How do I sync audio from a separate mic with my video?
Clap once at the start, then let Premiere Pro or DaVinci Resolve line the mic recording up with the camera’s own audio by waveform, or slide the mic track by hand until the two clap spikes start on the same frame. Then check the last minute as well: if the mic has drifted on a long recording, change the mic clip’s duration by exactly the amount it is off instead of nudging it again and again.
The steps at a glance
Syncing is two jobs: line the two recordings up once, then make sure they stay lined up to the end. In order:
- Record a clap and keep the camera’s own audio.
- Check the files for variable frame rate before you sync.
- Measure the offset with the free audio sync offset finder.
- Sync by waveform in Premiere Pro or DaVinci Resolve.
- Or line up the clap by hand, in CapCut or any editor.
- Check sync at the end of the recording.
- Fix drift by changing the mic clip’s duration.
- Watch three moments at full speed, then export.
Written by Kevin Tabares, long-form YouTube editor since 2015: 1,277 videos and 152.2M+ views tracked on YT Jobs.
Any edit that arrives as a camera file plus a separate mic file starts with this job, which is why I built the free offset finder this guide uses.
Step 1: Record a clap and keep the camera’s own audio
Clap once, in frame and close to the mic, after both devices are recording: the frame where the hands meet and the spike on the waveform give you one exact sync point. On anything longer than a few minutes, clap again before you stop, so you can measure drift later.
Leave the camera’s own mic on even though you won’t use its sound. Automatic sync compares two recordings of the same moment; the DaVinci Resolve manual describes waveform syncing as matching the camera audio against the separately recorded production audio. Record the mic at 48 kHz, the sample rate in YouTube’s recommended upload settings.
Step 2: Check the files for variable frame rate before you sync
Phones, webcams and screen recorders often record at a variable frame rate (VFR), and VFR video can drift against a separate mic. The free dropped frames checker tells you whether a file is constant or variable. An Adobe employee’s Premiere Pro FAQ on VFR (January 2019) says Premiere decodes VFR clips that have audio with Preserve Audio Sync by default, one of the MPEG Source settings you see in the Effect Controls panel when the clip is open in the Source Monitor. The same FAQ says that option does not work on every file, and that it is better to convert to a constant frame rate before a proxy, consolidate or transcode workflow, naming Shutter Encoder and HandBrake. So if a VFR file still drifts, or you plan to use proxies, convert it first and sync the converted copy.
Step 3: Measure the offset with the free audio sync offset finder
Open the camera video and the mic recording in the free audio sync offset finder. It reports how far to move the mic audio in milliseconds and in frames, with a confidence score, measures the drift between the two clocks, and can hand you the mic audio already lined up as a WAV. Both recordings only need a few seconds of shared sound, and the files stay on your device. Each file can be up to 60 minutes long; for a longer recording, measure the start offset on copies of both files trimmed to their first few minutes, and check the end by hand in Step 6.
How close is close enough? ITU-R BT.1359, the broadcast recommendation on sound and picture timing, reports that on average viewers detect an error when sound arrives about 45 milliseconds before the picture, or about 125 milliseconds after it. Early sound is noticed far sooner, so when a sync point falls between frames, leave the audio a frame late rather than a frame early.
| Frame rate | One frame lasts | Sound early: noticed at about | Sound late: noticed at about |
|---|---|---|---|
| 24 fps | 41.7 ms | 1.1 frames | 3 frames |
| 25 fps | 40 ms | 1.1 frames | 3.1 frames |
| 30 fps | 33.3 ms | 1.4 frames | 3.8 frames |
| 60 fps | 16.7 ms | 2.7 frames | 7.5 frames |
The frame counts are my arithmetic from those two thresholds. Distance adds a little lateness by itself: as the offset finder page notes, sound travels about 34 cm per millisecond, so a camera 3 m away hears you about 9 ms after a collar mic.
