[FFmpeg-user] rgb8

[Diederick C. Niehorster]

HI Michael,

On Tue, Jun 20, 2023 at 9:14 AM Michael Koch
<astroelectronic at t-online.de> wrote:
>
> Am 20.06.2023 um 02:53 schrieb Roger Pack:
> > Can other apps use this dshow device?
>
> In VLC player it's incorrectly shown as a noisy rgb8 color video. Same
> output as in FFmpeg.
> In SharpCap I can open the camera directly (using the camera
> manufacturer's API), that works without problems, the data is
> uncompressed 8-bit or 16-bit grayscale.
> If I open it in SharpCap as a DirectShow device, then the video is very
> noisy but grayscale (no colors). Probably rgb8 converted to grayscale.
>
> >    If you plunk it into
> > graphstudionext does it work, what media format do you see on the
> > wires?
>
> See the attached screenshot.
>
> > I guess the only question is "is it actually palletized"?
> > Based on the source it seems like we weren't sure...
>
> What else could it be? DirectShow doesn't support 8-bit gray.
> It's sure that the pixel format is either 8-bit gray, or pal8 with a
> palette which contains 256 levels of gray.

I've only half been following this conversation, but i assume it must
be palettized, since thats what the format says it is and how the
other tools probably interpret it correctly.
Your screenshot was helpful. It shows that biCompression is 0x0000.
According to the docs, this value (BI_RGB, see
https://learn.microsoft.com/en-us/openspecs/windows_protocols/ms-wmf/4e588f70-bd92-4a6f-b77f-35d0feaf7a57)
means a palette is used:
https://learn.microsoft.com/en-us/windows/win32/api/wingdi/ns-wingdi-bitmapinfoheader#color-tables.

Now whether this can correctly be converted to a ffmpeg color format,
and what needs to be done for that, i don't know ;)

Cheers,
Dee