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Show HN: I made a free app to calibrate your turntable by simply playing a song

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Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#41

Post by netsharc »

astral303 wrote: post #23
patrakov wrote: post #5

Does it rely on the fact that music has a concept of notes with well-defined frequencies and that there is no such thing as 216 Hz (must be 207.6 or 220 Hz) when the music is played on a properly tuned instrument? Or does it use other heuristics?

I tried it out and the instructions have tips on what record to pick, they say to pick a well known version of a song (like not a live version etc), and preferably song with a beat, but it says it doesn’t use any 3rd party APIs or libraries, only Apple APIs. So my guess at to what it’s doing is using a ShazamKit recognition behind the scenes and looking at the frequencySkew value of the matched result. It also gives…

I guess a phone's camera can be used to count the RPM, e.g. by filming the label and counting how many milliseconds it needs to do a full rotation (1818ms for a 33 RPM record)

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#42

Post by plastic3169 »

Looks amazing and useful for me! The links don’t take me to the app store on my iphone and the app name is not in the heading I need to scroll past the copy to find what to search for. Minor annoyance but for some reason annoyed me a lot. That annoyance led me to hate the copy as I was searching for the app name and tried to skim the text. This is probably the first time I write any feedback to internet. I am usually not one that does that kind of thing haha. Ok, now I will search and install the app. I bet it’s great.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#43

Post by kazinator »

I'm skeptical; you have no idea whether a random song from a record player is in tune or not, without a reference copy of that song from digital media.

Is this zeroing in on traces of 60 cycle hum in the recording?

Or else, won't it adjust an out-of-tune song to be in concert pitch? (Mind you, that would be extremely useful if you're playing along with the track and don't want to adjust your instrument, or cannot do so.)

To get it to the correct speed, I would go through my record collection and find a tune with long, sustained notes. Find the same tune on Youtube and get a pitch reference for the note using a digital tuner. Then adjust the record player to match the pitch on that note, down to 1/10 of a Hz precision.

(In the first place, why would you have a record player without a built-in strobe light for adjusting the speed in 2024, when this was a common item even in lower income households in 1984.)

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#44

Post by padenot »

crazygringo wrote: post #26

This seems really clever -- kudos! I'm curious how it actually works? At first I assumed you were comparing the vinyl track to the reference digital track from some streaming service and either analyzing the frequencies with FFT or the timing of peaks. But I watched your demo video and you don't need to tell it anything about the song. Which makes me think you're rather doing an FFT and simply trying to match how wel…

ShazamKit, from that fetch the BPM, BPM detection from the mic, compare ?

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#46

Post by svantana »

sambeau wrote: post #33
crazygringo wrote: post #26

This seems really clever -- kudos! I'm curious how it actually works? At first I assumed you were comparing the vinyl track to the reference digital track from some streaming service and either analyzing the frequencies with FFT or the timing of peaks. But I watched your demo video and you don't need to tell it anything about the song. Which makes me think you're rather doing an FFT and simply trying to match how wel…

My first thought was that it is listening to the scratches rather than the music, but I guess they speed up as the record gets played and the arm moves inwards. So, my second guess is that it's listening to the pitch of the notes being played. Of course, old albums (especially punk albums) are probably tuned to whatever worked on the day—maybe a tuning fork, possibly a piano, maybe just to one of the instruments.

Umm, no, scratches meet the needle once per revolution, regardless of the needle's position. So that would definitely be a possible method. But not all records have scratches, or they could be at an angle, which would give the wrong estimate. Also, actual sounds on the record could have scratch-like qualities.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#47

Post by derefr »

crazygringo wrote: post #26

This seems really clever -- kudos! I'm curious how it actually works? At first I assumed you were comparing the vinyl track to the reference digital track from some streaming service and either analyzing the frequencies with FFT or the timing of peaks. But I watched your demo video and you don't need to tell it anything about the song. Which makes me think you're rather doing an FFT and simply trying to match how wel…

You can extract pitch information and compare it to a set of quantized reference pitches as an instrument tuning app does, sure.

But you can also extract BPM info and compare that to a set of quantized reference BPMs that anyone would ever bother to use.

And also, since you’re getting multiple pitches from multiple instruments in a time series, if you can isolate particular instruments, you can calculate the key the melody and/or harmony of the song is in.

Then, you could either come up with a heuristic, or just train a Bayesian filter, using datasets of “real” and “erroneous” (key, BPM) pairs.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#48

Post by LeoPanthera »

crazygringo wrote: post #26

This seems really clever -- kudos! I'm curious how it actually works? At first I assumed you were comparing the vinyl track to the reference digital track from some streaming service and either analyzing the frequencies with FFT or the timing of peaks. But I watched your demo video and you don't need to tell it anything about the song. Which makes me think you're rather doing an FFT and simply trying to match how wel…

It probably doesn't need to do an FFT, it just need to be able to count beats and have a database of BPM values for popular songs. You could use something like AcoustID/Chromaprint to identify the song you're playing.

A very simple idea, as all the best ideas are.

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#49

Post by peter_l_downs »

Strongly recommend updating your website to lead with some variation of "This is an offline iPhone app to help you calibrate your turntable's speed, all you need to do is play your records and the app will show you the current RPM" — wayyyyyyy too many words and other nonsense before I could figure out this is what it did.

Embed the demo video (the tweet you linked) too!

Looks great and if I still used records I would try it out! Congratulations on the launch.

EDIT: keep the rest of the writing if you'd like, I have no objection to it and I thought it was funny. But lead with what the app is and what it does!

Re: Show HN: I made a free app to calibrate your turntable by simply playing a song

#50

Post by hobofan »

shudza wrote: post #45

I've used to use an app (there are many) which measures angular velocity using accelerometer and displays RPM (you place the phone on the turntable). I can't see why would anyone need something other than that.

Complete noob here, but wouldn't the phones weight (especially with how big phones are nowadays) have a significant impact on the RPM by slowing it down?
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