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_ENUM_FRAMEINTERVALS: 4 .. _VIDIOC_ENUM_FRAMEINTERVALS:
5 5
6 ******************************** 6 ********************************
7 ioctl VIDIOC_ENUM_FRAMEINTERVALS 7 ioctl VIDIOC_ENUM_FRAMEINTERVALS
8 ******************************** 8 ********************************
9 9
10 Name 10 Name
11 ==== 11 ====
12 12
13 VIDIOC_ENUM_FRAMEINTERVALS - Enumerate frame i 13 VIDIOC_ENUM_FRAMEINTERVALS - Enumerate frame intervals
14 14
15 Synopsis 15 Synopsis
16 ======== 16 ========
17 17
18 .. c:macro:: VIDIOC_ENUM_FRAMEINTERVALS 18 .. c:macro:: VIDIOC_ENUM_FRAMEINTERVALS
19 19
20 ``int ioctl(int fd, VIDIOC_ENUM_FRAMEINTERVALS 20 ``int ioctl(int fd, VIDIOC_ENUM_FRAMEINTERVALS, struct v4l2_frmivalenum *argp)``
21 21
22 Arguments 22 Arguments
23 ========= 23 =========
24 24
25 ``fd`` 25 ``fd``
26 File descriptor returned by :c:func:`open( 26 File descriptor returned by :c:func:`open()`.
27 27
28 ``argp`` 28 ``argp``
29 Pointer to struct :c:type:`v4l2_frmivalenu 29 Pointer to struct :c:type:`v4l2_frmivalenum`
30 that contains a pixel format and size and 30 that contains a pixel format and size and receives a frame interval.
31 31
32 Description 32 Description
33 =========== 33 ===========
34 34
35 This ioctl allows applications to enumerate al 35 This ioctl allows applications to enumerate all frame intervals that the
36 device supports for the given pixel format and 36 device supports for the given pixel format and frame size.
37 37
38 The supported pixel formats and frame sizes ca 38 The supported pixel formats and frame sizes can be obtained by using the
39 :ref:`VIDIOC_ENUM_FMT` and 39 :ref:`VIDIOC_ENUM_FMT` and
40 :ref:`VIDIOC_ENUM_FRAMESIZES` functions. 40 :ref:`VIDIOC_ENUM_FRAMESIZES` functions.
41 41
42 The return value and the content of the ``v4l2 42 The return value and the content of the ``v4l2_frmivalenum.type`` field
43 depend on the type of frame intervals the devi 43 depend on the type of frame intervals the device supports. Here are the
44 semantics of the function for the different ca 44 semantics of the function for the different cases:
45 45
46 - **Discrete:** The function returns success 46 - **Discrete:** The function returns success if the given index value
47 (zero-based) is valid. The application shou 47 (zero-based) is valid. The application should increase the index by
48 one for each call until ``EINVAL`` is retur 48 one for each call until ``EINVAL`` is returned. The
49 `v4l2_frmivalenum.type` field is set to 49 `v4l2_frmivalenum.type` field is set to
50 `V4L2_FRMIVAL_TYPE_DISCRETE` by the driver. 50 `V4L2_FRMIVAL_TYPE_DISCRETE` by the driver. Of the union only
51 the `discrete` member is valid. 51 the `discrete` member is valid.
52 52
53 - **Step-wise:** The function returns success 53 - **Step-wise:** The function returns success if the given index value
54 is zero and ``EINVAL`` for any other index 54 is zero and ``EINVAL`` for any other index value. The
55 ``v4l2_frmivalenum.type`` field is set to 55 ``v4l2_frmivalenum.type`` field is set to
56 ``V4L2_FRMIVAL_TYPE_STEPWISE`` by the drive 56 ``V4L2_FRMIVAL_TYPE_STEPWISE`` by the driver. Of the union only the
57 ``stepwise`` member is valid. 57 ``stepwise`` member is valid.
58 58
59 - **Continuous:** This is a special case of t 59 - **Continuous:** This is a special case of the step-wise type above.
