Corrupt Voice Recorder Files. Can I repair these....?

2013-02-22 22:40:30

Ok I have spent days now doing search after search after search on this issue I am having.  I use the built in voice recorder app on my Samsung Galaxy Nexus to record various lectures and things of that nature.  90% of the time the recordings come out just fine.  The other 10% of the time I am left with either a file that will show it is playing, but no audio appears to be present or a file that plays nothing but this god awful white noise like I recorded a lawnmower or a generator or somthen.  I have gotten lucky repairing a few of the files with a hex editor but it was just that....luck.  After searching the internet I think the problem is the internal storage that the phone is writing to.  Something happens during the write process.  Below is the MediaInfo for one of the files that plays nothing but noise....

General
Complete name                            : C:\Users\Administrator.OLGWARROOM2\Desktop\130221164427i.3gp
Format                                  : MPEG-4
Format profile                          : 3GPP Media Release 4
Codec ID                                : 3gp4
File size                                : 1.28 MiB
Duration                                : 13mn 56s
Overall bit rate mode                    : Constant
Overall bit rate                        : 12.8 Kbps

Audio
ID                                      : 1
Format                                  : AMR
Format/Info                              : Adaptive Multi-Rate
Format profile                          : Narrow band
Codec ID                                : samr
Duration                                : 13mn 56s
Bit rate mode                            : Constant
Bit rate                                : 12.8 Kbps
Channel(s)                              : 1 channel
Sampling rate                            : 8 000 Hz
Bit depth                                : 13 bits
Stream size                              : 1.28 MiB (100%)
Title                                    : SoundHandle
Writing library                          :   
Language                                : English

I imported the audio into audacity as is and the as raw data but both times I get the 'tube' of noise.  Again, I repaired one of these by pure luck once before but I have no idea how.  The hex dump shows tons of data and the header appears to be right but then again, Ive noticed that the headers are never exactly the same even with fully working files from my voice recorder.  Can someone tell me how I can go about repairing these files to remove the noise, or at least remove enough of it to find the actual voice audio.  I have downloaded every piece of editing software on the planet to try and fix these files but I just don't have the expertise really understand what I need to do.  I can provide and info that is necessary.  Thank you guys in advance for any help or suggestions. 

Corrupt Voice Recorder Files. Can I repair these....?

Reply #1 – 2013-02-24 09:52:54

I can't really help you, but definitely, importing them as RAW audio in audacity (or any other audio editor) is NOT going to work. AMR is a voice codec, just like GSM or Speex.

You say that you've been modifying the header to try to fix it. Just in case, this is the description of the header:
http://www.developer.nokia.com/Community/Wiki/AMR_format

What I can understand from that doc, your file shoud have this structure:

0x23, 0x21, 0x41, 0x4D, 0x52, 0x0A,  [ 0x38 + 32 bytes ] for N packets