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+.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
+.. c:namespace:: V4L
+
+.. _VIDIOC_ENCODER_CMD:
+
+************************************************
+ioctl VIDIOC_ENCODER_CMD, VIDIOC_TRY_ENCODER_CMD
+************************************************
+
+Name
+====
+
+VIDIOC_ENCODER_CMD - VIDIOC_TRY_ENCODER_CMD - Execute an encoder command
+
+Synopsis
+========
+
+.. c:macro:: VIDIOC_ENCODER_CMD
+
+``int ioctl(int fd, VIDIOC_ENCODER_CMD, struct v4l2_encoder_cmd *argp)``
+
+.. c:macro:: VIDIOC_TRY_ENCODER_CMD
+
+``int ioctl(int fd, VIDIOC_TRY_ENCODER_CMD, struct v4l2_encoder_cmd *argp)``
+
+Arguments
+=========
+
+``fd``
+ File descriptor returned by :c:func:`open()`.
+
+``argp``
+ Pointer to struct :c:type:`v4l2_encoder_cmd`.
+
+Description
+===========
+
+These ioctls control an audio/video (usually MPEG-) encoder.
+``VIDIOC_ENCODER_CMD`` sends a command to the encoder,
+``VIDIOC_TRY_ENCODER_CMD`` can be used to try a command without actually
+executing it.
+
+To send a command applications must initialize all fields of a struct
+:c:type:`v4l2_encoder_cmd` and call
+``VIDIOC_ENCODER_CMD`` or ``VIDIOC_TRY_ENCODER_CMD`` with a pointer to
+this structure.
+
+The ``cmd`` field must contain the command code. Some commands use the
+``flags`` field for additional information.
+
+After a STOP command, :c:func:`read()` calls will read
+the remaining data buffered by the driver. When the buffer is empty,
+:c:func:`read()` will return zero and the next :c:func:`read()`
+call will restart the encoder.
+
+A :c:func:`read()` or :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>`
+call sends an implicit START command to the encoder if it has not been
+started yet. Applies to both queues of mem2mem encoders.
+
+A :c:func:`close()` or :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>`
+call of a streaming file descriptor sends an implicit immediate STOP to
+the encoder, and all buffered data is discarded. Applies to both queues of
+mem2mem encoders.
+
+These ioctls are optional, not all drivers may support them. They were
+introduced in Linux 2.6.21. They are, however, mandatory for stateful mem2mem
+encoders (as further documented in :ref:`encoder`).
+
+.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}|
+
+.. c:type:: v4l2_encoder_cmd
+
+.. flat-table:: struct v4l2_encoder_cmd
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 1 1 2
+
+ * - __u32
+ - ``cmd``
+ - The encoder command, see :ref:`encoder-cmds`.
+ * - __u32
+ - ``flags``
+ - Flags to go with the command, see :ref:`encoder-flags`. If no
+ flags are defined for this command, drivers and applications must
+ set this field to zero.
+ * - __u32
+ - ``data``\ [8]
+ - Reserved for future extensions. Drivers and applications must set
+ the array to zero.
+
+
+.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}|
+
+.. _encoder-cmds:
+
+.. flat-table:: Encoder Commands
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 3 1 4
+
+ * - ``V4L2_ENC_CMD_START``
+ - 0
+ - Start the encoder. When the encoder is already running or paused,
+ this command does nothing. No flags are defined for this command.
+
+ For a device implementing the :ref:`encoder`, once the drain sequence
+ is initiated with the ``V4L2_ENC_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. See :ref:`encoder` for more details.
+ * - ``V4L2_ENC_CMD_STOP``
+ - 1
+ - Stop the encoder. When the ``V4L2_ENC_CMD_STOP_AT_GOP_END`` flag
+ is set, encoding will continue until the end of the current *Group
+ Of Pictures*, otherwise encoding will stop immediately. When the
+ encoder is already stopped, this command does nothing.
+
+ For a device implementing the :ref:`encoder`, the command will initiate
+ the drain sequence as documented in :ref:`encoder`. 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_ENC_CMD_PAUSE``
+ - 2
+ - Pause the encoder. When the encoder has not been started yet, the
+ driver will return an ``EPERM`` error code. When the encoder is
+ already paused, this command does nothing. No flags are defined
+ for this command.
+ * - ``V4L2_ENC_CMD_RESUME``
+ - 3
+ - Resume encoding after a PAUSE command. When the encoder has not
+ been started yet, the driver will return an ``EPERM`` error code. When
+ the encoder is already running, this command does nothing. No
+ flags are defined for this command.
+
+.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}|
+
+.. _encoder-flags:
+
+.. flat-table:: Encoder Command Flags
+ :header-rows: 0
+ :stub-columns: 0
+ :widths: 3 1 4
+
+ * - ``V4L2_ENC_CMD_STOP_AT_GOP_END``
+ - 0x0001
+ - Stop encoding at the end of the current *Group Of Pictures*,
+ rather than immediately.
+
+ Does not apply to :ref:`encoder`.
+
+Return Value
+============
+
+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:`encoder` is still in
+ progress. It is not allowed to issue another encoder command until it
+ completes.
+
+EINVAL
+ The ``cmd`` field is invalid.
+
+EPERM
+ The application sent a PAUSE or RESUME command when the encoder was
+ not running.