8 ms·

How Audio Fingerprinting Works

259 points by dceddia 5y ago

heinrichf 5y ago
(2020). See also https://news.ycombinator.com/item?id=9870408 https://news.ycombinator.com/item?id=9870408, which I found more interesting (and that the author should probably have referenced).
- TacticalCoder 5y ago
  A very long time ago (around 2000) I came up with the idea to record my car's engine sound, use a FFT on that, find the dominant frequency change over time, and then use the car's gear ratio / wheel size to find back the power curve. I'd drive my car both ways on an empty street, in 2nd gear, from idle to the rev limiter. Then I'd compute the two curves and average them. It was fascinating: the curve plotted was matching nearly exactly the power curve given by the car manufacturer. I think it's the first Java program I wrote. I copy/pasted some discrete FFT code I found somewhere. It was a nice little project for it's way simpler than trying to fingerprint audio using FFT like Shazam does: yet I got to learn a bit about harmonics, FFT / amplitude over time vs amplitude over frequency, car drag coefficient, etc. As I never throw anything I probably still have that crappy code somewhere!
  - crmd 5y ago
    Cool stuff. You might enjoy this video[0] where Ben K. from Applied Science measures the RPM of his car engine via the cigarette lighter by measuring the inductive ignition spikes with an FFT on his scope. [0] https://youtu.be/t0ToYhjYV9I https://youtu.be/t0ToYhjYV9I
    - ComputerGuru 5y ago
      Thanks for sharing that! Aside from the excessive fawning over the scope that was a great video - I think it’s awesome that the result differed from expectations with the (spoiler alert!) DMC-12’s uneven firing pattern and made the whole thing more interesting.
  - analog31 5y ago
    You could also use the accelerometer in the phone to measure power transfer.
talkingtab 5y ago
Outstanding. I don't know much about audio or fingerprinting, but I know much more after reading this article. Thanks.
- motohagiography 5y ago
  Seconded. Absolutely superb. I use Audactity and ffmpeg for analyzing sounds all the time and had only intuited these foundations, which are described in such a straightforward way here.
allcentury 5y ago
Wonderful article, I knew some of this but learned a lot more.
dceddia 5y ago
I’ve wanted to learn more about DSP for a while and recently started working through The Scientist and Engineer’s Guide to DSP [0] and it’s been fantastic. It’s much heavier on explanations and lighter on math equations than other books or courses I’d seen previously. It’s helping me build some real intuition around this stuff. That book plus this article’s excellent explanations really helped things click for me and I’m very grateful to both authors! 0: https://www.dspguide.com/ https://www.dspguide.com/
- vitorsr 5y ago
  Conditioned on what you want to achieve, I would suggest against, strongly against, or very strongly against avoiding (applied) mathematics. In any case, I suggest flipping through the IEEE Signal Processing Magazine [1] and reevaluating your learning path. [1] https://signalprocessingsociety.org/publications-resources/ieee-signal-processing-magazine https://signalprocessingsociety.org/publications-resources/i...
  - knaik94 5y ago
    Can you elaborate on why you so strongly advise against it?
    - vitorsr 5y ago
      I can only invite you to flip through current technical texts in signal processing and go through the thought exercise of defining the envelope of prior knowledge required. I recommend the IEEE Signal Processing Magazine as it is the flagship magazine from the IEEE Signal Processing Society. IEEE magazine articles are written “to appeal to non-experts as well as experts in the field” [1] and therefore target a broad engineering audience while remaining current and being peer-reviewed. [1] https://magazines.ieeeauthorcenter.ieee.org/get-started-with-ieee-magazines/about-ieee-magazines https://magazines.ieeeauthorcenter.ieee.org/get-started-with...
  - dceddia 5y ago
    I'd say my goal is not so much about avoiding math but more about learning intuition-first rather than equations-first. Top-down vs. bottom-up, maybe. Most of material that I've encountered about math-heavy stuff tends to do the latter. I imagine there are many people who're great at picking apart an equation and deriving things from first principles; but for me, I find it more manageable to get the big picture first, visualize what's going on, and then finally learn the math behind it. So far the DSP Guide book is doing a great job of presenting things that way. Another good example of this kind of style is https://betterexplained.com/ https://betterexplained.com/ (some of their articles are great companions to these DSP topics actually!)
sytelus 5y ago
This is one amazing article. Bravo!
bla3 5y ago
(2020)

259 points by dceddia 5y ago

(2020). See also https://news.ycombinator.com/item?id=9870408 https://news.ycombinator.com/item?id=9870408, which I found more interesting (and that the author should probably have referenced).

