[FFmpeg-user] Apply format with overlay and -ss in front of inputfile is strange?

[Carl Eugen Hoyos]

nicolab <robelt2525 <at> gmail.com> writes:

> ffmpeg -f lavfi -i rgbtestsrc=d=10,format=yuv420p 
> -vcodec libx264 rgbtestsrc.mp4
> 
> This is visually rgb color[z] overlayed video.
> ffmpeg -i rgbtestsrc.mp4 -vf 
> split[x][z];[x]format=gray[x1];[x1][z]overlay
> -vcodec libx264 10.mp4
> 
> This is visually rgb color[z] overlayed video.
> ffmpeg -i rgbtestsrc.mp4 -ss 1 -vf
> split[x][z];[x]format=gray[x1];[x1][z]overlay 
> -vcodec libx264 11.mp4
> 
> This is visually rgb color[z] overlayed video, 
> but output file is visually gray.
> ffmpeg -ss 1 -i rgbtestsrc.mp4 -vf
> split[x][z];[x]format=gray[x1];[x1][z]overlay 
> -vcodec libx264 12.mp4

I can confirm that there may be an issue 
but it is not overlay-related:
$ ffmpeg -i input -vf 
"split[x][z];[x]format=gray[x1];[x1]nullsink" 
-strict -2 -vcodec jpeg2000 -ss 1 out1.avi

$ ffmpeg -ss 1 -i input -vf 
"split[x][z];[x]format=gray[x1];[x1]nullsink" 
-strict -2 -vcodec jpeg2000 out2.avi

Since the jpeg2000 encoder supports both gray 
and yuv420p input, the issue is easier to 
explain imo (but I have no expanation)...

Carl Eugen