First of all, I precise that I am a newbie at Audacity.
So I am trying to normalize several MP4 video files (in batch as I have a few hundred), and I heard that Audacity could perform this task. However, I didn’t manage to.
After installing ffmpeg, I was able to import mp4 files. And after normalizing several files at once, I tried to export them. That is where I am having issues.
After selecting “Export multiple” (That seems to be the only option allowing to select MP4 format) I select ‘custom ffmpeg export’ then the button ‘open custom ffmpeg format options’. In the new window, I select MP4 format, and one or another codec (I tried them all), and click OK for the export.
Unfortunately, the files I am getting aren’t MP4 files and neither video files. All I am getting is the audio.
Since Audacity is an audio editor, you’ll need another tool, such as a video editor or audio/video multiplexer to re-combine the audio & video.
If your video editor is going to re-encode (re-compress) the audio, which will probably be the default, it’s best to export to WAV then import the WAV into your video editor to minimize the number of times it’s compressed.
And just in case you don’t know this, Normalization is a mathematical concept that sets (or “maximizes”) the peak levels and it’s NOT “volume matching”. There are lots of quiet-sounding normalized/maximized files.
After selecting “Export multiple” (That seems to be the only option allowing to select MP4 format)
I don’t know why that’s happening, but of course you need one-long file to keep the audio & video synchronized.