[NFBCS] Repairing damaged audio files

[Steve Jacobson]

Dale,

Before you try too much, check the size of the files you can't play.  My very general rule of thumb is that WAV files that are stereo and are sampling at 44.1 or 48 KBPS take about 10 megabytes per minute.  WAV files that are not stereo or have a lower sampling rate can be much smaller.  MP3 or WMA files take around 1 megabyte per minute.  The latter varies some, though, depending upon other parameters.  Still, by using the above, you might be able to determine if you have actually lost part of the file, especially if the size is only a few kilobytes.  

In our 100 Accomplishments project here in Minnesota, we collected recordings from a number of people including from you as you know.  We ran into a couple of WAV files that would only play on certain players.  We never figured out why and we were able to work around it.  However, it means that is at least a small possibility that there is a compatibility issue that the right player might circumvent.  By all means, take Doug Lee up on his offer.  If he doesn't get anywhere, I would be glad to try one and see if I can get it to play using a couple of different players, but Doug has more knowledge of the various formats than I do.

Best regards,

Steve Jacobson

-----Original Message-----
From: NFBCS <nfbcs-bounces at nfbnet.org> On Behalf Of Doug Lee via NFBCS
Sent: Saturday, July 11, 2020 12:27 PM
To: NFB in Computer Science Mailing List <nfbcs at nfbnet.org>
Cc: Doug Lee <dgl at dlee.org>
Subject: Re: [NFBCS] Repairing damaged audio files

The short answer is that it's probably a difficult task that would require some pretty thorough examination of, and perhaps tweaking with, the data in
each file. Wav files are the simplest of the formats you mentioned, assuming they are not MP3 files disguised as wav files (that happens sometimes). Some media players will do their best to play wav and mp3 files even if
they are damaged; so I'm slightly surprised that you get no sound at all from those. I know less about the wma file format.

If these are not private in nature and we can work out a means, I would be willing to look at them to see if I can get anything out of them or at least figure out what's stopping them from playing. I have acquired a bit of
knowledge of sound file formats recently while writing a repair tool for TeamTalk Opus Ogg files (https://eur06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.dlee.org%2Ftaff%2F&data=02%7C01%7C%7C1316aace20c5403d4ec508d825bfcdd3%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637300853001695483&sdata=trdxTgvlZ%2FdxQ2RlVfFgBrd2UXVPDEts7Ve8C2eB2s4%3D&reserved=0 ).

On Sat, Jul 11, 2020 at 03:52:21PM +0000, NFBCS mailing list wrote:
I have a small number of wav & mp3, and 1 wma file that appear to be damaged - none of my media players or editors will play them.
I've tried using Audacity with the ffmpeg add-on, but it seems I'm not doing something right, and haven't been able to recover the audio.
Is there someone who could talk me through the recovery process like the lost newbie I am?
Thanks

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-- 
Doug Lee                 dgl at dlee.org                https://eur06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.dlee.org%2F&data=02%7C01%7C%7C1316aace20c5403d4ec508d825bfcdd3%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637300853001705486&sdata=FFppDgb4C99LNK4%2FBzAeodpyzzc2M5y4vRN1gXLNJzY%3D&reserved=0
Level Access             doug.lee at LevelAccess.com    https://eur06.safelinks.protection.outlook.com/?url=http%3A%2F%2Fwww.levelaccess.com%2F&data=02%7C01%7C%7C1316aace20c5403d4ec508d825bfcdd3%7C84df9e7fe9f640afb435aaaaaaaaaaaa%7C1%7C0%7C637300853001705486&sdata=oDHCvgzfdYWB2fcDZ0mzXQu%2B9SYHx5tS7lz8lntYecQ%3D&reserved=0
"It's not easy to be crafty and winsome at the same time, and few accomplish
it after the age of six." --John W. Gardner and Francesca Gardner Reese

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