David Knell wrote: > Steve Underwood wrote: >>> When there is Echo being generated from the far end, usually in a >>> bridged call. If you application is just an IVR, with no far end >>> connectivity, then you shouldn't need an echo can. If you are bridging >>> calls, then at some point you may need it, depending on what else is >>> in the loop. >>> >> This is VERY VERY WRONG. IVRs badly need echo cancellation. Without it >> they give very poor reliability detecting DTMF while the prompts are >> playing. If the system uses voice recognition, its reliability will be >> even worse. >> > With respect, this is at best half true. DTMF detection has always > worked just fine > without echo cancellation - the Dialogic, Aculab and Rhetorex cards > which I used > in the late 1990s managed it perfectly well; if the DTMF detection > code in * and FS > can't, then maybe that's something for its author to look at ;-) Try reading the Dialogic and Aculab documentation. Those cards used quite a bit of their DSP capability to remove the spillback of outgoing voice into their DTMF receivers. You'll find the DTMF detector in spandsp (not necessarily the ones in * or FS, which have been altered a bit) is superior to either Dialogic or Aculab's. > ASR - yes, maybe, but L&H's ASR1500 used to work perfectly well on the > same > hardware above back in the day. I'd be interested to see results of > testing an ASR > engine in with echo; unfortunately, most vendors appear to prohibit > the publication > of test results in their licensing. L&H used to work fine with the J series Dialogic cards. The Dialogic documents go into considerable details about the echo cancellation arrangements to make that happen.
Regards, Steve _______________________________________________ Freeswitch-users mailing list [email protected] http://lists.freeswitch.org/mailman/listinfo/freeswitch-users UNSUBSCRIBE:http://lists.freeswitch.org/mailman/options/freeswitch-users http://www.freeswitch.org
