[CELT-dev] Celt over RTP

Jean-Marc Valin jean-marc.valin at usherbrooke.ca
Wed Apr 22 06:32:27 PDT 2009

The most likely problem is the audio buffer (or maybe the jitter
buffer). When using CELT with 512-sample frames at 44.1 kHz, the delay
intruduced by CELT is 14.5 ms, no more, no less. The rest is caused by
your phone. As for RTP use, please have a look at the following draft:



Alexandre Savard a écrit :
> Hi, 
> we are currently implementing Celt codec into SFLphone, a sip/iax
> softphone.
> Sound quality seems to be good. However, we are experiencing an
> important latency, which makes small segments of sound to be interleaved
> with blanks.
> 1 channel of compressed audio data packets are sent using a fixed frame
> size of 512 samples at 44100 Hz, using a 128 byte-per-packets
> compression.
> Could this delay be due to an algorithmic latency? Changing Thread speed
> (sleep 1 - 8 ms) seemed to have no influence on the result.
> Is there a way to optimize celt parameters so that it can be sent using
> rtp? We will give it a try at a lower sampling rate, 32 kH.
> Congratulation, great work with this project.
> Thanks
> Alexandre Savard
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