Synchronization Issue


I have timing issues with an experiment that is very dependent on the accuracy of the audio and video stimuli. Unfortunately right when the experiment begins a temporal drift also begins where both the audio and video slowly become asynchronous. I have tried to chop up the audio files and to link each one to the video files to which they are related, but even then I feel as if there should be a more accurate solution. Any comments??? Thanks for your help!

Exactly what are you trying to do?

If you have specific video that needs to be paired with specific audio, you’d be better off with a single video file, as then the underlying media system will be explicitly working to ensure that the audio and video stay synchronized (be it QuickTime or DirectX).

Are you running on a Mac or Windows?

I have multiple jpeg files that are supposed to be paired with specific audio. The ultimate issue is that I need to have very accurate response time data, and when the audio and jpegs are misaligned my data is close to worthless. When you say single video file do you mean that I should include both the audio and video in the same file? I am using an imac. Thanks.

So, do you have one long audio file and multiple jpegs that are being presented in multiple trials? Is this what’s going on?

If this is the case (audio crossing trial boundaries), then this is definitely what will happen, and there is a solution. In the trial editor, you are given the option to present trials at regular intervals. This is primarily used to synchronize trials with an MRI machine, but ultimately, it’s how you get around the issue that there’s an unknown (and therefore assumed variable) amount of delay between trials. It’s small, but over many, many trials, it adds up and is very noticeable.