chroma optimizer and i frame boost?

[gnr]

is chroma optimizer (zone options) good for whole movie (not only the credits) encoding. and 2nd pass option i-frame boost (default 10) controls quality? should i leave it as default for all movies or need to change it sometimes.

thanks in advance.

[Jawor]

Originally posted by gnr
and 2nd pass option i-frame boost (default 10) controls quality? should i leave it as default for all movies or need to change it sometimes.

Values from 0 to 10 usually work fine. Setting it too high may result in so called keyframe pumping - sudden jumps of quality when I-frames are displayed.

[gnr]

did u mean setting it to 0 would be better and good for quality?

thanks

[thoralf]

Originally posted by gnr
did u mean setting it to 0 would be better and good for quality?

Leaving these settings at their defaults is probably a good idea. If you want max quality, you should go for a one-pass encode with a constant quant of 2 ...

With kind regards,
Thoralf.

[Jawor]

Originally posted by gnr
did u mean setting it to 0 would be better and good for quality?

I didn't notice a big difference between 0 and 10.

Originally posted by thoralf
Leaving these settings at their defaults is probably a good idea.

Yeah, there's nothing wrong with the default setting.

[gnr]

thanks for the reply. what about chroma optimizer for whole movie, ever tried?

[Jawor]

Chroma optimizer blurs colors in very dark and very bright areas where the human eye can't notice it, thus the codec can achieve better compression in these areas. sysKin, is my translation of your explanation at http://www.divx.howto.pl correct?

I never tried to use it for the whole movie. Perhaps I should try

[sysKin]

Originally posted by Jawor
Chroma optimizer blurs colors in very dark and very bright areas where the human eye can't notice it, thus the codec can achieve better compression in these areas. sysKin, is my translation of your explanation at http://www.divx.howto.pl correct?

Yes, that's what it does.
Also explained in Crusty's FAQ if I remember correctly.
It's not a problem if you use it for whole movies - I *think* I do that

[Jawor]

Originally posted by sysKin
Also explained in Crusty's FAQ if I remember correctly.

The explanation in Crusty's FAQ says:

-'Chroma Optimizer enabled' will do some extra magic on color information to minimize the stepped-stairs effect on edges. It will improve quality at the cost of encoding speed. It reduces PSNR by nature. The mathematical deviation to the original picture will get bigger - but the subjective image quality will raise (as mentioned, the "stair step artifacts" get less). Since it works with color information, you might want to turn it off when encoding in greyscale.

That's why I told the guy at DHT that chroma optimizer reduces the stepped-stairs effect ("schodkowatosc").

[gnr]

Originally posted by thoralf
Leaving these settings at their defaults is probably a good idea. If you want max quality, you should go for a one-pass encode with a constant quant of 2 ...

i always do 1cd rip, setting i frame boost to 0 will save some bits and those saved bits will be distrubute where necessary to improve quality. plz correct me if i am wrong.

[lordadmira]

Yes but there are reletively few key frames, so giving them a little more data won't affect much overall. It will actually increase quality since all those P and B frames will be predicted off those higher quality I frames. The benefit is greater the fewer key frames there are.

I leave chroma optimizer turned on as a standard default for all my encodes.

LA

[gnr]

thanks Jawor, thoralf, sysKin, lordadmira for the time, really appreciated.