1 .. SPDX-License-Identifier: GFDL-1.1-no-invariants-or-later
2
3 .. _v4l2-meta-fmt-uvc:
4
5 *******************************
6 V4L2_META_FMT_UVC ('UVCH')
7 *******************************
8
9 UVC Payload Header Data
10
11
12 Description
13 ===========
14
15 This format describes standard UVC metadata, extracted from UVC packet headers
16 and provided by the UVC driver through metadata video nodes. That data includes
17 exact copies of the standard part of UVC Payload Header contents and auxiliary
18 timing information, required for precise interpretation of timestamps, contained
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.
21
22 Each UVC payload header can be between 2 and 12 bytes large. Buffers can
23 contain multiple headers, if multiple such headers have been transmitted by the
24 camera for the respective frame. However, the driver may drop headers when the
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 previous header), or generally to
27 perform rate limiting when the device sends a large number of headers.
28
29 Each individual block contains the following fields:
30
31 .. flat-table:: UVC Metadata Block
32 :widths: 1 4
33 :header-rows: 1
34 :stub-columns: 0
35
36 * - Field
37 - Description
38 * - __u64 ts;
39 - system timestamp in host byte order, measured by the driver upon
40 reception of the payload
41 * - __u16 sof;
42 - USB Frame Number in host byte order, also obtained by the driver as
43 close as possible to the above timestamp to enable correlation between
44 them
45 * - :cspan:`1` *The rest is an exact copy of the UVC payload header:*
46 * - __u8 length;
47 - length of the rest of the block, including this field
48 * - __u8 flags;
49 - Flags, indicating presence of other standard UVC fields
50 * - __u8 buf[];
51 - The rest of the header, possibly including UVC PTS and SCR fields
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