1 .. SPDX-License-Identifier: GFDL-1.1-no-invari 1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2 2
3 .. _v4l2-meta-fmt-uvc: 3 .. _v4l2-meta-fmt-uvc:
4 4
5 ******************************* 5 *******************************
6 V4L2_META_FMT_UVC ('UVCH') 6 V4L2_META_FMT_UVC ('UVCH')
7 ******************************* 7 *******************************
8 8
9 UVC Payload Header Data 9 UVC Payload Header Data
10 10
11 11
12 Description 12 Description
13 =========== 13 ===========
14 14
15 This format describes standard UVC metadata, e 15 This format describes standard UVC metadata, extracted from UVC packet headers
16 and provided by the UVC driver through metadat 16 and provided by the UVC driver through metadata video nodes. That data includes
17 exact copies of the standard part of UVC Paylo 17 exact copies of the standard part of UVC Payload Header contents and auxiliary
18 timing information, required for precise inter 18 timing information, required for precise interpretation of timestamps, contained
19 in those headers. See section "2.4.3.3 Video a 19 in those headers. See section "2.4.3.3 Video and Still Image Payload Headers" of
20 the "UVC 1.5 Class specification" for details. 20 the "UVC 1.5 Class specification" for details.
21 21
22 Each UVC payload header can be between 2 and 1 22 Each UVC payload header can be between 2 and 12 bytes large. Buffers can
23 contain multiple headers, if multiple such hea 23 contain multiple headers, if multiple such headers have been transmitted by the
24 camera for the respective frame. However, the 24 camera for the respective frame. However, the driver may drop headers when the
25 buffer is full, when they contain no useful in 25 buffer is full, when they contain no useful information (e.g. those without the
26 SCR field or with that field identical to the 26 SCR field or with that field identical to the previous header), or generally to
27 perform rate limiting when the device sends a 27 perform rate limiting when the device sends a large number of headers.
28 28
29 Each individual block contains the following f 29 Each individual block contains the following fields:
30 30
31 .. flat-table:: UVC Metadata Block 31 .. flat-table:: UVC Metadata Block
32 :widths: 1 4 32 :widths: 1 4
33 :header-rows: 1 33 :header-rows: 1
34 :stub-columns: 0 34 :stub-columns: 0
35 35
36 * - Field 36 * - Field
37 - Description 37 - Description
38 * - __u64 ts; 38 * - __u64 ts;
39 - system timestamp in host byte order, m 39 - system timestamp in host byte order, measured by the driver upon
40 reception of the payload 40 reception of the payload
41 * - __u16 sof; 41 * - __u16 sof;
42 - USB Frame Number in host byte order, a 42 - USB Frame Number in host byte order, also obtained by the driver as
43 close as possible to the above timesta 43 close as possible to the above timestamp to enable correlation between
44 them 44 them
45 * - :cspan:`1` *The rest is an exact copy 45 * - :cspan:`1` *The rest is an exact copy of the UVC payload header:*
46 * - __u8 length; 46 * - __u8 length;
47 - length of the rest of the block, inclu 47 - length of the rest of the block, including this field
48 * - __u8 flags; 48 * - __u8 flags;
49 - Flags, indicating presence of other st 49 - Flags, indicating presence of other standard UVC fields
50 * - __u8 buf[]; 50 * - __u8 buf[];
51 - The rest of the header, possibly inclu 51 - The rest of the header, possibly including UVC PTS and SCR fields
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