TacticalCoder 5y ago
A very long time ago (around 2000) I came up with the idea to record my car's engine sound, use a FFT on that, find the dominant frequency change over time, and then use the car's gear ratio / wheel size to find back the power curve. I'd drive my car both ways on an empty street, in 2nd gear, from idle to the rev limiter. Then I'd compute the two curves and average them. It was fascinating: the curve plotted was matching nearly exactly the power curve given by the car manufacturer. I think it's the first Java program I wrote. I copy/pasted some discrete FFT code I found somewhere. It was a nice little project for it's way simpler than trying to fingerprint audio using FFT like Shazam does: yet I got to learn a bit about harmonics, FFT / amplitude over time vs amplitude over frequency, car drag coefficient, etc. As I never throw anything I probably still have that crappy code somewhere!
- crmd 5y ago
  Cool stuff. You might enjoy this video[0] where Ben K. from Applied Science measures the RPM of his car engine via the cigarette lighter by measuring the inductive ignition spikes with an FFT on his scope. [0] https://youtu.be/t0ToYhjYV9I https://youtu.be/t0ToYhjYV9I
  - ComputerGuru 5y ago
    Thanks for sharing that! Aside from the excessive fawning over the scope that was a great video - I think it’s awesome that the result differed from expectations with the (spoiler alert!) DMC-12’s uneven firing pattern and made the whole thing more interesting.
- analog31 5y ago
  You could also use the accelerometer in the phone to measure power transfer.

talkingtab 5y ago

Outstanding. I don't know much about audio or fingerprinting, but I know much more after reading this article. Thanks.

motohagiography 5y ago
Seconded. Absolutely superb. I use Audactity and ffmpeg for analyzing sounds all the time and had only intuited these foundations, which are described in such a straightforward way here.

allcentury 5y ago

Wonderful article, I knew some of this but learned a lot more.

dceddia 5y ago

I’ve wanted to learn more about DSP for a while and recently started working through The Scientist and Engineer’s Guide to DSP [0] and it’s been fantastic. It’s much heavier on explanations and lighter on math equations than other books or courses I’d seen previously. It’s helping me build some real intuition around this stuff. That book plus this article’s excellent explanations really helped things click for me and I’m very grateful to both authors! 0: https://www.dspguide.com/ https://www.dspguide.com/

vitorsr 5y ago
Conditioned on what you want to achieve, I would suggest against, strongly against, or very strongly against avoiding (applied) mathematics. In any case, I suggest flipping through the IEEE Signal Processing Magazine [1] and reevaluating your learning path. [1] https://signalprocessingsociety.org/publications-resources/ieee-signal-processing-magazine https://signalprocessingsociety.org/publications-resources/i...
- knaik94 5y ago
  Can you elaborate on why you so strongly advise against it?
  - vitorsr 5y ago
    I can only invite you to flip through current technical texts in signal processing and go through the thought exercise of defining the envelope of prior knowledge required. I recommend the IEEE Signal Processing Magazine as it is the flagship magazine from the IEEE Signal Processing Society. IEEE magazine articles are written “to appeal to non-experts as well as experts in the field” [1] and therefore target a broad engineering audience while remaining current and being peer-reviewed. [1] https://magazines.ieeeauthorcenter.ieee.org/get-started-with-ieee-magazines/about-ieee-magazines https://magazines.ieeeauthorcenter.ieee.org/get-started-with...
- dceddia 5y ago
  I'd say my goal is not so much about avoiding math but more about learning intuition-first rather than equations-first. Top-down vs. bottom-up, maybe. Most of material that I've encountered about math-heavy stuff tends to do the latter. I imagine there are many people who're great at picking apart an equation and deriving things from first principles; but for me, I find it more manageable to get the big picture first, visualize what's going on, and then finally learn the math behind it. So far the DSP Guide book is doing a great job of presenting things that way. Another good example of this kind of style is https://betterexplained.com/ https://betterexplained.com/ (some of their articles are great companions to these DSP topics actually!)

sytelus 5y ago

This is one amazing article. Bravo!

bla3 5y ago

(2020)