Why install FFmpeg Audacity?
Audacity is great by itself, why install something external like FFmpeg? What does it do? Simple: If you want to edit .mp4, .m4a and other files in Audacity, you need to install FFmpeg. It is simple to install and free, click below to download it:
FFMPEG WINDOWS INSTALLER or Dowload Zip version
How to install FFmpeg Audacity?
1- If you downloaded the FFmpeg windows installer (yellow button), simply open it and follow the instructions, it will install the codecs automatically
2- If you downloaded the Zip version and want to go the manual installation route. Double click to open it. Most modern operating systems will allow you to open and extract a .zip file directly. Open the Zip file and extract the .dlls to C:\Program Files (x86)\Audacity.
You are free to install it wherever you want, this is for keeping things neat and tidy. The go in Audacity and click on Edit>Preferences (Shortcut Ctrl+P) and look for libraries. Click on FFmpeg Library: Locate..
Then a box will appear. If you extracted the Lame dll where it was recommended, simply paste this location: C:\Program Files (x86)\Audacity\avformat-55.dll and click OK.
If you extracted the FFmpeg somewhere else, click browse and locate where you extracted it. Click ok and restart Audacity, done! You now have FFmpeg installed and can open mp4s.
Verification install ffmpeg audacity was successful
This last part is optional, most likely ffmpeg was installed correctly. But if you want to make sure, get yourself an .mp4 video file. In Audacity, click on file>open and select your mp4 file. If you see a loading screen that means it was installed correctly. If not, try the tutorial above again to re-install ffmpeg. Most likely the issue is in extracting or selecting of the folders.