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_G_PARM: 4 .. _VIDIOC_G_PARM:
5 5
6 ********************************** 6 **********************************
7 ioctl VIDIOC_G_PARM, VIDIOC_S_PARM 7 ioctl VIDIOC_G_PARM, VIDIOC_S_PARM
8 ********************************** 8 **********************************
9 9
10 Name 10 Name
11 ==== 11 ====
12 12
13 VIDIOC_G_PARM - VIDIOC_S_PARM - Get or set str 13 VIDIOC_G_PARM - VIDIOC_S_PARM - Get or set streaming parameters
14 14
15 Synopsis 15 Synopsis
16 ======== 16 ========
17 17
18 .. c:macro:: VIDIOC_G_PARM 18 .. c:macro:: VIDIOC_G_PARM
19 19
20 ``int ioctl(int fd, VIDIOC_G_PARM, v4l2_stream 20 ``int ioctl(int fd, VIDIOC_G_PARM, v4l2_streamparm *argp)``
21 21
22 .. c:macro:: VIDIOC_S_PARM 22 .. c:macro:: VIDIOC_S_PARM
23 23
24 ``int ioctl(int fd, VIDIOC_S_PARM, v4l2_stream 24 ``int ioctl(int fd, VIDIOC_S_PARM, v4l2_streamparm *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_streamparm 33 Pointer to struct :c:type:`v4l2_streamparm`.
34 34
35 Description 35 Description
36 =========== 36 ===========
37 37
38 Applications can request a different frame int 38 Applications can request a different frame interval. The capture or
39 output device will be reconfigured to support 39 output device will be reconfigured to support the requested frame
40 interval if possible. Optionally drivers may c 40 interval if possible. Optionally drivers may choose to skip or
41 repeat frames to achieve the requested frame i 41 repeat frames to achieve the requested frame interval.
42 42
43 For stateful encoders (see :ref:`encoder`) thi 43 For stateful encoders (see :ref:`encoder`) this represents the
44 frame interval that is typically embedded in t 44 frame interval that is typically embedded in the encoded video stream.
45 45
46 Changing the frame interval shall never change 46 Changing the frame interval shall never change the format. Changing the
47 format, on the other hand, may change the fram 47 format, on the other hand, may change the frame interval.
48 48
49 Further these ioctls can be used to determine 49 Further these ioctls can be used to determine the number of buffers used
50 internally by a driver in read/write mode. For 50 internally by a driver in read/write mode. For implications see the
51 section discussing the :c:func:`read()` functi 51 section discussing the :c:func:`read()` function.
52 52
53 To get and set the streaming parameters applic 53 To get and set the streaming parameters applications call the
54 :ref:`VIDIOC_G_PARM <VIDIOC_G_PARM>` and 54 :ref:`VIDIOC_G_PARM <VIDIOC_G_PARM>` and
55 :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` ioctl, re 55 :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` ioctl, respectively. They take a
56 pointer to a struct :c:type:`v4l2_streamparm` 56 pointer to a struct :c:type:`v4l2_streamparm` which contains a
57 union holding separate parameters for input an 57 union holding separate parameters for input and output devices.
58 58
59 .. tabularcolumns:: |p{3.7cm}|p{3.5cm}|p{10.1c !! 59 .. tabularcolumns:: |p{3.5cm}|p{3.5cm}|p{3.5cm}|p{7.0cm}|
60 60
61 .. c:type:: v4l2_streamparm 61 .. c:type:: v4l2_streamparm
62 62
63 .. flat-table:: struct v4l2_streamparm 63 .. flat-table:: struct v4l2_streamparm
64 :header-rows: 0 64 :header-rows: 0
65 :stub-columns: 0 65 :stub-columns: 0
66 :widths: 1 1 2 66 :widths: 1 1 2
67 67
68 * - __u32 68 * - __u32
69 - ``type`` 69 - ``type``
70 - The buffer (stream) type, same as stru 70 - The buffer (stream) type, same as struct
71 :c:type:`v4l2_format` ``type``, set by 71 :c:type:`v4l2_format` ``type``, set by the
72 application. See :c:type:`v4l2_buf_typ 72 application. See :c:type:`v4l2_buf_type`.
