[CELT-dev] A Question about VBR

Timothy B. Terriberry tterribe at xiph.org
Tue Dec 21 06:05:34 PST 2010

> One question though: could you explain briefly the difference between
> VBR and unconstrained VBR? And, in my case, the $64K question: is there

Constrained VBR still strictly limits the bitrate variation so that you 
only need to buffer one additional packet, at most, to be sure that you 
don't stall waiting for data if you're only reading at the average rate. 
This is important to maintain low delay. Unconstrained VBR removes this 
limit (and thus requires more buffering, and thus introduces more delay).

> any situation where CELT could produce more data than specified by
> nbCompressedBytes when encoding?

No. It is possible that the encoder can't fit the packet in the buffer 
you requested at all (currently around 12-13 bytes for stereo), in which 
case it will return CELT_CORRUPTED_DATA, but it won't produce a packet 
larger than the output buffer. We're actively working on reducing the 
situations when this occurs.

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