DC component precision in Tmpeg...

[Cox_Joe]

I have found that the DC component precision can be increased (8 to 9 to 10 bits) to get more quality in TMpeg, but if i increase it do my SVCD will be full compatible with the standard ?

I think it's an interresting question that can help a little bit people complaining about SVCD quality.

Thanx to all VCDhelp.com members and moderators

[a]

VCD supports only 8 bits, SVCD 8-10 bits. I'd be stumped to find an SVCD compatible DVD player that didn't support 10 bits, as it is included in the standard (and is also required by the player for DVD compatibility). Using 10 bits is also recommended, as it doesn't really grow the filesize that much.

.a

[BJ_M]

i also say 10 , but in some cases better quality dvd is from setting at 9 - this is true , but based on type of content .. check a lot of dvd's - they are done at 9 ..

[a]

Well hey, this is getting interesting :) What kind of content would give better quality and 9-bit precision rather than 10-bit? Any guidelines? I always do my encodes @ 10 bits and haven't even thought of this possibility, and I'm not too picky about overkill as long as I'm not actually degrading quality.

.a

[adam]

It is not recommend that you use 10 for SVCDs. Higher DC precision uses up your bitrate and, since your bitrate is limited with SVCD, this ends up hurting more than it helps. With low bitrate, under ~4mbits, you will actually get better quality with 8.

If you read the CCE manual it talks about this. CCE has an auto DC precision setting which adjusts this level according to the complexity of the scene and according to your bitrate levels. It says that lower dc will be applied to low bitrate scenes and high dc will be applied to high bitrate scenes, and in the same sentence it defines "low bitrate" as being anything under 4mbits. Any DC higher than 8 is probably not appropriate for SVCD except in extremely smooth scenes with little movement. So if you are using CCE then you can use its auto DC precision setting and achieve this result but if you use TMPGenc then leave it at 8.

[sammie]

I have also read several places that for TMPEGenc to leave it at 8. No real supporting info though. I'd love have a better understanding exactly what it does.

[BJ_M]

i got mixed up and was talking about dvd - not svcd .. so what adam says i concur with ..

i realize all over the web there are guides that say put it at 10 for everything , but i don't think people really understand exactly what this setting is and just assume higher must mean better.

[a]

Well, TMPGEnc just says "the higher precision, the smoother movie", so I just went on with that. I might actually do a test encode to see how much the settings differ, unless someone's done that already.

.a

[BJ_M]

the people at main concept also say to set it up as CCE does .. they suggest 9 for most dvd's ..

please let us know what your tests show ..

[sammie]

Just got a response from MainConcept support. They said low (8) precision would be best for low bitrate DVDs. Most (average and high bitrate) DVDs would benefit from higher numbers, 9 as suggested above or even 10 in some cases. They gave a blurb for checking something called I:mquant in their log to optimize the setting. Prbobably won't help anyone here sicne most folks don't use MainConcept. But the group at MainConcept seem pretty responsive and their advice has been pretty good so far so I think it's a good starting point for anyone wanting to do experiments. I presume that the setting means the same thing in the various encoders. If anyone can do some quick experiments bitrate appears to be a parameter to keep in mind.

[BJ_M]

they have some major talent at Main Concept -- some real pioneers in both video app and encoding .. in fact some of the best in the field .. i think Main Concept has very lofty plans .. anyway -- what they say I tend to listen to ..
yes - what you mentioned is posted on thier forum

[Cox_Joe]

thanx every one !