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 file container.

Let’s do it together.

STEPS for Windows PC

1. Download faad.exe

Click “Download (225kB)” of “FAAD2v20100614 CVS snapshot for Win32“.

Extract faad.exe from the downloaded zip file.
Place it in the “Downloads” folder, for example.

2. Download faac.exe

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 below.

3. 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 or
Extract setup.exe and click it to install.

4. 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.

5. 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 below.


Press Delete key to delete the selected area.
Press S key with control key to save.

6. 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.

7. 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.

Did you succeed?
If you encounter any difficulties, please feel free to post a comment.

Repair Service

If you want us to repair your corrupted files, please send email to

The price depends on the recording length recovered:

  • $10 for less than 10 minutes
  • $20 for 10-30 minutes
  • $30 for more than 30 minutes
  • $40 for more than 2 hours

You will pay the fee via PayPal.

If the file is very large, please upload it to Dropbox or Google Drive, etc. and give us the link.

Company Information

SysFrontier Inc.
3-23-16, Ekoda, Aoba Ward, Yokohama, 225-0005, Japan.

269 thoughts on “How to fix corrupted voice memo (m4a) files.”

  1. I have a M4A file that I can’t open it shows zero duration and the size of the memo is around 80 MB and I use Mac how can I fix it?

  2. I am getting stuck on step 6 with the decode. The command prompt says “Unable to find correct AAC sound track in the MP4 file”. Is there any way I can get some additional help?

    1. The file that you try to decode doesn’t seem to start with a correct byte of AAC sound data.
      Please extract another place from the original file, then try decoding.
      Keep doing so until you find the correct starting byte of audio data.

      1. Another place, such as where? I don’t understand hexidecimal, so I’m not clear what to remove or leave alone, to figure out how to make the right adjustments.

      2. WOW!!!!! Awesome!!!! I had the same problem with “Unable to find correct AAC sound track in the M4a file” until I deleted the mdat data correctly. In my case I had to start at the beginning of the file up until the t in mdat which was pretty far from beginning to mdat line. Thank you so much!!!!!

    1. During the execution of step6, it shows error: Maximum number of bitstream elements exceeded. Could anyone share how to proceed? Or how to recover the corrupted .M4a file? Thanks in advance for your help.

    1. The recording application may have crashed at the time of 9 minutes. In such a case, the rest of the recording has been lost forever.

  3. I never post online comments, but I will make an exception for this page. Your instructions helped me recover a corrupted iPhone recording I had thought to be lost, and what’s more, in a very simple, quick way (and without the high fees asked by recovery services). This made my day, and I thank you for that. Have a good one.

    1. I am with you on this one. I seldom post online but this page is a life saver! Awesomely great and easy to follow instructions? Check! Lost file recovered? Check! One happy human? Check check check!! My faith in Humanity is restored! Thank you Sys Frontier Inc!!!!!

  4. Dear sir, i want you to help me. I recorded a file which is related to university research purpose. now it is not working. it says that it is corrupted. I want you to help me. please please please…

    my email address is here.

    please help me. I tried your method, i think i cannot do it because my english is poor. please help to fix this

  5. Your instructions are very good! thanks al lot!

    However I have a problem with the last step, when i run faad.exe , the cmd prompt says “unable to find correct AAC sound track in the MP4 file.” What did I did wrong?

    Thanks in advance!

  6. Not sure this information has been posted elsewhere – this is absolutely golden and allowed me to recover what I thought might be a lost voice recording on my blackberry which crashed whilst recording.

    Thank you very much for your help.

  7. Thank you for your instruction.

    I got stuck at step 6 with the error: Bitstream value not allowed by specification.

    Please guide me to fix this error.

    1. It’s explained here a little further.

      I got the same error but the generated .wav worked fine for me. It is normally audible and when I went forward with the last step, I also got a repaired .m4a file that worked also fine 🙂

      Thanks a lot to Sysfrontier.

  8. Hi! I cannot find ‘mdat’ and not sure how to solve it. Could I send you the file? Thank you very much!

  9. Hello how do I find the mdat area ? I found the mdat tag but how do i determen the end of the area. I assume that the meat tag is the start of the area. I am using the 0xED editor.

    thank you for your information

    1. The 4 bytes before the mdat tag indicates the length of the mdat area. It might be in little endian byte order.

      1. There are 4 points in front of mdat. The 4 points are the eight zeros which are the four bytes ?

        00 00 00 00 6D 64 61 74 = ….mdat

        is this string of numbers what i need to delete including the mdat tag ?

        what length amounts 00 00 00 00 to ?

        I appreciate your answers greatly, I lack the common knowledge to translate the bytes into the length of the area. I have googled greatly but cannot find the “for dummies” version.

        1. Right, 8 zeros are the four bytes. But, these zeros should be replaced with correct length of mdat. It is impossible to do it by calculation because the file is not in the correct format. The only way I found is to decode and encode the remaining AAC audio data to regenerate the audio file again as I wrote in this article.

          1. WOOHOO it worked, i was thinking waaaaaaay too much. I thunk that an “area” in an hex editor must be something really complicated that would be something in the middle of the file that needed to be calculated………….

            Literally select from and including the first symbol in the left column of the hex editor to and including the letter “t” of “mdat” and delete the whole beginning area. Followed your steps and it just worked.

            Thank You Thank You Thank You

  10. When decoding i am facing below issue.

    recording162 file info:

    Error: PCE shall be the first element in a frame
    0% decoding recording162.

    Plz help me.

  11. Hi, got stuck at Step 6. Seems m4a file went from nearly 90Mb to 20mb. Is it possible to email you the file directly for assistance? Thanks,

  12. Just used these instructions to salvage a corrupted 45 minute research interview. The decoding and encoding worked flawlessly.

    The repaired file is twice the size of the original — this because the original was mono and the recovered file is stero.

