CCE Basic : Variable CBR ?

[waldok]

Doom9 wrote in the news :

<<This new CCE version is to replace CCE lite and [...]supports 2 <<pass CBR and VBR.

This leaves me wondering what a 2-pass CBR could be ?
Unless I completely miss the point, CBR is by nature single pass since it will allocate a fixed amount of bits per second, period. What would a second pass do about it, apart from doing the same encoding again ? - which I presume is not the case here ;)

What does the second pass act on in the encoded stream ? (can't act on the bitrate so...)
Is it just a "fake" name for a "light" almost constant 2-pass VBR?

I'm very interested in learning about it. Any MPEG or CCE experts please ?

Waldok:cool:

[dattrax]

The bitrate is given per second (25/30 frames of video) I suppose you could do 2 pass within the second and distribute the bits better within each frame.

Jim

[waldok]

I doubt it.
Maybe something like that could be done at gop level though.

Never heard odf

[waldok]

Maybe this is possible at the GOP level. Nevr heard of anything such as multipass CBR before though, hence my interest.
Anybody got links on some informative source ?

Waldok:cool:

[waldok]

Quote from afterdawn forum :

"this is why multi-pass encoding is only used in VBR encoding (the CBR encoding doesn't offer any flexibility for the encoder to determine the bitrate for each frame). "

What do you think ?

Waldok:cool:

[RB]

CCE SP 2.67 (just out but still beta) lets you do up to 9 CBR passes!

[waldok]

Bach,

Well, it makes sense as far as fine-tuning motion vectors is concerned, which may help slightly gaining some bitrate. Yet, considering the CBR constraint, there is not much room for this fine-tuning of motion-vectors and quantization I think. Did you try this already and see the real results ? Does it prove to be useful and efficient ?

Waldok:cool: