59 lines
2.3 KiB
ReStructuredText
59 lines
2.3 KiB
ReStructuredText
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.. Permission is granted to copy, distribute and/or modify this
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.. document under the terms of the GNU Free Documentation License,
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.. Version 1.1 or any later version published by the Free Software
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.. Foundation, with no Invariant Sections, no Front-Cover Texts
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.. and no Back-Cover Texts. A copy of the license is included at
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.. Documentation/media/uapi/fdl-appendix.rst.
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..
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.. TODO: replace it to GFDL-1.1-or-later WITH no-invariant-sections
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.. _v4l2-meta-fmt-uvc:
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*******************************
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V4L2_META_FMT_UVC ('UVCH')
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*******************************
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UVC Payload Header Data
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Description
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===========
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This format describes standard UVC metadata, extracted from UVC packet headers
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and provided by the UVC driver through metadata video nodes. That data includes
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exact copies of the standard part of UVC Payload Header contents and auxiliary
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timing information, required for precise interpretation of timestamps, contained
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in those headers. See section "2.4.3.3 Video and Still Image Payload Headers" of
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the "UVC 1.5 Class specification" for details.
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Each UVC payload header can be between 2 and 12 bytes large. Buffers can
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contain multiple headers, if multiple such headers have been transmitted by the
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camera for the respective frame. However, the driver may drop headers when the
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buffer is full, when they contain no useful information (e.g. those without the
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SCR field or with that field identical to the previous header), or generally to
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perform rate limiting when the device sends a large number of headers.
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Each individual block contains the following fields:
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.. flat-table:: UVC Metadata Block
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:widths: 1 4
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:header-rows: 1
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:stub-columns: 0
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* - Field
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- Description
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* - __u64 ts;
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- system timestamp in host byte order, measured by the driver upon
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reception of the payload
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* - __u16 sof;
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- USB Frame Number in host byte order, also obtained by the driver as
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close as possible to the above timestamp to enable correlation between
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them
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* - :cspan:`1` *The rest is an exact copy of the UVC payload header:*
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* - __u8 length;
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- length of the rest of the block, including this field
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* - __u8 flags;
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- Flags, indicating presence of other standard UVC fields
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* - __u8 buf[];
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- The rest of the header, possibly including UVC PTS and SCR fields
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