ProRes422, no 1080p???

[Graeme Nattress]

Sure you could write as 4:1.33 etc. So yes, it's a slightly higer chroma rate than DV's 4:1:1, but to declare it better, is like saying bad is slightly better than worse :-) 4:2:0 is fine for progressive, but horrible for interlace. Depends with which you're comparing.

Graeme

[Anders Holck]

And if you think about it, 3:1:1 in 1440x1080 is actually pretty much equal to the chroma resolution of a 4:1:1 1920x1080 signal, when you compare the Chroma channels of the original HD-SDI input.
with the HD-SDI output.
I believe this was the reason Sony settled on 3:1:1 in the first place. 3x1.333333333 is very close to 4.
So the input subsampler would do a 1.3333333:1 reduction on the Y channel, and a a 2:1 reduction on the Chroma channels.