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

[Robert Krüger]

On Wed, Aug 26, 2015 at 11:28 AM, Paul B Mahol <onemda at gmail.com> wrote:

> 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.
>

Thanks. I created ticket 4805. This also happens when using swsscale
directly using the api, which is where I ran into it. I just used the
command line to verify this. So the ticket is more general.