73 * - union { 73 * - union {
74 - ``parm`` 74 - ``parm``
75 * - struct :c:type:`v4l2_captureparm` 75 * - struct :c:type:`v4l2_captureparm`
76 - ``capture`` 76 - ``capture``
77 - Parameters for capture devices, used w 77 - Parameters for capture devices, used when ``type`` is
78 ``V4L2_BUF_TYPE_VIDEO_CAPTURE`` or 78 ``V4L2_BUF_TYPE_VIDEO_CAPTURE`` or
79 ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE`` 79 ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``.
80 * - struct :c:type:`v4l2_outputparm` 80 * - struct :c:type:`v4l2_outputparm`
81 - ``output`` 81 - ``output``
82 - Parameters for output devices, used wh 82 - Parameters for output devices, used when ``type`` is
83 ``V4L2_BUF_TYPE_VIDEO_OUTPUT`` or ``V4 83 ``V4L2_BUF_TYPE_VIDEO_OUTPUT`` or ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``.
84 * - __u8 84 * - __u8
85 - ``raw_data``\ [200] 85 - ``raw_data``\ [200]
86 - A place holder for future extensions. 86 - A place holder for future extensions.
87 * - } 87 * - }
>> 88 -
88 89
89 90
90 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm !! 91 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
91 92
92 .. c:type:: v4l2_captureparm 93 .. c:type:: v4l2_captureparm
93 94
94 .. flat-table:: struct v4l2_captureparm 95 .. flat-table:: struct v4l2_captureparm
95 :header-rows: 0 96 :header-rows: 0
96 :stub-columns: 0 97 :stub-columns: 0
97 :widths: 1 1 2 98 :widths: 1 1 2
98 99
99 * - __u32 100 * - __u32
100 - ``capability`` 101 - ``capability``
101 - See :ref:`parm-caps`. 102 - See :ref:`parm-caps`.
102 * - __u32 103 * - __u32
103 - ``capturemode`` 104 - ``capturemode``
104 - Set by drivers and applications, see : 105 - Set by drivers and applications, see :ref:`parm-flags`.
105 * - struct :c:type:`v4l2_fract` 106 * - struct :c:type:`v4l2_fract`
106 - ``timeperframe`` 107 - ``timeperframe``
107 - This is the desired period between suc 108 - This is the desired period between successive frames captured by
108 the driver, in seconds. 109 the driver, in seconds.
109 * - :cspan:`2` 110 * - :cspan:`2`
110 111
111 This will configure the speed at which 112 This will configure the speed at which the video source (e.g. a sensor)
112 generates video frames. If the speed i 113 generates video frames. If the speed is fixed, then the driver may
113 choose to skip or repeat frames in ord 114 choose to skip or repeat frames in order to achieve the requested
114 frame rate. 115 frame rate.
115 116
116 For stateful encoders (see :ref:`encod 117 For stateful encoders (see :ref:`encoder`) this represents the
117 frame interval that is typically embed 118 frame interval that is typically embedded in the encoded video stream.
118 119
119 Applications store here the desired fr 120 Applications store here the desired frame period, drivers return
120 the actual frame period. 121 the actual frame period.
121 122
122 Changing the video standard (also impl 123 Changing the video standard (also implicitly by switching
123 the video input) may reset this parame 124 the video input) may reset this parameter to the nominal frame
124 period. To reset manually applications 125 period. To reset manually applications can just set this field to
125 zero. 126 zero.
126 127
127 Drivers support this function only whe 128 Drivers support this function only when they set the
128 ``V4L2_CAP_TIMEPERFRAME`` flag in the 129 ``V4L2_CAP_TIMEPERFRAME`` flag in the ``capability`` field.
129 * - __u32 130 * - __u32
130 - ``extendedmode`` 131 - ``extendedmode``
131 - Custom (driver specific) streaming par 132 - Custom (driver specific) streaming parameters. When unused,
132 applications and drivers must set this 133 applications and drivers must set this field to zero. Applications
133 using this field should check the driv 134 using this field should check the driver name and version, see
134 :ref:`querycap`. 135 :ref:`querycap`.
