Speex dev - Apr 2008 - Suitability of speex for use with noisy, non-voice source material?

Question from new subscriber -

I'm working on a project to connect to remotely connect to a short-wave
receiver via a dial-up PPP/IP circuit. Turns out the dial-up circuit is only
stable (useful) to 14.4 kbps (faster modem training produces so many link errors
that the net circuit quality is unusable - one end is in a remote, rural
location), so looking for codec that can fit within this circuit minus PPP/IP
overhead (probably 10 kbps net based on testing so far.) Latency is a
consideration so I'm looking at voice-type encoding vs. streaming MP3. I was
going to try use of G726 but it's not configured below 16 kbps so hence my
resumed search for a codec.

In my initial searching I found speex, but before I try to engineer the
solution, I'd like to get any advice on use of speex in with the expected
source material, which is likely to be noisy (static and stuff mixed in with the
source audio). The source audio (monaural) will be pre-filtered to fit with
300-3000 Hz passband (can be slightly narrower if need be), and may not always
be a single voice (that is, may be>1 voices interfering with the audio
passband, or even non-voice such as tones and other stuff that would appear in
the passband of the receiver.) So based on this, would I want to avoid speex or
proceed to experimentation? By the way, this is just for a personal project, no
commercial intent.

Very tks,

Dave
wb0gaz at hotmail.com

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Hi Dave,

Sounds like Speex would be appropriate for your application. The best
way to check would be to actually try it with the stock encoder and
decoder (speexenc/speexdec). The conditions you list are not ideal, but
they'll affect any speech codec. Plus, in terms of free codecs, Speex is
definitely the only one that can do the job.

	Jean-Marc

david feldman a ?crit :
> Question from new subscriber -
> 
> I'm working on a project to connect to remotely connect to a
> short-wave receiver via a dial-up PPP/IP circuit. Turns out the
> dial-up circuit is only stable (useful) to 14.4 kbps (faster modem
> training produces so many link errors that the net circuit quality is
> unusable - one end is in a remote, rural location), so looking for
> codec that can fit within this circuit minus PPP/IP overhead
> (probably 10 kbps net based on testing so far.) Latency is a
> consideration so I'm looking at voice-type encoding vs. streaming
> MP3. I was going to try use of G726 but it's not configured below 16
> kbps so hence my resumed search for a codec.
> 
> In my initial searching I found speex, but before I try to engineer
> the solution, I'd like to get any advice on use of speex in with the
> expected source material, which is likely to be noisy (static and
> stuff mixed in with the source audio). The source audio (monaural)
> will be pre-filtered to fit with 300-3000 Hz passband (can be
> slightly narrower if need be), and may not always be a single voice
> (that is, may be>1 voices interfering with the audio passband, or
> even non-voice such as tones and other stuff that would appear in the
> passband of the receiver.) So based on this, would I want to avoid
> speex or proceed to experimentation? By the way, this is just for a
> personal project, no commercial intent.
> 
> Very tks,
> 
> Dave wb0gaz at hotmail.com
> 
> _________________________________________________________________ In
> a rush? Get real-time answers with Windows Live Messenger. 
>
http://www.windowslive.com/messenger/overview.html?ocid=TXT_TAGLM_WL_Refresh_realtime_042008
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