[FFmpeg-user] rgb8

[Michael Koch]

Am 30.05.2023 um 14:13 schrieb Paul B Mahol:
>
> rgb8 is as obvious from ffmpeg output:
>
> IO... rgb8                   3              8      2-3-3
>
> It means RED get 2 bits, GREEN get 3 bits and BLUE get 3 bits.
> It is using 1 byte, same like gray format.

I have a ASI178MM camera. This camera is normally used for astronomical 
observations with special software. But there does also exist a 
DirectShow driver.

I checked the options with this command:

ffmpeg -list_options 1 -f dshow -i video="ASI178MM Camera (ZWO Design)"

This is the output:

[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=3096x2080 
fps=1.0842e-12 max s=3096x2080 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=1280x960 
fps=1.0842e-12 max s=1280x960 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=1280x800 
fps=1.0842e-12 max s=1280x800 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=1280x720 
fps=1.0842e-12 max s=1280x720 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=1024x768 
fps=1.0842e-12 max s=1024x768 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=1024x600 
fps=1.0842e-12 max s=1024x600 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=960x960 
fps=1.0842e-12 max s=960x960 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=800x800 
fps=1.0842e-12 max s=800x800 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=800x600 
fps=1.0842e-12 max s=800x600 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=800x480 
fps=1.0842e-12 max s=800x480 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=768x576 
fps=1.0842e-12 max s=768x576 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=720x480 
fps=1.0842e-12 max s=720x480 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=640x480 
fps=1.0842e-12 max s=640x480 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=480x320 
fps=1.0842e-12 max s=480x320 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=320x240 
fps=1.0842e-12 max s=320x240 fps=30
[dshow @ 00000203f5b315c0]   pixel_format=rgb8  min s=320x200 
fps=1.0842e-12 max s=320x200 fps=30

As you can see, the only available pixel format is rgb8. This is very 
strange, because it's a monochrome camera. I think this is a bug in the 
DirectShow driver, and the pixel format is in fact 8-bit gray.
To confirm this, I did write a raw frame from the camera to a file:

ffmpeg -f dshow -video_size 1280x800 -framerate 5 -pixel_format rgb8 -i 
video="ASI178MM Camera (ZWO Design)" -f rawvideo -frames 1 -y test.raw

Then I did read this file, assuming that the pixel format is gray:

ffmpeg -s 1280x800 -pixel_format gray -f rawvideo -i test.raw -y gray.png

The result looks correct. Is it possible to do this in one command line? 
I mean just tell FFmpeg that the pixel format isn't rgb8 but gray, 
without making any modifications to the data?

Michael