[asterisk-users] about MusicOnHold / Playback

[unplug]

Hi,

  I have a problem about musiconhold/playback command in the dial
plan.  Actually, I have the following dial plan for inbound call.
[from-gateway]
exten => 1234,1,Answer()
exten => 1234,2,MusicOnHold(c1)
exten => 1234,3,Hangup()

When I using mobile to make call 1234, it works and I can hear music.
(below is the log from CLI)
    -- Executing Answer("SIP/203.193.26.242-087233a8", "")
    -- Executing MusicOnHold("SIP/203.193.26.242-087233a8", "")
    -- Started music on hold, class 'c1', on channel
'SIP/203.193.26.242-087233a8'
Aug 27 15:04:36 NOTICE[18840]: rtp.c:331 process_rfc3389: Comfort
noise support incomplete in Asterisk (RFC 3389). Please turn off on
client if possible. Client IP: 203.193.26.242

Then, I use a normal phone to make a call to 1234 thro' PSTN, I can't
hear any music and CLI shows there is a looping.  In the log below, it
tries to play the music but somehow it stops to play and go back to
answer to call again.  It shows spawn extension (from-gateway,1234,2)
exited ....  It seems that there is a problem in this command.
However, I can't find any hint in the message and even log.
    -- Executing Answer("SIP/203.193.26.242-08723500", "") in new stack
    -- Executing MusicOnHold("SIP/203.193.26.242-08723500", "c1") in new stack
    -- Started music on hold, class 'c1', on channel
'SIP/203.193.26.242-08723500'
    -- Stopped music on hold on SIP/203.193.26.242-08723500
  == Spawn extension (from-gateway, 1234, 2) exited non-zero on
'SIP/203.193.26.242-08723500'
    -- Executing Answer("SIP/203.193.26.242-08728a10", "") in new stack
    -- Executing MusicOnHold("SIP/203.193.26.242-08728a10", "c1") in new stack
    -- Started music on hold, class 'c1', on channel
'SIP/203.193.26.242-08728a10'
    -- Stopped music on hold on SIP/203.193.26.242-08728a10
  == Spawn extension (from-gateway, 1234, 2) exited non-zero on
'SIP/203.193.26.242-08728a10'
    -- Executing Answer("SIP/203.193.26.242-08723500", "") in new stack
    -- Executing MusicOnHold("SIP/203.193.26.242-08723500", "c1") in new stack
    -- Started music on hold, class 'c1', on channel
'SIP/203.193.26.242-08723500'
    -- Stopped music on hold on SIP/203.193.26.242-08723500
  == Spawn extension (from-gateway,1234, 2) exited non-zero on
'SIP/203.193.26.242-08723500'

Does anyone have the same problem as me?  Anyone can suggest me a
solution to solve it?  Thanks.