Optimal "Max I frame Interval"

[ripper64]

Hello,

what value for the setting "Maximum I Frame Interval" should I use? I use only PAL DVD's.

Why not set this setting to as high as possible, than you get only I frames at scene & angle changes, isn't that good for quality?

PS:
Adaptive Quantization: Hot or Not?

[communist]

Read the FAQ / Use the search function :o

For PAL set it to 250 (10s).
-Maximum I-frame interval: This setting tells the codec to insert a Keyframe (I-frame) every {value} frames. If a Keyframe is needed before that number is reached, the codec starts counting again. So while you can have Keyframes with lower intervals than the number you defined, you can't have higher intervals.
Standard recommended settings are 10x the framerate, i.e. 250 for 25 fps PAL clips, 300 for 29.979 NTSC clips etc. However, there is a visible effect called Keyframe-pumping. This resembles a slow degradation in quality in consecutive P- and B-frames with a sudden 'jump' in quality when a new Keyframe is inserted. Lowering the maximum I-frame interval in these cases can help. Setting it too high can cause bad seeking in files, because the seeking process uses only Keyframes, and less Keyframes=less accurate seeking.


As for AQ - there is thread about it :
http://forum.doom9.org/showthread.php?s=&threadid=79238

[ripper64]

I heard that AQ isn't very effective and sometimes even downgrade the quality, is this true?

[Sharktooth]

How about to :search: ?

[ripper64]

What topic then?

[Dams]

@communist or someone else : in which topic, we can found the sentences on max iframe interval ??

[Sharktooth]

In the FAQ or XVID guides.

[unmei]

about the AQ quality: i think you read that in a cartoon/anime related discussion.

[ripper64]

Originally posted by Sharktooth
In the FAQ or XVID guides. I've read the'm all, but they only give the definition of Adaptive Quantization, and I just want to know if it's recommended.

[piscator]

It's impossible to give a recommendation. First of all, it depends on your own (subjective) preferences. And if you find it useful or not also depends on the chosen bitrate and the movie's compressability. So why don't you experiment yourself a bit and see what you like? If you don't like to experiment, use the settings in the Doom9 guide. Make sure to read crusty's FAQ in the sticky or the DivX Guide (http://download.divx.com/divx/DivXUserGuide52.exe). The DivX guide explains the different MPEG4 settings well. Note that AQ is 'more or less' the same as PsychoVisual Enhancements in DivX.

greetz,
Piscator

[Soulhunter]

About I-frames:

Originally posted by sysKin

I don't get it - you want *more* i-frames? Why? The more i-frames the lower your quality. You only ever need them for seeking in the file, and if you don't want to seek, you don't want them at all...

[Bruce Willis]

in AVImux, in the in/output settings, there is a checkbox 'create legacy index'. Does it enable searching without the use of keyframes?

BTW i never force keyframes myself, because of the pumping effect

i never use AQ, because it's ugly as hell

:)