    In this case the “mdat” string was not found. So I found the beginning of what looked like data and deleted everything prior to it. It appears the absence of this string was what caused the corruption in the first place.

    Thank you for taking the time to describe this process and the available tools. This is a valuable and informative technique!

  13. Hello, thank you for your time and helpfulless! I am finally feeling hopeful but now that I’ve downloaded all the files and got iHex, I’m realizing I can’t open the faac file and that you clearly wrote STEPS for Windows PC!

    Do you know if there is another decoder for mac? And encoder? Maybe some more steps?! lol I’m willing to pay to get my m4a files fixed. I can’t open them in iTunes (no error, just won’t load) or QuickTime (gives an error that the file is either damaged or unsupported). I downloaded and deleted them from iTunes (as well as my iPhone) a few months ago so now all I have is the corrupted file :s

    Thank you!

  14. I have a file that is corrupt from an iPhone recording app.
    It contains evidence of a conversation with in a legal matter and the app crashed at some point, but not after it capture over 10MB of audio.

    I tried fixing it myself, but failed.

    Can you assist me?
    This is extremely important to me.

    How can I get this file to you?

  15. I have a very important file 12MB

    It is not working cause the phone crashed while it was recording. It’s m4a and I need it recovered fast.

    I will pay for service.

    Can you please help and tell me next steps?

  16. Works great!

    Was able to decode 72% of the file before the following error : ‘PCE shall be first element in a frame’

    A .wav file is still created but is missing the other 28% of the audio – Any suggestions?



  18. Found your webpage a few days ago. Worked on following your instructions. I suspect it took me longer to get to a successful conclusion than most.

    Yesterday, I tried again. I finally figured out how much of the corrupted file to delete with the binary editor in Step 5; finally remembered to add the .m4a extension to Step 6 with faad.exe; finally was able to get to Step 7 and faac.exe; faac.exe started running and in no time I had a ‘repaired’ file; and, I opened the repaired file to hear the voices on the recording that I thought I had lost for good.

    Though I may have struggled more than most, the fact remains that you have provided us with such a really simple process that generates such an amazing result. Thank you so much.

  19. Oh my goodness! an amazing article dude. Thanks Nonetheless I am experiencing concern with ur rss . Don’t know why Unable to subscribe to it. Is there anybody getting identical rss drawback? Anybody who is aware of kindly respond. Thnkx

      1. i think this is the same problem as mine… how can i find the beginning byte? can you give me step by step instruction for this method. thanks

      2. This is also my problem. I’m excited to find this method of repairing m4a audio, and I was able to complete the directions using an m4a file that I knew was “good” but the file I’m trying to fix doesn’t have mdat. While searching online I found a website that will fix my file for $35 and they provided a sample, so I believe my file can be fixed, but I don’t have the needed mdat. I’m not tech savvy, but I am persistent and methodical. Can you give us more details about finding the beginning byte of raw audio? Could you recommend a link where we could learn more about that? We were to DELETE data before and including mdat, and save the remaining file. I’ve tried to DELETE starting at different points, but nothing has worked yet. In any case, what needs to be deleted would start at the beginning of the file in all cases. Is that a true statement? THANKS SO MUCH!

        1. Please skip thousands of zero-value bytes and specify the beginning of some non-zero values. Delete all the bytes before that specified point and decode the rest by faad.exe.

      3. Thank you for your encouragement! I have not given up;) I have tried deleting the block of zeros itself and I’ve tried deleting from the block of 0s to the beginning- no luck yet. I’ve tried deleting half the file. No luck. All those tries (plus 4 others) have produced “Error: Channel coupling no yet implemented.” However, when I deleted a little less that half of the data I got a different message. “Error: PCE shall be the first element in the frame.” I wanted to reiterate that I do think something can be retrieved because I heard a sample of it from a website that wanted $35 to fix the file. If I had not heard that sample I would never have thought some of the m4a audio could be retrieved. I appreciate your help. I will keep trying and follow up with what I find. Thank you!

        1. I see Wyatt wrote: “Was able to decode 72% of the file before the following error : ‘PCE shall be first element in a frame’” I felt I should clarify my last post to say I also got that message but it did not decode any of the file. 0%. No .wav file. Richard

  20. Hi! I try to recover a voice file broken but when I do the 6 step the command prompt window says “Error opening file” and anything happen…

    What I suppose to do?
    Thank you in advance.

  21. Figured it out! The wording on step 6 just confused me a bit; thought it meant the beginning of the word “mdat”, to the end of the t, not everything up until the last letter of “mdat”. I appreciate you making this available.

    And I’ve just this minute gotten the recovered version; the entire 1.15 hour lecture I recorded! I’m really happy for this, because it was the most important of the series, and I only expected about half that to be saved in there after seeing an expensive audio recovery service’s assessment. You’re a gentleman and a scholar and I wish you nothing but happiness and success in your endeavors. Have a great day!

  22. Excellent advice. So nice to find a well written process, using good tools, from someone who understands the audio codecs and wrappers. I am very grateful to Sysfrontier and the author/s.

  23. I have a 25 minute file that was unfortunately corrupted. Any chance you have time to re-package for me? I’m on mac and not .root savvy. Thanks

  24. i have the file in a .m4a but file will not play back quicktime say it can not open itunes does do anything can not hear in preview area


    i gave for lost my m4a file, and you really healp me 😀

    Thank you, seriouly!

  26. hi
    thank you for your information but when i go to the cmd and type faad filename.m4a it responses:
    *********** Ahead Software MPEG-4 AAC Decoder V2.7 ******************

    Build: Jun 14 2010
    Copyright 2002-2004: Ahead Software AG
    Floating point version

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License.


    Unable to find correct AAC sound track in the MP4 file.

        1. The area that contains encoded audio data might be screwed up. I need to take a look at the file to know if I can repair it or not.

  27. help me out ,unable to resolve it .
    is there any way to recover..?

