:: int ioctl( int fd, int request, struct v4l2_decoder_cmd *argp ) +.. c:function:: int ioctl( int fd, VIDIOC_DECODER_CMD, struct v4l2_decoder_cmd *argp ) + :name: VIDIOC_DECODER_CMD + + +.. c:function:: int ioctl( int fd, VIDIOC_TRY_DECODER_CMD, struct v4l2_decoder_cmd *argp ) + :name: VIDIOC_TRY_DECODER_CMD Arguments @@ -24,10 +29,8 @@ Arguments ``fd`` File descriptor returned by :ref:`open() <func-open>`. -``request`` - VIDIOC_DECODER_CMD, VIDIOC_TRY_DECODER_CMD - ``argp`` + pointer to struct :c:type:`v4l2_decoder_cmd`. Description @@ -37,7 +40,7 @@ These ioctls control an audio/video (usually MPEG-) decoder. ``VIDIOC_DECODER_CMD`` sends a command to the decoder, ``VIDIOC_TRY_DECODER_CMD`` can be used to try a command without actually executing it. To send a command applications must initialize all fields -of a struct :ref:`v4l2_decoder_cmd <v4l2-decoder-cmd>` and call +of a struct :c:type:`v4l2_decoder_cmd` and call ``VIDIOC_DECODER_CMD`` or ``VIDIOC_TRY_DECODER_CMD`` with a pointer to this structure. @@ -56,204 +59,140 @@ These ioctls are optional, not all drivers may support them. They were introduced in Linux 3.3. -.. _v4l2-decoder-cmd: +.. tabularcolumns:: |p{1.1cm}|p{2.4cm}|p{1.2cm}|p{1.6cm}|p{10.6cm}| + +.. c:type:: v4l2_decoder_cmd + +.. cssclass:: longtable .. flat-table:: struct v4l2_decoder_cmd :header-rows: 0 :stub-columns: 0 - :widths: 1 1 2 1 1 - - - - .. row 1 - - - __u32 - - - ``cmd`` - - - - - - - The decoder command, see :ref:`decoder-cmds`. - - - .. row 2 - - - __u32 - - - ``flags`` - - - - - - - Flags to go with the command. If no flags are defined for this - command, drivers and applications must set this field to zero. - - - .. row 3 - - - union - - - (anonymous) - - - - - - - - - - .. row 4 - - - - - struct - - - ``start`` - - - - - Structure containing additional data for the - ``V4L2_DEC_CMD_START`` command. - - - .. row 5 - - - - - - - __s32 - - - ``speed`` - - - Playback speed and direction. The playback speed is defined as - ``speed``/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. - - - .. row 6 - - - - - - - __u32 - - - ``format`` - - - Format restrictions. This field is set by the driver, not the - application. Possible values are ``V4L2_DEC_START_FMT_NONE`` if - there are no format restrictions or ``V4L2_DEC_START_FMT_GOP`` if - the decoder operates on full GOPs (*Group Of Pictures*). 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. - - - .. row 7 - - - - - struct - - - ``stop`` - - - - - Structure containing additional data for the ``V4L2_DEC_CMD_STOP`` - command. - - - .. row 8 - - - - - - - __u64 - - - ``pts`` - - - Stop playback at this ``pts`` or immediately if the playback is - already past that timestamp. Leave to 0 if you want to stop after - the last frame was decoded. - - - .. row 9 - - - - - struct - - - ``raw`` - - - - - - - - .. row 10 - - - - - - - __u32 - - - ``data``\ [16] - - - Reserved for future extensions. Drivers and applications must set - the array to zero. - - + :widths: 11 24 12 16 106 + + * - __u32 + - ``cmd`` + - + - + - The decoder command, see :ref:`decoder-cmds`. + * - __u32 + - ``flags`` + - + - + - Flags to go with the command. If no flags are defined for this + command, drivers and applications must set this field to zero. + * - union + - (anonymous) + - + - + - + * - + - struct + - ``start`` + - + - Structure containing additional data for the + ``V4L2_DEC_CMD_START`` command. + * - + - + - __s32 + - ``speed`` + - Playback speed and direction. The playback speed is defined as + ``speed``/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. + * - + - + - __u32 + - ``format`` + - Format restrictions. This field is set by the driver, not the + application. Possible values are ``V4L2_DEC_START_FMT_NONE`` if + there are no format restrictions or ``V4L2_DEC_START_FMT_GOP`` if + the decoder operates on full GOPs (*Group Of Pictures*). 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. + * - + - struct + - ``stop`` + - + - Structure containing additional data for the ``V4L2_DEC_CMD_STOP`` + command. + * - + - + - __u64 + - ``pts`` + - Stop playback at this ``pts`` or immediately if the playback is + already past that timestamp. Leave to 0 if you want to stop after + the last frame was decoded. + * - + - struct + - ``raw`` + - + - + * - + - + - __u32 + - ``data``\ [16] + - Reserved for future extensions. Drivers and applications must set + the array to zero. + + + +.. tabularcolumns:: |p{5.6cm}|p{0.6cm}|p{11.3cm}| .. _decoder-cmds: .. flat-table:: Decoder Commands :header-rows: 0 :stub-columns: 0 - :widths: 3 1 4 - - - - .. row 1 - - - ``V4L2_DEC_CMD_START`` - - - 0 - - - Start the decoder. When the decoder is already running or paused, - this command will just change the playback speed. That means that - calling ``V4L2_DEC_CMD_START`` when the decoder was paused will - *not* resume the decoder. You have to explicitly call - ``V4L2_DEC_CMD_RESUME`` for that. This command has one flag: - ``V4L2_DEC_CMD_START_MUTE_AUDIO``. If set, then audio will be - muted when playing back at a non-standard speed. - - - .. row 2 - - - ``V4L2_DEC_CMD_STOP`` - - - 1 - - - Stop the decoder. When the decoder is already stopped, this - command does nothing. This command has two flags: if - ``V4L2_DEC_CMD_STOP_TO_BLACK`` is set, then the decoder will set - the picture to black after it stopped decoding. Otherwise the last - image will repeat. mem2mem decoders will stop producing new frames - altogether. They will send a ``V4L2_EVENT_EOS`` event when the - last frame has been decoded and all frames are ready to be - dequeued and will set the ``V4L2_BUF_FLAG_LAST`` buffer flag on - the last buffer of the capture queue to indicate there will be no - new buffers produced to dequeue. This buffer may be empty, - indicated by the driver setting the ``bytesused`` field to 0. Once - the ``V4L2_BUF_FLAG_LAST`` flag was set, the - :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl will not block anymore, - but return an ``EPIPE`` error code. If - ``V4L2_DEC_CMD_STOP_IMMEDIATELY`` is set, then the decoder stops - immediately (ignoring the ``pts`` value), otherwise it will keep - decoding until timestamp >= pts or until the last of the pending - data from its internal buffers was decoded. - - - .. row 3 - - - ``V4L2_DEC_CMD_PAUSE`` - - - 2 - - - Pause the decoder. When the decoder has not been started yet, the - driver will return an ``EPERM`` error code. When the decoder is - already paused, this command does nothing. This command has one - flag: if ``V4L2_DEC_CMD_PAUSE_TO_BLACK`` is set, then set the - decoder output to black when paused. - - - .. row 4 - - - ``V4L2_DEC_CMD_RESUME`` - - - 3 - - - Resume decoding after a PAUSE command. When the decoder has not - been started yet, the driver will return an ``EPERM`` error code. When - the decoder is already running, this command does nothing. No - flags are defined for this command. + :widths: 56 6 113 + + * - ``V4L2_DEC_CMD_START`` + - 0 + - Start the decoder. When the decoder is already running or paused, + this command will just change the playback speed. That means that + calling ``V4L2_DEC_CMD_START`` when the decoder was paused will + *not* resume the decoder. You have to explicitly call + ``V4L2_DEC_CMD_RESUME`` for that. This command has one flag: + ``V4L2_DEC_CMD_START_MUTE_AUDIO``. If set, then audio will be + muted when playing back at a non-standard speed. + * - ``V4L2_DEC_CMD_STOP`` + - 1 + - Stop the decoder. When the decoder is already stopped, this + command does nothing. This command has two flags: if + ``V4L2_DEC_CMD_STOP_TO_BLACK`` is set, then the decoder will set + the picture to black after it stopped decoding. Otherwise the last + image will repeat. mem2mem decoders will stop producing new frames + altogether. They will send a ``V4L2_EVENT_EOS`` event when the + last frame has been decoded and all frames are ready to be + dequeued and will set the ``V4L2_BUF_FLAG_LAST`` buffer flag on + the last buffer of the capture queue to indicate there will be no + new buffers produced to dequeue. This buffer may be empty, + indicated by the driver setting the ``bytesused`` field to 0. Once + the ``V4L2_BUF_FLAG_LAST`` flag was set, the + :ref:`VIDIOC_DQBUF <VIDIOC_QBUF>` ioctl will not block anymore, + but return an ``EPIPE`` error code. If + ``V4L2_DEC_CMD_STOP_IMMEDIATELY`` is set, then the decoder stops + immediately (ignoring the ``pts`` value), otherwise it will keep + decoding until timestamp >= pts or until the last of the pending + data from its internal buffers was decoded. + * - ``V4L2_DEC_CMD_PAUSE`` + - 2 + - Pause the decoder. When the decoder has not been started yet, the + driver will return an ``EPERM`` error code. When the decoder is + already paused, this command does nothing. This command has one + flag: if ``V4L2_DEC_CMD_PAUSE_TO_BLACK`` is set, then set the + decoder output to black when paused. + * - ``V4L2_DEC_CMD_RESUME`` + - 3 + - Resume decoding after a PAUSE command. When the decoder has not + been started yet, the driver will return an ``EPERM`` error code. When + the decoder is already running, this command does nothing. No + flags are defined for this command. Return Value |