H.264 Out of Sync w/Flash Player: The Fix

I was working on new screencast tutorials for SpokenWord.org, and I wanted to use H.264 encoding for the video because the quality seemed better than most of the other options available. But I also wanted to use the JW Player, which uses Flash. The only problem was that while the H.264 file was great using the Quicktime player, it was out-of-sync when viewed using the Flash player. Thanks to The Google I came across what seemed like a whacky explanation and workaround. Andrew Wallace suggested that the Flash player not only decouples audio and video, but that it also time-compresses (in the audio track only!) period of pure silence. Sure enough, he appears to be right. And his suggested workaround does indeed solve the problem. I added a continuous track of white noise attenuated to -70dB from peak to the entire presentation. It’s inaudible because of the low level, but the Flash player sees it as non-silence and reproduces the audio track in-sync with the video. Strange but true!


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