1 .. SPDX-License-Identifier: GFDL-1.1-no-invari 1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 .. c:namespace:: V4L 2 .. c:namespace:: V4L
3 3
4 .. _VIDIOC_DECODER_CMD: 4 .. _VIDIOC_DECODER_CMD:
5 5
6 ********************************************** 6 ************************************************
7 ioctl VIDIOC_DECODER_CMD, VIDIOC_TRY_DECODER_C 7 ioctl VIDIOC_DECODER_CMD, VIDIOC_TRY_DECODER_CMD
8 ********************************************** 8 ************************************************
9 9
10 Name 10 Name
11 ==== 11 ====
12 12
13 VIDIOC_DECODER_CMD - VIDIOC_TRY_DECODER_CMD - 13 VIDIOC_DECODER_CMD - VIDIOC_TRY_DECODER_CMD - Execute an decoder command
14 14
15 Synopsis 15 Synopsis
16 ======== 16 ========
17 17
18 .. c:macro:: VIDIOC_DECODER_CMD 18 .. c:macro:: VIDIOC_DECODER_CMD
19 19
20 ``int ioctl(int fd, VIDIOC_DECODER_CMD, struct 20 ``int ioctl(int fd, VIDIOC_DECODER_CMD, struct v4l2_decoder_cmd *argp)``
21 21
22 .. c:macro:: VIDIOC_TRY_DECODER_CMD 22 .. c:macro:: VIDIOC_TRY_DECODER_CMD
23 23
24 ``int ioctl(int fd, VIDIOC_TRY_DECODER_CMD, st 24 ``int ioctl(int fd, VIDIOC_TRY_DECODER_CMD, struct v4l2_decoder_cmd *argp)``
25 25
26 Arguments 26 Arguments
27 ========= 27 =========
28 28
29 ``fd`` 29 ``fd``
30 File descriptor returned by :c:func:`open( 30 File descriptor returned by :c:func:`open()`.
31 31
32 ``argp`` 32 ``argp``
33 pointer to struct :c:type:`v4l2_decoder_cm 33 pointer to struct :c:type:`v4l2_decoder_cmd`.
34 34
35 Description 35 Description
36 =========== 36 ===========
37 37
38 These ioctls control an audio/video (usually M 38 These ioctls control an audio/video (usually MPEG-) decoder.
39 ``VIDIOC_DECODER_CMD`` sends a command to the 39 ``VIDIOC_DECODER_CMD`` sends a command to the decoder,
40 ``VIDIOC_TRY_DECODER_CMD`` can be used to try 40 ``VIDIOC_TRY_DECODER_CMD`` can be used to try a command without actually
41 executing it. To send a command applications m 41 executing it. To send a command applications must initialize all fields
42 of a struct :c:type:`v4l2_decoder_cmd` and cal 42 of a struct :c:type:`v4l2_decoder_cmd` and call
43 ``VIDIOC_DECODER_CMD`` or ``VIDIOC_TRY_DECODER 43 ``VIDIOC_DECODER_CMD`` or ``VIDIOC_TRY_DECODER_CMD`` with a pointer to
44 this structure. 44 this structure.
45 45
46 The ``cmd`` field must contain the command cod 46 The ``cmd`` field must contain the command code. Some commands use the
47 ``flags`` field for additional information. 47 ``flags`` field for additional information.
48 48
49 A :c:func:`write()` or :ref:`VIDIOC_STREAMON` 49 A :c:func:`write()` or :ref:`VIDIOC_STREAMON`
50 call sends an implicit START command to the de 50 call sends an implicit START command to the decoder if it has not been
51 started yet. Applies to both queues of mem2mem 51 started yet. Applies to both queues of mem2mem decoders.
52 52
53 A :c:func:`close()` or :ref:`VIDIOC_STREAMOFF 53 A :c:func:`close()` or :ref:`VIDIOC_STREAMOFF <VIDIOC_STREAMON>`
54 call of a streaming file descriptor sends an i 54 call of a streaming file descriptor sends an implicit immediate STOP
55 command to the decoder, and all buffered data 55 command to the decoder, and all buffered data is discarded. Applies to both
56 queues of mem2mem decoders. 56 queues of mem2mem decoders.
