#964 Multichannel-Recording gets out-of-sync when UDP packets lost

Marc Sowen

I have a 2h multichannel-recording with two people in Mumble, where one resulting file is 3 seconds shorter than the other. In the beginning everything is ok, but after 30 minutes there were some UDP transmission problems caused by one user doing heavy uploads on his side. Right after the transmission error, the channels were heavily out-of-sync.

By looking at the source, I found some code generating silent samples when there are missing samples - but only when the silence period is larger than 100ms. Do you think that our silence period was shorter? BTW, I used WAV for recording.

Our settings are shown on the screenshots found here:




  • Stefan H.

    Stefan H. - 2013-02-20

    That is interesting. We'll have to try to reproduce that to make sure but - from what I remember of the code - it is very well possible that loss might cause syncing issues we did not consider.

    This might be a duplicate of https://sourceforge.net/p/mumble/bugs/846/

  • Marc Sowen

    Marc Sowen - 2013-02-21

    In https://sourceforge.net/p/mumble/bugs/846/ they say explicitly "Recording in .wav does not produce this problem.". That's why I opened up a new ticket. I didn't check for error in the compressed formats though, since I guess it'll make things even more complicated.

    I did some further investigations. When I add 2-3 seconds of silence (using Audacity) right after the garbled voice part in the 30th minute, the streams seem to be in-sync until the end.

  • Richard Smith

    Richard Smith - 2013-10-31

    This is still happening with the latest version of the client app. I also have this issue when recording in wav, but cannot yet confirm it happening in any other audio format. However I don't have any further information regarding UDP transmission errors.

    Has there been any progress on this issue?

  • Stefan H.

    Stefan H. - 2013-11-07
    • status: open --> closed
    • Version: --> unspecified