How to figure Quality percentage

[ChrisBensch]

Normally using AutioGK for DVDs, I set the quality mode to 75% (DivX5/6) and just let AutoGK work it's magic. Now I'm encoding HDTV streams and would like to achieve the same quality level. How can I use the DivX 6 "quality based" encoding option to ensure I'm getting around 75%? I'm not sure what Quant to use to achieve something close. Any ideas of how to figure that out?

[ChrisBensch]

I've done some side-by-side comparisons of Matrix Revolutions at Quant=2 and Quant=3, and I can't really tell the difference. The only major thing I see is the Quant=3 encode is about half the size of the q=2 (4.8GB vs 8.5GB). I'm sure there are some differences, I guess I'm just torn between multipass encoding and singlepass quality based encoding...too many opinions.

[jggimi]

Download "The Official DivX® 5.2 User Guide" from http://www.divx.com/divx/create/divxpro/guides/ -- you can read up on the different encoding options in detail. The guide is well written, shows graphical examples, is available in four languages, and is fairly well hidden from the casual web browser now that DivX 6 has been released.

[ChrisBensch]

Although your link was useful, it still doesn't address my question. My question is how to determine a percentage of quality, ie. AutoGK allows you to set 75% quality...how is 75% determined?

[stephanV]

Defining quality in percentages is plain wrong and misleading. It probably determines it by deviding your target bit rate by the bit rate obtained by a q2 encode or something.

[jggimi]

AGK uses 75% as the default.

You may change the percentage. Both DivX and XviD will convert your requested percentage into a quantizer value for single pass encoding.

[ChrisBensch]

Alright, so I guess now that I've done all this, and read and reread the guides...I have a possibly dumb question: Will quality be truly higher encoding with quant=2, or with a 3-pass fixed bitrate (ie 4Mbps to fit profiles)?

[stephanV]

You cant go much higher in quality than a quant 2 encoding. If 4Mbps will be better depends on too many things to not give an ambigious answer on this.