Videomaker – Learn video production and editing, camera reviews › Forums › Technique › Sound › Audio Sync › Hi Ted, I would start by
I would start by testing results between your recording format. My feeling is that if you’re using mp3 as a recording format you will experience such problems. You might get better results in WAV format, however, there’s no guarantee. I think the root issue is that the device does not have the same time-base format as video. That means the device will interpret time differently. In your case the H4 compresses the time. It’s only noticeable when you’re recording for longer durations.
As for compensating for that time compression, you’re technique of slowing down the video fractionally makes perfect sense. Although, I think that could be damaging to the quality of the video so I’ll suggest another idea. If you can find a few places (say every 8-10 minutes) in your video where there’s a lull or a similar audio environment (such as an applause or silence), cut the audio in those places and then slide each section and align them to fit naturally with the video. Then fill in the gaps with some selections from that audio file the imitate the audio environment of that particular scene. Make sure to mix it in using you volume/gain controls so that it sounds natural.
Another technique is to stretch the audio and adjust the pitch to compensate for the slow down. This in many ways can be easier to pull off than my first suggestion. But, you’ll need the right software/audio filter effects to do it. What do you have at your disposal?