preset question

[firered]

what dose the @q=3 mean? and where in xvid is it at? and is it for 1st or 2nd pass?

Also Im not sure if im using the presets correctly but for some reason half way through the movie it becomes grainy and blurry, half of the movie is clear and sharp and then when its in the middle it becomes grainy and blurry what am i doing wrong

[neutrogenik]

@q3 means encoding at a constant quantizer : 3 and it's generally used for 1 pass (regardless of the filesize).

http://img444.imageshack.us/img444/5696/clipboard017bi.jpg

What do you want to do : having the best quality for a precise filesize or having the best quality whatever the size ?

[firered]

@q3 means encoding at a constant quantizer : 3 and it's generally used for 1 pass (regardless of the filesize).

http://img444.imageshack.us/img444/5696/clipboard017bi.jpg

What do you want to do : having the best quality for a precise filesize or having the best quality whatever the size ?


yea having the best quality for a precise filesize? I also thought the presets were for 2 pass encoding?

[neutrogenik]

use general purpose presets, i was using custom for some tests :)

If you want best quality then yes, 2-pass encoding is the better, it looks for the best bitrate at 1st pass then encode at 2nd pass using 1st pass informations.

[foxyshadis]

The blurriness sounds like you're targeting a bitrate, and eventually rate control kicks in and limits the later bitrate severely to make up for all the extra that the beginning used. (Which is why you want to target a quantizer if you're going for pure quality.)

[firered]

The blurriness sounds like you're targeting a bitrate, and eventually rate control kicks in and limits the later bitrate severely to make up for all the extra that the beginning used. (Which is why you want to target a quantizer if you're going for pure quality.)

but the target quantizer is only for 1 pass mode correct?
And the presets metioned in these boards are for 1 pass or 2 pass modes?

[foxyshadis]

Either. The highest quality ones only need 1-pass, the lower ones can be both but 2-pass will usually see a better quality distribution.

[firered]

what about the presets metioned on this board do they need 1 or 2 pass

[Teegedeck]

What preset have you been using? It seems to indicate that I haven't set the quantizer restrictions tightly enough. Because otherwise you'd get a severely oversized file but not a movie that goes bad halfway through.

Thanks for testing.

Two-pass aims at gettig the best out of a given, restricted filesize. It gets more important the smaller that filesize is. If you don't need to reach a specific filesize, constant quantizer is better.

BTW, the presets read like '1st pass at const. quant=3'! You set that quantizer as a zone in the first pass. For the second pass you have to change that back to 'weight=1'.

This means, the presets were meant for two-pass.

Of course you can also use the presets for constant-quantizer encoding but it makes little sense. The quantizer restrictions won't work then, so that quality cannot be guaranteed.

[firered]

I have been using these presets

normal extreme compression: VHQ=1, AQ, EQM v3 ULR, 1st pass @q=4, curve-compr. H30, L15, quantizer-restrictions min. 4, max. 7
slow extreme compression: VHQ=4, VHQ for b-frames, AQ, EQM v3 ULR, 1st pass @q=4, curve-compr. H30, L15, quantizer-restrictions min. 4, max. 7
normal strong compression: VHQ=1, EQM v3 LR, 1st pass @q=3, curve-compr. H20, L7, quantizer-restrictions min. 3, max. 6

[Teegedeck]

Thanks, more 'restrictive restrictions' are about to follow.

[firered]

so what should I do?

[Teegedeck]

It seems you were aiming for a too-low filesize. Either that or you have accidentally set a zone with a high quantizer to start in the middle of the movie. Like, a forgotten credits-zone from a previous encoding.

I guess it's about time for me to devise a general compressibility-test that'll make it easier for everyone to guess what preset to use.

[firered]

It seems you were aiming for a too-low filesize. Either that or you have accidentally set a zone with a high quantizer to start in the middle of the movie. Like, a forgotten credits-zone from a previous encoding.

I guess it's about time for me to devise a general compressibility-test that'll make it easier for everyone to guess what preset to use.

let me know ill be happy to test anything new using your presets

[Teegedeck]

Here's a first attempt at a compressibility-->preset table. (http://forum.doom9.org/showthread.php?p=796900#post796900)