[speex-dev] auto-detection of frame boundary

Jean-Marc Valin jean-marc.valin at hermes.usherb.ca
Mon May 12 11:02:22 PDT 2003

> Hereÿs the situation: 3 frames are being transferred back to back over
> RTP.  The total payload is known (thus the TOTAL frame size).  Weÿd
> like to decode all 3. 
> According to IETF RTP Profile (appendix C, of Jean-Marcÿs Speex Codec
> Manual, verison 1.0),  ´itÿs only necessary to consider the sequence
> of bits as output by the Speex encoder, and present the same sequence
> to the decoder¡, I kind of got the impression that length-prefix PER
> FRAME is not necessary, as long as speex_decode() is called 3 times.
> Is this true ?

That's right, if you call speex_encode 3 times, you can call
speex_decode 3 times. Note that you need to let Speex do the
concatenation of the frames. If you try to concatenate the bytes
yourself, you risk problems because sometimes the frames don't end a
byte boundary.


Jean-Marc Valin, M.Sc.A.
LABORIUS (http://www.gel.usherb.ca/laborius)
Université de Sherbrooke, Québec, Canada

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