Quote:
Originally Posted by Brother John
This is fantastic news! Thx for that patch, Dark Shikari. Now, there’s no chance you might get super-bored and port CRF to Xvid?  |
CRF wouldn't work in Xvid except at high quantizers; if your video is mostly QP2, the only thing you can do is drop a frame to QP1 (waste of bits) or raise it to QP3; not much leeway. H.264's logarithmic quantizer gives one vastly more room to do such a thing.
Xvid has really really nasty restrictions on quantizers. From what I recall:
1. A "DQuant" block is a block that has a different quantizer from the previous block. In the case of VAQ, this would be an edge block, for example.
2. DQuant blocks cannot have a difference of more than +/- QP from the frame QP (I think).
3. DQuant blocks cannot use 4mv. (WTF? Why?)
4. DQuant blocks cannot use GMC. (WTF? Why?)
5. B-frames have even weirder restrictions on quantizers.
6. The quantizer scale as a whole is crap. It has less quantizer resolution at high qualities, and high quantizer resolution at low qualities (i.e. the difference between 1 and 2 and 3 is much bigger than the difference between 25 and 26 and 27). The only real reason other than simplicity to lower quantizer resolution is to save bits when encoding QP_deltas... but
this means you spend more bits on QP_deltas at lower bitrates, where it actually matters, but fewer bits at higher bitrates, where it hardly matters at all. How senseless.