My adventures in audio processing

One of my lifetime side projects is tweaking audio. I love the challenge of learning the art of processing an audio signal. I hate the sound of most terrestrial radio stations. I love hearing SACD and great vinyl on a $20,000 sound system.

So in my spare time, I like to play around with audio. In the past year I’ve been working to conceive a killer preset for an online radio station I had to kill a decade ago but intend to revive in the near months ahead. The digital music landscape has changed much in 10 years: so much music is streamed via playlists now, which don’t convey much personality, in contrast to a radio format. Challenge accepted. I’m ready to put to use all this knowledge I’ve gained in my spare time.

Around November, I determined that my preset-in-development was ready for a public debut – it sounds hot and clear and not crushed by a zealous compressor or a bass line that fucks the other elements out of prominence. It’s a preset that produces a brighter intense sound that induces chills of energy throughout my body every time I run music through it. It is awesome.

So, yeah, debut time.

But while I was testing a production environment tonight, I encountered an issue that I couldn’t immediately diagnose. What I learned through trial-and-error:

  • (and in retrospect this does seem stupidly obvious, but…) DO NOT stream an output of a sample rate that is not an even low multiple (2 or 3) of the receiving input. Example: playing a 192khz FLAC file into an audio processor that’s sampling at 44.1khz. The processor was recurrently spitting out artifacts as I played the file, and it suddenly dawned on me that the sample rate of FLAC was so different than mp3 that the default setting probably wasn’t set to handle FLAC well. (Suspicion confirmed, problem solved, total time ~30 mins).
  • Do not sample at a high frequency unless you’re sure your production machine can handle it. I’m not yet sure whether my configuration can withstand a chain that processes the audio at a high sample rate before it’s mixed down to a broadcast signal, however I’ll be troubleshooting this question further and (hopefully) eventually understanding what besides the CPU can bottleneck this audio chain to a point of choking it every couple of minutes.

I’ll talk more about this project as I make more progress. Hopefully will have a website up by end of this month!


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