Step 4: Sync by waveform in Premiere Pro or DaVinci Resolve
Premiere Pro, which Adobe’s current help now calls Adobe Premiere:
- Put both clips in a sequence, select them, choose Clip > Synchronize and pick the audio option, which uses an audio track channel as the reference. You can then merge them in the timeline.
- For several cameras, Clip > Create Multi-Camera Source Sequence can sync on Audio, and its Offset Audio by field shifts the separate audio by up to 100 frames either way.
- For Merge Clips in the Project panel, Adobe’s help lists In points, Out points, Timecode and Clip Marker as the sync points, and it lists auto sync using audio waveforms among the limitations of merged clips. The dependable waveform route is Clip > Synchronize in the timeline, then merge; in the Project panel, mark the clap with an In point on both clips.
DaVinci Resolve, from the Resolve 21 manual: put the video and audio files in one bin, right-click the bin, choose Auto Sync Audio and set Synchronize Using to Waveform. Leave Use channel number on Auto or pick a clean channel, tick Retain embedded audio to keep the camera sound on its own track, and press Sync. If a clip fails, run it again on that pair alone. If you marked the clap on both files with an In point, Out point or marker, select the pair, right-click and choose Audio Sync > Auto Sync Audio with In, Out or Marker; multicam clips use Angle Sync set to Sound. Trim > Slip Audio nudges the sync by one frame or a tenth of a frame.
Step 5: Or line up the clap by hand, in CapCut or any editor
Without automatic sync, or when it locks onto the wrong spot, put the camera clip and the mic clip on two tracks with waveforms showing, zoom in until single frames are visible, and drag the mic clip until both clap spikes start on the same frame. Play it: you should hear one sharp clap, not two. Then mute the camera audio. The Resolve manual lists a clapperboard, a hand clap or the flash of a tablet slate app as sync references; without any of those, a hard p or b, or a cup put down on a table, also works.
Step 6: Check sync at the end of the recording
A file that is perfect at the start can be off at the end: the camera and the recorder each keep time with their own clock, and a tiny difference adds up. Check the tail clap, or any hard sound in the last minute. If the two still meet, you are done. If not, note how many frames apart they are and whether the mic is late or early.
On files up to 60 minutes, the offset finder measures this at the start, middle and end of the overlap and gives the drift in milliseconds per minute, with the clip speed that cancels it; its own example is a mic file 0.01% fast, 0.36 seconds ahead after an hour. A steady drift is off by half as much in the middle. If the error jumps around instead, go back to Step 2 and check for variable frame rate.
Step 7: Fix drift by changing the mic clip’s duration
Nudging the mic again every few minutes chases the error forever. Change the speed of the whole mic clip instead, so the start and end claps both land. If the claps are L apart on the camera and the mic arrives d late at the second one, set its speed to (L + d) ÷ L × 100%, or to (L minus d) ÷ L × 100% if it arrives early. With claps near both ends, that means making the clip d shorter when the mic runs late and d longer when it runs early.
| Mic at the end of a 60:00 recording | New mic clip duration | Speed |
|---|---|---|
| 0.5 s late | 59:59.5 | 100.014% |
| 0.5 s early | 60:00.5 | 99.986% |
| 1 s late | 59:59 | 100.028% |
In Premiere Pro, select the mic clip, choose Clip > Speed/Duration and type the new Duration (the speed follows while the two are linked). In Resolve, right-click the clip and choose Change Clip Speed, which accepts a percentage, a frame rate or a duration. Pitch correction (Maintain audio pitch in Premiere Pro, Pitch Correction in Resolve) is optional at drift this small: at half a second an hour the speed changes by about 0.014% and the pitch by about a quarter of a cent, so the voice sounds the same without it. The offset finder can also do this for you: its download can correct the drift by resampling the mic to the video’s timing. If your editor wants the new duration as timecode, the free timecode calculator turns a length in seconds into hours, minutes, seconds and frames at your timeline’s frame rate.
