I’m curious, what’s the deal here? I was able to open any/all MP4’s with version 2.0.6 instead of 2.1.0. I would think that this is more of a bug if anything… It gives the error of being an Advanced Audio Codec.
Any possible explanations?
You may need to re-link or re-download FFmpeg.
Go to Edit → Preferences → Libraries and try “Locate”. If that doesn’t work, click “Download” to download and re-install.
Another explanation would be if these are not the same files that you were opening before but are corrupted files or files that have been crippled with Digital Rights Management.
If the problem continues after reinstalling FFmpeg 2.2.2, download “MediaInfo” from http://mediainfo.sourceforge.net/en/Download/Windows and post the text output from that for one of the problem files. Get the MediaInfo version without installer, because the installer may have malware or adware.
Also post the log from Help > Show Log… top right of the Audacity menu after trying to import the file.
Gale