Change max quantizer value in DivX 5.0.1?

[augi]

The maximum quantizer value in DivX 5.0.1 Pro is 12 by default.Jonny's compressibility tool sets it to 2 when it does it's pass.Should I set it to 2 also when I compress my movie?So far I was using the default value (12) with B-frames and GMC on and no quarter pixels.But I read that increasing the quantizer will result in bad quality.What should I do?

[dragoman]

Hi,

First you need to understand that with DivX a lower quantizer results in better quality, hence the terms "min" and "max" are a bit misleading.

Yes, if you set your "max quantizer" higher the quality overall will be a bit lower, but not necessarily. Here's how it works:

When using two-pass VBR encoding, the 1st pass analyzes every frame according to your desired bitrate and assigns values to each frame. Some frames are easier to encode than others, and thus get assigned a higher quantizer. This means that these easy frames are compressed much more than other, more-difficult frames.

The default max quantizer is 12, which means that through the entire movie you are encoding, the highest quantizer the codec can use for any given frame is 12. Setting this value higher will allow the codec to set a higher quantizer for low-detail frames, which in theory could allocate more bits for the rest of the movie. In this case, increasing the max quantizer could increase the quality of the movie.

However, most often this is not the case. Because of the way divx encodes, setting the max quantizer very high will not result in a quality boost, but a quality loss (for more details email me).

To your question:
The maximum quantizer value in DivX 5.0.1 Pro is 12 by default.Jonny's compressibility tool sets it to 2 when it does it's pass.Should I set it to 2 also when I compress my movie?

No, you should not set your min and max quantizers to 2. What jonny's program is doing is encoding a percentage of the movie at 100% quality (the maximum quality attainable, basically the codec will use a quantizer of 2 for every frame). This is done to measure the compressibility of the movie for a more accurate resolution choice. For more details on compressibility check check the Gordianknot faq.

My recommendation is to play with the settings a little to see what gets you the best results. I have encoded hundreds of movies, and personally I use the default quantizer range (2-12) on most movies, occasionally I drop the max quantizer to 10, but that's it.

Hope I was clear enough...

dragoman