[NFBCS] Repairing damaged audio files

Sat Jul 11 18:44:57 UTC 2020

	What operating system are you using? Even if it is a supported file
type, Windows sometimes cannot play certain files, regardless of the player,
and you have to download software for the additional support. Also, you
might want to try a free trial of a sound editor rather than just a playback
program as these sometimes support more file types.

-----Original Message-----
From: NFBCS [mailto:nfbcs-bounces at nfbnet.org] On Behalf Of Steve Jacobson
via NFBCS
Sent: Saturday, July 11, 2020 11:23 AM
To: NFB in Computer Science Mailing List
Cc: Steve Jacobson
Subject: Re: [NFBCS] Repairing damaged audio files

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.o
rg%2Ftaff%2F&data=02%7C01%7C%7C1316aace20c5403d4ec508d825bfcdd3%7C84df9e
7fe9f640afb435aaaaaaaaaaaa%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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-- 
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"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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