- ``cmd``
- -
- -
+ -
+ -
- The decoder command, see :ref:`decoder-cmds`.
- .. row 2
- ``flags``
- -
- -
+ -
+ -
- Flags to go with the command. If no flags are defined for this
- command, drivers and applications must set this field to zero.
+ command, drivers and applications must set this field to zero.
- .. row 3
- (anonymous)
- -
- -
- -
+ -
+ -
+ -
- .. row 4
- -
+ -
- struct
- ``start``
- -
+ -
- Structure containing additional data for the
- ``V4L2_DEC_CMD_START`` command.
+ ``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.
+ ``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.
+ 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.
+ 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.
+ 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.
+ the array to zero.
- 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.
+ 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
- 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.
+ 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
- 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.
+ 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
- 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.
+ 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.
projects / deliverable / linux.git / blobdiff