TIL How To Batch-Process Audio Files With Effect Chains

Every now and then I record an audio file for a tutorial or some such. I always do it in the same place, with the same equipment. And then I have to clean it up using VST/AU plug-ins in a DAW (digital audio workstation).

Today I learned how to automate this process using REAPER, a very nice, very scriptable, very powerful DAW. Because TIL that Reaper comes with a CLI!

Basically, the Reaper CLI allows me to call it with a file containing processing instructions. The file must contain both paths to audio files and details about what to do with them. My example file ~/Desktop/process.txt looks like this:

  FXCHAIN "Tutorials.RfxChain"
  OUTPATH "/Users/czottmann/Desktop/processed-tracks/"

The file paths are pretty self-explanatory, the interesting part is the <CONFIG …> directive. As described in the docs, I tell Reaper to use an FX chain called “Tutorial” and save the processed files in ~/Desktop/processed-tracks/.

The “Tutorials” FX chain didn’t exist, I needed to create it first. So, in Reaper:

  1. I imported an applicable audio file into Reaper. (For setting my baseline, the applicable audio file was one of the voiceovers I did for a tutorial.)
  2. I configured the FX chain for that track. Gate, de-esser, compressor etc.
  3. I saved the FX chain using the name “Tutorials” in Reaper’s default FX chains directory.

And with that done, the CLI could be used:

/Applications/REAPER.app/Contents/MacOS/REAPER \
  -batchconvert ~/Desktop/process.txt

Reaper starts up, does the processing, saves the results in the output folder (which should be created beforehand), and quit once done.

Pretty cool.


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Carlo Zottmann @czottmann