VAQ: Making Xvid's Adaptive Quantization Not Suck

[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?

I did some tests with wizboy11’s binary and short clips (10000 frames) from five PAL DVDs.

Originally Posted by Xvid_Encraw

-cq 2 -qmatrix "Heini MR.xcm" -bquant_ratio 100 -bquant_offset 100 -qpel -bvhq -zones 0,w,1,O
-lumimasking added for VAQ encodings.

File sizes (in Matroska container)

           |   size (KByte)   | Diff. | Diff. by frame type (%)
sample     | VAQ off | VAQ on |   %   |   I   |   P   |   B
-----------+---------+--------+-------+-------+-------+--------
1 dialogue | 100958  |  87338 | -13.4 | -11.3 | -23.0 | +7.5
-----------+---------+--------+-------+-------+-------+--------
2 night    | 186572  | 169400 |  -9.2 |  -8.6 | -14.2 | +2.7
-----------+---------+--------+-------+-------+-------+--------
3 CG       | 180319  | 156962 | -13.0 |  -9.5 | -19.9 | +5.1
-----------+---------+--------+-------+-------+-------+--------
4 action   | 246899  | 218558 | -11.5 |  -8.1 | -16.3 | +2.0
-----------+---------+--------+-------+-------+-------+--------
5 noisy    | 460090  | 403804 | -12.2 | -10.9 | -18.6 | +2.9

Not much to say about visual quality. There’s hardly ever any significant difference between VAQ clips non-VAQ ones. And then only when comparing still frames. So ~10% smaller files without quality or speed drop. I think I might like that.