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

[Paul B Mahol]

On 8/26/15, Robert Krueger <krueger at lesspain.de> wrote:
> 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.

Looking at code and if I'm not missing something it's just not implemented to
be used like that, perhaps better to fill bug report.