One of the more vexing problems in the world of online video is dealing with situations where audio and video get out of sync. This can happen at almost any stage of the production workflow, and there can be a lot of reasons for it. However, I wanted to point out one particular reason why this might happen at the encoding stage, as it’s an issue we’ve run across here at OIT on a number of occasions.
If you’re creating .mp4 files, as a lot of us are these days, via QuickTime Pro or the QuickTime export options in another editor, and streaming those files via QuickTime Streaming Server, you’ll want to tweak a particular setting called RTP Payload Encoding. There are two options for this setting, and the default is usually H.264. If you choose that setting, and if your video is longer than 10 minutes or so, in our experience audio and video will gradually drift out of sync during playback, and you’ll have sync problems if you try to seek to particular parts of the video. If you play the video locally on your machine, however, there are usually no discernible sync problems.
Magically, if you select “QuickTime” for this setting, the synch problems disappear.
You can use the screenshot below and the following steps to find and modify this setting in QuickTime Pro:
- Open the video you want to export in QuickTime Pro. Select “Movie to Hinted Movie” in the Export options.
- Click the “Options” button.
- Under “H.264 Video,” click the “Track Hinter Settings” button.
- From the “RTP Payload Encoding” drop-down box, select QuickTime.