135 * - __u32 136 * - __u32
136 - ``readbuffers`` 137 - ``readbuffers``
137 - Applications set this field to the des 138 - Applications set this field to the desired number of buffers used
138 internally by the driver in :c:func:`r 139 internally by the driver in :c:func:`read()` mode.
139 Drivers return the actual number of bu 140 Drivers return the actual number of buffers. When an application
140 requests zero buffers, drivers should 141 requests zero buffers, drivers should just return the current
141 setting rather than the minimum or an 142 setting rather than the minimum or an error code. For details see
142 :ref:`rw`. 143 :ref:`rw`.
143 * - __u32 144 * - __u32
144 - ``reserved``\ [4] 145 - ``reserved``\ [4]
145 - Reserved for future extensions. Driver 146 - Reserved for future extensions. Drivers and applications must set
146 the array to zero. 147 the array to zero.
147 148
148 149
149 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm !! 150 .. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}|
150 151
151 .. c:type:: v4l2_outputparm 152 .. c:type:: v4l2_outputparm
152 153
153 .. flat-table:: struct v4l2_outputparm 154 .. flat-table:: struct v4l2_outputparm
154 :header-rows: 0 155 :header-rows: 0
155 :stub-columns: 0 156 :stub-columns: 0
156 :widths: 1 1 2 157 :widths: 1 1 2
157 158
158 * - __u32 159 * - __u32
159 - ``capability`` 160 - ``capability``
160 - See :ref:`parm-caps`. 161 - See :ref:`parm-caps`.
161 * - __u32 162 * - __u32
162 - ``outputmode`` 163 - ``outputmode``
163 - Set by drivers and applications, see : 164 - Set by drivers and applications, see :ref:`parm-flags`.
164 * - struct :c:type:`v4l2_fract` 165 * - struct :c:type:`v4l2_fract`
165 - ``timeperframe`` 166 - ``timeperframe``
166 - This is the desired period between suc 167 - This is the desired period between successive frames output by the
167 driver, in seconds. 168 driver, in seconds.
168 * - :cspan:`2` 169 * - :cspan:`2`
169 170
170 The field is intended to repeat frames 171 The field is intended to repeat frames on the driver side in
171 :c:func:`write()` mode (in streaming m 172 :c:func:`write()` mode (in streaming mode timestamps
172 can be used to throttle the output), s 173 can be used to throttle the output), saving I/O bandwidth.
173 174
174 For stateful encoders (see :ref:`encod 175 For stateful encoders (see :ref:`encoder`) this represents the
175 frame interval that is typically embed 176 frame interval that is typically embedded in the encoded video stream
176 and it provides a hint to the encoder 177 and it provides a hint to the encoder of the speed at which raw
177 frames are queued up to the encoder. 178 frames are queued up to the encoder.
178 179
179 Applications store here the desired fr 180 Applications store here the desired frame period, drivers return
180 the actual frame period. 181 the actual frame period.
181 182
182 Changing the video standard (also impl 183 Changing the video standard (also implicitly by switching
183 the video output) may reset this param 184 the video output) may reset this parameter to the nominal frame
184 period. To reset manually applications 185 period. To reset manually applications can just set this field to
185 zero. 186 zero.
186 187
187 Drivers support this function only whe 188 Drivers support this function only when they set the
188 ``V4L2_CAP_TIMEPERFRAME`` flag in the 189 ``V4L2_CAP_TIMEPERFRAME`` flag in the ``capability`` field.
189 * - __u32 190 * - __u32
190 - ``extendedmode`` 191 - ``extendedmode``
191 - Custom (driver specific) streaming par 192 - Custom (driver specific) streaming parameters. When unused,
192 applications and drivers must set this 193 applications and drivers must set this field to zero. Applications
193 using this field should check the driv 194 using this field should check the driver name and version, see
194 :ref:`querycap`. 195 :ref:`querycap`.
195 * - __u32 196 * - __u32
196 - ``writebuffers`` 197 - ``writebuffers``
197 - Applications set this field to the des 198 - Applications set this field to the desired number of buffers used
198 internally by the driver in :c:func:`w 199 internally by the driver in :c:func:`write()` mode. Drivers
199 return the actual number of buffers. W 200 return the actual number of buffers. When an application requests
200 zero buffers, drivers should just retu 201 zero buffers, drivers should just return the current setting
201 rather than the minimum or an error co 202 rather than the minimum or an error code. For details see
202 :ref:`rw`. 203 :ref:`rw`.
