On January 1, 2016 we packed up all our earthly goods and headed south to Canada. (Yes, it’s true. When you live in Minnesota, it’s possible to move south to Canada. Look at the map!) Having lived here for a little over a year, here are some thoughts about living here, in no particular order:

1. “Sorry” is more of a greeting than just an apology.
2. Canadians really are polite; but put them behind the wheel of a car and all bets are off.
3. Universal healthcare works. Americans love to go on and on about socialized medicine; but I’m here to tell you: it works.
4. Bumper stickers are rare here.
5. People don’t really talk politics. Well, they talk about U.S. politics.
6. Left turn arrows on traffic lights are rare. It makes for interesting moments when the light changes.
7. The electric utility is called “hydro”, which given the Greek origin of the word makes little sense until you realize that it stands for “hydroelectric.”
8. Youth music is well-supported - both through private and public funding.
9. State-church separation is fuzzier. For example, the Catholic school system is tax-payer funded. But only the Catholic schools. It has something to do with the Canadian Charter (a.k.a Constitution.) It was apparently some sort of historical compromise in the 1800’s.
10. Don’t order iced tea in Canada. It’s way too sweet.
11. As a practical matter, you can’t be elected Prime Minister unless you speak both English and French fluently. This is a really good thing.^[How many languages does Donald Trump speak fluently, for example?]
12. Speaking of politics, campaigns are time-limited to 6 weeks before an election. How cool is that?
13. Poutine sounds horrible, but it’s actually pretty good.

I’ve written previously about extracting and processing mp3 files from web pages. The use case that I described, obtaining Russian word pronunciations for Anki cards is basically the same although I’m now obtaining many of my words from Forvo. However, Forvo doesn’t seem to apply any audio dynamic range processing or normalization to the audio files. While many of the pronunciation mp3’s are excellent as-is, some need post-processing chiefly because the amplitude is too low. However, being lazy by nature, I set out to find a way of improving the audio quality automatically before I insert the mp3 file into my new vocabulary cards.

As before, the workflow depends heavily on Hazel to identify and process files coming out of Forvo. The download button on their website, sends the mp3 files to the Downloads directory. The first rule in the workflow just grabs downloaded mp3 files and moves them to ~/Documents/mp3 so that I can work on them directly there.

Another Hazel rule renames the verbosely-titled files to just the single Russian word being pronounced. It’s just neater that way.

rename 's/(pronunciation_ru_)(.*)/$2/' *.mp3

This uses the convenient rename command that you can obtain via Homebrew.

The final rule, grabs the newly-renamed mp3 file and performs a series of audio processing steps:

ffmpeg -i "$1" tmp.wav;
sox tmp.wav temp_out.wav norm gain compand 0.02,0.20 5:-60,-40,-10 -5 -90 0.1;
ffmpeg -i temp_out.wav -codec:a libmp3lame -qscale:a 2 tmp.mp3;
lame --mp3input -b 64 --resample 22.50 tmp.mp3 tmp;
mv tmp "$1";
rm tmp.mp3;
rm tmp.wav;
rm temp_out.wav

The first line ffmpeg -i "$1" tmp.wav; simply writes a temporary .wav file that we can process using sox. The second line invokes sox with a number of options that normalize and improve the dynamic range of the audio. Finally we use ffmpeg to convert the .wav file back to .mp3, compress the .mp3 file and then clean up.

Now I have excellent normalized audio for my cards, with no work for me!

See also:

• sox compand options - outlines a number of options for dynamic range compression using sox.
• Using ffmpeg to convert .wav to .mp3
• Using ffmpeg to convert .mp3 to .wav
• Introduction to processing audio files with SoX
• SoX homepage - the source