57 57
58 In principle, these ioctls are optional, not a 58 In principle, these ioctls are optional, not all drivers may support them. They were
59 introduced in Linux 3.3. They are, however, ma 59 introduced in Linux 3.3. They are, however, mandatory for stateful mem2mem decoders
60 (as further documented in :ref:`decoder`). 60 (as further documented in :ref:`decoder`).
61 61
62 .. tabularcolumns:: |p{2.0cm}|p{1.1cm}|p{2.2cm 62 .. tabularcolumns:: |p{2.0cm}|p{1.1cm}|p{2.2cm}|p{11.8cm}|
63 63
64 .. c:type:: v4l2_decoder_cmd 64 .. c:type:: v4l2_decoder_cmd
65 65
66 .. cssclass:: longtable 66 .. cssclass:: longtable
67 67
68 .. flat-table:: struct v4l2_decoder_cmd 68 .. flat-table:: struct v4l2_decoder_cmd
69 :header-rows: 0 69 :header-rows: 0
70 :stub-columns: 0 70 :stub-columns: 0
71 :widths: 1 1 1 3 71 :widths: 1 1 1 3
72 72
73 * - __u32 73 * - __u32
74 - ``cmd`` 74 - ``cmd``
75 - 75 -
76 - The decoder command, see :ref:`decoder 76 - The decoder command, see :ref:`decoder-cmds`.
77 * - __u32 77 * - __u32
78 - ``flags`` 78 - ``flags``
79 - 79 -
80 - Flags to go with the command. If no fl 80 - Flags to go with the command. If no flags are defined for this
81 command, drivers and applications must 81 command, drivers and applications must set this field to zero.
82 * - union { 82 * - union {
83 - (anonymous) 83 - (anonymous)
84 * - struct 84 * - struct
85 - ``start`` 85 - ``start``
86 - 86 -
87 - Structure containing additional data f 87 - Structure containing additional data for the
88 ``V4L2_DEC_CMD_START`` command. 88 ``V4L2_DEC_CMD_START`` command.
89 * - 89 * -
90 - __s32 90 - __s32
91 - ``speed`` 91 - ``speed``
92 - Playback speed and direction. The play 92 - Playback speed and direction. The playback speed is defined as
93 ``speed``/1000 of the normal speed. So 93 ``speed``/1000 of the normal speed. So 1000 is normal playback.
94 Negative numbers denote reverse playba 94 Negative numbers denote reverse playback, so -1000 does reverse
95 playback at normal speed. Speeds -1, 0 95 playback at normal speed. Speeds -1, 0 and 1 have special
96 meanings: speed 0 is shorthand for 100 96 meanings: speed 0 is shorthand for 1000 (normal playback). A speed
97 of 1 steps just one frame forward, a s 97 of 1 steps just one frame forward, a speed of -1 steps just one
98 frame back. 98 frame back.
99 * - 99 * -
100 - __u32 100 - __u32
101 - ``format`` 101 - ``format``
102 - Format restrictions. This field is set 102 - Format restrictions. This field is set by the driver, not the
103 application. Possible values are ``V4L 103 application. Possible values are ``V4L2_DEC_START_FMT_NONE`` if
104 there are no format restrictions or `` 104 there are no format restrictions or ``V4L2_DEC_START_FMT_GOP`` if
105 the decoder operates on full GOPs (*Gr 105 the decoder operates on full GOPs (*Group Of Pictures*). This is
106 usually the case for reverse playback: 106 usually the case for reverse playback: the decoder needs full
107 GOPs, which it can then play in revers 107 GOPs, which it can then play in reverse order. So to implement
108 reverse playback the application must 108 reverse playback the application must feed the decoder the last
109 GOP in the video file, then the GOP be 109 GOP in the video file, then the GOP before that, etc. etc.
110 * - struct 110 * - struct
111 - ``stop`` 111 - ``stop``
112 - 112 -
113 - Structure containing additional data f 113 - Structure containing additional data for the ``V4L2_DEC_CMD_STOP``
114 command. 114 command.
