Previously, an assert will be triggered in case it is not a mono stream. With the CL, the mono file stream will be copied into a strereo stream and mixed with the channel stream. More detail about the fix please refer to http://code.google.com/p/webrtc/issues/detail?id=36 Review URL: http://webrtc-codereview.appspot.com/93020 git-svn-id: http://webrtc.googlecode.com/svn/trunk@322 4adac7df-926f-26a2-2b94-8c16560cd09d