efficiently downscaling subsampled video to full resolution chroma

[Douglas Bagnall]

hi

My element wants to analyse small video frames with the luma and
chroma planes at the same resolution. The source video has subsampled
chroma.

If I scale the video first (i.e. videoscale ! videoconvert), I lose
chroma information because it goes down to half resolution before
being scaled up. If I convert the chroma first, I waste time doubling
the large chroma planes just to shrink them again.

I'm guessing I have to do the latter and just not worry about it. Is
that the case?

regards
Douglas Bagnall