Video won't play after recording? Here is why, and how to fix it

By the FixMP4 engineering team · Updated October 9, 2026 · Tested on real H.264, HEVC and AAC recordings

You recorded something important, the recording seemed fine, and now the video will not play. The file has a normal size, but players show an error, a black screen or a duration of 0:00. This guide walks through the possible causes, from the simplest (a missing codec) to the most common serious one (a recording that never finished writing its index), and shows how to fix each one.

If you just want to try a repair: Open the free repair tool. The diagnosis and a 15-second preview are free.

Step 1: rule out a codec problem

Before assuming the file is damaged, check whether your player simply cannot decode the format:

• Modern iPhones record in HEVC (H.265). Older Windows PCs need the HEVC extension, and some older Android devices and TVs cannot play it.
• Try VLC, which includes almost every codec. If VLC plays the file, it is not corrupted.
• Open the file on the device that recorded it. If it plays there, the problem is the other device.

If VLC also fails, shows "moov atom not found" or plays a couple of seconds and stops, the file is structurally damaged. Go to step 2.

Step 2: understand what went wrong during the recording

A video file is written in two stages. While you record, the frames are appended to the file. When you stop, the device writes the index (in MP4 and MOV files this is the "moov atom") that lists every frame. If the second stage never happens, the file contains all the frames but no index, and nothing can play it. Typical reasons:

• Battery died while recording.
• Crash or freeze: the camera app, the phone or OBS crashed.
• Storage full: the card or phone ran out of space mid-recording.
• Card removed or a loose connection on an external recorder.
• Overheating: phones and action cameras shut down when they get too hot.
• Interrupted transfer: the file was cut short while copying, downloading or syncing.

Step 3: diagnose the file

Drop the file into the FixMP4 repair tool. In a second you will see a plain-English diagnosis, for example:

• "The index (moov atom) is missing",
• "The media data ends early: the recording was cut off",
• "The file header is damaged",
• "The box structure breaks at byte 1,234,567".

This takes no upload and costs nothing.

Step 4: repair it

How the repair works depends on what is damaged:

• Index missing (most common). FixMP4 rebuilds the index from the media data. For video you add a short healthy clip from the same device with the same settings as a reference; the codec settings are copied from it, and every frame in the broken file is located and indexed. For audio-only recordings the reference is usually optional.
• Index present but file cut off. The surviving index is reused, frames that are no longer in the file are dropped, and a clean file is written. No reference needed.
• Header damaged. The tool finds the surviving parts of the file even when the first bytes are gone and writes a new header.

You then watch the first 15 seconds of the repaired video. If you are happy with the result, a subscription ($9/month or $29/year, cancel anytime) lets you export the full file.

Device-specific notes

iPhone and Android phones

Phones record MP4 or MOV with H.264 or HEVC and AAC audio, which FixMP4 supports. Make the reference clip with the same camera settings (resolution, frame rate, HDR, "High Efficiency" vs "Most Compatible").

GoPro, DJI and action cameras

These cameras write standard MP4 with H.264 or HEVC. They also add a telemetry or metadata track; FixMP4 skips data it does not recognise and restores video and audio. Use a reference recorded in the same mode (resolution, frame rate, lens, stabilisation setting).

OBS and screen recorders

If OBS crashed while recording to plain MP4, the file has no index. FixMP4 can rebuild it when OBS used H.264 or HEVC with AAC audio; record a few seconds with the same settings as the reference. For the future, record to MKV or "fragmented MP4" and remux afterwards: those formats survive crashes.

Dashcams and security cameras

Many dashcams write MP4 with H.264. Some use their own variants or PCM audio, which are not supported; the free preview will tell you.

What cannot be fixed

Be wary of any tool that promises to fix everything. Some damage is permanent:

• a 0-byte file or a file full of zeros contains no video,
• frames that were overwritten cannot be restored, only skipped,
• codecs FixMP4 does not support yet: ProRes, AV1, VP9, MPEG-4 Part 2, PCM/ALAC/Opus audio.

Because the preview is free, you will know before paying whether your file can be repaired.

Prevent it next time

• Stop the recording before turning off the device or removing the card.
• Keep batteries charged and storage free for long recordings.
• Let devices cool down during long sessions in the sun.
• Use crash-safe formats when your software offers them.

Related guides: fix "moov atom not found", repair MP4 files, repair MOV files and why recordings get corrupted.

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