[Speex-dev] Transmitting synthetic speech using Speex?

Reed Hedges reed at mobilerobots.com
Fri May 26 08:13:27 PDT 2006

Tom Grandgent wrote:
> Have you tried using 16kHz wideband?  The sound quality is far superior to 
> narrowband, IMO, even if you have to turn the VBR quality down (to say, 2) 
> to save bandwidth.

Thanks for the info Tom!

Probably narrowband is hurting me, but my system is currently built on that. I 
want to try to get acceptable performance from narrowband if possible before 
trying to add wideband support to the system.

Consistant, noise-free synthesized speech certainly has fewer potentially 
problematic aspects to it though, I agree... Maybe we should all just make 
people type their communications in to a keyboard :)


> Tom
> Reed Hedges <reed at mobilerobots.com> wrote:
>> Hello, I'm wondering if anyone has done this before and has any advice, or if 
>> anyone in general has ideas about it.
>> I just implemented transmitting synthesized speech (text-to-speech) over Speex 
>> (narrowband) in an application.  I'm using Swift from Cepstral 
>> (http://www.cepstral.com). The voice I'm using is a pretty deep male voice.  I'm 
>> telling Swift to generate audio at 8khz, then encoding each chunk of audio 
>> output by Swift and sending it to a client.
>> One interesting thing I've noticed is that as I increase Speex's encoding 
>> quality, the output in the client sounds smoother (at my normal quality value of 
>> 5 or 6 it sounds OK but occasionally has a hesitation or glitch) but "thinner" 
>> -- less full or less resolution.   Using the noise filter and changing the 
>> complexity parameter don't seem to matter.
>> I'll be experimenting with this more, but if anyone is interested I can send 
>> some audio data generated by the Swift synthesizer.  Or, if anyone has any 
>> suggestions for how to tweak the synthesized audio for better encoding by Speex, 
>> that would also be helpful (I don't know very much about audio or audio signal 
>> processing yet.)
>> Thanks!
>> Reed

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