[FFmpeg-user] scale filter does not do anything when only color matrix is changed

[Robert Krüger]

Hi,

I created two files using these command lines:

ffmpeg -i fcp7_xdcam_ex_1080_25p_1s.mov -vf
scale=in_color_matrix=bt709:out_color_matrix=bt601 -c:v ffv1 -an
scale_test_bt601.nut

ffmpeg -i fcp7_xdcam_ex_1080_25p_1s.mov -c:v ffv1 -an
scale_test_unscaled.nut

Using framemd5 I verified that the resulting output is identical. Is this
some sort of optmization of swsscale (i.e. not doing anything when size and
pixel format remain unchanged)? Can it be forced to do the conversion
anyway? I know that there is also vf_colormatrix but that is much more
limited than swscale and it's not LGPL.

Thanks in advance,

Robert