FAQ:MP3 export problems

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Why does Audacity crash or use excessive processing time on MP3 export?

If Audacity crashes or hangs when exporting MP3s, or the export takes a long time to process, the usual reason is that your chosen Project Rate (the sample rate bottom left of the Audacity screen) is very different from the sample rate of the audio track on the screen (as shown in Hz on the Track Control Panel above the mute/solo buttons). As a result, resampling has to be done while exporting, which can create problems on long tracks. Try resampling the track to your chosen Project Rate before exporting as MP3. To do this, select all the track by clicking in the Track Control Panel, then Tracks > Mix > Mix and Render. If there is any silence added to the end of the track as a result of the resampling, you can select and delete it. Now when you export the MP3, the process should go smoothly and quickly. If it doesn't, there could be a number of reasons, e.g. if you have a virus scanner set to scan all created files, this will slow the process of writing the exported file considerably. The higher the bit rate you export at, the larger the file will be, so giving a greater time penalty if you enable virus scanning.


Why is my exported MP3 invalid / will not play?

Sometimes the exported MP3 may be invalid and only a few bytes in size; as a result, it will not play and give an error.

The safest solution is to always set your Project Rate to 44100 Hz. Make a rule to check this before you export, because importing a file of some other sample rate may change the Project Rate to that rate.

Do this from the Quality pane of Preferences using the Default Sample Rate setting.

LAME will automatically downsample from 44100 Hz to a lower sample rate at 56 kbps or lower, because low bit rates may give poor quality with higher sample rates. If especially desired, any valid sample rate/bit rate combination can be enforced by using the command line exporter in the current version of Audacity (choose "external program" in "Save as type" in the Export File dialog). Or export as WAV from Audacity, then use LAME.exe at the command line to convert to MP3.


Why does my exported MP3 play too fast?

If the MP3 plays at the wrong speed (usually too fast), then the sample rate you exported it at is unsuitable for your player application. Once again, the safe solution is to always set your Project Rate to 44100 Hz.

Do this from the Quality pane of Preferences using the Default Sample Rate setting.

This was a known problem with Adobe Flash Player until some way into version 9: for the file to play properly, the sample rate had to be 11025 Hz or a multiple thereof, such as 22050 Hz or 44100 Hz. This is fixed in the current Adobe Flash Player.


Why does my exported MP3 have low volume or no sound?

If you can see your exported MP3 is playing because the timer on the media player is moving, but it has no sound, make sure the sound device is not muted (in the player or in the system control panel), and make sure the correct playback device is being used (in the player preferences or in the system control panel). If this is not the problem, go back to Audacity and make sure the -....+ gain slider on the Track Control Panel (where the mute/solo buttons are) is set centrally at "Gain: 0 db". If this slider is over to left, it will reduce or kill the volume in the exported MP3.


Why is my exported MP3 larger than the imported one?

If you import an MP3 file into Audacity, then after export you find it is much larger than before, this is because the bit rate you exported it at is higher than the bit rate of the original file.

Audacity defaults to 128 kbps bit rate then remembers the last used bit rate if you change it.

If you need the exported MP3 to be the same size as before:

  1. Find out the bit rate of the imported file by opening it in Windows Media Player and clicking File > Properties, or in Apple Music/iTunes, right-click or control-click over the file and click Song Info/Get Info. You can also use standalone programs like MediaInfo.
  2. Click File > Export > Export as MP3, then click the Options button.

If you export a low bit rate MP3 at the same bit rate as the original you will be degrading its quality much more than if you exported it at a higher bit rate. The penalty of the higher bit rate is that the new file would be larger and that file merge tools might no longer be able to join the new MP3 to others that had the original bit rate. If you export a high bit rate MP3 at the same bit rate you are helping to minimize quality loss (but are not saving anything in file size).



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