[CELT-dev] Variable frame size and API changes

Alexander Carôt Alexander_Carot at gmx.net
Wed May 19 04:12:01 PDT 2010

Hello again,

I actually think that the flexibility CELT offers by providing any desired framesize is a great feature, which IMHO should be maintained. I understand your point as an interesting approach, however I'd rather vote for having it as an additional feature, which does not violate the existing implementation (if possible at all).

Best regards

-- A l e x  

Dr.-Ing. Alexander Carôt 
Email : Alexander at Carot.de 
Tel.: +49 (0)177 5719797 

Am 18.05.2010 um 05:17 schrieb Jean-Marc Valin:

> Hi everyone,
> I've recently been making various changes to the way the modes work and 
> the supported frame size. On new feature that may be of interest to some 
> is that CELT should soon support changing the frame size dynamically 
> within a stream. By that I mean varying the amount of audio (in time) 
> transmitted at once, not the compressed size -- which has always been 
> variable. That would allow dynamically trading compression efficiency 
> for delay.
> Now, one potential side effect of this work is that I may actually 
> remove some of the flexibility in the frame size. So far, CELT has 
> always been insanely flexible when it came to choosing the frame size. 
> For example, you could encode with frames of (e.g. 494 samples if you 
> wanted to). What I'm now considering is restricting the available frame 
> sizes to 2.5 ms, 5 ms, 10 ms and 20 ms. Those could be supported at any 
> sampling rate where 2.5 ms represents an even number of samples, e.g. 32 
> kHz or 48 kHz. However, that would exclude 44.1 kHz, so I'd like to know 
> if people are actually using CELT at that sampling rate? One other side 
> effect is that you would no longer have frames that are a power of two 
> in samples -- unless you use 51.2 kHz as the sampling rate (which would 
> be supported).
> Any comments on this? Anyone has major reasons not to do that?
> Cheers,
> 	Jean-Marc
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