Change video speed without chipmunking the audio

JAD uses FFmpeg's atempo filter to pitch-correct audio after speed adjustment. For moderate speed changes (0.5× to 2×), speech and music maintain their original pitch (the audio resamples time without changing pitch). For more extreme values (0.1× or 4×+), the atempo filter operates in chained passes. Note that at extreme slow speeds, audio quality degrades as samples are stretched beyond natural limits.

JAD supports speed values from 0.1× (10% speed, 10× slow motion effect) to 16× (16 times faster, used for time-lapse creation from regular footage). The atempo filter has a usable range of 0.5–2× per pass, so values outside this range are applied in multiple chained passes. At 0.1× with audio, quality degrades noticeably — for extreme slow motion, mute the audio track or use a dedicated slow-motion capture device.

Yes — this is one of the most common use cases. A 60-minute screen recording at 10× speed produces a 6-minute time-lapse. Set the speed multiplier to 10 and optionally mute the audio (stretched speech at 10× is unintelligible). For even faster time-lapse (e.g. 4 hours of footage into 2 minutes), use 120× which requires chained atempo passes — use the discard audio option for these extreme ratios.