Bug while exporting to m4a

Hi all,

I use Audacity 2.0.3 to export mp3 files to m4a. Most of the time the export is fine. But sometimes, the end result is an empty file and I can’t understand what causes the error.

Please try for yourself with the attached file. Can you help me? Is this a bug?

In case, this may help, the log below.


11:25:08: Audacity 2.0.3
11:25:19: Trying to load FFmpeg libraries...
11:25:19: Trying to load FFmpeg libraries from default path, 'C:Program Files (x86)Ffmpeg For Audacityavformat-52.dll'.
11:25:19: Looking up PATH environment variable...
11:25:19: PATH = 'C:Windowssystem32;C:Windows;C:WindowsSystem32Wbem;C:WindowsSystem32WindowsPowerShellv1.0;c:Program Files (x86)ATI TechnologiesATI.ACECore-Static;c:Program Files (x86)Common FilesRoxio Shared10.0DLLShared;c:Program Files (x86)Common FilesRoxio SharedDLLShared;C:Program Files (x86)QuickTimeQTSystem'
11:25:19: Checking that 'C:Program Files (x86)Ffmpeg For Audacity' is in PATH...
11:25:19: Avertissement :FFmpeg directory is not in PATH.
11:25:19: Temporarily appending ';C:Program Files (x86)Ffmpeg For Audacity' to PATH...
11:25:19: Checking for monolithic avformat from 'C:Program Files (x86)Ffmpeg For Audacityavformat-52.dll'.
11:25:19: Erreur :Impossible de trouver le symbole « avutil_version » dans la bibliothèque dynamique (erreur 127 : the specified procedure could not be found.)
11:25:19: avformat not monolithic
11:25:19: Loading avutil from 'C:Program Files (x86)Ffmpeg For Audacityavutil-50.dll'.
11:25:19: Loading avcodec from 'C:Program Files (x86)Ffmpeg For Audacityavcodec-52.dll'.
11:25:19: Loading avformat from 'C:Program Files (x86)Ffmpeg For Audacityavformat-52.dll'.
11:25:19: Returning PATH to previous setting...
11:25:19: Actual avutil path C:Program Files (x86)Ffmpeg For Audacityavutil-50.dll
11:25:19: Actual avcodec path C:Program Files (x86)Ffmpeg For Audacityavcodec-52.dll
11:25:19: Actual avformat path C:Program Files (x86)Ffmpeg For Audacityavformat-52.dll
11:25:19: Importing symbols...
11:25:19: All symbols loaded successfully. Initializing the library.
11:25:19: Retrieving FFmpeg library version numbers:
11:25:19:    AVCodec version 0x344802 - 52.72.2 (built against 0x344802 - 52.72.2)
11:25:19:    AVFormat version 0x344002 - 52.64.2 (built against 0x344002 - 52.64.2)
11:25:19:    AVUtil version 0x320f01 - 50.15.1 (built against 0x320f01 - 50.15.1)
11:25:19: FFmpeg libraries loaded successfully.
11:25:19: File name is c:usersnicolasdocumentsprojet jeuxsoundsound on ubuntu devorganic_nav_11.mp3
11:25:19: Mime type is *
11:25:19: Opening with libsndfile
11:25:19: Opening with libmad
11:25:19: Open(c:usersnicolasdocumentsprojet jeuxsoundsound on ubuntu devorganic_nav_11.mp3) succeeded

It’s too short. I added some noise to the end and it exports perfectly. Koz

Thanks. Is there a minimun length? Why is that?

I don’t know, but I’m not shocked it does that. Unlike WAV and AIFF, m4a and aac are very highly managed, compressed formats. I suspect it’s the same reason you can’t do an Analyze > Plot Spectrum if the sample is too short. There isn’t enough sound there for the tools to do an intelligent job.

Also remember FFMpeg is a free knockoff of the “real” software. I didn’t try it, but it’s possible iTunes for Windows will create an aac file from your work.


The FFmpeg command-line executable displays the same issue, so it’s an FFmpeg problem, not an Audacity problem.

It does. Follow the procedure here http://wiki.audacityteam.org/wiki/Exporting_your_Audacity_Project_into_iTunes_and_iPod#convert but choose “AAC Encoder” in iTunes instead of the MP3 Encoder.

Note that like MP3, AAC has silence padding at the start. If you want the exact length with the sound effect starting at exactly the correct time, choose “Apple Lossless Encoder” in iTunes instead (but remember not all players will play it). All players will play WAV.