    Error opening file: 1.m4a

    C:\Documents and Settings\KINGU1\My Documents\Downloads\New Folder>faad.exe “1.m
    *********** Ahead Software MPEG-4 AAC Decoder V2.7 ******************

    Build: Jun 14 2010
    Copyright 2002-2004: Ahead Software AG
    Floating point version

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License.


    Error opening file: 1.m4a

  28. Am not at all tech savvy but really appreciating your clear instructions and am desperate to retrieve a recorded interview on voice memo. I think I’ve got the process up to step 6 but then I get this message “is not recognised as an internal or external command, operable programme or batch file.”

    Can you help?

      1. Definitely all in the same folder. File route is C:/Users/Sarah> into which I am putting faad.exe and the file name in double quotation marks. It can’t read it – I get the same error message. What am I doing wrong?

        1. In the command prompt window, please type “cd C:/Users/Sarah” and “faad …”.
          Or, please move all files to the Downloads folder and follow the instructions on the article.

          1. Still struggling. I have tried deleting everything from mdat to the start with HxD and I’ve also tried deleting more but it seems to make no difference. The file – several versions of it – are in the downloads folder and so are faad and faac but I just cannot get it to work from the command prompt. I can see that there is 3.88MB in the file and I tried to look at in on a video recovery programme and can see that there is a recording there. Any other ideas?

          2. Did you put all of faad.exe and your m4a files together into the same folder? In the command prompt, please type “dir” to make sure that you have faad.exe there.

  29. Hello, Im getting the error “faad.exe is not recognized as an internal or external commad, operable program or batch file” Any ideas? Im on 64win virtual machine…
    Thanks for the help

  30. Worked beautifully. A corrupted bb playbook voice memo mpa file recovered on windows 7 using Frhed as the editor. Stumbled over what was to be deleted at first but caught on at eventually: “Select from the beginning *of the file* to the “t” of “mdat”.

    This page absolutely deserves it’s spot at the top of the google search results. Great job and a great site, thank you!

  31. I recorded a short story for my granddaughter on voice memo but it is corrupted. I tried your well written instructions many times but am too much of an old timer. Can you fix the file for me if I send it to you?

      1. Hi! Can you please help me with my corrupt file? I followed all the steps, yet I am still unable to play my voice memo. Your help will be much appreciated! This voice memo means a lot to me. Thank you so much. I look forward to hearing back from you soon.

  32. Thanks a lot for the explanation!

    It worked quite well but! after decoding it says:

    Error: Bitstream Value not allowed by specification

    I tried to encode – got the *.wav an die repaired one but all without playing. May I send you my file to have a closer look?

    Best wishes!

  33. as an addition: if there is an easy way to fix it I will try to do this on my own. It would be great if you just could help me. This is an important interview for my thesis! Would be more than great to have this problem solved!

    1. It is very difficult to know what really happens in your file. You may send it to me so that I can find the problem.

  34. May I please email you my file?
    It’s less than ten minutes long and I’ve been trying to do this for over a week..the recording was on an iphone 6 on ‘voice recorder pro’ app, while recording I accidentally turned the phone’s saved as an mp4 file with aac format..has about 5mb data and 00:00 literally does not have mdat anywhere in the binary editor, I’ve also compared it to several good versions to match it up.. heres the message im getting now, ive tried it as mp4 and m4a–

    20150929-140454(2).m4a file info:

    | Config: 2 Ch |
    | Ch | Position |
    | 00 | Left front |
    | 01 | Right front |

    Error: Bitstream value not allowed by specification


    I am hoping to hear from you via email so I may send you the clip, it’s very important and maybe you will be able to help others who have had this exact issue, it’s been almost impossible to find anyone else with this specific experience.

    Thank you so much!!

  35. Heya i am for the primary time here. I came across this board and I find It really useful & it helped me out much. I hope to provide something again and aid others like you helped me.

  36. Hasithaq says:
    March 29, 2015 at 12:28 AM
    it does not work for me. there is an error indicating “Error opening file “SoundFile-8.m4a”

    im stuck at step 6 like the guy above, anyone can help?

  37. Hi!
    Thanks for the very clear explanation… However…. There is no mdat to be found in the file. So I can’t make it work. I have tried to reverse engineer what else I can think of, by comparing in the hex editor the codes of a valid m4a file with my corrupted file. But nothing working yet.

    Could you please help me out? Hope to hear from you soon.


  38. When I originally commented I clicked the “Notify me when new comments are added” checkbox and now each time a comment is added I get several emails with the same comment. Is there any way you can remove me from that service? Appreciate it!

  39. Hi

    I am getting the following error when using faad.exe:

    Error: Channel coupling not yet implemented

    Any chance you could assist or even take a look at the file.

    Thanks in advance.

  40. Hi Thank you for sharing your expertise, the universe is grateful!
    I am not that tech savvy and I’m sure you will make fun of me that i have a mac!
    could you please decode a voice recording that got corrupt when my battery died.
    please help my daughter needs it for a college essay.. her future rides on it (no just kidding, but it is important info!)

  41. Hello, I followed each step and it seems to work fine until step 6. Instead of giving me a .wav file it says “Error: Array index out of range”. I am attempting to fix a corrupted .m4a music file

  42. exelente informacion. Pude recuperar la informacion del audio, apesar que en el paso 6 salio el error “Error: Bitstream value not allowed by specification”.

    solo hay que continuar al paso 7 con el archivo wav generado en el paso 6.

    saludos gracias por compartir la informacion.

