[CELT-dev] A Question about VBR

Jean-Marc Valin jmvalin at jmvalin.ca
Tue Dec 21 07:35:55 PST 2010

John Ridges <jridges at masque.com> a écrit :
> One question though: could you explain briefly the difference between
> VBR and unconstrained VBR? And, in my case, the $64K question: is there
> any situation where CELT could produce more data than specified by
> nbCompressedBytes when encoding?

That *cannot* happen. What constrained vs unconstrained VBR means is  
how the bit-rate is used over time. In constrained VBR mode, the  
encoder assumes that the network speed is the same as the average  
bit-rate so it constrains the bit-rate to not add more than one frame  
of delay due to network transmission. In unconstrained VBR, the  
encoder assumes that the network is fast enough to transmit at the max  
speed, so it uses the best possible bit-rates at any time -- always  
subject to the max bit-rate specified.


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