[FFmpeg-user] Causes of color bars?

Marton Balint cus at passwd.hu
Tue Jul 14 10:53:42 EEST 2020

On Mon, 13 Jul 2020, Simon wrote:

> I think I have determined that as far as ffmpeg is concerned there is no
> input. I added the flag -color_bars false, which I believe tells ffmpeg not
> to display color bars in response to lost input. Sure enough, the color bars
> went away. I interpret this as telling me that there was no signal, as
> opposed to there being a signal that contained color bars.
> So now, assuming my logic is sound, my question would be how can ffmpeg
> detect the connected signal is present (it "knows" which channel is "live")
> and yet not read the video signal?

Detection of format (resolution, frame rate) is implemented in ffmpeg, but 
maybe not the detection of pixel format (rgb, or yuv420/422/444). Maybe 
your HDMI signal is RGB and that is the reason it is detected as no 
signal... I'd start experimenting with -raw_format rgba and see if it 
makes a difference.


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