[speex-dev] Memory leak in denoiser + a few questions

Jean-Marc Valin Jean-Marc.Valin at USherbrooke.ca
Tue Mar 30 14:35:55 PST 2004

> Reverberation suppression?

Basically, it means that if you are in a room with lots of echo (long
decay), I can reduce it a bit.

> I guess this would help reduce local source echoes?  I've never 
> _noticed_ that to be a problem in my use, but I would imagine that 
> using a notebook's built-in microphone, you'd get some echo off of the 
> screen and stuff [also from the whole room]..
> Most of these echoes aren't so bad, but I guess they might make the 
> encoding job harder.  I'd sure rather see the echo cancellation 
> finished [not that I have any say on what you work on!!!].

Well, I'm still looking for help :)

> Here's the numbers I got doing vad on 655 seconds of audio (about half 
> is speech, half is absolute silence [0's]).
> P3-600: 25 seconds
> Athlon XP 1700+ (1.45Ghz): 5 seconds
> P4 2.8Ghz: 8.8 seconds.

These numbers sound like a problem I has a while ago with the decoder.
The VAD shouldn't take much CPU so I suspect there might be floating
point underflows in some part, slowing down the Intel CPUs a lot (for
some reason, the AMD CPUs seem to handle underflows faster).

> Anyway, I think I might need to find a less computationally intensive 
> VAD solution for the conference.  VAD is currently only used when 
> people connect via the PSTN, so they presumably have a decent SNR, and 
> I may be able to get away with an energy envelope type of thing, 
> without needing frequency domain analysis.  But before I go and start 
> coding this, is there any simple optimizations that can be done to the 
> preprocessor when it is  being used only for the VAD decision?

Have you tried using the (less accurate) VAD that's in the codec itself


Jean-Marc Valin
Université de Sherbrooke, Québec, Canada

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