Recording Audio/Video out of sync

[tech10]

I have a client with users using 3CX Video Conferencing screen sharing to record themselves doing basic how-to videos of a few minutes in length. This has been working OK, but for one user - when she records the webinar, her audio and video are out of sync. She shares her screen (entire screen), presses record, minimizes the screen, and starts performing her task while talking her way through it. When the recording of the conference arrives, it is as if the audio recording starts instantly but the video is about 25 seconds (at least on one 2-minute recording I watched) ahead of the audio, with the first 25-ish seconds of the video missing - toward the end, the video shows the user ending the meeting, then the screen goes black, but the audio continues until the end.

For example:
Audio: "Open your browser, log into the website, then click on the Hoopty Hoop link. The page will load, click Start. A silly picture of a bear will appear. Start clicking on this picture of a bear. If you click the bear for 5 seconds, it turns red. Click click click click click...there, see the bear turned red. Now it will start dancing. See, isn't that fun! After a few more seconds, his head will explode and candy will rain down. Count the pieces of candy and put it in your spreadsheet." (end audio)
Video: (shows red bear, shows bear dancing, head explodes and candy rains down, shows user clicking "end meeting", screen goes black...and is black for about 20 seconds until the audio ends).

Hopefully that makes sense and someone can let me know what to look for to troubleshoot.

This is in Google Chrome.

 

[NickD_3CX]

Hi!
I have been reading your example and I am trying to understand one important part, is the audio not played at the right moment as the video, or is video just a black screen at certain points?

I don't remember having heard of this kind of behavior, but do you think your client would agree to have a look at the video recording?
Also, would it be possible to send me the WebMeeting link of the Organizer to see the logs are still there?

Any of this information, if you have it, please send it in a PM, not in the public thread.

 

[tech10]

NickD_3CX - I just sent a PM.

I guess another way to describe the issue is that the video track is shifted ~25 seconds back relative to the audio. So the recording starts off with the audio describing something that happened 25 seconds ago on the video track, but that video can't be seen as the video track starts at 25 seconds into the recording. The video ends with the meeting being closed, while the audio continues describing things about 25 seconds after it occurred in the video. Hopefully that makes sense...I have attached an image that may help explain.

 

[NickD_3CX]

Thanks for the explanation, it is not clear. Let me check and get back to you.

[UPDATE]
This can happen if there is packet loss between the location where the Organizer is and the Web Meeting server.
Packet loss can be attributed to things like a bad internet line, bad WiFi connection, bandwidth not being enough, etc.

The reason is that the video and audio streams are sent separately to the Web Meeting servers, and when you have requested a recording, the WM server tries to "sync" the audio/video into one file. If there is packet loss, the "sync" process might not sync those 2 correctly.