[Asterisk-Users] (Yet another) Music on hold problem and another...

[Tom Samplonius]

On Tue, 15 Mar 2005 16:29:53 -0500, C F <shmaltz at gmail.com> wrote:
> Your problem with MOH has to do with the fact that Asterisk needs a
> timing source to play back music on hold. So when there is an audio
> stream coming in asterisk can use that incoming stream as a timing
> source. If however silence suppression is used, then asterisk has no
> timing source therefore MOH doesn't work. You can get a timing source
> by loading ztdummy. Look up asterisk timing on the wiki
> The wiki is located here:
> www.voip-info.org

  That is actually incorrect.  Zaptel timing is not required or used by MOH.

  But Asterisk's RTP implementation does use the incoming stream to
time the outgoing stream.  So if there are no incoming packets, no
outgoing packets are sent, and you don't hear the music.  This means
that you can't use VAD/Silence detection on any SIP end-points with
Asterisk.  This affects any sounds played by Asterisk, including
annoucements, ring-backs, etc., not just MOH.

Tom