203 * - __u32 204 * - __u32
204 - ``reserved``\ [4] 205 - ``reserved``\ [4]
205 - Reserved for future extensions. Driver 206 - Reserved for future extensions. Drivers and applications must set
206 the array to zero. 207 the array to zero.
207 208
208 209
209 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm !! 210 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
210 211
211 .. _parm-caps: 212 .. _parm-caps:
212 213
213 .. flat-table:: Streaming Parameters Capabilit 214 .. flat-table:: Streaming Parameters Capabilities
214 :header-rows: 0 215 :header-rows: 0
215 :stub-columns: 0 216 :stub-columns: 0
216 :widths: 3 1 4 217 :widths: 3 1 4
217 218
218 * - ``V4L2_CAP_TIMEPERFRAME`` 219 * - ``V4L2_CAP_TIMEPERFRAME``
219 - 0x1000 220 - 0x1000
220 - The frame period can be modified by se 221 - The frame period can be modified by setting the ``timeperframe``
221 field. 222 field.
222 223
223 224
224 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm !! 225 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}|
225 226
226 .. _parm-flags: 227 .. _parm-flags:
227 228
228 .. flat-table:: Capture Parameters Flags 229 .. flat-table:: Capture Parameters Flags
229 :header-rows: 0 230 :header-rows: 0
230 :stub-columns: 0 231 :stub-columns: 0
231 :widths: 3 1 4 232 :widths: 3 1 4
232 233
233 * - ``V4L2_MODE_HIGHQUALITY`` 234 * - ``V4L2_MODE_HIGHQUALITY``
234 - 0x0001 235 - 0x0001
235 - High quality imaging mode. High qualit 236 - High quality imaging mode. High quality mode is intended for still
236 imaging applications. The idea is to g 237 imaging applications. The idea is to get the best possible image
237 quality that the hardware can deliver. 238 quality that the hardware can deliver. It is not defined how the
238 driver writer may achieve that; it wil 239 driver writer may achieve that; it will depend on the hardware and
239 the ingenuity of the driver writer. Hi 240 the ingenuity of the driver writer. High quality mode is a
240 different mode from the regular motion 241 different mode from the regular motion video capture modes. In
241 high quality mode: 242 high quality mode:
242 243
243 - The driver may be able to capture h 244 - The driver may be able to capture higher resolutions than for
244 motion capture. 245 motion capture.
245 246
246 - The driver may support fewer pixel 247 - The driver may support fewer pixel formats than motion capture
247 (eg; true color). 248 (eg; true color).
248 249
249 - The driver may capture and arithmet 250 - The driver may capture and arithmetically combine multiple
250 successive fields or frames to remo 251 successive fields or frames to remove color edge artifacts and
251 reduce the noise in the video data. 252 reduce the noise in the video data.
252 253
253 - The driver may capture images in sl 254 - The driver may capture images in slices like a scanner in order
254 to handle larger format images than 255 to handle larger format images than would otherwise be
255 possible. 256 possible.
256 257
257 - An image capture operation may be s 258 - An image capture operation may be significantly slower than
258 motion capture. 259 motion capture.
259 260
260 - Moving objects in the image might h 261 - Moving objects in the image might have excessive motion blur.
261 262
262 - Capture might only work through the 263 - Capture might only work through the :c:func:`read()` call.
263 264
264 Return Value 265 Return Value
265 ============ 266 ============
266 267
267 On success 0 is returned, on error -1 and the 268 On success 0 is returned, on error -1 and the ``errno`` variable is set
268 appropriately. The generic error codes are des 269 appropriately. The generic error codes are described at the
269 :ref:`Generic Error Codes <gen-errors>` chapte 270 :ref:`Generic Error Codes <gen-errors>` chapter.
Linux® is a registered trademark of Linus Torvalds in the United States and other countries.
TOMOYO® is a registered trademark of NTT DATA CORPORATION.