  43. Dear,
    I have read and tried to use your instructions to
    “How to fix corrupted voice memo (m4a) files”. I can successfully use the binary editor and delete the “mdat” data. But when I use the faad.exe software it does not produce a .wav file. Can you help? I am willing to email you the file and PAY YOU to repair It. Please respond ASAP. This is an extremely important file. So please respond
    Thank you,
    Al Internicola

  44. I have to admit I haven’t tried this at all, but out of all the help out there this post addresses my problem exactly. I have file with 13 mb but 0 seconds. I am completely lost from direction one, it might as well be in Chinese. I will however pay you via paypal if you will do it for me. I know this was posted a whole ago, so you might have rescinded your offer for help. I am desperate. Oh, and I need it by today or its no help. =D! Pretty pretty pretty please!

  45. I kept failing and kept re reading your instructions. Thank you for saving this tutorial online. A must have !

    Next thing, change the Recording app! haha

  46. very much useful for me, but i stuck up @ 6% with the error “Maximum number of beatstream elements exceeded” how to overcome this ?

  47. Can you help me? Yesterday I recorded a voice memo, it took all day. I couldn’t get it right so I kept trying. Finally I got it and it’s 4 1/2 hours long. It worked fine and was all there. Right after I finished I chose a name and saved the file. The phone died moments later, it was out of battery. This morning, I cannot play the file on the phone. It’s visible, I can move the mark anywhere on the file and see the entire waveform. But when I hit play the pause symbol comes up, but it doesn’t move along the waveform, it doesn’t play. I backed up the phone to itunes, and it doesn’t show up in the voice memo or music folder with the other voice memos. So I opened the backup file with Dr. Fone for iOS by wondershare. With that program I can see the file, it’s 87.7mb. I don’t know if that’s big enough, I’m not sure of the bit depth or sample rate the voice memo app records at, so I can’t say how large it should be. I chose to extract the file and I placed in the folder with the faad etc. The name of the file is Mads Message.m4a (Mads is a person). After the first step with the faad.exe, it says this in the cmd window “Error opening file: Mads”
    I don’t know what to do. I tried so hard to record it, I don’t think I could do it again. It’s, very important. They’re the last things I want to say to someone, who was the most significant person to me in all my 35 years. It explains important things. I hope you can help.

    1. Thank you for contacting us.
      You are trying to fix the very important file.
      Can you check again that the m4a file and the faad.exe are in the same directory?
      If they are so, could you try to do the step 5 and 6 again?
      Please make sure that you delete the area from the beginning of the file to the “t” of “mdat”.

      1. Thanks for your reply. I tried again, and I made sure I had the .m4a file, faad.exe and faac.exe all in the downloads folder. I opened the file in the binary editor. Now when you said “Select from the beginning of the file to the “t” of “mdat”.”, I wasn’t sure if you meant through the T all the way to the period, or right before the T only highlighted through the A, so I tried it both ways. So then get to the CMD prompt and I get to “cd Downloads”, then I type “faad.exe Mads Message.m4a” (Mads Message.m4a is the name of the file). I tried using “Mads Message.m4a”, and “MadsMessage.m4a”, Both times it does give me the software information for the faad.exe program, and then right below that it will just say “error opening file”, followed by the file name. So I am unable to make it through step 6, I am unable to generate the wave file.
        I will say that after examining the file in the binary editor, and comparing it with other working voice memos from the same time period, recorded on the same iOS version, there appears to be no footer. I don’t believe there is a moov atom or I guess anything that would normally be after that, I’m not sure if that is correct though as this is all new to me as of yesterday. So I tried Deleting through the T of mdat on my corrupt file, and to the T. Then I took the moov atom and eveything after that including what I guess is the footer with the date, os version etc., I took all that after the moov atom from a working voice memo and placed it at the end of my corrupt file, and then tried step 6 again, same result. Any ideas?

  48. Thank you very much for this tutorial! Just helped me fix a client’s audio file which I would have been in trouble if I had lost it.


  49. hi i have tried multiple times but keep getting error: bitstream value not allowed by specification 0% decoding i would be very grateful if i could send you the file to see if it is recoverable ? thank you in anticipation

  50. Hi Sysfrontier,

    I was very encouraged to see this thread as I am dealing with the same issue. I recorded an important interview using the Quick Voice app on an iPhone 5. After stopping the recording, the phone ran out of batteries. Upon reopening the app, the 45 minute interview still shows as being 8.5 MB but it has a length of 0:00. It is an m4a ACC file. I am working on a mac and am not able to use the encoding and decoding software nor am I savvy enough to edit the header.

    I have had a diagnostic test run on the corrupt file and I know it is fixable but the company who ran the test charges exorbitant prices.

    Is there ANY way you can repackage the file for me? I can share with you a m4a file of comparable length that is playable.

    I am desperate.


  51. Good afternoon. I have a 12 minute VoiceMemo file which won’t play (it’s an interview) – could I possibly pay you to fix it for me? Thanks in advance and kindest regards

  52. Hi there.
    Thank you for the instructions.
    could you please clarify step 5 ?
    should i delete this whole section? 🙁 sorry to be thick.

    1. Yes, please delete the section including “mdat”. For the decoding error, I need to take a closer look at the file data.

      1. Thank you for the reply Sysfrontier! i have deleted alll of the characters in front of the Mdat section and FAAD came back with an error “error: array index out of range”. :\ im sure it is something i am doing wrong, but i cant seem to figure out what 🙁

        thanks once again.

  53. I just wanted to thank you. Even though the file only kept the first 8 minutes of a 25 minute conversation….and i did lose the most important part, I have to thank you for this guide. Every little step is needed to fix the file. It just sucks I have to live with this loss…..

  54. Good morning! Thank you for your help! I’m eager to recover this file, I’m somewhat computer savvy. (or used to be 15 years ago anyway) honestly, i have tried many things but Im unable to do anything with this one. I was sick when it would’t play anymore after the first play, this one of the only files that truly has a significance in meaning to me.
    My only problem is I am unable to transfer or sync it from my phone to my iTunes, it is the only file I’m unable to do so. Do you have any suggestions on how I do this or software that I can crack my iPhone 6plus operating system to pull the file? Thank you so so much!

