How to fix corrupted voice memo (m4a) files.
Do you have broken voice memo files? You can fix those files by
yourself. I will show you the steps in this article. Voice memo
files have the extension “m4a”. It is audio data encoded in the AAC
format and encapsulated in MPEG4 file container. You may fix files
recorded with other programs like QuickVoice or on Android. File
extensions may be mp4 or 3gp.
The m4a files get broken when some parts of header lost correct
information. For example, when the bytes indicating the length of the
audio data become 0, the file can not be replayed any more on iPhone,
iPad, Mac or Windows PC.
But, in some cases you can fix the broken header by yourself by
extracting the audio data, encoding it, and putting it into the new
Let’s do it together.
STEPS for Windows PC
- Download faad.exe
Open http://rarewares.org/aac-decoders.php Click “Download (225kB)” of
“FAAD2v20100614 CVS snapshot for Win32“. faad
Extract faad.exe from the downloaded zip file. Place it in the
“Downloads” folder, for example.
- Download faac.exe
Open http://rarewares.org/aac-encoders.php Click “Download (191kB)”
for “FAACv1.28 Binary for Win32“.faac
Extract faac.exe from the downloaded zip file. Place it in the same
folder as above.
For example, you see faad.exe and faac.exe in the Downloads folder as
- Download binary editor
You can choose any favorite binary editor. If you don’t know well, I
will recommend HxD. Download a zip file from
http://mh-nexus.de/en/downloads.php?product=HxD Extract setup.exe and
click it to install.
- Place the file to the same directory.
Move your voice memo file from your iPhone to PC via iTunes. You can
use other tools like iFunbox.
Please place the copied file to the same directory as where you placed
the above faad.exe and faac.exe. We call the file “20140615
163625.m4a”, for example.
- Open the file with binary editor.
Please copy the broken m4a file to some folder for backup. Start HxD
or your binary editor program and open the broken m4a file.
Press F key with control key to open the Find box. Type “mdat” and
press the Find button.
Select from the beginning of the file to the “t” of “mdat” as shown
Press Delete key to delete the selected area. Press S key with control
key to save.
- Decode by faad.exe
Press R key with Windows key to open the dialog. Type “cmd” and press
OK button to open the Command Prompt.
In the command prompt window that was opened, type “cd Downloads” to
move the Downloads folder. Type faad.exe “20140615 163625.m4a” and
press the Enter key. In seconds or tens of seconds, you will find the
decoded wave file named “20140615 163625.wav“.
Check if the command histories are like below. cmd1
- Encode by faac.exe
In the command prompt window, type faac.exe -b 160 -o repaired.m4a
“20140615 163625.wav” and press the Enter key.
In seconds or minutes, you will find the encoded file named
repaired.m4a. Please replay the repaired.m4a to see the audio content
is what you want.
Check if the command histories are like below. cmd2
SysFrontier Inc. 3-23-16, Ekoda, Aoba Ward, Yokohama, 225-0005, Japan.