healing File Repair

Repair a damaged recording file.

Repairing corrupted audio usually requires a computer, but there are a few approaches you can try depending on the recording format and the type of damage.

info

Repairing corrupted audio files is a more advanced process and usually requires a computer. You can use this guide to transfer the recording before attempting any repair. Always create a backup copy first.

Start with the file type

Each format uses a different encoder. This guide focuses on WAV (.wav) and MPEG4-based files such as .m4a and .aac.

MPEG4 files are more complex than standard WAV files because they use lossy compression, but they can sometimes still be repaired if the file header is intact.

Try audio software first

Many damaged recordings can be opened or converted by audio tools such as VLC, iTunes, Windows Media Player, or other editors.

  1. Download VLC Player and install it.
  2. Open VLC Media Player.
  3. Use the Convert/Save option.
  4. Add the damaged recording file.
  5. Choose a destination folder and file name.
  6. Start the conversion process.

Repair with FFmpeg

  1. Download FFmpeg.
  2. Extract the archive and open the bin folder containing the ffmpeg executable.
  3. Copy the damaged audio file into that folder.
  4. Open a command line window in that location.
  5. Run a copy-based repair command similar to this:
ffmpeg -i damagedfile.m4a -c copy fixedfile.m4a

Advanced repair with FAAD2

If the AAC stream inside a damaged .m4a file is still present but the MP4 container is broken, you can try a more advanced repair using the FAAD2 library. This method is intended for advanced users on macOS or Windows.

What you need

Install FAAD2 on your system first.

  • macOS: install via Homebrew.
  • Windows: download a faad.exe binary, for example from the FAAD2 releases page.

macOS install command:

brew install faad2

Step 1: Prepare the damaged file

Open the corrupted .m4a file in a hex editor.

  • macOS: Hex Fiend
  • Windows: HxD

At the beginning of the file:

  • Remove all leading zero bytes.
  • Remove the MP4 container header containing isom.
  • Keep only the AAC stream data starting with 00 D0 00 07.

Save the cleaned file as raw.aac.

warning

The file must start exactly with AAC frame data for this method to work.

Step 2: Decode the AAC stream

Open Terminal on macOS or Command Prompt on Windows.

Run one of the following commands:

macOS

faad -a out.aac raw.aac

Windows

faad.exe -a out.aac raw.aac

This should create a repaired file named out.aac.

Step 3: Verify the repaired file

Try playing the new out.aac file. If the AAC stream was recovered correctly, it should now play normally.

Step 4: Convert back to M4A (optional)

If needed, you can convert the repaired AAC stream back into an .m4a container using FFmpeg:

ffmpeg -i out.aac repaired.m4a

This will create repaired.m4a.

Summary: remove the damaged MP4 header, decode the raw AAC stream with FAAD, and optionally convert it back to .m4a.