Revisited this chost after dinner and managed to hack my way out of using intermediate files and ImageMagick. As follows:
ffmpeg -ss $STARTTIME -an -sn -i "$VIDEOIN" -filter_complex \ 'format=gbrp,extractplanes=r+g+b[cR][cG][cB];\ [cR]setpts=PTS+$((TIMESTEP * 0))/TB[sR];\ [cG]setpts=PTS+$((TIMESTEP * 1))/TB[sG];\ [cB]setpts=PTS+$((TIMESTEP * 2))/TB[sB];\ [sG][sB][sR]mergeplanes=0x001020:gbrp[outGBR]'\ -pix_fmt yuv420p -map '[outGBR]' -an -sn -map_metadata -1\ -frames:v 1 -y rgb_test.png
Turns out there is a planar """RGB""" format supported, it's GBRP. No math for me, cheers and thanks!
You can also make a short clip with this same general technique (or by using a factor for adjusting SETPTS instead of an offset.) Example above. Scene changes are a nightmare this way though, so be careful about that.
