[Speex-dev] Speex Usage

Steve Checkoway s at pahtak.org
Wed Aug 3 12:26:24 PDT 2011

On Aug 3, 2011, at 12:16 PM, John Henry wrote:

> Would speex be a valid method for compressing/decompressing audio for
> live communications?

I believe this is one of the intended uses.

> Trying to find something that I can use that would decrease the
> bandwidth requirements tremendously, and still be able to be performed
> quick enough for live discussion over the air between two
> communications devices.

Speex will certainly decrease the bandwidth. I'm using it to stream audio over a 3G internet connection and it works quite well. Especially for frames of silence which take only 5 bits for 20 ms of silence. (You can also just not send data, but I didn't bother since sending a UDP packet with just a few bytes for the RTP header and 1 byte of data every 20 ms wasn't too much of an overhead.)

> I have connected two communications devices via the Ethernet,
> streaming audio via UDP, and the only latency is the internet service
> provider and net itself, about 200ms - 750ms depending upon
> connection. But I want to find something that will give me a much much
> lower bandwidth requirement than "fully uncompressed audio". I wrote
> my own quick compressor that cuts the bandwidth in about half, but
> still, want to see "how low can I go". hence the current interest in
> speex.

750 ms seems like a pretty big lag for a live conversation, but maybe not so bad. My use didn't require two-way interaction, so I just used a 1 s buffer which worked quite well. Of course, that's on top of whatever the delay from the network was. I suspect that I could have gone quite a bit lower.

Steve Checkoway

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