[XviD-devel] chroma down-sampling

[Michael Niedermayer]

Hi

On Monday 21 October 2002 15:39, peter ross wrote:
> hello,
>
> [warning: --pedantic]
> is anyone familar with (progressive) chroma sampling, because iam
> wondering if a round-up average is better than a round-down average?
> in order to convert yuyv->yv12, the conversion function must down-
> sample (or halve) the chroma info.
>
> for those unitiated: yuyv/rgb specifies chroma on each line, whereas
> yv12 (4:2:0) specifies chrom on every second line.
>
> ive seen three ways to perform sampling: (c1 and c2 represent adjacent
> yuyv chroma lines)
>
> * simply use chroma=c1, and ignore each second line of chroma.
>   i believe ffmpeg/mplayer does this.
mplayer has both fast (ignore c2) and accurate (with various filters like 
linear & cubic downsample filters) 

[...]

Michael