[Cin] 10-bit 422 Video capture not part of the UVC spec?

[Terje J. Hanssen]

We have some threads this month discussing the performance of UVC 
HDMI-USB3 Vide Capture stics/dongles or devices.
If technical specs are available, sadly often deficient, they may manage 
422 chroma subsampling, but limited to 8-bit "Deep color" (4KVC00) or 
"YUY2" (ms2130)

1. To repeate the illustrative article 8-Bit vs 10-Bit Video Color 
Explained (millions/banding vs billion shades):
https://fujifilm-x.com/en-us/series/the-filmmakers-handbook/8-bit-or-10-bit-video-color-explained/


2. In a couple of learn.microsoft articles, 10- and 16-bit YUV Video 
Formats are recommended for capturing, processing, and displaying video, 
while 8-bit YUV color formats that are recommended for video rendering. 
To extract and learn the most relevant YUV formats in this context from 
the table
https://learn.microsoft.com/en-us/windows/win32/medfound/10-bit-and-16-bit-yuv-video-formats#preferred-yuv-formats

    YUY2 4:2:2     Packed     8 bits pr channel
    Y210     4:2:2 Packed     10
    NV12     4:2:0 Planar     8
    P010     4:2:0 Planar     10

3. So I found an interesting discussion on the Digital Photography 
Review forum:
Cheapest (and decent) way to record 10 bits HDMI on Windows?
https://www.dpreview.com/forums/thread/4562209

Extract here an interesting section from the first reply of Mar 19, 2021:

    It almost looks like 10-bit may not be part of the UVC specs unless
    the device does hardware H.264 or HEVC decoding, there are no 10-bit
    color formats that appear in
    https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/drivers/media/usb/uvc/uvcvideo.h?h=v5.11.7
    such as p010, and I would expect that if the UVC spec supported p010
    video it would have appeared in the Linux kernel by now.

If someone can confirm this is the case also today, we don't need to 
search for cheap or inexpensive HDMI-USB3 Video capture stick/dongles 
with 10-bit 422 output support.
Down In the same thread also some high-priced UVC compliant devices are 
mentioned, but they tend to support 10-bit on HDMI input and so 
downscale it to 8-bit on USB3 output.


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