ProTools Sync: The Short Video Problem
I mistakenly assumed this issue was fixed several versions ago, but I’ve seen it again recently in ProTools 10. It could be caused by code deep in the video playback core of the software. It could even be caused by some quirk with Quicktime, which ProTools uses for the video decode heavy lifting. I’m documenting it here in case anyone else encounters it — it can be difficult to diagnose and sometimes isn’t simple to solve.
This error occurs when the video file is shorter than the audio. In other words, audio extends past the end of the video. Then audio is highlighted in the Edit window and a Bounce to Quicktime command is issued. For whatever reason, sometimes the video is stretched — frames are added or lengthened — so that the length of the video and audio are the same.
This is a huge problem for several reasons:
The audio and video drift out of sync getting worse toward the end.
The video may look strange, or in extreme cases, terrible.
There is no error message or indication during the Bounce. You have to review the video outside of ProTools to find the problem.
WHY IT MAY SEEM LIKE A DIFFERENT PROBLEM
Video sync can tricky, both in terms of the mistakes we can make because we’re human, and because ProTools is an audio-centric tool that also allows video. The plethora of video codecs makes testing every permutation a challenge for software developers too. Given the number of other things that can go wrong, the short video problem feels especially insidious.
1. Don’t combine the video and audio using ProTools; don’t bounce to Quicktime.
2. Pad the video at the end.
3. Cut the audio to end as soon or sooner than the video.