115 * - 115 * -
116 - __u64 116 - __u64
117 - ``pts`` 117 - ``pts``
118 - Stop playback at this ``pts`` or immed 118 - Stop playback at this ``pts`` or immediately if the playback is
119 already past that timestamp. Leave to 119 already past that timestamp. Leave to 0 if you want to stop after
120 the last frame was decoded. 120 the last frame was decoded.
121 * - struct 121 * - struct
122 - ``raw`` 122 - ``raw``
123 * - 123 * -
124 - __u32 124 - __u32
125 - ``data``\ [16] 125 - ``data``\ [16]
126 - Reserved for future extensions. Driver 126 - Reserved for future extensions. Drivers and applications must set
127 the array to zero. 127 the array to zero.
128 * - } 128 * - }
129 - 129 -
130 130
131 131
132 .. tabularcolumns:: |p{5.6cm}|p{0.6cm}|p{11.1c 132 .. tabularcolumns:: |p{5.6cm}|p{0.6cm}|p{11.1cm}|
133 133
134 .. cssclass:: longtable 134 .. cssclass:: longtable
135 135
136 .. _decoder-cmds: 136 .. _decoder-cmds:
137 137
138 .. flat-table:: Decoder Commands 138 .. flat-table:: Decoder Commands
139 :header-rows: 0 139 :header-rows: 0
140 :stub-columns: 0 140 :stub-columns: 0
141 :widths: 56 6 113 141 :widths: 56 6 113
142 142
143 * - ``V4L2_DEC_CMD_START`` 143 * - ``V4L2_DEC_CMD_START``
144 - 0 144 - 0
145 - Start the decoder. When the decoder is 145 - Start the decoder. When the decoder is already running or paused,
146 this command will just change the play 146 this command will just change the playback speed. That means that
147 calling ``V4L2_DEC_CMD_START`` when th 147 calling ``V4L2_DEC_CMD_START`` when the decoder was paused will
148 *not* resume the decoder. You have to 148 *not* resume the decoder. You have to explicitly call
149 ``V4L2_DEC_CMD_RESUME`` for that. This 149 ``V4L2_DEC_CMD_RESUME`` for that. This command has one flag:
150 ``V4L2_DEC_CMD_START_MUTE_AUDIO``. If 150 ``V4L2_DEC_CMD_START_MUTE_AUDIO``. If set, then audio will be
151 muted when playing back at a non-stand 151 muted when playing back at a non-standard speed.
152 152
153 For a device implementing the :ref:`de 153 For a device implementing the :ref:`decoder`, once the drain sequence
154 is initiated with the ``V4L2_DEC_CMD_S 154 is initiated with the ``V4L2_DEC_CMD_STOP`` command, it must be driven
155 to completion before this command can 155 to completion before this command can be invoked. Any attempt to
156 invoke the command while the drain seq 156 invoke the command while the drain sequence is in progress will trigger
157 an ``EBUSY`` error code. The command 157 an ``EBUSY`` error code. The command may be also used to restart the
158 decoder in case of an implicit stop in 158 decoder in case of an implicit stop initiated by the decoder itself,
159 without the ``V4L2_DEC_CMD_STOP`` bein 159 without the ``V4L2_DEC_CMD_STOP`` being called explicitly. See
160 :ref:`decoder` for more details. 160 :ref:`decoder` for more details.
161 * - ``V4L2_DEC_CMD_STOP`` 161 * - ``V4L2_DEC_CMD_STOP``
162 - 1 162 - 1
163 - Stop the decoder. When the decoder is 163 - Stop the decoder. When the decoder is already stopped, this
164 command does nothing. This command has 164 command does nothing. This command has two flags: if
165 ``V4L2_DEC_CMD_STOP_TO_BLACK`` is set, 165 ``V4L2_DEC_CMD_STOP_TO_BLACK`` is set, then the decoder will set
166 the picture to black after it stopped 166 the picture to black after it stopped decoding. Otherwise the last
167 image will repeat. If 167 image will repeat. If
168 ``V4L2_DEC_CMD_STOP_IMMEDIATELY`` is s 168 ``V4L2_DEC_CMD_STOP_IMMEDIATELY`` is set, then the decoder stops
169 immediately (ignoring the ``pts`` valu 169 immediately (ignoring the ``pts`` value), otherwise it will keep
170 decoding until timestamp >= pts or unt 170 decoding until timestamp >= pts or until the last of the pending
171 data from its internal buffers was dec 171 data from its internal buffers was decoded.