  55. Hi, I had mistakenly formatted my memory card of my android phone. Later on I recovered the files using an data recovery software. The most important files for me were a few voice records of my class lecture. But those files were recovered as .m4a files, & they were corrupted. Then I followed the methods described in this article. For the 1st one, I could recover about 60 min of the total 80 min file. But the rest of them I could only recover a very little part of the files. Could you please comment on this issue? & help me in recovering the full files?
    Thank you very much!

    1. I’m sorry, but the parts that were not recovered can be lost forever due to the corruption of the audio data when the card was formatted.

  56. Hello, I am not tech savvy at all. Really hopeful you can help. I have two recordings on my Samsung s5 phone which used to play fine. They both show the original file name, and it seems the correct byte size and duration too. I don’t recall treating them differently than my other recordings on my phone which still play fine. Maybe I’ve stopped playing them through to the end before either turning off my phone or going to another selection..? but the other files are still ok, and I imagine I did the same with them. I see the volume bars moving when I play these two, but there is no sound. Both recorded on same date — the dates are still there. In this case, could you please help me? I really hope so. Thank you!!

    1. Can you compare the file size of the corrupted one with the working one?
      The size has an linear relationship with the recording length.
      If the file still has enough size, there’s a probability to recover the file by fixing the header, which is used for application to know necessary parameters to decode the compressed audio data.

      1. Thank you for your quick reply! Gee… I don’t understand completely. It’s over my head. The corrupted files’ full lengths are still accurately indicated. One file is 50 seconds, and the other 1 minute and 35 seconds. May I send them to you to recover? They are short but every second precious to me and irreplaceable. (Recordings of my child’s voice.) I was devastated when I discovered they wouldn’t play sound any more. If so, thank you so, so much!!!

  57. Hi,

    First of all, I would like to thank the author of this article for the effort in helping those with corrupted mp4 files.

    I just want to seek your help in explaining the meaning of this error, after decoding:

    Error: PCE shall be the first element in a frame

    Thanks in advance for any explanation.

  58. Hi, this is Sun who is lived in Korea.
    First of all, Thank you for your detailed explanation about how to repair my corrupted m4a file even if I haven’t succeed, yet.
    I followed your description but I have in trouble because “corrupted.wav“ file was not appeared.
    even though I typed faad.exe “corrupted.m4a” , “corrupted.wav“ file was not appeared like below figure.

    I send an email for more detail explanation.
    Thank you.

  59. awesome!!!, it really fix it, i recorded a 13 hours voice memo with my iPhone s4, it was fine, but it crashed when I was plugin the head phones and by mistake I select the option to cut the audio, well since then it was´t able to play, even it wasn´t able to pass to the iTunes… This is the only solution I get in the whole web, and it fix my voice memo, now i can hear it, ATTENTION: IT ONLY FIX 4 HOURS, well is better something than nothing, i just follow the instruction, thanks,

  60. Well SysFrontier, I am getting the “Error: Array index out of range” What does that mean? What should I do or not do?

  61. Great, i can do it. Thank you a lot

    I have met all the errors that you guys listed above.
    The first time, i was not succesful because the of the long path road of the folder that contains all the files (Downloads\a\b\c\d…), you should put all in a folder in DESKTOP and simplify all the file names).

    My advice: Just create simple name for files and simple path road for the folder. It will work the second time

    Don’t give up

  62. Hey, I am trying this.. 5 m4a files have been deleted ive saved them by using a program but the problem is saved files are corrupted!

    When I use this method only saves 2 seconds or so… I want full I need to learn where does it get broken!

    I have also used on a healthy m4a file.. 8 minutes .. only 2 minutes saved…

    Can I get over this?

  63. Hi, i have the same problem. I’ve been trying to find the bytes since my file doesn’t have the mdat string. After following the steps sometimes i get a tiny wav file, is it suposed to happen? Originaly, my recording is around 12min within a 6.1 MB file.

    1. It may be possible that the recording data was not saved to the file due to application crash.
      In this case, a shorter wav file is generated than expected.

  64. Hi there. I followed the instruction closely but still got
    Z.m4a file info:

    Error: Bitstream value not allowed by specification
    0% decoding Z.m4a”
    (Z is the file name)

    What to do in this situation?

  65. I have a question: when I look for the line “mdat in hxd editor, I see many instances. what instance should I delete?

  66. Hello, after following step no.6 I get this:
    *********** Ahead Software MPEG-4 AAC Decoder V2.7 ******************

    Build: Jun 14 2010
    Copyright 2002-2004: Ahead Software AG
    Floating point version

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License.


    ice_video_20160612-123444.m4a file info:

    Error: Bitstream value not allowed by specification
    0% decoding ice_video_20160612-123444.m4a.

    What might seem the problem?

  67. Hello, I’m leaving a comment because I really need this file fixed, I would do the work myself, and I have been, but I have not been able to find the correct “mdat” tag that is said to be found. So if its not too much to ask can you take a look at it and see if you can fix it? Thanks alot

  68. Hello! Thank you for your sulotion! I’ve got some problems:
    In the first try, I got “Error: Bitstream value not allowed by specification” after running faad in command line.
    I reopened the target m4a file and find a other “MDAT”. Than I tried deleting the contents from the beginning of the file to the “t” of “mdat” again.
    Reran faad, the same error showed again…..”Error: Bitstream value not allowed by specification”
    Do you have any suggestion about what could possibly lead to this error?

    BTW: May I have your authority to translate this article into Chinese and repost it to some social network?

    1. Addition:
      Even If i tried the samd steps using a correct/uncorrupted m4a file, the same error after faad still exist……..

  69. Hi !

    Hmmm thanks for the help but doesn’t work for me. Is it normal that the WAV file and repaired file are each both 1ko ?

    The last step doesn’t give the same command window as yours. I don’t have the columns frame; bitrates, elapse; playCPU,etc.