60 The function returns success if the given i 60 The function returns success if the given index value is zero and
61 ``EINVAL`` for any other index value. The ` 61 ``EINVAL`` for any other index value. The ``v4l2_frmivalenum.type``
62 field is set to ``V4L2_FRMIVAL_TYPE_CONTINU 62 field is set to ``V4L2_FRMIVAL_TYPE_CONTINUOUS`` by the driver. Of
63 the union only the ``stepwise`` member is v 63 the union only the ``stepwise`` member is valid and the ``step``
64 value is set to 1. 64 value is set to 1.
65 65
66 When the application calls the function with i 66 When the application calls the function with index zero, it must check
67 the ``type`` field to determine the type of fr 67 the ``type`` field to determine the type of frame interval enumeration
68 the device supports. Only for the ``V4L2_FRMIV 68 the device supports. Only for the ``V4L2_FRMIVAL_TYPE_DISCRETE`` type
69 does it make sense to increase the index value 69 does it make sense to increase the index value to receive more frame
70 intervals. 70 intervals.
71 71
72 .. note:: 72 .. note::
73 73
74 The order in which the frame intervals are 74 The order in which the frame intervals are returned has no
75 special meaning. In particular does it not 75 special meaning. In particular does it not say anything about potential
76 default frame intervals. 76 default frame intervals.
77 77
78 Applications can assume that the enumeration d 78 Applications can assume that the enumeration data does not change
79 without any interaction from the application i 79 without any interaction from the application itself. This means that the
80 enumeration data is consistent if the applicat 80 enumeration data is consistent if the application does not perform any
81 other ioctl calls while it runs the frame inte 81 other ioctl calls while it runs the frame interval enumeration.
82 82
83 .. note:: 83 .. note::
84 84
85 **Frame intervals and frame rates:** The V4 85 **Frame intervals and frame rates:** The V4L2 API uses frame
86 intervals instead of frame rates. Given the 86 intervals instead of frame rates. Given the frame interval the frame
87 rate can be computed as follows: 87 rate can be computed as follows:
88 88
89 :: 89 ::
90 90
91 frame_rate = 1 / frame_interval 91 frame_rate = 1 / frame_interval
92 92
93 Structs 93 Structs
94 ======= 94 =======
95 95
96 In the structs below, *IN* denotes a value tha 96 In the structs below, *IN* denotes a value that has to be filled in by
97 the application, *OUT* denotes values that the 97 the application, *OUT* denotes values that the driver fills in. The
98 application should zero out all members except 98 application should zero out all members except for the *IN* fields.
99 99
100 .. c:type:: v4l2_frmival_stepwise 100 .. c:type:: v4l2_frmival_stepwise
101 101
102 .. flat-table:: struct v4l2_frmival_stepwise 102 .. flat-table:: struct v4l2_frmival_stepwise
103 :header-rows: 0 103 :header-rows: 0
104 :stub-columns: 0 104 :stub-columns: 0
105 :widths: 1 1 2 105 :widths: 1 1 2
106 106
107 * - struct :c:type:`v4l2_fract` 107 * - struct :c:type:`v4l2_fract`
108 - ``min`` 108 - ``min``
109 - Minimum frame interval [s]. 109 - Minimum frame interval [s].
110 * - struct :c:type:`v4l2_fract` 110 * - struct :c:type:`v4l2_fract`
111 - ``max`` 111 - ``max``
112 - Maximum frame interval [s]. 112 - Maximum frame interval [s].
113 * - struct :c:type:`v4l2_fract` 113 * - struct :c:type:`v4l2_fract`
114 - ``step`` 114 - ``step``
115 - Frame interval step size [s]. 115 - Frame interval step size [s].
