This guide worked 100% for me - it takes you through each step. Afterwards, the m4a file plays! Note: this is completely free. http://sysfrontier.com/en/2014/12/31/hello-world/
Also pasting instructions in case the link goes down in future:
How to fix corrupted voice memo (m4a) files.
Do you have broken voice memo files? You can fix those files by
GIGO [garbage in, garbage out] does apply...
...however - a good mix, master or especially restoration engineer could pull apparent newness out of a low quality file - that's essentially the same task as recovering a track from an old 78 RPM record, or remastering the Beatles albums from the original multitracks.
You work to eliminate the 'bad' & ...
You could try rewriting the file using ffmpeg with the following command:
ffmpeg -i damagedfile.mp4 -c copy fixedfile.aac
Alternatively you may use FAAD and a hex editor (e.g. Hexplorer). Find out where the actual data starts in a hex editor. Not always after the mdat entry - there may be alot of zeros in the beginning of the file.
Simply copy everything ...
Mp3 is a lossy compression format, the removal of frequencies is permanent. There are lossless files such as flac files which 'pack' the file down to a smaller file size that can then be 'unpacked'. But if they are all 128kbps Mp3 then your out of luck. All those effects you listed are symptoms of destructive compression. You could 'improve' them with ...
I'd switch to command line rather than relying on the Finder (I take it you're using a Mac because you're into sound, it's only a guess from personal statistics, I'm not categorizing or anything).
Use your terminal, navigate to /Volumes/ using
cd /Volumes/<disk name>
Type ls and press enter (it's short for list, it'll list the files it finds in the ...
The problem you have is that the WAV header has not been created correctly. If you are working on a Mac then you can try this application which I wrote to fix broken WAV files. https://www.dropbox.com/s/ofzrbiqebut05zk/fixwav?dl=0
Also this is the methodology I used.
I've had this happen before, howevr it was while recording the screen of my computer. Not certain if you've done the same or used a camera IRL. However easiest way to see if there's audio in a file is to play the file in VLC and press CMD+I or CTRL+I (Window>Media Information)
Notice under CODEC Details "Stream 0" & "Stream 1". 0 is your video and 1 is ...
Try opening the file with some advanced video players just to find out if the audio is gone or there's a codec error.
Two video players that I use when having this sort of problems is Quick Time and Video Lan.
If indeed there's no audio attached to the video - there's little to be done - maybe useing a disk data recovery tool depending on the recording ...
You could take a look at Zynaptiq Unchirp and Unfilter, but they are expensive options. It's not guaranteed to work but it's an option worth demoing. It really depends on how important these files are too you.
This worked for me. It can get from easy and quick to advanced and slow very quickly.