We have a caller arrive on a trusted application endpoint, which we then back-to-back into a conference. We have another application with a trusted application endpoint that announces the call, and then plays music on hold into the conference using the SpeechSynthesisConnector class.
The problem we have is that the music that we are playing fluctuates wildly in volume (probably greater than 16db) thru the track. It is dependent on the music but the times that the volume fluctuates is predictable and repeatable for an individual track.
One track from an album jumps around many times. Other tracks from the same album can cause different reproducible fluctuations, with one 4 minute track producing only one.
I have tried converting the mp3 to wma and setting it as the local music on hold source for a lync client. When the client puts their leg of the conference on hold the caller hears the same fluctuations, so it is nothing to do with the way we are feeding the audio into the conference.
I have tried downsampling to 8bit 8khz as this forum entry suggests http://social.msdn.microsoft.com/Forums/eu/ucma
nagedsdk/thread/1f1c674f-6fb2-44e6-9201-124fa6dfaf50 but no change.
I have also tried passing the music thru a bandpass filter (300-3500hz). This appeared to affect it but not fix it. Has also tried playing with volume levels with no success.
This appears to be a problem with the Lync MCU.