172 172
173 For a device implementing the :ref:`de 173 For a device implementing the :ref:`decoder`, the command will initiate
174 the drain sequence as documented in :r 174 the drain sequence as documented in :ref:`decoder`. No flags or other
175 arguments are accepted in this case. A 175 arguments are accepted in this case. Any attempt to invoke the command
176 again before the sequence completes wi 176 again before the sequence completes will trigger an ``EBUSY`` error
177 code. 177 code.
178 * - ``V4L2_DEC_CMD_PAUSE`` 178 * - ``V4L2_DEC_CMD_PAUSE``
179 - 2 179 - 2
180 - Pause the decoder. When the decoder ha 180 - Pause the decoder. When the decoder has not been started yet, the
181 driver will return an ``EPERM`` error 181 driver will return an ``EPERM`` error code. When the decoder is
182 already paused, this command does noth 182 already paused, this command does nothing. This command has one
183 flag: if ``V4L2_DEC_CMD_PAUSE_TO_BLACK 183 flag: if ``V4L2_DEC_CMD_PAUSE_TO_BLACK`` is set, then set the
184 decoder output to black when paused. 184 decoder output to black when paused.
185 * - ``V4L2_DEC_CMD_RESUME`` 185 * - ``V4L2_DEC_CMD_RESUME``
186 - 3 186 - 3
187 - Resume decoding after a PAUSE command. 187 - Resume decoding after a PAUSE command. When the decoder has not
188 been started yet, the driver will retu 188 been started yet, the driver will return an ``EPERM`` error code. When
189 the decoder is already running, this c 189 the decoder is already running, this command does nothing. No
190 flags are defined for this command. 190 flags are defined for this command.
191 * - ``V4L2_DEC_CMD_FLUSH`` 191 * - ``V4L2_DEC_CMD_FLUSH``
192 - 4 192 - 4
193 - Flush any held capture buffers. Only v 193 - Flush any held capture buffers. Only valid for stateless decoders.
194 This command is typically used when th 194 This command is typically used when the application reached the
195 end of the stream and the last output 195 end of the stream and the last output buffer had the
196 ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` 196 ``V4L2_BUF_FLAG_M2M_HOLD_CAPTURE_BUF`` flag set. This would prevent
197 dequeueing the capture buffer containi 197 dequeueing the capture buffer containing the last decoded frame.
198 So this command can be used to explici 198 So this command can be used to explicitly flush that final decoded
199 frame. This command does nothing if th 199 frame. This command does nothing if there are no held capture buffers.
200 200
201 Return Value 201 Return Value
202 ============ 202 ============
203 203
204 On success 0 is returned, on error -1 and the 204 On success 0 is returned, on error -1 and the ``errno`` variable is set
205 appropriately. The generic error codes are des 205 appropriately. The generic error codes are described at the
206 :ref:`Generic Error Codes <gen-errors>` chapte 206 :ref:`Generic Error Codes <gen-errors>` chapter.
207 207
208 EBUSY 208 EBUSY
209 A drain sequence of a device implementing 209 A drain sequence of a device implementing the :ref:`decoder` is still in
210 progress. It is not allowed to issue anoth 210 progress. It is not allowed to issue another decoder command until it
211 completes. 211 completes.
212 212
213 EINVAL 213 EINVAL
214 The ``cmd`` field is invalid. 214 The ``cmd`` field is invalid.
215 215
216 EPERM 216 EPERM
217 The application sent a PAUSE or RESUME com 217 The application sent a PAUSE or RESUME command when the decoder was
218 not running. 218 not running.
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