On Feb 21, 2008, at 4:50 PM, Benny Prijono wrote: > On 2/21/08, Norman Franke <norman at myasd.com> wrote: >> >> Although, in my experience using a tonegen often results in tones >> that are >> not understood by a number of other systems. I'm not sure if this >> is due to >> audio volume issues or what, but we've had a number of systems >> that can't >> understand some or all digits from the tonegen. Sending SIP INFO >> messages to >> our Cisco to then generate them always works. > > The tone generator heavily depends on the quality of sine wave > generation, and in PJMEDIA, I use a sine wave emulation which I > thought should give good balance between quality and speed. With this > method, speed definitely is much better than using math.h, but > quality, well turns out not to be perfect. I'm aware that the longer > the tone is, the more deviation it'll have from the perfect tone. > > Have a look at tonegen.c for more info. Thanks for the feedback > though. Perhaps there should be an option to use a better one, since this one is incompatible with some remote systems. Oddly, it seemed some digits would work, like zero. Nine seemed to be a constant problem, which uses a higher frequency according to: http://en.wikipedia.org/ wiki/DTMF Norman Franke Answering Service for Directors, Inc. www.myasd.com
