On Thu, Aug 20, 2009 at 11:06 AM, Steve Underwood <ste...@coppice.org>wrote:
> On 08/20/2009 05:22 AM, Michael Collins wrote: > > > > There is no noise on those 3 beeps. In fact, for something that's > been > > through ulaw/alaw compression those beeps are very clean. They are > > quite > > short, though. > > > > > > Heck yeah they're short! Steve, in your experience is there a > > practical way to detect a beep that short without chewing up system > > resources or having lots of false positives? > > -MC > > > The tone samples I just looked at are about 130ms long. The problem is > the detector is trying to be a very open ended detector of anything > narrowband enough to be a single tone, and of any duration beyond some > small minimum. Its difficult to make such a thing voice immune unless > you can also count on a very large signal to noise ratio. With a digital > trunk you can probably rely on a large SNR, but what happens when people > use analogue lines? There is a reason why DTMF detectors try hard to > work down to about 10dB SNR. :-) > > Steve > Thanks for the lesson uncle Steve! I'm guessing that the OP will need a new strategy. Possibly waiting for silence? Not sure what's the best way to go but I'm interested in hearing if someone has a solution. -MC
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