    Thx for help !

  70. If your file doesn’t contain “mdat”, delete from beginning of file till you hit “00 CC” in HEX or “.Ì” in text. Delete everything from start up UNTIL “00 CC”, DO NOT delete “00 CC”.

    Area to delete:

    I you have more zeroes than I have highlighted here, no biggie since I ad more as well, but deleted them in order to illustrate.

    Good luck!

  71. Hello.
    I have a m4a corrupted file and I’ve followed all steps above. In principle I found no errors, but no luck. The output from the faad command (the wav file) is much shorter than the original m4a file (the original is about 24 MB and the wav only 4 MB). If I look with HxD inside the wav, I find that the file has OxOO nearly all its bytes. The final file after faac is even smaller (less than 1 MB, although it have some non OxOO bytes). One more question: the original file has at the beginning the signature: ftypmp42 which corresponds with M4V MPEG-4 files. Is that normal?

  72. Hi, I have a fix corrupted m4a file and i would like recover it!
    The size of the corrupted file is about 110 MB. I followed all the steps but after FAAD command i had a file of 5 KB and after FAAC command i had a file of 1 KB.
    Can you help me please?


  73. Hello,

    I would be so so thankful if you could help me. I was recording a voicememo but then my phone ran out of battery so I guess it was not saved correctly. I cannot play the voicememo on my phone and neither can I download it to itunes. Is there anything I can do to recover it?

    Thank yo so much in advance.

  74. Help please. when i put the M4a. file in the binary editor, it was all 00 00 00 00 00 till the end. i cant find the t to mdat. help please. why is it all 00 00 ?

  75. First of al my m4a file didn’t have the mdat, but I erased the ftypm4a section.

    and after I opened with faad.exe with cmd and I get

    audio.m4a file info:

    Error: Maximum number of bitstream elements exceeded
    0% decoding audio.m4a.

    I’m using a virtual machine windows7 but I don’t think it’s the problem.
    The audio file is really long like 1.5 hour maybe it is?

  76. Hello,
    unfortunately I stuck at point 6 (decoding by faad.exe), getting a message “unable to find correct AAC sound track in the MP4 file”.

    Maybe I should upload the file and send you the link?

    Regards from Germany!

  77. Thanks a lot, Sysfrontier. Your steps helped but my original file had a recording of 60 min yet the repaired file was only able to recover the first 9 minutes of it. Any ideas or suggestions? Thanks a lot

    1. What is the size of the file? Is it same as the size of a working file with 60 min? It may be possible that the data after first 9 minutes has slipped off due to app crash.

  78. On step 6, I got “cd Downloads” and “faad.exe “20140615 163625.m4a” without problem, but when I pressed enter, I got an output saying “Error opening file ‘ 20140615 163625.m4a'” Any ideas? Thank you!

    This is the whole log:

    Microsoft Windows [Version 10.0.14393]
    (c) 2016 Microsoft Corporation. All rights reserved.

    C:\Users\seanc>cd Downloads

    C:\Users\seanc\Downloads>faad.exe “20140615 163625.m4a”
    *********** Ahead Software MPEG-4 AAC Decoder V2.7 ******************

    Build: Jun 14 2010
    Copyright 2002-2004: Ahead Software AG
    Floating point version

    This program is free software; you can redistribute it and/or modify
    it under the terms of the GNU General Public License.


    Error opening file: 20140615 163625.m4a


  79. AMAZING! You just saved my girlfriends life!

    Had a HR dismisall interview recorded and needed to write it up but it got corrupt, ii tried loads but this worked!

  80. If you got: bitstream value not allowed by specification error, and near the beginning of your file, in the hex editor, you see that the file format is “ftypdash”, it means you should use ffmpeg to decode your file.

    Go grab the ffmpeg binaries and use this command from the binary directory:
    ffmpeg -i input.m4a -vn -acodec copy output.m4a


  81. Dear SysFrontier,
    I want to ask a question, but this is all I could find for “comments.” I hope you read it and reply. I followed your instructions and all went fine until the very end. After the command prompt box responded: “encoding [name of my file].wav to repaired.m4s” there is nothing written below the headings frame / elapsed / play/cpu. I was able to find a file called “repaired.m4a” but it was only 678 bytes instead of the original 11.4 mbytes of the original. I notice that there is also a .wav file of only 44 bytes. Can you tell me what went wrong, or shall I send you the file for repair? Thanks!

  82. p.s. I tried a second time, and I notice that the Error message I got after the Faad.exe “filename.m4a” was: Channel coupling not yet implemented.m4a
    Thanks for any feedback.

  83. Amazing. I just recovered some broken recording from BB10.
    I couldn’t fine mdat as well, so I just deleted few first zeros of file till first different symbol and it allowed me to decode file.

    Thank you!

      1. Hi! I have a problem with faad.exe followed by file name, the response I get is “faad is not recognized as internal or external command, operable program or batch file”…. What I am doing wrong?

  84. I have one corrupted audio file, but I can’t recover it by this method, the problem is in faad.exe. when I try to call faad in command promt to decode audio file, the answer is:
    Error: Channel coupling not yet implemented
    0% decoding aaa.m4a
    Please help, what can I do to fix this ?

    1. We need to look into the file to see how the data gets corrupted.
      If you want us to do so, please send us via Dropbox or Google drive.

  85. Dear Sysfrontier!
    I had same problem as Sachin. 2 files went through this algorythm.
    1st file was about 14 min. – became 1min 36 sec, 2nd one 57 min. – became almost 15 min.
    And this error – “Maximum number of bitstream elements exceeded”, when using faad.exe.
    Answering to question about size – 1 file was 13,1 Mb – became 1,44 and 2nd one was 53,4 – became 12,1.
    I have to fix them up urgently,because my future job depends on these 2 files, so please , if you have any suggetions, tell!
    Thanx in advance.

