1.. Permission is granted to copy, distribute and/or modify this 2.. document under the terms of the GNU Free Documentation License, 3.. Version 1.1 or any later version published by the Free Software 4.. Foundation, with no Invariant Sections, no Front-Cover Texts 5.. and no Back-Cover Texts. A copy of the license is included at 6.. Documentation/userspace-api/media/fdl-appendix.rst. 7.. 8.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections 9 10.. _VIDIOC_ENUM_FMT: 11 12********************* 13ioctl VIDIOC_ENUM_FMT 14********************* 15 16Name 17==== 18 19VIDIOC_ENUM_FMT - Enumerate image formats 20 21 22Synopsis 23======== 24 25.. c:function:: int ioctl( int fd, VIDIOC_ENUM_FMT, struct v4l2_fmtdesc *argp ) 26 :name: VIDIOC_ENUM_FMT 27 28 29Arguments 30========= 31 32``fd`` 33 File descriptor returned by :ref:`open() <func-open>`. 34 35``argp`` 36 Pointer to struct :c:type:`v4l2_fmtdesc`. 37 38 39Description 40=========== 41 42To enumerate image formats applications initialize the ``type``, ``mbus_code`` 43and ``index`` fields of struct :c:type:`v4l2_fmtdesc` and call 44the :ref:`VIDIOC_ENUM_FMT` ioctl with a pointer to this structure. Drivers 45fill the rest of the structure or return an ``EINVAL`` error code. All 46formats are enumerable by beginning at index zero and incrementing by 47one until ``EINVAL`` is returned. If applicable, drivers shall return 48formats in preference order, where preferred formats are returned before 49(that is, with lower ``index`` value) less-preferred formats. 50 51Depending on the ``V4L2_CAP_IO_MC`` :ref:`capability <device-capabilities>`, 52the ``mbus_code`` field is handled differently: 53 541) ``V4L2_CAP_IO_MC`` is not set (also known as a 'video-node-centric' driver) 55 56 Applications shall initialize the ``mbus_code`` field to zero and drivers 57 shall ignore the value of the field. 58 59 Drivers shall enumerate all image formats. 60 61 .. note:: 62 63 After switching the input or output the list of enumerated image 64 formats may be different. 65 662) ``V4L2_CAP_IO_MC`` is set (also known as an 'MC-centric' driver) 67 68 If the ``mbus_code`` field is zero, then all image formats 69 shall be enumerated. 70 71 If the ``mbus_code`` field is initialized to a valid (non-zero) 72 :ref:`media bus format code <v4l2-mbus-pixelcode>`, then drivers 73 shall restrict enumeration to only the image formats that can produce 74 (for video output devices) or be produced from (for video capture 75 devices) that media bus code. If the ``mbus_code`` is unsupported by 76 the driver, then ``EINVAL`` shall be returned. 77 78 Regardless of the value of the ``mbus_code`` field, the enumerated image 79 formats shall not depend on the active configuration of the video device 80 or device pipeline. 81 82 83.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| 84 85.. c:type:: v4l2_fmtdesc 86 87.. flat-table:: struct v4l2_fmtdesc 88 :header-rows: 0 89 :stub-columns: 0 90 :widths: 1 1 2 91 92 * - __u32 93 - ``index`` 94 - Number of the format in the enumeration, set by the application. 95 This is in no way related to the ``pixelformat`` field. 96 * - __u32 97 - ``type`` 98 - Type of the data stream, set by the application. Only these types 99 are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``, 100 ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``, 101 ``V4L2_BUF_TYPE_VIDEO_OUTPUT``, 102 ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``, 103 ``V4L2_BUF_TYPE_VIDEO_OVERLAY``, 104 ``V4L2_BUF_TYPE_SDR_CAPTURE``, 105 ``V4L2_BUF_TYPE_SDR_OUTPUT``, 106 ``V4L2_BUF_TYPE_META_CAPTURE`` and 107 ``V4L2_BUF_TYPE_META_OUTPUT``. 108 See :c:type:`v4l2_buf_type`. 109 * - __u32 110 - ``flags`` 111 - See :ref:`fmtdesc-flags` 112 * - __u8 113 - ``description``\ [32] 114 - Description of the format, a NUL-terminated ASCII string. This 115 information is intended for the user, for example: "YUV 4:2:2". 