If your solo tracks aren't in sync after recording then you are experiencing what is known as audio drift. Some drift can be expected just due to slightly different speeds in the sound cards of each participant see:
However, recent browser updates have introduced some audio performance issues that may be a contributing factor as well. The syncing problem tends to be related to CPU usage on the computer and is most prevalent in older / slower computers. Also running lots of programs in the background can hog enough CPU power to cause issues.
We have been actively optimizing our code to run as efficiently as possible to help combat this problem until the browser vendors deploy a fix for this issue. We have been able to cut CPU usage by almost 50% in some cases so you may find that the problem has been solved in your next recording.
If you are still noticing issues with track synchronization after out latest update then here are some things you can do to mitigate the issue.
- Ensure that you and your participants are upgraded to the latest version of your browser. As of now (Oct 12 2017) the latest version of Chrome is 61 and Firefox is 56.
- Use a modern computer and operating system. We know it isn't always possible to control what your guests are using but try to make sure everyone is using the most modern hardware / software as possible.
- Complete close any unnecessary programs during recording. Ask this of your guests as well.
Click away from the zencast tab to another tab in order to put the zencastr tab in the background. This will keep the browser from needing to draw any UI elements and cut down on CPU usage while recording.
- Change the sample rate of your audio device to 44100. This will make it so Zencastr doesn't need to resample your audio and will help ease the CPU burden. see How to change the sample rate of your audio devices.
The browser vendors are working on an update that will resolve this problem so you won't need to worry about these issues for much longer. We expect this update in December and appreciate your patience while we do our best to mitigate the problem until then.