media/v4l/vidioc-g-parm.rst

1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
13 VIDIOC_G_PARM - VIDIOC_S_PARM - Get or set streaming parameters
44 frame interval that is typically embedded in the encoded video stream.
50 internally by a driver in read/write mode. For implications see the
63 .. flat-table:: struct v4l2_streamparm
64     :header-rows:  0
65     :stub-columns: 0
68     * - __u32
69       - ``type``
70       - The buffer (stream) type, same as struct
73     * - union {
74       - ``parm``
75     * - struct :c:type:`v4l2_captureparm`
76       - ``capture``
77       - Parameters for capture devices, used when ``type`` is
80     * - struct :c:type:`v4l2_outputparm`
81       - ``output``
82       - Parameters for output devices, used when ``type`` is
84     * - __u8
85       - ``raw_data``\ [200]
86       - A place holder for future extensions.
87     * - }
88       -
95 .. flat-table:: struct v4l2_captureparm
96     :header-rows:  0
97     :stub-columns: 0
100     * - __u32
101       - ``capability``
102       - See :ref:`parm-caps`.
103     * - __u32
104       - ``capturemode``
105       - Set by drivers and applications, see :ref:`parm-flags`.
106     * - struct :c:type:`v4l2_fract`
107       - ``timeperframe``
108       - This is the desired period between successive frames captured by
110     * - :cspan:`2`
112 	This will configure the speed at which the video source (e.g. a sensor)
113 	generates video frames. If the speed is fixed, then the driver may
118 	frame interval that is typically embedded in the encoded video stream.
123 	Changing the video standard (also implicitly by switching
124 	the video input) may reset this parameter to the nominal frame
130     * - __u32
131       - ``extendedmode``
132       - Custom (driver specific) streaming parameters. When unused,
136     * - __u32
137       - ``readbuffers``
138       - Applications set this field to the desired number of buffers used
139 	internally by the driver in :c:func:`read()` mode.
144     * - __u32
145       - ``reserved``\ [4]
146       - Reserved for future extensions. Drivers and applications must set
154 .. flat-table:: struct v4l2_outputparm
155     :header-rows:  0
156     :stub-columns: 0
159     * - __u32
160       - ``capability``
161       - See :ref:`parm-caps`.
162     * - __u32
163       - ``outputmode``
164       - Set by drivers and applications, see :ref:`parm-flags`.
165     * - struct :c:type:`v4l2_fract`
166       - ``timeperframe``
167       - This is the desired period between successive frames output by the
169     * - :cspan:`2`
172 	:c:func:`write()` mode (in streaming mode timestamps
176 	frame interval that is typically embedded in the encoded video stream
183 	Changing the video standard (also implicitly by switching
184 	the video output) may reset this parameter to the nominal frame
190     * - __u32
191       - ``extendedmode``
192       - Custom (driver specific) streaming parameters. When unused,
196     * - __u32
197       - ``writebuffers``
198       - Applications set this field to the desired number of buffers used
199 	internally by the driver in :c:func:`write()` mode. Drivers
204     * - __u32
205       - ``reserved``\ [4]
206       - Reserved for future extensions. Drivers and applications must set
212 .. _parm-caps:
214 .. flat-table:: Streaming Parameters Capabilities
215     :header-rows:  0
216     :stub-columns: 0
219     * - ``V4L2_CAP_TIMEPERFRAME``
220       - 0x1000
221       - The frame period can be modified by setting the ``timeperframe``
227 .. _parm-flags:
229 .. flat-table:: Capture Parameters Flags
230     :header-rows:  0
231     :stub-columns: 0
234     * - ``V4L2_MODE_HIGHQUALITY``
235       - 0x0001
236       - High quality imaging mode. High quality mode is intended for still
240 	the ingenuity of the driver writer. High quality mode is a
241 	different mode from the regular motion video capture modes. In
242 	high quality mode:
244 	-  The driver may be able to capture higher resolutions than for
247 	-  The driver may support fewer pixel formats than motion capture
250 	-  The driver may capture and arithmetically combine multiple
252 	   reduce the noise in the video data.
254 	-  The driver may capture images in slices like a scanner in order
258 	-  An image capture operation may be significantly slower than
261 	-  Moving objects in the image might have excessive motion blur.
263 	-  Capture might only work through the :c:func:`read()` call.
268 On success 0 is returned, on error -1 and the ``errno`` variable is set
270 :ref:`Generic Error Codes <gen-errors>` chapter.