116 * - __u32 117 - ``pixelformat`` 118 - The image format identifier. This is a four character code as 119 computed by the v4l2_fourcc() macro: 120 * - :cspan:`2` 121 122 .. _v4l2-fourcc: 123 124 ``#define v4l2_fourcc(a,b,c,d)`` 125 126 ``(((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24))`` 127 128 Several image formats are already defined by this specification in 129 :ref:`pixfmt`. 130 131 .. attention:: 132 133 These codes are not the same as those used 134 in the Windows world. 135 * - __u32 136 - ``mbus_code`` 137 - Media bus code restricting the enumerated formats, set by the 138 application. Only applicable to drivers that advertise the 139 ``V4L2_CAP_IO_MC`` :ref:`capability <device-capabilities>`, shall be 0 140 otherwise. 141 * - __u32 142 - ``reserved``\ [3] 143 - Reserved for future extensions. Drivers must set the array to 144 zero. 145 146 147 148.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}| 149 150.. _fmtdesc-flags: 151 152.. flat-table:: Image Format Description Flags 153 :header-rows: 0 154 :stub-columns: 0 155 :widths: 3 1 4 156 157 * - ``V4L2_FMT_FLAG_COMPRESSED`` 158 - 0x0001 159 - This is a compressed format. 160 * - ``V4L2_FMT_FLAG_EMULATED`` 161 - 0x0002 162 - This format is not native to the device but emulated through 163 software (usually libv4l2), where possible try to use a native 164 format instead for better performance. 165 * - ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM`` 166 - 0x0004 167 - The hardware decoder for this compressed bytestream format (aka coded 168 format) is capable of parsing a continuous bytestream. Applications do 169 not need to parse the bytestream themselves to find the boundaries 170 between frames/fields. 171 172 This flag can only be used in combination with the 173 ``V4L2_FMT_FLAG_COMPRESSED`` flag, since this applies to compressed 174 formats only. This flag is valid for stateful decoders only. 175 * - ``V4L2_FMT_FLAG_DYN_RESOLUTION`` 176 - 0x0008 177 - Dynamic resolution switching is supported by the device for this 178 compressed bytestream format (aka coded format). It will notify the user 179 via the event ``V4L2_EVENT_SOURCE_CHANGE`` when changes in the video 180 parameters are detected. 181 182 This flag can only be used in combination with the 183 ``V4L2_FMT_FLAG_COMPRESSED`` flag, since this applies to 184 compressed formats only. This flag is valid for stateful codecs only. 185 * - ``V4L2_FMT_FLAG_ENC_CAP_FRAME_INTERVAL`` 186 - 0x0010 187 - The hardware encoder supports setting the ``CAPTURE`` coded frame 188 interval separately from the ``OUTPUT`` raw frame interval. 189 Setting the ``OUTPUT`` raw frame interval with :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` 190 also sets the ``CAPTURE`` coded frame interval to the same value. 191 If this flag is set, then the ``CAPTURE`` coded frame interval can be 192 set to a different value afterwards. This is typically used for 193 offline encoding where the ``OUTPUT`` raw frame interval is used as 194 a hint for reserving hardware encoder resources and the ``CAPTURE`` coded 195 frame interval is the actual frame rate embedded in the encoded video 196 stream. 197 198 This flag can only be used in combination with the 199 ``V4L2_FMT_FLAG_COMPRESSED`` flag, since this applies to 200 compressed formats only. This flag is valid for stateful encoders only. 201 202 203Return Value 204============ 205 206On success 0 is returned, on error -1 and the ``errno`` variable is set 207appropriately. The generic error codes are described at the 208:ref:`Generic Error Codes <gen-errors>` chapter. 209 210EINVAL 211 The struct :c:type:`v4l2_fmtdesc` ``type`` is not 212 supported or the ``index`` is out of bounds. 213 214 If ``V4L2_CAP_IO_MC`` is set and the specified ``mbus_code`` 215 is unsupported, then also return this error code. 216