N-pass encoding

[barazuk]

Below I see thread about 1-pass.

How about supporting 3,4-pass encoding, exist in DivX?

I try to use it, but cann't notice substantial visual quality enhanchement. Filesize changed, and I suppose (I hope:) ), that bitrate distributed more accuracy, than in 2-pass encoding.

It is not perceptible only by me, or by all readers that tried more then 3 passes?

How objective criteria may be used to evaluate quality enhanchement and necessity of further passes?

Is support of 3,4-pass encoding in AutoGK necessary / desirable / needless / harmfull?

Just note, that simple (not based on bitrate distribution on passes) this support not need too much time to built-in ;)

[jggimi]

N-pass encoding has been discussed ad naseum in Doom9's DivX Encoding forum. We've had members who've run tests with many passes. Please search for "n-pass" or "multipass" in that forum for much more information.

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From the DivX User Guide (http://www.divx.com/divx/divxpro/guides/), page 40:"Although it is possible to run as many nth passes as you like, 98-99% of the optimal quality is typically obtained in three passes or less..."Note that Doom9 follows suppliers' recommendations when conducting his MPEG-4 Codec Comparisons (http://www.doom9.org/codec-comparisons.htm). With DivX 5.11 he used:Slow mode, slow psy settings and no profile (b-frames are enabled though) With DivX 5.9 Fusion he used:Home theater profile, Balanced mode with 1-bframe for the first pass, Insane Quality mode for the 2nd pass, optimized H.263 quantizers and psychovisual: Shaping.AFAIK, no more than 2 passes were used with any MPEG-4 codec he's tested to date.

[barazuk]

From the DivX User Guide, page 40:

"Although it is possible to run as many nth passes as you like, 98-99% of the optimal quality is typically obtained in three passes or less..."


So, if developers recomends tree as maximal number of passess... May be supported this number?

[jggimi]

You missed misunderstood what I wrote below that. Let me clarify. Doom9 used only two passes for his codec comparisons. AFAIK, DivX Networks did not specify 3 or more.As in previous comparisons, codec makers were contacted two weeks prior to the start of encoding, and asked to provide a codec build to be tested, along with the suggested settings for my three movie sources. I have gotten suggested settings for every contestant, so if you think other settings would've yielded a more favorable result, you are more than welcome to take it up with the codec makers (and not with me.. I only used what I was told to).