Compressibility of over 100%?? (just curious)

[Cynric]

Hi all!
I'm just curious why AutoGK reports a compressibility of 140% at one Movie.. how is this possible and what does this in fact mean? I use a very high filesize of 2.2GB for the 1:40 avi, might this be the cause? AGK says "B Frames switched off", I thought these would raise the quality of the video, so why are they turned off at this large filesize?

ps: great work, len0x! the best dvd>avi converter i ever experienced!:cool:

[Teegedeck]

Compressibility is measured by encoding the file at quantizer=2, which is the lowest level of detail removement and thus the best quality the codec can deliver (not touching upon the issue of b-frames, quarterpixel etc. here). See this related thread (http://forum.doom9.org/showthread.php?s=&postid=622784).

It means that even at quant=2, the result will be smaller than what you aim for. It means you should try one of these steps (in that order):
1) throw out denoising filters
2) choose a bigger resolution (quite drastically bigger if compressibility is above 100%)

Choosing too low a resolution is a typical beginners' mistake which deprives you of the quality that XviD could deliver. (Had you not tested compressibility, you might not even have realized that you could go for unfiltered/higher resolution because XviD will usually prevent undersizing by just using quant=1 which doesn't look better than quant=2 but eats quite into bitrate.)

So if you get a compressiblity above, say, 80% you should better do something about it.

[Cynric]

hmm.. thanks a lot! i already use the dvd's full resolution for the movie (width of 720) and no denoising filters.
how can i now find out which is the max filesize to use for a highest quality result? or is there some option for autogk to stick to quant=2 and leave the file as big as it gets then?
wanted to backup all my LOTR special extended dvds on one dvd-r per movie (which normally need 2 dvd-9 each)

thanks for suggestions!

[Teegedeck]

Using AutoGK you are not using the DVD's full resolution at 720x. DVD resolution is 720x576 (for PAL) anamorphic, which means it gets resized to something like (bond, don't kill me...) 1024x576 by DVD players on the fly. Auto GK on the other hand doesn't offer you an option to also encode anamorphically but at a horizontal res of 720x just shrinks the vertical resolution to something like 400.

So you would be using the maximum resolution if you increased the zoom till the indicator for vertical resolution hits '100%', regardless of the indicator for horizontal resolution reaching more than 100%.

You could also think about using a high-bitrate matrix then, like SixOfNine. This would drastically blow up filesize but also raise quality.

[niamh]

or is there some option for autogk to stick to quant=2 and leave the file as big as it gets then?

I believe it's the quality slider (do I remember well?). Put it at 100%.

I'm not sure you can use your own matrices in autoGK, but if you don't want to go manual, you'll have to live with a smaller filesize :)
Personally I'd go the teegeedeck way and use SixOfNine, but then I use SixOfNine regardless ;)

[Sharktooth]

Blow up the resolution to 1024x*** and place a file called ".sharpmatrix" (without quotes) in the movie folder then try again.

[BigDid]

Originally posted by Sharktooth
... place a file called ".sharpmatrix" (without quotes) in the movie folder then try again.
Hi Cynric,

Above 1cd size, AGK will try by default to use a sharpmatrix; if not used softer matrix mention will show in log.
Can also be triggered by ctrl-F9 option.

Did

@ Sharktooth, OT, 31 words, difficult for me to seem clear :cool:

[Sharktooth]

:p

[Cynric]

thanks guys, working fine now, quality is awesome :D
main reason why i couldnt complete the rendering before was my damn cpu, making lots of mistakes due to too few volts... now set the right voltage (damn last bios update lost it) and agk is runnig fine since yesterday, producing perfect avis :)

@niamh: oops...my fault...never recognized, there was a quality percentage button ;)