1.. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later 2.. c:namespace:: V4L 3 4.. _VIDIOC_ENUM_FMT: 5 6********************* 7ioctl VIDIOC_ENUM_FMT 8********************* 9 10Name 11==== 12 13VIDIOC_ENUM_FMT - Enumerate image formats 14 15Synopsis 16======== 17 18.. c:macro:: VIDIOC_ENUM_FMT 19 20``int ioctl(int fd, VIDIOC_ENUM_FMT, struct v4l2_fmtdesc *argp)`` 21 22Arguments 23========= 24 25``fd`` 26 File descriptor returned by :c:func:`open()`. 27 28``argp`` 29 Pointer to struct :c:type:`v4l2_fmtdesc`. 30 31Description 32=========== 33 34To enumerate image formats applications initialize the ``type``, ``mbus_code`` 35and ``index`` fields of struct :c:type:`v4l2_fmtdesc` and call 36the :ref:`VIDIOC_ENUM_FMT` ioctl with a pointer to this structure. Drivers 37fill the rest of the structure or return an ``EINVAL`` error code. All 38formats are enumerable by beginning at index zero and incrementing by 39one until ``EINVAL`` is returned. If applicable, drivers shall return 40formats in preference order, where preferred formats are returned before 41(that is, with lower ``index`` value) less-preferred formats. 42 43Depending on the ``V4L2_CAP_IO_MC`` :ref:`capability <device-capabilities>`, 44the ``mbus_code`` field is handled differently: 45 461) ``V4L2_CAP_IO_MC`` is not set (also known as a 'video-node-centric' driver) 47 48 Applications shall initialize the ``mbus_code`` field to zero and drivers 49 shall ignore the value of the field. 50 51 Drivers shall enumerate all image formats. 52 53 .. note:: 54 55 After switching the input or output the list of enumerated image 56 formats may be different. 57 582) ``V4L2_CAP_IO_MC`` is set (also known as an 'MC-centric' driver) 59 60 If the ``mbus_code`` field is zero, then all image formats 61 shall be enumerated. 62 63 If the ``mbus_code`` field is initialized to a valid (non-zero) 64 :ref:`media bus format code <v4l2-mbus-pixelcode>`, then drivers 65 shall restrict enumeration to only the image formats that can produce 66 (for video output devices) or be produced from (for video capture 67 devices) that media bus code. If the ``mbus_code`` is unsupported by 68 the driver, then ``EINVAL`` shall be returned. 69 70 Regardless of the value of the ``mbus_code`` field, the enumerated image 71 formats shall not depend on the active configuration of the video device 72 or device pipeline. 73 74.. c:type:: v4l2_fmtdesc 75 76.. cssclass:: longtable 77 78.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.5cm}| 79 80.. flat-table:: struct v4l2_fmtdesc 81 :header-rows: 0 82 :stub-columns: 0 83 :widths: 1 1 2 84 85 * - __u32 86 - ``index`` 87 - Number of the format in the enumeration, set by the application. 88 This is in no way related to the ``pixelformat`` field. 89 * - __u32 90 - ``type`` 91 - Type of the data stream, set by the application. Only these types 92 are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``, 93 ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``, 94 ``V4L2_BUF_TYPE_VIDEO_OUTPUT``, 95 ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``, 96 ``V4L2_BUF_TYPE_VIDEO_OVERLAY``, 97 ``V4L2_BUF_TYPE_SDR_CAPTURE``, 98 ``V4L2_BUF_TYPE_SDR_OUTPUT``, 99 ``V4L2_BUF_TYPE_META_CAPTURE`` and 100 ``V4L2_BUF_TYPE_META_OUTPUT``. 101 See :c:type:`v4l2_buf_type`. 102 * - __u32 103 - ``flags`` 104 - See :ref:`fmtdesc-flags` 105 * - __u8 106 - ``description``\ [32] 107 - Description of the format, a NUL-terminated ASCII string. This 108 information is intended for the user, for example: "YUV 4:2:2". 109 * - __u32 110 - ``pixelformat`` 111 - The image format identifier. This is a four character code as 112 computed by the v4l2_fourcc() macro: 113 * - :cspan:`2` 114 115 .. _v4l2-fourcc: 116 117 ``#define v4l2_fourcc(a,b,c,d)`` 118 119 ``(((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24))`` 120 121 Several image formats are already defined by this specification in 122 :ref:`pixfmt`. 123 124 .. attention:: 125 126 These codes are not the same as those used 127 in the Windows world. 128 * - __u32 129 - ``mbus_code`` 130 - Media bus code restricting the enumerated formats, set by the 131 application. Only applicable to drivers that advertise the 132 ``V4L2_CAP_IO_MC`` :ref:`capability <device-capabilities>`, shall be 0 133 otherwise. 134 * - __u32 135 - ``reserved``\ [3] 136 - Reserved for future extensions. Drivers must set the array to 137 zero. 138 139 140.. tabularcolumns:: |p{8.4cm}|p{1.8cm}|p{7.1cm}| 141 142.. cssclass:: longtable 143 144.. _fmtdesc-flags: 145 146.. flat-table:: Image Format Description Flags 147 :header-rows: 0 148 :stub-columns: 0 149 :widths: 3 1 4 150 151 * - ``V4L2_FMT_FLAG_COMPRESSED`` 152 - 0x0001 153 - This is a compressed format. 