  86. Hi, I had the same problem as joanna ” faad is not recognized as internal or external command, operable program or batch file”

    What did we do wrong ?

    1. Please make sure you have faad.exe and the m4a file in the same directory such as Downloads.
      You need to do “cd” to the directory in the command window.

  87. I just found this really useful guideline.. Thank you admin!
    During the repairing process, I experienced the ”faad is not recognized as internal or external command, operable program or batch file” problem, which turn out I was not using the right directory (I created 1 folder inside “Downloads” folder).
    I also experienced with “Maximum number of bitstream elements exceeded” problem, but in my case, the wav file was there, so I just tried to encode it using faac.exe.
    Then, the repaired.m4a file is a little bit smaller than original.m4a, but it is much better than not at all.
    Thank you again..

  88. You guys are a life-saver. I’ve tried every possible method using audacity and other softwares which didn’t work. I came here as a last resort and you saved my day. Thanks a million guyss

  89. hello i have been recording a voice clip for 45 minutes and sudenly my phone shut off
    when i did restard and i started to record again (a new 1 minute recording) and i noticed that the phone had mix the new file with the old one i was recording and had created a new recording file 45 mb. but when i play the file it just play me the last recording i made while the file has much more information.
    i cannot reach the raw m4a data that are still in the file and it just play me the last 1 minute recording i made. there are two audios merged in one file and i want to fix the first long recording data that there are inside

  90. This was really helpful (for someone who doesn’t use cmd very often, it was really informative and had every detail covered). Still, at first I encountered an error using faad: “channel coupling not yet implemented” and lost any hope – but then I tried to delete every bit one by one after the “mdat” in binary editor HxD and tried the new file with faad until it worked eventually (after five or six tries). I have to admit though the file seems to have lowered in pitch by a tiny bit – is it possible this has something to do with the sample rate? All in all, I’m very happy to have my recording back, so thanks!

  91. hi please help i followed the instructions but when i try step 6 on cmd
    it says
    error opening file:Audio_05_09_2017_16_44_26

    i dont know why if you could help me it would mean so much to me
    its a 8minute thing or something i put my heart and soul into it and i dont think ill ever feel the way i felt again to recreate it again

  92. I am getting message — “Unexpected channel configuration change” after 6 th step. And when I finish the process; I get the file name repaired.wav but of zero duration. CAn you please explain what can be the problem. My file is of 44.7 MB and if I am not wrong it should be of 35 min. length

  93. Hello, can you please tell me what to do since i am stuck in step 5. I couldn’t find “mdat”

    Please help, i need this m4a file.

    Thank you

  94. Thank you very much! I repaired a voice memo successfully. It was very important for me.
    I followed the exact description. The only thing what I didn’t understand was that ‘cd Downoads’ command, “to move” the Downloads folder, but after I just did what you say, it works fine and everything was a piece of cake.

    Great!!! Thnx!!!

    1. The size implies that the audio data has been lost forever from the file.
      It is impossible to restore the original data from the 72KB file.

      1. That’s strange, because the Web app “Treasured” say it could recover at least 1/3 of the record. I think I’m doing the wrong thing with the “mdat” header … Can you take a look ?

  95. Hey sysfrontier,

    thank you for your turtorial! I do it for my friend and it work in my case. But I have i think we lost a little bit records.
    The original file have 65,7 MB and the repaired file only 34,4 MB (37,36 min).
    The WAV file have 379 MB (37.36 min)

    The faad.exe only decode till 31%…
    Can we repaire more than this??

    Thank you for your Support!

  96. It’s just awesome! 😀
    I had recorded a call while talking with my girl but the recorder didn’t record it properly.. It created a corrupt .m4a file. I was so disappointed.. 🙁 But now I am happy to see it recovered after following above steps. Thanks Team..

  97. Hi, my phone battery died while I was recording audio (m4a), and the file duration is zero but still has file size (37.8mb). Can this solution fix my file?

  98. Hy sysfrontier,

    My files m4a is corrupted due by end batterie of my phone.
    The file have 65Mb, so what could be the cost if you do the repair?



  99. I tried this fix on a 50 minute voice memo, but got the error “PCE shall be the first element in a frame” in FAAD, and the recovered .wav file is only 3 minutes long.
    Any suggestions?

      1. The strange thing is, the file was working before, and the filesize is the same as other similar length .m4a (~50mb)
        Somehow the file just stopped working

  100. Thank you Sysfrontier for this complete tutorial. I had one corrupted M4A file and thanks to your information I could restore this important file. I would recommend this post for anybody that have this kind of problems. I’m very happy because I found this post.

  101. AMAZING!!!! Thank you sooo much! Repaired 2 corrupted m4a’s using this guide. So grateful for your kindness and generosity in supplying this page.

  102. Hi! I was trying to recover 2 different MP4 files recorded by EasyVoiceRecorder on Android 2.3. They were recorded on different days and were both about the same length, 70 and 73 mb. (Almost 3 hours) Failed due to no space left. When removing the header and trying to decode with Fadd, both times the resulting file is a stereo WAV file of exactly 6.33 MB (6,647,852 bytes)

    So seems this is not a problem with the defective files but with the decoder. The data in the Hex editor HxD seems to all be there to the end. So I was thinking, it says it’s for Win32 but I’m using Windows 10 64 bit, does this break the decoder and I should try on a 32 bit OS? (FAAD2v20100614 CVS snapshot for Win32)


    1. No I just tried on a 32 bit XP and same exact file size results! BTW, the original files are supposed to 63 or 64 kbps, Mono, 44 kHz. These files do not show any details in Windows explorer though.

      1. Well, I tested a GOOD file. Same length, about 74 mb, length 2 hr 36m. faad wouldn’t decode it at all without removing the header. After removing the header it decoded it to a file size which was exactly the same length of 74 mb, but the resulting file is exactly 7 min 2 .208 seconds! It’s a Stereo file of 44,100 Hz, 32 bit float. It plays fine.

