What is adaptive quantization used for?

[puffpio]

I've searched through the forum but can't figure out/find what it does and if I should use it.

I read somewhere that it's source dependant...but dependant on what? When should I be using it?

[mod]

Hi, maybe this will be too simple, but..

see here (http://forum.doom9.org/showthread.php?s=&threadid=73022)

[Yong]

Quote form mplayer/mencoder man page (http://www.mplayerhq.hu/DOCS/man/en/mplayer.1.html):

lumi_mask
Adaptive quantization allows the macroblock quan- tizers to vary inside each frame.
This is a 'psychosensory' setting that is supposed to make use of the fact that the human eye tends to notice fewer details in very bright and very dark parts of the picture.
It compresses those areas more strongly than medium ones, which will save bits that can be spent again on other frames,
raising overall subjective quality and possibly reducing PSNR.

Try to search lumi_mask, dark_mask, tcplx_mask, scplx_mask and border_mask on mplayer man page for more infos. :)

[bond]

stop!

you cant mix up different adaptive quant implementations from different encoders!

This is a 'psychosensory' setting that is supposed to make use of the fact that the human eye tends to notice fewer details in very bright and very dark parts of the picture.
It compresses those areas more strongly than medium ones, which will save bits that can be spent again on other frames,
raising overall subjective quality and possibly reducing PSNR.this is definitely only true for the adaptive quant of xvid but NOT for x264 and ateme/nero

eg x264's current, not stable, aq was written only for reducing blocks in blue sky and dark areas, nothing less nothing more
it does this by using more bits in dark areas. in contrary to what xvid does, by using less bits in dark areas!!!

ateme's aq is again different