On Mon, 21 Feb 2005, Steven Boswell II wrote:
> >If you have a progressive frame in 4:2:0, then
> >the first chroma line is the average from lines 1
> >and 2. The second chroma line is the average of
> >3 and 4.
Right - for 4:2:0. The "average from lines 1 and 2" and 'lines 3 and
4' are the ":0" of 4:2:0. 4:1:1 is not subsampled vertically.
> So, if I have a DV file of a 3-2 pulldown of a
If you have a DV file you have 4:1:1 data and not 4:2:0 so there's
no chroma line switching needed.
> 24fps source, and I want to convert it back to
> 24fps, I first have to swap lines 2 & 3 of every 4
> lines of the 4:1:1 color, in order to get the
> progressive-frame color to come out right.
With 4:1:1 all that I think is needed is to undo the 2:3 pulldown to
get rid of the repeated fields. That will give you a 24 (well,
24000/1001 ;)) 4:1:1 progressive image. Then later on when you
convert to 4:2:0 y4mscaler will do the right thing with respect to
the chroma.
> >Of course - but I got a headache the last time I
> >looked at the sources :)
>
> Eeek...I hope the author responds & gives us an idea
> of how feasible this is.
It shouldn't be _too_ hard to use the chroma subsampling numbers
from the stream in place of hardcoded divide by 2 and 4. Perhaps
getting yuvkineco handling 4:1:1 data will be sufficient.
Cheers,
Steven Schultz
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