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Some friends and I have started a weekly podcast, and have decided to add video to it, currently we are using Audacity to record audio and an SX30IS powershot to record video. When I place both of the files in my editing program and sync the audio track to the video, the audio and video are sync perfectly at the beginning but are off by ~4secs at the end of the 20 min video, any idea what is causing this and how to fix it?

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Yes. I can tell you exactly what is wrong.

Your synch is off because the frame rate you 'think' you are recording, isn't the frame rate you are editing at. Consequently when you lay in the audio, it loses synch.

Specs of this camera say that it will record at '30fps' but it is highly likely you are actually shooting at a non-integer frame rate of 29.97fps, consequently you need to adjust the frame rate in the timeline to suit. This will more than likely be the case if you have the video mode set to 'NTSC' anywhere in the camera.

It might also be worth confirming the real frame rate using Quicktime player and checking in the movie inspector.

Pull-up/pull-down issues are almost always caused by a frame-rate imbalance.

If you are unable to adjust the frame-rate to correct this, you can use a pull-up/pull-down timeshift to fix the issue. If the issue is simply an integer to non-integer frame rate issue, a timeshift of 0.1% should do it.

  • That does indeed appear to be the problem. However, I can’t seem to find a program that would do such a shift. Are there any free tools to achieve the desired shift? – Connor Clarke May 26 at 3:24
  • What video editor are you using? – Mark May 26 at 3:42
  • My first port of call would be to alter the project timeline frame rate in the vision editor prior to conforming the production audio into the timeline. Keep the audio at the same rate, but conform the vision to the correct frame rate. – Mark May 26 at 5:48
  • Lightworks, although i am open to using another one if it allows this type of transformation. – Connor Clarke May 26 at 18:24
  • I was able to resolve the issue, Thanks for the help! – Connor Clarke May 26 at 20:18

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