diff options
Diffstat (limited to 'Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst')
| -rw-r--r-- | Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst | 41 |
1 files changed, 27 insertions, 14 deletions
diff --git a/Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst b/Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst index ccf83b05afa7..57f0066f4cff 100644 --- a/Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst +++ b/Documentation/media/uapi/v4l/vidioc-decoder-cmd.rst @@ -56,14 +56,16 @@ The ``cmd`` field must contain the command code. Some commands use the A :ref:`write() <func-write>` or :ref:`VIDIOC_STREAMON` call sends an implicit START command to the decoder if it has not been -started yet. +started yet. Applies to both queues of mem2mem decoders. A :ref:`close() <func-close>` or :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` call of a streaming file descriptor sends an implicit immediate STOP -command to the decoder, and all buffered data is discarded. +command to the decoder, and all buffered data is discarded. Applies to both +queues of mem2mem decoders. -These ioctls are optional, not all drivers may support them. They were -introduced in Linux 3.3. +In principle, these ioctls are optional, not all drivers may support them. They were +introduced in Linux 3.3. They are, however, mandatory for stateful mem2mem decoders +(as further documented in :ref:`decoder`). .. tabularcolumns:: |p{1.1cm}|p{2.4cm}|p{1.2cm}|p{1.6cm}|p{10.6cm}| @@ -167,26 +169,32 @@ introduced in Linux 3.3. ``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. + + For a device implementing the :ref:`decoder`, once the drain sequence + is initiated with the ``V4L2_DEC_CMD_STOP`` command, it must be driven + to completion before this command can be invoked. Any attempt to + invoke the command while the drain sequence is in progress will trigger + an ``EBUSY`` error code. The command may be also used to restart the + decoder in case of an implicit stop initiated by the decoder itself, + without the ``V4L2_DEC_CMD_STOP`` being called explicitly. See + :ref:`decoder` for more details. * - ``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 + image will repeat. 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. + + For a device implementing the :ref:`decoder`, the command will initiate + the drain sequence as documented in :ref:`decoder`. No flags or other + arguments are accepted in this case. Any attempt to invoke the command + again before the sequence completes will trigger an ``EBUSY`` error + code. * - ``V4L2_DEC_CMD_PAUSE`` - 2 - Pause the decoder. When the decoder has not been started yet, the @@ -209,6 +217,11 @@ On success 0 is returned, on error -1 and the ``errno`` variable is set appropriately. The generic error codes are described at the :ref:`Generic Error Codes <gen-errors>` chapter. +EBUSY + A drain sequence of a device implementing the :ref:`decoder` is still in + progress. It is not allowed to issue another decoder command until it + completes. + EINVAL The ``cmd`` field is invalid. |