[speex-dev] Speex latency

Jean-Marc Valin jean-marc.valin at hermes.usherb.ca
Fri Mar 21 07:08:22 PST 2003

> What kind of latency is expected using 8,16,32 khz?

Depending on the sampling rate, the latency is 30-36 ms (frame size is
20 ms). 

> I am trying to do a realtime stream server, and I am having latency above
> >500ms ( I capture the sound using the mic, encode it and send it to the
> client).
> I am using ALSA system, a SB128 PCI and a 800Mhz P3 . What can I do to lower
> the latency?
> I tried a test : arecord -t raw | speexenc - - | speexdec - and I found that
> I also have a 500 ms latency.

There are likely 3 problems with your setup:
1) arecord might have a big latency (probably reads the audio big chunks
at a time)
2) speexenc/speexdec has a larger latency than the codec itself (which
you get using libspeex) because of the packets/pages in the Ogg file.
3) The pipes all do some buffering which probably causes additional


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

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