[x264-devel] Re: CABAC performance

[Mathieu Monnier]

> If CABAC is compared with CAVLC the gains are MUCH less. As far as I
> know only a few percent (something like 4%?). The gains achieved by
> CABAC are mainly due to CA (Context Adaptivity) and only to a small
> degree due to BAC (Binary Arithmetic Coding). With context adaptivity
> VLC's are almost as good.

CABAC at medium rate is 10% less bitrate than CAVLC. At high bitrates, 
it shouldn't be more efficient that CAVLC since probabilities at high 
bitrates tends to become uniform. At low bitrate, it should be quite 
more efficient.

Seeing how h264 is used ( very low bitrate on cell phones, low bitrate 
in HD ), CABAC is a must. Only with HD-DVD - Bluray would CABAC be less 
interesting. But seeing how they didn't care about CAVLC when they 
implemented high profile, I think at that time CAVLC was already long 
forgotten.

Regards,

Mathieu


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