Alessandro Russo wrote: > > we are using Asterisk 1.4.18.1 <http://1.4.18.1/> on debian 4.0 etch, > pwlib 1.10 and openh323 1.18. > > We are using MeetMe for conference calls and with two participants > there is no echo problems, but with more than two participants there > is a lot of echo that sometimes disappear for a short time and all > function well. > > Someone have some suggestions?? > > Do you ever used app_conference > http://sourceforge.net/projects/appconference/ ?? >
Alessandro, Are you certain that the echo isn't being introduced by someone on the conference using a speakerphone? This would cause what is known as acoustic echo <http://en.wikipedia.org/wiki/Echo_cancellation#Acoustic_echo> and it's always my first suspect in a situation like the one you are describing. This is not a problem that is specific to Asterisk and I'm fairly certain there is nothing that can be done within your configuration to correct it. Instructing the conference participants to mute their phones when they aren't speaking or to use their handsets should reduce acoustic echo. Some phones <http://www.voip-info.org/wiki/view/Uni-Ta+Technology> also claim to have a "full-duplex speakerphone with advanced acoustic echo cancellation," but caveat emptor. That said, I'm not an expert on echo cancellation and I have an installation where the users are making similar complaints about echo during conference calls. I'd greatly appreciate it if anyone on the list corrected any misunderstandings that I might have on the subject. As an aside, how is the timing on your conference server. The MeetMe application relies on it to mix the audio in conferences. You should get at least 99.98% output from zttest (as shown below) or the audio quality will suffer. This is an overall quality issue and is not necessarily related to your echo problems. [r...@astconf ~]# zttest Opened pseudo zap interface, measuring accuracy... 99.999413% 99.995407% 99.995499% 99.998047% 99.996483% 99.997849% 99.999008% ... --- Results after 107 passes --- Best: 100.000 -- Worst: 99.995 -- Average: 99.997687, Difference: 99.997815 Regards, Matthew Roth InterMedia Marketing Solutions Software Engineer and Systems Developer _______________________________________________ -- Bandwidth and Colocation Provided by http://www.api-digital.com -- asterisk-users mailing list To UNSUBSCRIBE or update options visit: http://lists.digium.com/mailman/listinfo/asterisk-users
