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

Terje J. Hanssen terjejhanssen at gmail.com
Fri Feb 10 13:44:39 CET 2023

Den 10.02.2023 04:03, skrev Andrew Randrianasulu:
> пт, 10 февр. 2023 г., 04:37 Terje J. Hanssen via Cin 
> <cin at lists.cinelerra-gg.org>:
>     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.
> Isn't such question more for Maintainer?
> |
> M:	Laurent Pinchart <laurent.pinchart at ideasonboard.com>
> L:	linux-media at vger.kernel.org
> S:	Maintained
> W:	http://www.ideasonboard.org/uvc/
> T:	git git://linuxtv.org/media_tree.git  <http://linuxtv.org/media_tree.git>
> F:	drivers/media/usb/uvc/
> F:	include/uapi/linux/uvcvideo.h
> |
> "
> from 
> https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/tree/MAINTAINERS
> I looked at (hopefully) uvc spec, but mostly for interlace info
> https://www.spinelelectronics.com/pdf/UVC%25201.5%2520Class%2520specification.pdf
> I'll look for guid info some more..
>     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.

What I meant to say is that (my thought ) 8-bit YUY2 output support 
seems to be the current limit of HDMI-USB3 Video Capture sticks like in 
the new ms2130.
I saw that the (previous) USB2 model that still was announced in 
parallell didn't support YUY2. But I expect this is just a question of 
time as the chip technology evolves - so maybe the next model and UVC 
then get 10-bit 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.
> Apparently hacked Cx driver can output 16 bits as ADC, but then we 
> have question of feeding it with good enough signal (vhs-decode just 
> vampires into VCR guts.)
> Is any real external vhs (ish) sources worth 10 bits path?

There have been discussions about that. VHS/Video8 is low-end composite 
video, while S-Video (2) and Component Video (3) are better. But cheap 
ADC to HDMI adapters, sadly also often with missing technical specs, 
most probably at best output 8-bit(?) At least here 8-bit YUY2 ms2130 
may fit well.
Digital cameras with direct HDMI output on the other hand may utilize 

As a generic reference, I compare this with "The Digitization of VHS 
Videotapes – Technical Bulletin 31

    Digitization Set-up Two with an external capture device
    while Set-up _Three is Digitization with an internal (PCIe) capture card

The Digitization procedure/Video compressor section discuss 10-bit vs 8-bit


    Using 10-bit is advocated by many, although several institutions
    also use 8-bit (see Appendix B). It is debatable whether 10-bit is
    required for VHS video but some believe that because of VHS’s
    shortcomings in the area of resolution, luminance and colour range,
    capturing the finer details becomes more important.Footnote 29 It is
    believed that capturing at higher quality will ultimately produce a
    better result if significant manipulation occurs, such as editing of
    files, and a better result if future compression of the file is

> https://github.com/happycube/cxadc-linux3
> ===
> cxadc is an alternative Linux driver for the Conexant CX2388x series 
> of video decoder/encoder chips used on many PCI TV tuner and capture 
> cards.
> *Note!* cx23885 and cx23888 are incompatible chips.
> The new driver configures the CX2388x to capture in its raw output 
> mode in 8-bit or 16-bit unsigned samples from the video input ports, 
> allowing these cards to be used as a low-cost 28-54Mhz 10bit ADC for 
> SDR and similar applications.
> ====
> vhs-decode wiki has some ffmpeg command encoding raw captures  into 
> prores 10bit file
> https://github.com/oyvindln/vhs-decode

Very interesting reading. I admit I have never heard about "vhs-decode" 
before and do not yet have an overview of what it includes.

> ===
> VHS-Decode produces two timebase corrected 16-bit |GREY16| headerless 
> files separated into chroma/luma composite video signals in the |.tbc| 
> format alongside |.json| and |.log| files, usable with the LD-Decode 
> family of tools ld-analyse, ld-process-vbi, ld-process-vits and 
> ld-dropout-correct.
> The gen chroma scrips will use decoded .tbc files and generate 
> standard video files by default a lossless, interlaced top field first 
> and high-bitrate (roughly 70-100 Mb/s) FFV1 codec video which, which 
> although ideal for archival and further processing.
> For editing due to lack of support of FFV1 and sharing online without 
> de-interlacing is not supported properly, as such the two commands are 
> provided below to make suitable files for this use.
> Both commands will automatically use the last file generated as the input.
> For editors this transcodes an FFV1/V210 output to a "/near 
> complient/" interlaced ProRes HQ file:
> |ffmpeg -hide_banner -i "$1.mkv" -vf setfield=tff -flags +ilme+ildct 
> -c:v prores -profile:v 3 -vendor apl0 -bits_per_mb 8000 -quant_mat hq 
> -mbs_per_slice 8 -pixel_format yuv422p10lep -color_range tv 
> -color_primaries bt709 -color_trc bt709 -colorspace bt709 -c:a s24le 
> -vf setdar=4/3,setfield=tff "$1_ProResHQ.mov" |
> For basic online sharing you can use this command to convert the FFV1 
> output to a de-interlaced lossy upscaled MP4:
> |ffmpeg -hide_banner -i "$1.mkv" -vf 
> scale=in_color_matrix=bt601:out_color_matrix=bt709:1440x1080,bwdif=1:0:0 
> -c:v libx264 -preset veryslow -b:v 15M -maxrate 15M -bufsize 8M 
> -pixel_format yuv420p -color_primaries bt709 -color_trc bt709 
> -colorspace bt709 -aspect 4:3 -c:a libopus -b:a 192k -strict -2 
> -movflags +faststart -y "$1_1440x1080_lossy.mp4" |
> ====
> Maaay be we still can use pci-e capture card with normal inputs, just 
> process raw captures to see if there any difference between 8 and 10 bit?

I think I don't mess with internal proprietary PCIe capture cards 
anymore. I had once a Pinnacle DV500/DVD system for Windows 98 (or was 
it 95).

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>     Cin at lists.cinelerra-gg.org
>     https://lists.cinelerra-gg.org/mailman/listinfo/cin
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