How to fix or listen to broken m4a voice memo file

[gabepsu]

I have the latest version (I believe?) of Audacity, 2.0.6
I am running OSX Yosemite version 10.10.2

I recorded a voice memo on my iPhone and the battery shut down so I believe the recording did not save properly. On my iPhone the file shows as 00:00 in length however the file itself is over 540MB. I transferred the file to my MAC via USB cable through iTunes and saved to desktop. I also transferred a much smaller recording which did save properly.

After following some videos on YouTube and on this forum, I tried importing raw data in Audacity and mimicked the settings I found in the smaller recording, which was 16bit PCM with sample rate 22050 Hz.

However after trying this, the file still only opens as static. Is there anything else I am missing to be able to access this audio recording?

[kozikowski]

to my MAC via USB cable through iTunes

Did it play while it was in iTunes?

Open up the other successful file in QuickTime, make sure it plays and Command-I INFO. What does INFO say that file is? The busted file is likely to have the same specifications.

The Raw tools in Audacity depend on you to to tell it everything about the file. It makes no assumptions or presets. Noise is usually what you get when you guess wrong

Koz

[kozikowski]

Did you install the FFMpeg software? I don't think plain Audacity will know what an m4a file is.

http://audacityteam.org/download/mac

Koz

[Gale Andrews]

Did you install the FFMpeg software? I don't think plain Audacity will know what an m4a file is.

On Mac only, Audacity can import unprotected M4A, MP4 and MOV files without FFmpeg, assuming QuickTime understands the file.

QuickTime may not be able to understand an M4A file containing PCM audio, so it may be worth trying FFmpeg.


Gale

[gabepsu]

Hi Koz - The broken file did not open in iTunes. I opened the successful file in Quick Time and I got this for INFO:

Format: AAC, 22050 Hz, Stereo (L R)
Data Size: 55KB
Data Rate: 24.57 kbit/s

I have installed the FFMpeg software according to the instructions on the Faq page
I have restarted Audacity.
I tried importing Raw Data again using the following settings:

Encoding: Signed 16 bit PCM
Byte order: Default endianness
Channels: 2 Channels (Stereo)
Start offset: 0 bytes
Amount to import: 1% (because its 540mb)
Sample rate: 22050

.......and I still just get noise?

Gale - Is there a way to check that the FFMpeg installed correctly?

[gabepsu]

Also - I did just see that on the sidebar showing the settings for the imported file read as:
Stereo, 22050 Hz, 32 bit float (not 16)

would that have anything to do with it?
is there a place for me to add Data Rate, such as that I found on the successful file (24.57 kbit/s)?

[Gale Andrews]

I opened the successful file in Quick Time and I got this for INFO:

Format: AAC, 22050 Hz, Stereo (L R)
Data Size: 55KB
Data Rate: 24.57 kbit/s

I have installed the FFMpeg software according to the instructions on the Faq page
I have restarted Audacity.
I tried importing Raw Data again using the following settings:

Encoding: Signed 16 bit PCM
Byte order: Default endianness
Channels: 2 Channels (Stereo)
Start offset: 0 bytes
Amount to import: 1% (because its 540mb)
Sample rate: 22050

.......and I still just get noise?

If that file was 16-bit PCM stereo 22050 Hz then QuickTime should be saying that it's 705 kbps.

The file could be Big Endian, given an Apple app produced it.

I would suggest you import 100%.

Is there a way to check that the FFMpeg installed correctly?

Look at Audacity > Preferences... then the Libraries section to see if F, C and U numbers are listed for FFmpeg.

If the file lacks proper headers then FFmpeg will not be able to open it. If you want to force FFmpeg to try to open it in Audacity, use File > Import > Audio..., then choose "FFmpeg-compatible files" before selecting the file.

I did just see that on the sidebar showing the settings for the imported file read as:
Stereo, 22050 Hz, 32 bit float (not 16)

would that have anything to do with it?

No - that's just the resolution Audacity opens the file at, determined by "Default Sample Format" in the Quality section of Audacity Preferences. If the settings in Raw Audio are correct and the data is legitimate, then the default 32-bit sample format setting would import the audio correctly.


Gale

[kozikowski]

Did you check that QuickTime has export options? You may be able to get QuickTime to convert the work into something that will slide right into Audacity instead of trying to painfully force Audacity to open an odd format (click on the pix).

Koz

[gabepsu]

Thx Koz - I tried exporting via Quicktime as you suggested but it still won't allow me to open it.

Gale - Thx again for all of the detailed help, as well.
I tried importing again using Big endian and importing 100% and I still get noise and no waveform.
I did check the FFmpeg settings as you mentioned and they are installed.
If the file is lacking the proper headers, is there anything I can do to correct this?

Also - since u mentioned that

If that file was 16-bit PCM stereo 22050 Hz then QuickTime should be saying that it's 705 kbps.

could I do anything to correct this on my end in the settings of the import for the broken file?

[Gale Andrews]

I tried importing again using Big endian and importing 100% and I still get noise and no waveform.
I did check the FFmpeg settings as you mentioned and they are installed.

What happens if you import the bad file into Audacity by File > Import > Audio..., then choose "FFmpeg-compatible files" before selecting the file?

Does the good file import properly if you Import Raw with the settings you were trying?

Does the bad file Import Raw at the length you were expecting , with noise along the whole length?

If the file is lacking the proper headers, is there anything I can do to correct this?

Import Raw should solve that by bypassing the headers or lack of them, if the file really contains PCM audio. When you enter the details manually you're supplying the information that the headers should be supplying.

since u mentioned that

If that file was 16-bit PCM stereo 22050 Hz then QuickTime should be saying that it's 705 kbps.

could I do anything to correct this on my end in the settings of the import for the broken file?

Probably not. You could try MediaInfo to get a second opinion about the good file http://mediaarea.net/en/MediaInfo/Download/Mac_OS, but they don't say if it runs on Yosemite or not.

Presumably Quick Time can't play the bad file?


Gale