How far can go the b-frames ?

[ProtOx]

I'm encoding O'Brother, and it's not a very compressive movie,
I'd to know how far can go the b-frame :
Can I get a nice result with

- 0.193 bits
- 43% compressibility test
- 3 b-frames
- 656x272

I've seen in a tonz of guides that the best is about 55/60% of a compressibility check .. but what about b-frames ??

Thx for your help :p

[Teegedeck]

The problem is, 43% can look good, but you only really know afterwards. Try it with this setup before you start applying filters BUT you have to use a 640x resolution - the resolution must be a multiple of 16!! Give it a go and let me know the result.

Edit: And use VHQ=4 at all means.

[ProtOx]

oK.. thx for your quick answer ;)
I'm encoding it right now.

Do you know if I can encode a small part with GK ?
Just to try different settings ..

[Teegedeck]

Well, you can abort the second pass after some time to have a look, but the stats are read linearly; i.e. you can't jump from scene to scene for test-encoding, like it was possible with Nandub.

Edit: Oh, I understand you want to test it before you actually do a first pass. Well, you can try to simulate the frame quantizers by restricting, say I-frames to 3 and P-frames to 5 in a CBR-encoding, but this will actually look much worse than the result of a two-pass because it doesn't take actual framesizes into account.

[ProtOx]

OkEy, I've finished my rip :
After encoding for the first time with the large 656x272 resolution,
I've seen that a small buggy-block was on the rip on the down left ..

Pretty strange !

So I've tryed to re-encode another time with another resolution (542x230) to gain a better compressibility test (65%)

My second rip is ok, the final result is pretty good .. not excellent .. but good ( but O'Brother is a strange movie, not really compressive, with alot of moves )

Anyway I've encoded 'Divine Intervention' in OGM ..
I'm crying about the PERFECT quality .. damn .. 3 b-frames ..

Too good !!
> XViD ROCKS UR ASS ! :devil:

[Teegedeck]

Thanks for giving us a feedback! :)

Originally posted by ProtOx
resolution (542x230)

As said before, don't use odd resolutions, it makes it harder for the codec to compress the picture. MPEG4-codecs use macroblocks to process the picture. These are square and of even size. Therefore: As soon as the resolution isn't a multiple of 16, XviD will have to use macroblocks that are only 8x8 pixels and - as you can imagine - that means using a couple more of them... This is proven to a) reduce compressiblity and b) to yield strange bugs, sometimes. And 542x230 can't be divided by 16, it cannot be divided by 8, it cannot even be divided by 4! I don't know what XviD will do internally in such a case, but it can't be good.:eek: