linux 4.1.15-8-default x86_64
audacity 2.1.1 - distribution release
I would like to have a job (chain?) that reads whatever files are in a directory, adjust the volume, write it back with the same name. I have about 5000 audio files I would like to normalize. They are a mix of MP3 and M4A files.
I started to create a chain but discovered there is no export command for m4a files. The File::Export Audio method recommended in the manual did not produce an export command for m4a.
adjust the volume… I have about 5000 audio files I would like to normalize.
You said two different things there. Effect > Normalize doesn’t set volume of the work. It works on sound peaks, such as the tips of the blue waves. Not loudness.
That’s why the ACX AudioBook people have two different specifications, one for peaks and a different one for volume.
I know there’s a struggle with the latest version of pre-built data libraries that Audacity uses to import and export advanced compressed file types. I don’t think all the normal settings are available.
Normalize can be used in a Chain to make the peak amplitude the same in all files. (As koz mentioned, just because audio files have the same peak (maximum) amplitude does not necessarily mean they will sound the same “loudness”).
Exporting M4A is not supported in Chains, but if you export as WAV you can probably use another program to batch convert them the M4A.
There is one way to do this. Chris’s Compressor was designed so he could listen to opera in the car. He couldn’t deal with the volume variations between the acts and segments of the show. Turn the volume up…turn the volume down. The default settings do a reasonable job of leveling out music going through. I increase the first value, compression, from the default 0.5 to 0.77 and the resulting shows have about the same sound and evenness as the local radio station.