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.. tabularcolumns:: |p{4.4cm}|p{4.4cm}|p{8.7cm}| 75 76.. c:type:: v4l2_fmtdesc 77 78.. flat-table:: struct v4l2_fmtdesc 79 :header-rows: 0 80 :stub-columns: 0 81 :widths: 1 1 2 82 83 * - __u32 84 - ``index`` 85 - Number of the format in the enumeration, set by the application. 86 This is in no way related to the ``pixelformat`` field. 87 * - __u32 88 - ``type`` 89 - Type of the data stream, set by the application. Only these types 90 are valid here: ``V4L2_BUF_TYPE_VIDEO_CAPTURE``, 91 ``V4L2_BUF_TYPE_VIDEO_CAPTURE_MPLANE``, 92 ``V4L2_BUF_TYPE_VIDEO_OUTPUT``, 93 ``V4L2_BUF_TYPE_VIDEO_OUTPUT_MPLANE``, 94 ``V4L2_BUF_TYPE_VIDEO_OVERLAY``, 95 ``V4L2_BUF_TYPE_SDR_CAPTURE``, 96 ``V4L2_BUF_TYPE_SDR_OUTPUT``, 97 ``V4L2_BUF_TYPE_META_CAPTURE`` and 98 ``V4L2_BUF_TYPE_META_OUTPUT``. 99 See :c:type:`v4l2_buf_type`. 100 * - __u32 101 - ``flags`` 102 - See :ref:`fmtdesc-flags` 103 * - __u8 104 - ``description``\ [32] 105 - Description of the format, a NUL-terminated ASCII string. This 106 information is intended for the user, for example: "YUV 4:2:2". 107 * - __u32 108 - ``pixelformat`` 109 - The image format identifier. This is a four character code as 110 computed by the v4l2_fourcc() macro: 111 * - :cspan:`2` 112 113 .. _v4l2-fourcc: 114 115 ``#define v4l2_fourcc(a,b,c,d)`` 116 117 ``(((__u32)(a)<<0)|((__u32)(b)<<8)|((__u32)(c)<<16)|((__u32)(d)<<24))`` 118 119 Several image formats are already defined by this specification in 120 :ref:`pixfmt`. 121 122 .. attention:: 123 124 These codes are not the same as those used 125 in the Windows world. 126 * - __u32 127 - ``mbus_code`` 128 - Media bus code restricting the enumerated formats, set by the 129 application. Only applicable to drivers that advertise the 130 ``V4L2_CAP_IO_MC`` :ref:`capability <device-capabilities>`, shall be 0 131 otherwise. 132 * - __u32 133 - ``reserved``\ [3] 134 - Reserved for future extensions. Drivers must set the array to 135 zero. 136 137 138.. tabularcolumns:: |p{6.6cm}|p{2.2cm}|p{8.7cm}| 139 140.. _fmtdesc-flags: 141 142.. flat-table:: Image Format Description Flags 143 :header-rows: 0 144 :stub-columns: 0 145 :widths: 3 1 4 146 147 * - ``V4L2_FMT_FLAG_COMPRESSED`` 148 - 0x0001 149 - This is a compressed format. 150 * - ``V4L2_FMT_FLAG_EMULATED`` 151 - 0x0002 152 - This format is not native to the device but emulated through 153 software (usually libv4l2), where possible try to use a native 154 format instead for better performance. 155 * - ``V4L2_FMT_FLAG_CONTINUOUS_BYTESTREAM`` 156 - 0x0004 157 - The hardware decoder for this compressed bytestream format (aka coded 158 format) is capable of parsing a continuous bytestream. Applications do 159 not need to parse the bytestream themselves to find the boundaries 160 between frames/fields. 161 162 This flag can only be used in combination with the 163 ``V4L2_FMT_FLAG_COMPRESSED`` flag, since this applies to compressed 164 formats only. This flag is valid for stateful decoders only. 165 * - ``V4L2_FMT_FLAG_DYN_RESOLUTION`` 166 - 0x0008 167 - Dynamic resolution switching is supported by the device for this 168 compressed bytestream format (aka coded format). It will notify the user 169 via the event ``V4L2_EVENT_SOURCE_CHANGE`` when changes in the video 170 parameters are detected. 171 172 This flag can only be used in combination with the 173 ``V4L2_FMT_FLAG_COMPRESSED`` flag, since this applies to 174 compressed formats only. This flag is valid for stateful codecs only. 175 * - ``V4L2_FMT_FLAG_ENC_CAP_FRAME_INTERVAL`` 176 - 0x0010 177 - The hardware encoder supports setting the ``CAPTURE`` coded frame 178 interval separately from the ``OUTPUT`` raw frame interval. 179 Setting the ``OUTPUT`` raw frame interval with :ref:`VIDIOC_S_PARM <VIDIOC_G_PARM>` 180 also sets the ``CAPTURE`` coded frame interval to the same value. 181 If this flag is set, then the ``CAPTURE`` coded frame interval can be 182 set to a different value afterwards. This is typically used for 183 offline encoding where the ``OUTPUT`` raw frame interval is used as 184 a hint for reserving hardware encoder resources and the ``CAPTURE`` coded 185 frame interval is the actual frame rate embedded in the encoded video 186 stream. 187 188 This flag can only be used in combination with the 189 ``V4L2_FMT_FLAG_COMPRESSED`` flag, since this applies to 190 compressed formats only. This flag is valid for stateful encoders only. 191 * - ``V4L2_FMT_FLAG_CSC_COLORSPACE`` 192 - 0x0020 193 - The driver allows the application to try to change the default 194 colorspace. This flag is relevant only for capture devices. 195 The application can ask to configure the colorspace of the capture device 196 when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with 197 :ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set. 198 * - ``V4L2_FMT_FLAG_CSC_XFER_FUNC`` 199 - 0x0040 200 - The driver allows the application to try to change the default 201 transfer function. This flag is relevant only for capture devices. 202 The application can ask to configure the transfer function of the capture 203 device when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with 204 :ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set. 205 * - ``V4L2_FMT_FLAG_CSC_YCBCR_ENC`` 206 - 0x0080 207 - The driver allows the application to try to change the default 208 Y'CbCr encoding. This flag is relevant only for capture devices. 209 The application can ask to configure the Y'CbCr encoding of the capture device 210 when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with 211 :ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set. 212 * - ``V4L2_FMT_FLAG_CSC_HSV_ENC`` 213 - 0x0080 214 - The driver allows the application to try to change the default 215 HSV encoding. This flag is relevant only for capture devices. 216 The application can ask to configure the HSV encoding of the capture device 217 when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with 218 :ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set. 219 * - ``V4L2_FMT_FLAG_CSC_QUANTIZATION`` 220 - 0x0100 221 - The driver allows the application to try to change the default 222 quantization. This flag is relevant only for capture devices. 223 The application can ask to configure the quantization of the capture 224 device when calling the :ref:`VIDIOC_S_FMT <VIDIOC_G_FMT>` ioctl with 225 :ref:`V4L2_PIX_FMT_FLAG_SET_CSC <v4l2-pix-fmt-flag-set-csc>` set. 226 227Return Value 228============ 229 230On success 0 is returned, on error -1 and the ``errno`` variable is set 231appropriately. The generic error codes are described at the 232:ref:`Generic Error Codes <gen-errors>` chapter. 233 234EINVAL 235 The struct :c:type:`v4l2_fmtdesc` ``type`` is not 236 supported or the ``index`` is out of bounds. 237 238 If ``V4L2_CAP_IO_MC`` is set and the specified ``mbus_code`` 239 is unsupported, then also return this error code. 240