Video and Audio Out of Sync? Causes and How to Fix It

Key Takeaways

• If video and audio are out of sync by the same amount throughout, try a player audio-delay adjustment or a permanent timestamp offset.
• If the gap grows, investigate timing, recording clocks and conversion settings. A single delay cannot correct a changing gap.
• Check another player and a wired audio output before changing the file.
• Constant-frame-rate conversion can help with an editor’s variable-frame-rate compatibility problem. It does not automatically repair every kind of drift.

When you hear a word before the speaker’s lips move, or see a clap before hearing it, both tracks may be present but timed differently. The useful first question is whether that difference stays the same, grows gradually or appears suddenly after a cut.

Diagnose the pattern before changing anything

Keep the original file. Reset any existing player sync adjustment, play at normal speed and check a clear event near the beginning, middle and end. A visible clap, a door closing or a close-up of speech works better than background music.

Write down whether the sound comes before or after the matching picture at each point. The following patterns suggest different next steps:

What you observe	What to investigate	First action
Roughly the same gap throughout	Track start times, merge offsets or output-device latency	Try a fixed delay
A gap that increases gradually	Timing interpretation, recording-clock mismatch or altered playback speed	Compare the original and converted file
Sync jumps after one cut or glitch	Missing material, a bad join or a timestamp discontinuity	Inspect that point in the source or editing timeline
Only one player or audio device has the problem	Playback settings, decoding performance or device latency	Try another player and wired sound

These are clues, not proof of one particular cause. If a video plays correctly through the laptop speakers but falls behind through Bluetooth headphones, start with the audio connection. If playback stutters while the gap grows, try a less demanding playback setup before processing the media.

Separately saved audio and video can also start at different moments. Merging them into one container does not guarantee their start times match. Confirm they belong to the same edit: a track from a version with a different introduction or missing scene cannot be aligned everywhere with one offset.

Quick fix: adjust audio delay in the player

Look for an audio synchronization or audio-delay control in your player. Adjust a little, replay the same event and check whether it improves. Players can label the direction differently, so follow the result on screen rather than assuming a positive number always means the same thing.

• Sound happens first: delay the audio.
• Picture happens first: advance the audio relative to the video, or delay the video if the player supports that.

Check the middle and end again. A player adjustment changes playback; it does not rewrite the media file, and another device will not necessarily inherit it. Reset the adjustment to zero before evaluating a repaired file.

Permanent fix for a constant offset with FFmpeg

The examples below assume FFmpeg is installed and use input.mkv as a placeholder for your file. Change the input filename and choose a new output filename. The 0.300-second offsets are hypothetical examples, not measurements of your video.

Sound is 0.300 seconds early

Delay the audio while keeping the video from the unshifted input:

ffmpeg -i input.mkv -itsoffset 0.300 -i input.mkv -map 0:v:0 -map 1:a:0 -c copy fixed-audio.mkv

Sound is 0.300 seconds late

Delay the video instead:

ffmpeg -i input.mkv -itsoffset 0.300 -i input.mkv -map 1:v:0 -map 0:a:0 -c copy fixed-video.mkv

In these commands, inputs 0 and 1 are two reads of the same file. -itsoffset applies to the following input; a positive value delays it. The maps select the first video and audio tracks, and -c copy avoids re-encoding. See the FFmpeg input-offset documentation.

Replace 0.300 with the correction you need, in seconds. Delaying video can leave a short opening interval without a video frame, so inspect the beginning as well as the dialogue. Both examples intentionally select one video track and one audio track; they do not preserve subtitle or additional audio tracks. Keep the original if you need those streams.

Stream copying preserves the encoded media quality. It cannot fix an offset that changes during playback. A container change alone is not a timing repair either: the TS-to-MP4 explanation shows how remuxing differs from re-encoding.

What to do when audio drifts over time

First compare the original recording with the converted or exported file. If the original stays in sync, return to it rather than repeatedly converting an already faulty export.

Variable frame rate means the spacing between video frames can vary. It is not inherently broken: a compatible player follows the timestamps. Trouble can arise when an editing workflow interprets that timing incorrectly. A constant-frame-rate intermediate can help in that situation.

For example, to create a 30 fps editing copy:

ffmpeg -i input.mkv -map 0:v:0 -map 0:a:0 -vf "fps=30" -c:v libx264 -crf 20 -preset medium -c:a aac -b:a 192k editing-copy.mp4

Choose a rate appropriate to your source and project; 30 is an example, not a universal repair value. The FFmpeg fps filter creates regular frame spacing by dropping or duplicating frames. This command re-encodes video and audio, so it takes longer than stream copying and can change quality. It requires an FFmpeg build with the libx264 encoder.

Import the intermediate into the editor and export again. This approach is most useful when the original timestamps are sound and the editing workflow mishandles them. It does not reconstruct timestamps that are already wrong or replace missing footage.

If drift remains in multiple players, check whether separately recorded audio runs slightly faster or slower than the video. That calls for a duration or speed adjustment in an editor, followed by start-point alignment. Measure matching events far apart to establish the rate difference. If the gap changes suddenly at a cut, repair that section or reassemble matching source material rather than stretching the whole track.

Verify the result before replacing anything

Open the new file with player sync adjustments reset. Check the same events near the start, middle and end, then seek around the file and check the final scene. Confirm the intended audio language is selected and the opening and ending are intact.

If the beginning is aligned but the ending still drifts, return to the timing diagnosis. Increasing a fixed delay will only move the point where the two tracks happen to line up.