This is how I fixed my audio sync issues on my Elgato Game Capture HD.
The problem is that my commentary would be about .5-1.5 seconds too early so it would be painfully obvious and kind of ruin the point of the video. Turns out the problem seems to be leaving the Live Commentary button constantly running will create some sort of sync problem, and will mess things up. To fix it, all I did was make sure that the live commentary was turned off when I press record.
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