A video that freezes partway while the audio keeps playing

When the picture freezes and the sound keeps going, the audio track is fine and the video track has hit something the player cannot decode in time, or cannot decode at all. The single most useful test is whether it freezes at the same moment every time. A fixed timestamp points at damage in the file; a freeze that wanders points at playback, such as a slow drive or a video format your Mac finds hard to decode.

Audio and video are stored as separate tracks inside the same file. The player reads both, and when the video decoder stalls, the audio carries on because nothing is wrong with it. That is why this symptom is so common and why it rarely means the whole file is lost.

The test that sorts everything else

Play the video three times from a few seconds before the freeze and note the exact time on the scrubber each time.

• Same frame every time: the file has a problem at that point. Skip to the section on damage.
• Different points, or it plays cleanly on the second try: the file is probably fine and the problem is how it is being played. Start with the next section.

Then try a second Apple viewer. Select the file in the Finder and press Space for Quick Look, or open it in QuickTime Player if you started somewhere else. If one plays through and the other freezes, the file is readable and the issue is the player or its settings.

When the freeze moves around: playback problems

The file is on a slow or busy drive. High-bitrate footage (4K from a phone, a drone or a camera) needs a steady read speed. Playing from a USB hub, a network share or an older external drive can starve the video decoder while the much lighter audio stream keeps up. Copy the file to your internal drive and play it from there. If the freeze disappears, the drive was the bottleneck.

The format is hard work for your Mac. HEVC, especially 10-bit HDR footage, decodes easily on recent Apple silicon Macs and can be heavy on older Intel models. When the decoder falls behind, the picture pauses and the audio does not. Opening Activity Monitor during playback and seeing very high CPU use is a strong hint. H.264 vs HEVC explains which Macs handle which codec comfortably.

The file is still being written. A recording that is still syncing from a cloud folder, or a download that has not finished, will freeze at the point where the data stops. Wait for the sync to complete, then check the size in Get Info again.

The fix for a format problem is a copy in something easier to decode. In the Finder, right-click the video and choose Encode Selected Video Files, then pick a lower resolution or H.264. QuickTime Player’s File > Export As does a similar job. Both write a new file and leave the original alone.

When it freezes at the same point: damage in the file

A freeze at a fixed timestamp usually means some video frames are damaged or missing. Common causes:

• A transfer that hiccuped, leaving a run of bad data in the middle of the file.
• A memory card or external drive with a failing region.
• A camera or phone that lost power or storage briefly while recording.
• A file that was re-saved or trimmed by an app that did not finish cleanly.

Compressed video depends on keyframes: complete pictures stored every so often, with the frames in between recorded as changes from them. If a keyframe is damaged, every frame that depends on it has nothing to build on, so the picture holds on the last good image until the next keyframe arrives. That is why a freeze often lasts a second or several seconds and then the video jumps back to life, sometimes with a smear of blocky color first.

If the original is still on the camera, card or phone, copy it again. Many freezes come from a bad copy, not a bad recording, and a fresh copy costs nothing. How to check whether a video file is corrupted walks through confirming the second copy is clean.

Try re-encoding the file. Re-encoding with Encode Selected Video Files forces every frame through a decoder. Sometimes the new file plays straight through the damaged point with a brief glitch instead of a long freeze. Sometimes the encode stops at the damage, which at least confirms where the problem is.

Repairing the file when there is no clean copy

Manatee has a Repair mode for damaged video, including MP4, MOV, MKV and most other common formats. Drag the file onto the menu bar icon or the window, or right-click it in the Finder and choose Services > Fix with Manatee. It rebuilds the file’s structure around the frames that can still be decoded and writes a new copy beside the original, which it never changes.

The result is labeled honestly. Fixed means the new copy plays through. Partial means some of it was recoverable, for example the first eleven minutes of a longer recording. Not fixable means there was not enough intact structure to work with. What it cannot do is recreate frames whose data is gone: the recovered copy may still skip over the damaged moment, but it will play past it rather than stalling there.

Everything happens on your Mac, which matters for personal footage, and every feature is free for the first 24 hours. After repair, if the picture and sound end up slightly out of step, audio out of sync after a conversion covers why and what to do.

Screen recordings that freeze

Screen recordings deserve a separate note. They are often recorded at a variable frame rate: when nothing on screen changes, very few frames are stored. Some players and editors interpret a long stretch without new frames as a freeze, even though the recording is simply showing a still screen. If the “frozen” section is a moment where nothing moved, the file may be perfectly fine. Converting it to MP4 gives it a steady frame rate, which most players and editors handle more predictably.

Questions

Why does the audio keep playing if the file is damaged? Audio and video are separate tracks, and the audio track is usually much smaller, so damage in a region of the file is more likely to land on video data. The player keeps playing whichever track it can still decode.

Can I just cut out the frozen part? If the rest plays normally, yes. QuickTime Player’s Edit > Trim keeps a section of the video, and saving the trimmed version creates a new file. You lose the damaged seconds, which were unrecoverable anyway.

Will converting the file fix a freeze? It fixes freezes caused by a hard-to-decode format. It does not restore frames that are damaged; at best the converted copy passes the bad moment with a short glitch instead of a stall.