I have recently discovered a very interesting problem that I have been unable to resolve. Let me give some background. I converted from Windows Media Services to IIS Media Services 4 about four months ago. I am encoding live streams with H.264 codec, at three levels of increasing quality, and its really an awesome end product. Since I first converted though, I have got random reports back from some viewers that while watching a live stream, the audio of that stream would switch to something not at all related to the video they are viewing.
At first, I thought maybe I had introduced some archived audio or another audio source into my live stream. But checking my encoder settings, I found that I had not. I played back archived copy of the live stream, and found no unusual audio in it. So thus I ruled out my encoder and the server that archives the file. Next I guessed the viewers having the problem may have two media players open at the same time, so I adjusted the code in my players to only allow them to open one player from my site at a time. But the issue persisted. It sounded so bizarre and random I figured it must be something specific about their PCs (the vast majority of my viewers made no such complaints and I could not duplicate the problem). Yet still, multiple viewers continued to report the problem.
Then, several days ago, I was watching one of my own live streams, and sure enough, at intervals throughout the live stream, the audio being played was from an old archived file. The server would stream the correct audio for a period, and then randomly, cut to and archived audio clip, then just as randomly, cut back to the live audio. It did this intermittently for the entire live broadcast (approximately two hours).
Since this was happening during live streaming, it afforded me the ability to do some troubleshooting. I checked out my encoders and found none of them were using anything but live sources. None of them were encoding archived content. I played a stream coming directly from the server I use to create my archives, and it was not experiencing the problem. I then started going through my alternate streaming servers that I have in place as backup and failover streaming servers to connect to in the event my primary streaming server goes down. The stream from my failover server did not have the problem. I then opened another stream to my primary server from another computer - and it did not have the problem!
So on one PC, I was pulling a stream from my primary encoder and the audio was intermittently messing up. While on another PC, streaming from the same server, the audio was fine. So I then I am guessing maybe my player was holding cached files from an old session that it was playing instead of live files. So I again modified my player to force it to clear the cache before starting a new stream. And now I will wait to see if the issue reappears.
So I've spent a couple months trying to figure this out, and thought I would post it here to see if anyone else has had the same problem, and if so how they fixed it.
Cheers!