Black & white movie - should it turn out smaller or larger than normal?

[a13antichrist]

I'm trying to flask the movie "Pi"... I figured since it was b&w it would come out great at a much lower bitrate than normal.. but in fact it came out twice as big as usual - 3Gb for the 83 minutes of the film when the source vobs themselves are only 5gb. Is there any way I'm going to be able to get this thing down to a reasonable size, or is black & white out of the question?

Settings I used are:

DivX codec 4.12, 1-pass
1200kpbs, min quant. 2, max quant. 4
Radium MPG3 128kpbs

Flask 0.6

These are the same settings I've used for every other movie so far, except that I normally use 1800 rather than 1200.

[a13antichrist]

Not all at once now, guys..

[UncasMS]

b&w or colour doesnt matter at all - they will be just as big.
all else is a matter of settings.

[setarip]

Sorry to disagree with the moderator, but from my own experience B&W videos do, in fact, compress less than do color videos. I guess that with the limited (maximum 256) gradations, ther are, logically, less compressible.

[a13antichrist]

Uncas if it is indeed just a matter of settings, how come the output file at 1200kpbs is twice the size of my standard rips at 1800?

setarip should I be seeing this much of a difference though? & is there any chance of finding a way around it?

[khp]

This has been discussed before

http://forum.digital-digest.com/showthread.php?s=&threadid=1433

With all other things beeing equal BW movies compresses slightly better than color movies.
But due to the different nature of BW movies (worse image quality
poor camera control) BW movies might somtimes compress worse than newer quality movies.

[khp]

1200kpbs, min quant. 2, max quant. 4

If u want the divx4 codec to work well at 1200 kbs u should use a much higher max quantizer. Unless u are an expert I strongly recommend always using the default value 12. This alone may well explain ur problems.

I'am not familliar with the movie PI, if it's a cartoon this may also contribute to ur problems.

[khp]

These are the same settings I've used for every other movie so far, except that I normally use 1800 rather than 1200.

This also explain alot, with MQ=4, the codec can't go anywhere near 1200 kbs, but with 1800 it works better.

Quantizers override bitrate settings, so in general if u have problems with files comming out much larger than expected raise the MQ this will allow the codec to compress the source more.

Sorry about the multiple post.

[a13antichrist]

Isn't the thing with cartoons because of the bright colours & very sharp edges where the change in image is greatest? With a b&w film that should be reduced, rather than accentuated... no?

As it happens it's not a cartoon anyway.. it's a film by the same director as Requiem For A Dream..

Okay well I'll try it again at 1200 & 2-8.. I don't normally do any movies at less than 8 MaxQ because I was under the impression that that was basically turning it into the Fast Motion Codec.. & this movie is definitely not an action movie...
Anyway thanks for your replies..

[khp]

Okay well I'll try it again at 1200 & 2-8.. I don't normally do any movies at less than 8 MaxQ because I was under the impression that that was basically turning it into the Fast Motion Codec..

This is true, but should be solved by using 2-pass encoding instead of playing with the quantizers. That will give u the best (OK maybe more like a compromize) of both worlds, decent lowmotion quality and good filesize prediction.

[UncasMS]

@ setarip

would be pretty boring if we all agreed


from my experiences b&w didnt turn out to be much different to colour films.
on the other hand, it is impossible to really judge, since you will hardly have the chance to compare the same movie in colour or b&w

moreover, i'm not using divx4 but nandub and always reach my desired fiesize (or get a smaller one, if the movie is saturated).
thus i dont dare judging the specific settings you took but still believe that it is more or less a matter of settings.

[setarip]

To UncasMS

"would be pretty boring if we all agreed"

There'd also be no need for forums ;>}

[a13antichrist]

Re: To UncasMS

Originally posted by setarip


There'd also be no need for forums ;>}

Sure there would be.. we still need you lot to teach us kids who don't know bugger all...

Uncas I hope you're right about it being aboutt he settings because I've done 50+ DVD -> rips and NEVER have I had a single one be more than 2.1Gb.. even Meet Joe Black I managed to fit onto 3 CDs with DVD quality. THis is the very first B&W I've tried - whatsmore, it's only 90 minutes - & it comes out more than twice the size of almost every other film I've converted..

I'll keep y'all updated..

[a13antichrist]

Well..

at 1200 & 2-12, it came out 860Mb. Can't cmompare that to anything though as I've never done a movie with anything close to those settings before.

At 1800 & 2-6, it came out 1850Mb. Which is about 4-500Mb more than I'd normally get for a movie of that length at those settings.
Oh well. A tleast it's done.

[Angie]

Originally posted by a13antichrist
Isn't the thing with cartoons because of the bright colours & very sharp edges where the change in image is greatest? With a b&w film that should be reduced, rather than accentuated... no?

B&W movies also tend to be grainy, often on purpose for artistic effect. It's a good bet that the grains make more randomness in the movie that doesn't compress well.