        So apparently faad is not compatible with this mp4 format. It can’t even decode a good file properly… Any other decoders I can try?


  103. Hi, I have a corrupted file due to losing battery on my phone.

    The recording is quite large, 391mb.

    Just wondering if you can please provide some help for how to recover this file through my mac, alternatively are you able to fix this for me? And at what cost and how long would this take?

    Thank you 🙂

  104. I just recoreded an 1,5 hour session with my mother talking about my late father’s youth when the battery of my phone died. I recovered the audiofile but couldn’t play it. The method you described worked perfectly, thanks!

  105. hi, thanks for all, but i need to ask why my 20 min corrupted m4a audio file when i follow ur steps goes to just 1 min ? also i get an msg “error channel coupling not yet implemented”
    tried with 2 files.

  106. Trying to repair file .m4a with 27 mb with your instructions above.

    First, the file I opened with HxD, but could not find “mdat” but however I fould 2 lines as shown in figure above “M4A mp4” and deleted upto . . . and saved it.

    Also, I executed FAAD as said, but file just shows 1 KB.

    Please help.

  107. Thank you sooo much for your help! Repaired 1 corrupted m4a’s using this guide. So grateful for your kindness and generosity in supplying this page.

  108. Thanks so much! I was recording a class and dropped my phone so it turned off. When i tried to play the audio it didn’t let me until i did this. Thanks! You rock

  109. Just wanted to thank you for posting this …. these instructions helped me recover several interviews and voice recordings I had stored on my Android phone (Samsung Galaxy S6). The files were critical for a new story I was writing. I’m on Windows 10 in Winter of 2018. Thanks so much!!!

    Arigato gozaymusu!!

  110. Thank you sooo much for your help! Repaired 1 corrupted m4a’s using this guide. So grateful for your kindness and generosity in supplying this page.

  111. Thank you so much for these instructions, I didn’t bother with the re-encoding (faac) as that wasn’t important to me, but I recovered all but the last few words of an hour-long recording I was almost certain I had lost.

  112. Hi!

    Very useful information, indeed. I was able to save at least five corrupted files, hopefully!!

    But, the last file I tried to rescue is the most difficult. When I try this method, I get the error “Error: Gain control not yet implemented4a.”.

    Here is the information from a file recorded minutes earlier under the same setup (wich plays fine):

    Format : MPEG-4
    Format profile : Base Media / Version 2
    Codec ID : mp42
    File size : 38.5 MiB
    Duration : 1h 23mn
    Overall bit rate mode : Constant
    Overall bit rate : 64.7 Kbps
    Encoded date : UTC 2018-02-20 09:15:47
    Tagged date : UTC 2018-02-20 09:15:47

    ID : 1
    Format : AAC
    Format/Info : Advanced Audio Codec
    Format profile : HE-AAC / LC
    Codec ID : 40
    Duration : 1h 23mn
    Bit rate mode : Constant
    Bit rate : 64.0 Kbps
    Nominal bit rate : 96.0 Kbps
    Channel(s) : 1 channel
    Channel positions : Front: C
    Sampling rate : 44.1 KHz / 22.05 KHz
    Compression mode : Lossy
    Stream size : 38.1 MiB (99%)
    Title : SoundHandle
    Language : English
    Encoded date : UTC 2018-02-20 09:15:47
    Tagged date : UTC 2018-02-20 09:15:47

    I tried to decode with Nero and FFMpeg, no success. Maybe I’m not using the right commands.

    Any solution?

  113. Please, guy help me. I have an issue on the step 6 too. faad.exe”20180402.m4a” is not recognized as internal or external command, operable program or batch file. Please, help me on this issue.

    1. Please confirm that you are in the same directory as where faad.exe resides.
      Type “dir” to see if faad.exe exists.
      If not, please use “cd” to change the directory to where you have faad.exe.

      1. I downloaded the faad and faac softwares in the same folder “Downloads” as well as my audio file. It is a recorded file for a concert that we prepare. I need just to relisten to the music and voice to get prepare. And i had this issue. It was recorded on my Blackberry Z3 phone.

        I tried to change the folder and put the faad and faac.exe and the audio file on the desktop and try it again, but it doesnot work. Could you help me please? This file is so important. The other team member didn’t record our vocal sessions so I’m really lost. I spent already 5 hours to do it. Help me please. Should I send the file to you via a share link to see if you can fix it for me? Please…

        1. Otherwise, maybe it’s best for me to forego this project and go back to my Excel spreadsheets, waiting for another vocal session maybe….. I’m sad for not having succeeded while using your advice. Lost in encoding steps…

  114. Ooooh ok it’s well noted. I’ll send you a wetransfer link very very soon. Kind regards. I did many researches online, in french-speaking forums also. But, I found very limited options.

  115. Dear sysfrontier,

    It’s a very great method. I am really able to retrieve the audio files, but in most cases the duration of the repaired file is too shorter than the first damaged file. So. I want to humbly request if you could please help me to be able to have complete files.


    1. It is possible that some of the last part gets lost due to app crash. In such cases, it’s impossible to recover the lost data.

  116. I’ve followed the steps.
    When I execute faad.exe, I obtain the message
    “Channel coupling not yet implemented”
    0% done
    Have you an idea ?
    Thanks a lot !

  117. i am getting this error “array index out of reach” at the step of faad.exe “name.m4a” please tell me how to fix it?

    1. array index out of range at faad.exe stage. tell me what is the problem i removed the mdat and till beginning

    2. It may be possible that not only the header part, but the data part is damaged. We are sorry, but it is impossible to restore the audio in such a case.

  118. When i do step 6, i have a file .wav of 33Kb (the original is of 58Mb).
    When i do step 7, i have a repaired file ok 1 Kb (the “repaired.m4a” is a file of 1Kb. it doesn’t work.)

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