[asterisk-users] MeetMe

[Matthew Jordan]

----- Original Message -----
> From: "Jerry Geis" <geisj at pagestation.com>
> To: "Asterisk Users Mailing List - Non-Commercial Discussion" <asterisk-users at lists.digium.com>
> Sent: Monday, October 1, 2012 5:01:43 PM
> Subject: [asterisk-users] MeetMe
> 
> I am using Meeting on 1.4.43 with a handfull of devices, like 10 to
> 20
> in a Meetme.
> 
> I can "tell" a difference (as two of the devices are close to each
> other) that they are
> not fully in "sync". One was slightly behind the other... Any way to
> get
> them more in sync?
> Is it the delay from starting each device in the MeetMe? time to
> start
> device 1 till device X?
> I was expecting them to be all receiving the data for audio at the
> same
> time.

Nothing happens "at the same time", unless you're broadcasting information
over some transport that supports multicast sends.  There's always going to
be some interspersing of transmissions, if for no other reason than each
participant's channel in the conference has to be serviced after the media
has been mixed.  With a sufficient number of participants, there will be
some 'delay' between when the audio is sent to participant #1 to
participant #n.

Even if we assume that the transmissions are being done completely
"in parallel" using multiple threads, you can still overcome the capabilities
of a system by having a sufficiently large number of participants in a
conference.  That is, for any given system, you can always add more
participants, such that, eventually, a thread will not be serviced immediately
when it has data to send to a participant.  A context switch will have to occur,
resulting in the data being sent to said participant at a latter time,
resulting in the work being done not "at the same time".

Note that recent versions of Asterisk (10+) have a revamped conferencing
application (ConfBridge) that, in performance tests, performed much better
than MeetMe.  A big limitation of MeetMe is its reliance on DAHDI for
mixing.  ConfBridge removed this limitation, and typically can mix more
participants at a faster rate.

--
Matthew Jordan
Digium, Inc. | Engineering Manager
445 Jan Davis Drive NW - Huntsville, AL 35806 - USA
Check us out at: http://digium.com & http://asterisk.org