154 * - ``V4L2_FMT_FLAG_EMULATED`` 155 - 0x0002 156 - This format is not native to the device but emulated through 157 software (usually libv4l2), where possible try to use a native 158 format instead for better performance. 159 * - ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM`` 160 - 0x0004 161 - The hardware decoder for this compressed bytestream format (aka coded 162 format) is capable of parsing a continuous bytestream. Applications do 163 not need to parse the bytestream themselves to find the boundaries 164 between frames/fields. 165 166 This flag can only be used in combination with the 167 ``V4L2_FMT_FLAG_COMPRESSED`` flag, since this applies to compressed 168 formats only. This flag is valid for stateful decoders only. 169 * - ``V4L2_FMT_FLAG_DYN_RESOLUTION`` 170 - 0x0008 171 - Dynamic resolution switching is supported by the device for this 172 compressed bytestream format (aka coded format). It will notify the user 173 via the event ``V4L2_EVENT_SOURCE_CHANGE`` when changes in the video 174 parameters are detected. 175 176 This flag can only be used in combination with the 177 ``V4L2_FMT_FLAG_COMPRESSED`` flag, since this applies to 178 compressed formats only. This flag is valid for stateful codecs only. 179 * - ``V4L2_FMT_FLAG_ENC_CAP_FRAME_INTERVAL`` 180 - 0x0010 181 - The hardware encoder supports setting the ``CAPTURE`` coded frame 182 interval separately from the ``OUTPUT`` raw frame interval. 183 Setting the ``OUTPUT`` raw frame interval with :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` 184 also sets the ``CAPTURE`` coded frame interval to the same value. 185 If this flag is set, then the ``CAPTURE`` coded frame interval can be 186 set to a different value afterwards. This is typically used for 187 offline encoding where the ``OUTPUT`` raw frame interval is used as 188 a hint for reserving hardware encoder resources and the ``CAPTURE`` coded 189 frame interval is the actual frame rate embedded in the encoded video 190 stream. 191 192 This flag can only be used in combination with the 193 ``V4L2_FMT_FLAG_COMPRESSED`` flag, since this applies to 194 compressed formats only. This flag is valid for stateful encoders only. 195 * - ``V4L2_FMT_FLAG_CSC_COLORSPACE`` 196 - 0x0020 197 - The driver allows the application to try to change the default 198 colorspace. This flag is relevant only for capture devices. 199 The application can ask to configure the colorspace of the capture device 200 when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with 201 :ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set. 202 * - ``V4L2_FMT_FLAG_CSC_XFER_FUNC`` 203 - 0x0040 204 - The driver allows the application to try to change the default 205 transfer function. This flag is relevant only for capture devices. 206 The application can ask to configure the transfer function of the capture 207 device when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with 208 :ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set. 209 * - ``V4L2_FMT_FLAG_CSC_YCBCR_ENC`` 210 - 0x0080 211 - The driver allows the application to try to change the default 212 Y'CbCr encoding. This flag is relevant only for capture devices. 213 The application can ask to configure the Y'CbCr encoding of the capture device 214 when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with 215 :ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set. 216 * - ``V4L2_FMT_FLAG_CSC_HSV_ENC`` 217 - 0x0080 218 - The driver allows the application to try to change the default 219 HSV encoding. This flag is relevant only for capture devices. 220 The application can ask to configure the HSV encoding of the capture device 221 when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with 222 :ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set. 223 * - ``V4L2_FMT_FLAG_CSC_QUANTIZATION`` 224 - 0x0100 225 - The driver allows the application to try to change the default 226 quantization. This flag is relevant only for capture devices. 227 The application can ask to configure the quantization of the capture 228 device when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with 229 :ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set. 230 231Return Value 232============ 233 234On success 0 is returned, on error -1 and the ``errno`` variable is set 235appropriately. The generic error codes are described at the 236:ref:`Generic Error Codes <gen-errors>` chapter. 237 238EINVAL 239 The struct :c:type:`v4l2_fmtdesc` ``type`` is not 240 supported or the ``index`` is out of bounds. 241 242 If ``V4L2_CAP_IO_MC`` is set and the specified ``mbus_code`` 243 is unsupported, then also return this error code. 244