Which is better 4:1:1 or 4:2:0?
 

Please help me understand. Which is better 4:1:1 or 4:2:0?
I know NTSC dv uses 4:1:1 AND PAL dv uses 4:2:0. I have also heard the new AVCHD uses 4:2:0.

They both subsample the color channels 4:1, just in different patterns. I think in general 4:2:0 will be more pleasing, since it's equally inaccurate in H and V directions.

MPEG-2 also uses 4:2:0, so NTSC DVD's are 4:2:0 as well. Which means that 4:1:1 shot footage converted to MPEG-2 is sort of taking one problem and massaging it into another problem.

Adam Wilt seems to disagree (at least as far as multigeneration work in 4:2:0 vs. 4:1:1):

"The theory here is that by evenly subsampling chroma in both H and V dimensions, you get a better image than the seemingly unbalanced 4:1:1, where the vertical color resolution appears to be four times the horizontal color resolution. Alas, it ain't so: while 4:2:0 works well with PAL and SECAM color encoding and broadcasting, interlace already diminishes vertical resolution, and the heavy filtering needed to properly process 4:2:0 images causes noticeable losses; as a result, multigeneration work in 4:2:0 is much more subject to visible degradation than multigeneration work in 4:1:1."

http://www.adamwilt.com/DV-FAQ-tech.html#colorSampling

As Joshua pointed out 4:1:1 is a pain for DVD's.

4:1:1 encoded to a DVD becomes 4:1:0 which is disgusting chroma. This is because with 4:1:1 every line has a new sample 4 pixels wide. Every line however does have a new value of chroma. 4:2:0 on the other hand alternates every other line. So when you encode 4:1:1 video to a 4:2:0 DVD every other line throws out the chroma information making it a 4:1:0.

It is true however that interlace does not do as well with 4:2:0. It is hard to have an interlaced source use a block that is 2x2 pixels in size since every other line is actually a new moment in time. With progressive video 4:2:0 is far superior.

If you do not plan on rendering multiple generations of your 4:2:0 source then you shouldn't have anything to worry about. If you do need to do some heavy effects work use a different format such as uncompressed. You will not gain any chroma detail but you also will not loose any with multiple generations of 4:2:0.

If second generation means encoding to DVD then the slight loss from 4:2:0 will be much much less then the loss of dropping down to 4:1:0.

This is yet another reason why 4:2:2 is better and not just for keying. 4:2:2 allows you to go in any direction in terms of format or compression without any loss beyond the limits of that format.

Besides 4:1:1 is kind of a dead format if you think about it. Really the only thing in the world that uses 4:1:1 is NTSC DV. PAL DV, digital broadcasts, both flavors of HDV, DVD and pretty much every internet format all use 4:2:0.

John,

I certainly won't disagree with Adam, but his point is about multi-generational use.

From a pure format perspective, if you take a 4:4:4 image and convert to 4:1:1 and 4:2:0, the 4:2:0 is more pleasing, in my opinion. If your destination is MPEG-2, 4:2:0 is a theoretically better acquisition format, since the color space is the same.

Josh

I agree with you. I was just offering additional information for Mike Tesh since he didn't indicate much in his question, "Which is better 4:1:1 or 4:2:0?".