Audio Repair and Restoration

How to fix audio that is out of sync with video in REAPER

By StudioRescue Editorial

Published August 13, 2026

Out-of-sync audio is one of those problems that feels random until you name it. You line up a voiceover, a podcast video, or a song against footage in REAPER, hit play, and the mouth and the sound do not match. The good news is that there are really only two causes, and each has a clear test and a clear fix. Guessing wastes time, so the first job is to tell them apart.

The two problems, and why the difference matters

A constant offset means the audio is early or late by the same amount from start to finish. The word and the lips are always, say, 120 milliseconds apart. This is the easy one. Nothing is stretched or broken, the two pieces just start at different times, and sliding one of them fixes the whole clip at once.

Drift is different. The start might look perfect, but by a minute in the audio is noticeably ahead of or behind the picture, and it keeps getting worse. Drift means the audio and the video are running at slightly different speeds. Sliding the audio cannot fix this, because there is no single offset that works. You line up the start and the end goes wrong, or the other way around.

Load the video into REAPER so you can see the sync

You cannot fix what you cannot see, so bring the picture into the session next to the audio.

A useful trick is to leave the video's own audio in the project, muted, as a reference. It is already perfectly in sync with the picture, so you can line your new audio up against it visually and by ear instead of squinting at lips.

Fix 1: a constant offset

This is the common case and it takes about a minute.

1. Find a moment with a sharp, visible sound: a clapperboard, a hand clap, a door, or a hard p or t at the start of a word.
2. Zoom in on that spot on the timeline so you can see the picture frame and the audio waveform together.
3. Drag the audio item left or right until the transient sits under the exact frame where the sound happens. For fine moves, select the item and nudge it with the arrow keys, or set an exact position in the item's properties.
4. Play a few different spots across the clip to confirm it holds everywhere, not just at the point you lined up.

Fix 2: drift from variable frame rate video

Drift usually is not a REAPER problem at all. Phones, webcams, and most free screen recorders save video with a variable frame rate (VFR), where the frames per second quietly change during the recording. Audio tools and many editors assume a steady, constant frame rate, so the two slowly disagree and the sound walks away from the picture.

The dependable fix is to convert the video to a constant frame rate (CFR) before you work with it, then re-sync:

1. Run the original video through a free converter such as HandBrake or Shutter Encoder and export it at a constant frame rate. In HandBrake, choosing a constant frame rate forces every part of the file to one steady rate.
2. Replace the file in REAPER with the converted version, set the project frame rate to match, and re-import your audio.
3. Line up the start with a sharp reference sound as in Fix 1. Because the video is now constant, the end should hold too.

If you truly cannot re-encode the footage, you can compensate inside REAPER by stretching the audio by a tiny percentage so its length matches the video, using the item's playback rate or time stretching. This is a workaround, not a clean fix: it is fiddly to dial in, it changes the audio slightly, and it only works if the drift is steady. Re-encoding to CFR is almost always the better route.

One more speed-related cause worth ruling out: a sample-rate mismatch. Video audio is usually 48 kHz. If your REAPER project or your exported audio is at a different rate than the video app expects, playback can run slightly fast or slow and look like drift. Set your project sample rate to match the video's audio, and export at that same rate.

What this will not fix

Lining up audio and video solves timing, and only timing.

• It will not fix recording latency you heard while tracking. That is a monitoring delay from your buffer settings, a separate issue. See how to fix latency while recording in REAPER.
• It will not repair audio that is choppy or full of dropouts. Gaps and glitches are a buffer or CPU problem, covered in how to fix crackle and clicks in a recording.
• It will not clean up the sound of the recording itself, only its position in time. Noise, room, and tone are their own jobs.
• It cannot save footage where the video itself skips or freezes. If the picture drops frames, no audio move lines it back up.

If it still will not line up

Quick order to work through when sync is still fighting you:

1. You lined up the wrong reference. Pick a single, unmistakable transient with a clear visual, not a soft word, and match that frame exactly.
2. It is drift you treated as offset. If a start-line-up keeps failing at the end, stop nudging and convert the video to a constant frame rate.
3. The project frame rate is wrong. A mismatched setting in Project Settings › Video can make the display misleading. Set it to the real rate of the file.
4. REAPER is silent, not just out of sync. If you are getting picture but no sound at all, that is a device or routing problem, not timing. See REAPER has no sound? How to fix it.