If your editor only changes speed in coarse steps, cut the mic at pauses and re-sync each piece, short enough that the drift inside it stays under a frame: at half a second an hour, one 30 fps frame builds up in about four minutes.
Step 8: Watch three moments at full speed, then export
Scrubbing hides sync errors. Play ten seconds at the start, the middle and the end at full speed, watching mouths on p, b and m. Keep the camera audio muted, since two copies of a voice a few milliseconds apart sound hollow. Before upload, YouTube Help’s fix for audio out of sync is to give the audio and video tracks the same duration, and its upload settings ask for the frame rate you recorded. The video upload checker reads the frame rate and audio track from your export.
Short takes versus long recordings
How careful sync has to be depends on how long each recording runs. Short takes leave drift almost no time to build up: the lessons I edit for English by Erin Marie are recorded in short takes, one point per take. Long recordings are where it shows: Swaylemc’s full Minecraft movies, which I edit, run from one to almost four hours, and at the offset finder’s example rate of 0.01% a four-hour recording would end about 1.4 seconds apart.
On long sessions with a separate mic, clap at both ends and check the end before the edit starts. Drift fixed on one clip is a single speed change; drift found after the cut has to be fixed on every piece of the timeline. With several cameras and mics the order is the same, as in editing podcast videos and editing interviews.
Audio sync FAQ
How do I sync external audio with video in Premiere Pro?
Put the camera clip and the mic clip in a sequence, select both, choose Clip > Synchronize and pick the audio option. Clip > Create Multi-Camera Source Sequence can also sync on Audio. For Merge Clips, Adobe’s help lists In points, Out points, Timecode and Clip Marker as sync points, so sync by waveform in the timeline first, then merge.
How do I auto sync audio in DaVinci Resolve?
Put both files in one bin, right-click the bin, choose Auto Sync Audio, set Synchronize Using to Waveform and press Sync. Tick Retain embedded audio to keep the camera sound. If a clip fails, run it again on that video and audio pair alone.
Why does my audio go out of sync over time?
The camera and the recorder each keep time with their own clock, and a tiny difference adds up over a long recording; a variable frame rate file can drift too. If a variable file still drifts, convert it to a constant frame rate, then change the mic clip’s duration by the amount it is off at the end.
How many milliseconds out of sync is noticeable?
ITU-R BT.1359 reports that viewers on average detect sound about 45 milliseconds early or about 125 milliseconds late. At 30 fps that is roughly 1.4 frames early or 3.8 frames late, so if you have to choose, leave the audio a frame late.
Why is my audio out of sync only after uploading to YouTube?
YouTube Help says to make sure the audio and video tracks have the same duration, since an audio track that is shorter or longer than the video may not sync correctly. Also export at the frame rate you recorded, as YouTube’s upload settings ask.
Sources
Premiere Pro: Adobe Help (Premiere desktop), Synchronize audio and video, Synchronize clips in the Timeline panel, Merge clips in the Project panel, Limitations of merged clips, Create a multi-camera source sequence and Speed/Duration, read October 20, 2026. DaVinci Resolve: Blackmagic Design, DaVinci Resolve 21 Reference Manual, chapters 20, 49 and 58, read October 20, 2026. VFR and Preserve Audio Sync: FAQ on Variable Frame Rate media in Premiere Pro by an Adobe employee (January 22, 2019), read October 20, 2026. Thresholds: Recommendation ITU-R BT.1359-1, read October 20, 2026. YouTube Help, Troubleshoot audio or video issues with uploads and recommended upload encoding settings, read October 20, 2026. Tool features, the 34 cm per millisecond and the 0.01% example: the offset finder and dropped frames checker pages. Frame counts, speeds, the 1.4 seconds and the quarter of a cent: my own arithmetic. Erin Marie’s takes: talking head guide; Swaylemc’s running times: Minecraft horror mod channels.