How a 0.2s audio sync bug slipped past a drift corrector in a video app

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HaramLite, a desktop app that strips music from video locally without cloud uploads, discovered a subtle audio-video sync bug in its browser extension. The extension mutes a video's original audio and plays a separately processed track, using a timeline map to skip segments where music was removed. A flaw in the re-anchoring logic caused audio to lag by roughly 0.2 seconds on ordinary playbacks, making users hear the first word of sentences twice. The bug evaded detection because the app's periodic drift corrector only triggered at a 0.35-second threshold, well above the 0.2-second leak. The fix involved computing audio position from the seek target rather than the element's current time, and applying a tighter 0.05-second tolerance specifically at jump points.

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