MP4 plays but has no sound: how to find the cause and fix it

By the FixMP4 engineering team · Updated October 21, 2026 · Tested on real H.264, HEVC and AAC recordings

When an MP4 plays picture but no sound, the cause is one of three things: the player cannot decode the audio codec (common with AC-3, E-AC-3, DTS, PCM or Opus audio), the file has no audio track or a silent one, or the recording was interrupted so the audio frames are no longer indexed. The first two are fixed by changing player or converting the audio; only the third is real corruption, and that is what an index rebuild repairs. Work through the checks below in order: they take a minute and avoid paying for a repair you do not need.

Step 1: rule out the obvious

• Check the system volume, the player's own volume and that the right output device (headphones, HDMI, Bluetooth) is selected.
• Play another video in the same player. If that one also has no sound, the problem is the computer, not the file.
• Try the file in VLC, which ships its own decoders for almost every audio format. If it has sound in VLC, the file is fine and your usual player lacks a codec.

Step 2: see what audio the file contains

Use MediaInfo (free, Windows/macOS/Linux) or FFmpeg:

`` ffprobe -hide_banner your-video.mp4 ``

Look for a line starting with Stream #0:1 and Audio:.

Converting the audio to AAC (no quality loss for video)

This copies the video stream untouched and re-encodes only the audio:

`` ffmpeg -i input.mp4 -c:v copy -c:a aac -b:a 192k output.mp4 ``

HandBrake can do the same with a graphical interface (choose AAC in the Audio tab), but it also re-encodes the video.

Step 3: when it is real corruption

If a recording was cut off by a dead battery, a full card or an app crash, the file often still contains both video and audio data but the index (the moov atom) that tells players where each frame lives is missing or incomplete. Symptoms:

• The file will not open at all, or shows 0:00 duration, even though its size is large.
• A recovery tool or "repair" produced a file with picture but no sound, because it only rebuilt the video track.

FixMP4 rebuilds both the H.264/HEVC video track and the AAC audio track from the raw data, using a healthy reference clip from the same device to learn the settings. The free preview lets you hear whether audio was recovered before you export anything.

Open the free repair tool

Cases where sound cannot be recovered

• The device never recorded audio (mic disabled, external mic unplugged, some slow-motion or time-lapse modes).
• The audio was stored in a separate file (some professional cameras and screen recorders write a separate WAV).
• The section of the file holding the audio was overwritten or zero-filled.

Device-specific causes

• iPhone and iPad: videos recorded while another app held the microphone (a call, some music apps) can have a silent track. Screen recordings have no sound unless you long-press the record button in Control Center and turn the microphone on; internal app audio is not always captured either, because some apps block it.
• Android: some phones write Opus or AMR audio in screen recordings and third-party camera apps; older players cannot decode them, which shows up as silent playback. Converting the audio to AAC fixes it.
• GoPro, DJI and other action cameras: audio is disabled in some high-frame-rate, time-lapse and HyperSmooth modes, so there is simply no audio stream. DJI drones never record audio from the aircraft itself.
• OBS Studio: check Settings > Output > Audio Track and the Audio Mixer. Recording to MKV and remuxing to MP4 later avoids losing the file in a crash; see fix OBS recordings.
• Zoom and Teams: if the local recording did not finish converting, the audio may be in a separate file in the recording folder. See fix Zoom recording.
• Premiere Pro, DaVinci Resolve and other editors: an export with the audio channel set to none or a muted track produces a silent but valid file. Re-export from the project; repairing the export will not help.

Audio plays but is out of sync or cuts out

That is a different problem from no sound. If the file is healthy, a remux often fixes small timestamp issues:

`` ffmpeg -i input.mp4 -c copy -fflags +genpts output.mp4 ``

For a constant offset, VLC can shift audio temporarily (J and K keys), and FFmpeg can apply a fixed delay with -itsoffset. If sync drifts in a recording that was interrupted, the index was likely rebuilt with wrong timing; rebuilding it from a reference clip with matching settings usually corrects that.

Extracting the audio on its own

Sometimes you only need the sound, for example from a lecture recording. If the audio is AAC, copy it out without re-encoding:

`` ffmpeg -i input.mp4 -vn -c:a copy audio.m4a ``

For other codecs, use -c:a aac or -c:a libmp3lame to get a widely playable file.

Checklist

1. Another video in the same player has sound? If not, fix the computer's audio.
2. VLC plays it with sound? Then it is a codec issue: use VLC or convert the audio.
3. ffprobe shows no Audio stream? Nothing was recorded; check the device setting.
4. Recording was interrupted and the file will not open or is silent everywhere? Rebuild the index of both tracks.

FixMP4 compared with other options