Know that
(OSLEC)
pretty well. Wanna test new algorithms but
need wav data. Echo Cancel is also still under research process, VAD is
part of a good echo canceller as it freezes the algo processing in case
of double-talk. Generally a modified Geigel algo or energy based algo are
used.
I have new algorithms
and want to test them. Unfortunately, I don't have enough data, there are
out there very expensive databases such as (AURORA...) but don't think
they are really suitable for my tests.
Zelda
At 01:55 19/02/2008, you wrote:
KMTDBOURSE wrote:
> Hi,
>
> Thanks a lot for describing the vad algo it seems rather
a basic
> algo and I am surprised it is not more sophisticated. I hear also
from
> speex users (must be same algo?) that the vad algo is very
poor and
> should be improved. That is what I am doing, try to improve vad and
> echo cancellation algorithms. I would appreciate a link where I can
> find data files (audio) to download on which I can perform tests. Of
> course I will feedback the freeswitch community in case of
improvment.
>
> best
>
> Zelda
There is a pretty good free echo canceller at
www.rowetel.com,
although
FreeSwitch can't directly use it as it is GPL software. It does,
however, mean that free and open workable algorithms for robust EC do
exist.
VAD is different. It is still a research topic. You can see this from
the way the VAD algorithms in things like G.729 have been revised over
the codec's lifetime, as further research has been done. The algorithms
G.729 and AMR use are encumbered by patents, otherwise cloning them
would be excellent start. VAD for speech recognition is relatively
straightforward. When you can buffer the audio, and look forwards and
backwards in time, it become much easier to identify the start and end
of voice bursts. It becomes hard when you can only look back in a low
latency scenario.
Steve
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