116 116
117 117
118 .. c:type:: v4l2_frmivalenum 118 .. c:type:: v4l2_frmivalenum
119 119
120 .. tabularcolumns:: |p{4.9cm}|p{3.3cm}|p{9.1cm 120 .. tabularcolumns:: |p{4.9cm}|p{3.3cm}|p{9.1cm}|
121 121
122 .. flat-table:: struct v4l2_frmivalenum 122 .. flat-table:: struct v4l2_frmivalenum
123 :header-rows: 0 123 :header-rows: 0
124 :stub-columns: 0 124 :stub-columns: 0
125 125
126 * - __u32 126 * - __u32
127 - ``index`` 127 - ``index``
128 - IN: Index of the given frame interval 128 - IN: Index of the given frame interval in the enumeration.
129 * - __u32 129 * - __u32
130 - ``pixel_format`` 130 - ``pixel_format``
131 - IN: Pixel format for which the frame i 131 - IN: Pixel format for which the frame intervals are enumerated.
132 * - __u32 132 * - __u32
133 - ``width`` 133 - ``width``
134 - IN: Frame width for which the frame in 134 - IN: Frame width for which the frame intervals are enumerated.
135 * - __u32 135 * - __u32
136 - ``height`` 136 - ``height``
137 - IN: Frame height for which the frame i 137 - IN: Frame height for which the frame intervals are enumerated.
138 * - __u32 138 * - __u32
139 - ``type`` 139 - ``type``
140 - OUT: Frame interval type the device su 140 - OUT: Frame interval type the device supports.
141 * - union { 141 * - union {
142 - (anonymous) 142 - (anonymous)
143 - OUT: Frame interval with the given ind 143 - OUT: Frame interval with the given index.
144 * - struct :c:type:`v4l2_fract` 144 * - struct :c:type:`v4l2_fract`
145 - ``discrete`` 145 - ``discrete``
146 - Frame interval [s]. 146 - Frame interval [s].
147 * - struct :c:type:`v4l2_frmival_stepwise` 147 * - struct :c:type:`v4l2_frmival_stepwise`
148 - ``stepwise`` 148 - ``stepwise``
149 - 149 -
150 * - } 150 * - }
151 - 151 -
152 - 152 -
153 * - __u32 153 * - __u32
154 - ``reserved[2]`` 154 - ``reserved[2]``
155 - Reserved space for future use. Must be 155 - Reserved space for future use. Must be zeroed by drivers and
156 applications. 156 applications.
157 157
158 158
159 Enums 159 Enums
160 ===== 160 =====
161 161
162 .. c:type:: v4l2_frmivaltypes 162 .. c:type:: v4l2_frmivaltypes
163 163
164 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm 164 .. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.5cm}|
165 165
166 .. flat-table:: enum v4l2_frmivaltypes 166 .. flat-table:: enum v4l2_frmivaltypes
167 :header-rows: 0 167 :header-rows: 0
168 :stub-columns: 0 168 :stub-columns: 0
169 :widths: 3 1 4 169 :widths: 3 1 4
170 170
171 * - ``V4L2_FRMIVAL_TYPE_DISCRETE`` 171 * - ``V4L2_FRMIVAL_TYPE_DISCRETE``
172 - 1 172 - 1
173 - Discrete frame interval. 173 - Discrete frame interval.
174 * - ``V4L2_FRMIVAL_TYPE_CONTINUOUS`` 174 * - ``V4L2_FRMIVAL_TYPE_CONTINUOUS``
175 - 2 175 - 2
176 - Continuous frame interval. 176 - Continuous frame interval.
177 * - ``V4L2_FRMIVAL_TYPE_STEPWISE`` 177 * - ``V4L2_FRMIVAL_TYPE_STEPWISE``
178 - 3 178 - 3
179 - Step-wise defined frame interval. 179 - Step-wise defined frame interval.
180 180
181 Return Value 181 Return Value
182 ============ 182 ============
183 183
184 On success 0 is returned, on error -1 and the 184 On success 0 is returned, on error -1 and the ``errno`` variable is set
185 appropriately. The generic error codes are des 185 appropriately. The generic error codes are described at the
186 :ref:`Generic Error Codes <gen-errors>` chapte 186 :ref:`Generic Error Codes <gen-errors>` chapter.
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