[speex-dev] frame size

Jean-Marc Valin Jean-Marc.Valin at USherbrooke.ca
Fri Jun 30 02:41:11 PDT 2006

Le jeudi 29 juin 2006 à 13:50 +0530, Lokesh Mogra a écrit :
> Hi,
> I hv a query.
> while decoding a voice session, i saw that one side of voice was using
> speex/16K with vbr=off and other with speex/16K with vbr=on.
> Packet Size in first case is 70 Bytes
> Packet Size in second case is 104/106/118 Bytes etc.

Sounds normal so far.

> when i send these packets for decoding the decoded ouput is 640 bytes in all
> the case.

It's 320 *samples*, regardless of the format (float or short) you use.

> Now speex with vbr=off, is decoding well, but the other side is very noicy.
> By looking at their RTP Timestamps, i saw that in first case, difference
> between two RTP Packets is 320 ms.

you mean 320 *samples*? Speex frames are 20 ms long.

> while in second case with vbr=on, difference between two RTP Packets is 640
> ms.


> do we have to do anything special while decoding speex, in case of vbr=on.

I don't know what your problem is, but it's not the VBR. All VBR does is
change the bit-rate at the encoder, but the decoder should handle that


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