[mikeash]

Just a nitpick, JPEG always encodes the color channels at half resolution. It's amazing how difficult it is to notice this, though.

[brigade]

No, there are 4:4:4 and 4:2:2 modes in JPEG.

H.264 also defines such modes, but no consumer hardware decoders support them so they aren't commonly used.

[mikeash]

My mistake, I must have been going off what's common versus what's allowed. Thanks for pointing it out.

[dunham]

Apple's jpeg animation hack used 4:4:4 so the blocks wouldn't interfere with each other. It's a neat hack, worth reading about if you haven't seen it yet: https://docs.google.com/document/pub?id=1GWTMLjqQsQS45FWwqNG...

[mikeash]

Holy moly. What a hack.