How does the 1 Pass quality base encode works?

[duartix]

I'm perhaps double posting now, but it stroke me that the answer is more likely in this forum than in the XVid one. Sorry for that.

But what does a value of 85% quality mean?

I find this option a lot useful to me for encoding music videos since I don't mind about filesize but just getting good enough quality and stuffing a few dozens in a CD.
As a bonus I only have to do one pass.

[obelix]

Constant quality means fixed quantisizer. When you use 100% you get the same result as minquant = maxquant = 2. When you reduce quality (I use 97%) you increase the quantisizers, I guess both of them.

[-h]

1-pass quality mode makes DivX use an 'average quantizer' for the whole clip. Depending on the slider setting, the quantizer could be 3.4, which would actually result in a sequence of frames with quants of (3, 3, 4, 4, 3) repeated.

The formula used to select this 'average quantizer' is:

((16-2)/100 * (100-quality)) + 2

So, a quality of 85% will give:

(0.14 * 15) + 2 = 4.1

So your movies are using quantizers like (4, 4, 4, 4, 5, 4, 4, 4, 4, 4) or thereabouts - no way to be certain, since DivX4 actually uses a random number generator to decide when to change quantizers to reach the desired average.

-h

[DJ Bobo]

I don't know if it's a bug or something, but DivX don't let you change the keyframe setting in the quality mode. And there is also no scene detection in this mode.

So I would recommend to set the wanted keyframe in bitrate mode, then switch to the quality mode.

I think a setting of 5 seconds will be OK, that means:
* 120 for 23,976fps video
* 125 for 25fps video
* 150 for 29,97fps video

[movmasty]

@bobotns
yes is true,why divx 4.12 doesnt let to set max kf interval in quality mode ?????????

@ -h, i guess that you refer to divx 4.12 quality mode?

wmv quality settings works differently,

fixed quantizer, that change every 3/4 numbers...i guess.