Based on kernel version 5.7.10
. Page generated on 2020-07-23 22:17 EST
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 | .. Permission is granted to copy, distribute and/or modify this .. document under the terms of the GNU Free Documentation License, .. Version 1.1 or any later version published by the Free Software .. Foundation, with no Invariant Sections, no Front-Cover Texts .. and no Back-Cover Texts. A copy of the license is included at .. Documentation/media/uapi/fdl-appendix.rst. .. .. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections .. _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:function:: int ioctl( int fd, VIDIOC_ENCODER_CMD, struct v4l2_encoder_cmd *argp ) :name: VIDIOC_ENCODER_CMD .. c:function:: int ioctl( int fd, VIDIOC_TRY_ENCODER_CMD, struct v4l2_encoder_cmd *argp ) :name: VIDIOC_TRY_ENCODER_CMD Arguments ========= ``fd`` File descriptor returned by :ref:`open() <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. The ``flags`` field is currently only used by the STOP command and contains one bit: If the ``V4L2_ENC_CMD_STOP_AT_GOP_END`` flag is set, encoding will continue until the end of the current *Group Of Pictures*, otherwise it will stop immediately. A :ref:`read() <func-read>` or :ref:`VIDIOC_STREAMON <VIDIOC_STREAMON>` call sends an implicit START command to the encoder if it has not been started yet. After a STOP command, :ref:`read() <func-read>` calls will read the remaining data buffered by the driver. When the buffer is empty, :ref:`read() <func-read>` will return zero and the next :ref:`read() <func-read>` call will restart the encoder. A :ref:`close() <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. These ioctls are optional, not all drivers may support them. They were introduced in Linux 2.6.21. .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| .. 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{8.7cm}| .. _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. * - ``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. mem2mem encoders will send a ``V4L2_EVENT_EOS`` event when the last frame has been encoded 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. * - ``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{8.7cm}| .. _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. 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. EINVAL The ``cmd`` field is invalid. EPERM The application sent a PAUSE or RESUME command when the encoder was not running. |