1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2.. c:namespace:: V4L 3 4.. _VIDIOC_ENCODER_CMD: 5 6************************************************ 7ioctl VIDIOC_ENCODER_CMD, VIDIOC_TRY_ENCODER_CMD 8************************************************ 9 10Name 11==== 12 13VIDIOC_ENCODER_CMD - VIDIOC_TRY_ENCODER_CMD - Execute an encoder command 14 15Synopsis 16======== 17 18.. c:macro:: VIDIOC_ENCODER_CMD 19 20``int ioctl(int fd, VIDIOC_ENCODER_CMD, struct v4l2_encoder_cmd *argp)`` 21 22.. c:macro:: VIDIOC_TRY_ENCODER_CMD 23 24``int ioctl(int fd, VIDIOC_TRY_ENCODER_CMD, struct v4l2_encoder_cmd *argp)`` 25 26Arguments 27========= 28 29``fd`` 30 File descriptor returned by :c:func:`open()`. 31 32``argp`` 33 Pointer to struct :c:type:`v4l2_encoder_cmd`. 34 35Description 36=========== 37 38These ioctls control an audio/video (usually MPEG-) encoder. 39``VIDIOC_ENCODER_CMD`` sends a command to the encoder, 40``VIDIOC_TRY_ENCODER_CMD`` can be used to try a command without actually 41executing it. 42 43To send a command applications must initialize all fields of a struct 44:c:type:`v4l2_encoder_cmd` and call 45``VIDIOC_ENCODER_CMD`` or ``VIDIOC_TRY_ENCODER_CMD`` with a pointer to 46this structure. 47 48The ``cmd`` field must contain the command code. Some commands use the 49``flags`` field for additional information. 50 51After a STOP command, :c:func:`read()` calls will read 52the remaining data buffered by the driver. When the buffer is empty, 53:c:func:`read()` will return zero and the next :c:func:`read()` 54call will restart the encoder. 55 56A :c:func:`read()` or :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` 57call sends an implicit START command to the encoder if it has not been 58started yet. Applies to both queues of mem2mem encoders. 59 60A :c:func:`close()` or :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>` 61call of a streaming file descriptor sends an implicit immediate STOP to 62the encoder, and all buffered data is discarded. Applies to both queues of 63mem2mem encoders. 64 65These ioctls are optional, not all drivers may support them. They were 66introduced in Linux 2.6.21. They are, however, mandatory for stateful mem2mem 67encoders (as further documented in :ref:`encoder`). 68 69.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}| 70 71.. c:type:: v4l2_encoder_cmd 72 73.. flat-table:: struct v4l2_encoder_cmd 74 :header-rows: 0 75 :stub-columns: 0 76 :widths: 1 1 2 77 78 * - __u32 79 - ``cmd`` 80 - The encoder command, see :ref:`encoder-cmds`. 81 * - __u32 82 - ``flags`` 83 - Flags to go with the command, see :ref:`encoder-flags`. If no 84 flags are defined for this command, drivers and applications must 85 set this field to zero. 86 * - __u32 87 - ``data``\ [8] 88 - Reserved for future extensions. Drivers and applications must set 89 the array to zero. 90 91 92.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}| 93 94.. _encoder-cmds: 95 96.. flat-table:: Encoder Commands 97 :header-rows: 0 98 :stub-columns: 0 99 :widths: 3 1 4 100 101 * - ``V4L2_ENC_CMD_START`` 102 - 0 103 - Start the encoder. When the encoder is already running or paused, 104 this command does nothing. No flags are defined for this command. 105 106 For a device implementing the :ref:`encoder`, once the drain sequence 107 is initiated with the ``V4L2_ENC_CMD_STOP`` command, it must be driven 108 to completion before this command can be invoked. Any attempt to 109 invoke the command while the drain sequence is in progress will trigger 110 an ``EBUSY`` error code. See :ref:`encoder` for more details. 111 * - ``V4L2_ENC_CMD_STOP`` 112 - 1 113 - Stop the encoder. When the ``V4L2_ENC_CMD_STOP_AT_GOP_END`` flag 114 is set, encoding will continue until the end of the current *Group 115 Of Pictures*, otherwise encoding will stop immediately. When the 116 encoder is already stopped, this command does nothing. 117 118 For a device implementing the :ref:`encoder`, the command will initiate 119 the drain sequence as documented in :ref:`encoder`. No flags or other 120 arguments are accepted in this case. Any attempt to invoke the command 121 again before the sequence completes will trigger an ``EBUSY`` error 122 code. 123 * - ``V4L2_ENC_CMD_PAUSE`` 124 - 2 125 - Pause the encoder. When the encoder has not been started yet, the 126 driver will return an ``EPERM`` error code. When the encoder is 127 already paused, this command does nothing. No flags are defined 128 for this command. 129 * - ``V4L2_ENC_CMD_RESUME`` 130 - 3 131 - Resume encoding after a PAUSE command. When the encoder has not 132 been started yet, the driver will return an ``EPERM`` error code. When 133 the encoder is already running, this command does nothing. No 134 flags are defined for this command. 135 136.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}| 137 138.. _encoder-flags: 139 140.. flat-table:: Encoder Command Flags 141 :header-rows: 0 142 :stub-columns: 0 143 :widths: 3 1 4 144 145 * - ``V4L2_ENC_CMD_STOP_AT_GOP_END`` 146 - 0x0001 147 - Stop encoding at the end of the current *Group Of Pictures*, 148 rather than immediately. 149 150 Does not apply to :ref:`encoder`. 151 152Return Value 153============ 154 155On success 0 is returned, on error -1 and the ``errno`` variable is set 156appropriately. The generic error codes are described at the 157:ref:`Generic Error Codes <gen-errors>` chapter. 158 159EBUSY 160 A drain sequence of a device implementing the :ref:`encoder` is still in 161 progress. It is not allowed to issue another encoder command until it 162 completes. 163 164EINVAL 165 The ``cmd`` field is invalid. 166 167EPERM 168 The application sent a PAUSE or RESUME command when the encoder was 169 not running. 170