| 1 | .. -*- coding: utf-8; mode: rst -*- |
| 2 | |
| 3 | .. _VIDIOC_ENUM_FMT: |
| 4 | |
| 5 | ********************* |
| 6 | ioctl VIDIOC_ENUM_FMT |
| 7 | ********************* |
| 8 | |
| 9 | *man VIDIOC_ENUM_FMT(2)* |
| 10 | |
| 11 | Enumerate image formats |
| 12 | |
| 13 | |
| 14 | Synopsis |
| 15 | ======== |
| 16 | |
| 17 | .. c:function:: int ioctl( int fd, int request, struct v4l2_fmtdesc *argp ) |
| 18 | |
| 19 | Arguments |
| 20 | ========= |
| 21 | |
| 22 | ``fd`` |
| 23 | File descriptor returned by :ref:`open() <func-open>`. |
| 24 | |
| 25 | ``request`` |
| 26 | VIDIOC_ENUM_FMT |
| 27 | |
| 28 | ``argp`` |
| 29 | |
| 30 | |
| 31 | Description |
| 32 | =========== |
| 33 | |
| 34 | To enumerate image formats applications initialize the ``type`` and |
| 35 | ``index`` field of struct :ref:`v4l2_fmtdesc <v4l2-fmtdesc>` and call |
| 36 | the ``VIDIOC_ENUM_FMT`` ioctl with a pointer to this structure. Drivers |
| 37 | fill the rest of the structure or return an EINVAL error code. All |
| 38 | formats are enumerable by beginning at index zero and incrementing by |
| 39 | one until EINVAL is returned. |
| 40 | |
| 41 | Note that after switching input or output the list of enumerated image |
| 42 | formats may be different. |
| 43 | |
| 44 | |
| 45 | .. _v4l2-fmtdesc: |
| 46 | |
| 47 | .. flat-table:: struct v4l2_fmtdesc |
| 48 | :header-rows: 0 |
| 49 | :stub-columns: 0 |
| 50 | :widths: 1 1 2 |
| 51 | |
| 52 | |
| 53 | - .. row 1 |
| 54 | |
| 55 | - __u32 |
| 56 | |
| 57 | - ``index`` |
| 58 | |
| 59 | - Number of the format in the enumeration, set by the application. |
| 60 | This is in no way related to the ``pixelformat`` field. |
| 61 | |
| 62 | - .. row 2 |
| 63 | |
| 64 | - __u32 |
| 65 | |
| 66 | - ``type`` |
| 67 | |
| 68 | - Type of the data stream, set by the application. Only these types |
| 69 | are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``, |
| 70 | ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``, |
| 71 | ``V4L2_BUF_TYPE_VIDEO_OUTPUT``, |
| 72 | ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE`` and |
| 73 | ``V4L2_BUF_TYPE_VIDEO_OVERLAY``. See :ref:`v4l2-buf-type`. |
| 74 | |
| 75 | - .. row 3 |
| 76 | |
| 77 | - __u32 |
| 78 | |
| 79 | - ``flags`` |
| 80 | |
| 81 | - See :ref:`fmtdesc-flags` |
| 82 | |
| 83 | - .. row 4 |
| 84 | |
| 85 | - __u8 |
| 86 | |
| 87 | - ``description``\ [32] |
| 88 | |
| 89 | - Description of the format, a NUL-terminated ASCII string. This |
| 90 | information is intended for the user, for example: "YUV 4:2:2". |
| 91 | |
| 92 | - .. row 5 |
| 93 | |
| 94 | - __u32 |
| 95 | |
| 96 | - ``pixelformat`` |
| 97 | |
| 98 | - The image format identifier. This is a four character code as |
| 99 | computed by the v4l2_fourcc() macro: |
| 100 | |
| 101 | - .. row 6 |
| 102 | |
| 103 | - :cspan:`2` |
| 104 | |
| 105 | |
| 106 | .. _v4l2-fourcc: |
| 107 | .. code-block:: c |
| 108 | |
| 109 | #define v4l2_fourcc(a,b,c,d) (((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24)) |
| 110 | |
| 111 | Several image formats are already defined by this specification in |
| 112 | :ref:`pixfmt`. Note these codes are not the same as those used |
| 113 | in the Windows world. |
| 114 | |
| 115 | - .. row 7 |
| 116 | |
| 117 | - __u32 |
| 118 | |
| 119 | - ``reserved``\ [4] |
| 120 | |
| 121 | - Reserved for future extensions. Drivers must set the array to |
| 122 | zero. |
| 123 | |
| 124 | |
| 125 | |
| 126 | .. _fmtdesc-flags: |
| 127 | |
| 128 | .. flat-table:: Image Format Description Flags |
| 129 | :header-rows: 0 |
| 130 | :stub-columns: 0 |
| 131 | :widths: 3 1 4 |
| 132 | |
| 133 | |
| 134 | - .. row 1 |
| 135 | |
| 136 | - ``V4L2_FMT_FLAG_COMPRESSED`` |
| 137 | |
| 138 | - 0x0001 |
| 139 | |
| 140 | - This is a compressed format. |
| 141 | |
| 142 | - .. row 2 |
| 143 | |
| 144 | - ``V4L2_FMT_FLAG_EMULATED`` |
| 145 | |
| 146 | - 0x0002 |
| 147 | |
| 148 | - This format is not native to the device but emulated through |
| 149 | software (usually libv4l2), where possible try to use a native |
| 150 | format instead for better performance. |
| 151 | |
| 152 | |
| 153 | |
| 154 | Return Value |
| 155 | ============ |
| 156 | |
| 157 | On success 0 is returned, on error -1 and the ``errno`` variable is set |
| 158 | appropriately. The generic error codes are described at the |
| 159 | :ref:`Generic Error Codes <gen-errors>` chapter. |
| 160 | |
| 161 | EINVAL |
| 162 | The struct :ref:`v4l2_fmtdesc <v4l2-fmtdesc>` ``type`` is not |
| 163 | supported or the ``index`` is out of bounds. |
| 164 | |
| 165 | |
| 166 | .. ------------------------------------------------------------------------------ |
| 167 | .. This file was automatically converted from DocBook-XML with the dbxml |
| 168 | .. library (https://github.com/return42/sphkerneldoc). The origin XML comes |
| 169 | .. from the linux kernel, refer to: |
| 170 | .. |
| 171 | .. * https://github.com/torvalds/linux/tree/master/Documentation/DocBook |
| 172 | .. ------------------------------------------------------------------------------ |