Entropy Coding - H.264

[Dave1024]

Hi,

What are the advantages for using CAVLC than VLC.

What are the advantages for using CABAC than Binary arithmatic coding .

I want to know how the context adaptive setup bring some gain in speed and compression ratio

:thanks:
Dave

[Blue_MiSfit]

I think you're confused.

As far as I know, there are only two entropy coding modes allowed in H.264: CAVLC and CABAC.

CABAC is quite a bit better. From what I understand, it usually nets you a 10% compression improvement over CAVLC, which is quite substantial.

CAVLC is faster to decode though, so for slow systems without hardware acceleration, I sometimes suggest using it over CABAC.

Cheers,
Derek

[Lyris]

CABAC is Binary Arithmetic Coding (b.a.c.)

[TheFluff]

If you read the OP, he seems to be well aware what CABAC and CAVLC are. What he wants to know is how the context adaptive part of them works. Unfortunately I can't answer that.

[LoRd_MuldeR]

Some references from the respective Wikipedia article:
* http://www.hpl.hp.com/techreports/2004/HPL-2004-76.pdf
* http://iphome.hhi.de/marpe/download/cabac_ieee03.pdf

BTW: I don't think it gives a "gain in speed", as CABAC is known to be pretty slow.

[Dave1024]

The steps and the def:: of CABAC and CAVLC know very well, but still search for "How the context model and its selection and updation will give better compression" Please explain if can

[jakor]

it's like a cat given and you need to feed him. If no context used - you use average meal distribution over the day which gives quite a coarse estimation. However if you know that he just ate, he's not likely to eat anymore, more likely go to sleep and you can predict that with a higher level of probability.
that's what using a context is.