asterisk users - Sep 2010 - Curious what 'early media' is in terms of Answer()

http://www.voip-info.org/wiki/index.php?page=Asterisk+cmd+Answer

Can someone clarify what "early media" is?  I noticed that NOT
answering
a call before dumping them into a queue that has music on hold will not
set up a leg to push music back over the calling SIP channel.  Tossing
an Answer command into the dialplan just before moving to the queue
alleviates this (in either situation the queue still works when someone
picks up the queued call).

This is more of a trivial question, but I'm interested in knowing where
(if anywhere, or if it's played at all) the music on hold is going when
there is no Answer command.  Incidentally, in 1.6.1.x the Answer appeared to be
explicit after dumping a call into a queue, which is how I came across
this issue after upgrading to 1.6.2.11.

hose

On Thu, Sep 9, 2010 at 4:38 PM, Hose <hose+asterisk at
bluemaggottowel.com> wrote:
> Can someone clarify what "early media" is?
>
Basically playing audio to the channel before actually answering the
channel (IE: Answer()).  You usually use Progress() at the start of
your dial plan to send 183 Session Progress SIP Message.

Usually used to play audio to the line, by passing toll charges as a
result of using Answer().

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