In a Nutshell
Audio files that don’t play can usually be repaired. We explain how to verify whether the file is really corrupt and how to deal with it. Most of the time, you will use Treasured for diagnostics and a customized app for repair.
What is an Audio Repair?
Audio stored in computer files is encoded: Audio wave signal is transformed into a digital representation, made of frames and bytes. Just like video, audio is usually compressed using codecs, allowing voice and music to occupy less space. Most common audio formats are AAC, Linear PCM, AMR, MP3.
Additional information about audio format and codec settings is also needed for the computer to understand encoded audio: Audio is stored inside media containers structured a bit like a book: cover, header, content, index and summary. Most popular audio containers use those file extensions: m4a, aif, caf, wav and 3gp
If any information inside the audio file is modified or is missing, it becomes unplayable. We talk about a corrupt audio file. Repairing the file, to make it playable again, consists in removing alien data and restoring all missing information.
Missing Codec: Repair not Needed
Multimedia systems on computers and devices cannot always reproduce all audio and video formats. Some systems are extensible and you can install additional codecs if the formats inside your file are not natively supported.
In such cases, your file doesn’t need to be fixed. Just proceed to install missing codecs.
Corrupt Audio, Corrupt Container: Repair is Needed
When your computer fails to open or read an audio file, many error messages can come up.Examples:
- “not a valid AIFF file”
- “The movie could not be opened” – QuickTime Player. See detailed errors list
- “Audio File format not supported” – IntelliScore
- “An error occurred while saving the audio file (Error-2)” – MakeMusic Finale 2012
- “Unable to decode m4a file (is corrupt or not supported audio type)” – Windows
- “The specified format is not supported or cannot be translated. Use the Capabilities function to determine the supported formats.” – MediaMonkey
Sometimes the file opens but audio doesn’t work:
- Audio plays well at the beginning, then becomes silent or only noise is heard. Probably a corrupt index.
- Audio is too fast, too slow, high-pitched (“chipmunk” problem) or low-pitched. Probably a bad codec configuration.
Situations where a Repair is Needed
- Voice Recorder has created a damaged file due to device crash or incoming phone call.
- Voice files that have been deleted and recovered using any restore software. Typically those files won’t play so a repair is needed.
- Corrupted mp3 files not able to play in WMP.
- Software malfunction accidentally trashing an audio file.
- Unplayable AMR files. Possible causes are virus infection, or abrupt or inappropriate system shutdown while file was being used.
- Lack of header in AIFF files typically used in Voice Memos applications.
- AAC audio files that are playable during a few seconds and then become silent.
- WAV files accidentally modified or not gracefully terminated.
- Corrupt 3GP files from mobile devices, when recording suddenly stopped due to lack of battery or app crash.
- Deleted M4A files from mobile applications, once recovered (undeleted), need also to be fixed.
In case you need to repair or recover any damaged or broken audio file, just download Treasured and place a repair request.
Warning: Audio Repair is very hard, even for computer-skilled persons. You likely will spend hours or days, to no avail. Use our Repair Service if you need results.
Linear PCM is easier to repair than most other audio formats, because it’s just analog-to-digital conversion of the signal: no compression involved. Therefore, audio frames have a constant byte size, for example 4 bytes for 16 bits stereo PCM, so if you transplant audio data from the damaged file into a good container, it should work.
Warning: This method only works for Linear PCM audio files.
Step 1: Create a good audio file with same settings
We will create a good audio file with exactly the same settings as the damaged one and whose duration is slightly more than damaged file duration (10 seconds in this example).
First we record 11 seconds of audio, using for example QuickTime (File > New Audio Recording). We export it with the same exact settings as the damaged file. Here, QuickTime .mov with Linear PCM 16 bits stereo,Little Endian, 48000Hz:
We call our exported file placeholder.mov
Step 2: Copy hexadecimal PCM data from damaged file into placeholder
We need to transplant hexadecimal PCM data of damaged file into placeholder.mov, our working audio file. This hexadecimal surgery operation requires that you are familiar with hex editors.
First, find the range of data in damaged file where PCM media is stored. For 16 bits PCM audio, you can visually detect columns of data corresponding to high bytes, with typical values around 00 and FF, every 2 columns:
Now, make a copy of placeholder.mov in case something goes wrong.In your placeholder file, detect the area with same characteristics. It should start with mdat atom and go until the end of placeholder.mov:
Don’t include QuickTime container atoms in this range, those atoms must remain intact:
Now copy the block of damaged PCM data into placeholder, and paste in Overwrite mode just after mdat. Save your modified placeholder.
Step 3: Verify that audio file is repaired
Now hold your breath and open placeholder.mov, if everything was done correctly, it now plays audio from your damaged file.