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

grooved.okat.best

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

#201

Post by schobi »

okatbest wrote: post #63
miah_ wrote: post #51

This is a neat idea. I don't know why it needs to be an app on a phone though. I guess you "know" a phone has a microphone and the setup is minimal and you have a api for everything? It being a phone app leads me to believe the 'no data collected' bit is temporary as all phone apps eventually gobble data to sell. I have an Android so I can't try this out, as its in 'private beta' on Android currently. Would love to s…

Probably a smart idea to be suspicious of new apps, though I will say I am someone who care deeply about privacy. You can take a look at my previous project Boop ( https://boop.okat.best/ ), which is open source and has been on the App Store for 6 years, yet I still don't have any analytics or data collection in it. I have no clue how many people use it beyond download figures I get from Apple. I have considered maki…

I understand your hesitation in opening the code. Still, the idea seems really great, low complexity (quick local processing, no database of songs needed) and robust (any reasonable vinyl could work).

I suggest considering writing about it. Maybe a whitepaper? A publication? A patent application? May be colab with audio researchers? Or get sponsored from an audiophile record player manufacturer?

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

#202

Post by schobi »

phreeza wrote: post #109
netsharc wrote: post #41

Earlier quoted context omitted.

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)

I tried to build a prototype of something like this with opencv once, didn't get it to work reliably though. I have a feeling there should be a relatively simple signal processing version of this, basically a spatiotemporal Fourier transform, that should solve it.

I would go with something like sift features (or a non patented variant thereof if you plan commercial usage). You analyze a first picture and extract the center part. You run a feature detector on each image and the can cheaply match (scale and rotation invariant) against each other - this gives rotation and scaling.

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

#204

Post by phreeza »

schobi wrote: post #202
phreeza wrote: post #109

Earlier quoted context omitted.

I tried to build a prototype of something like this with opencv once, didn't get it to work reliably though. I have a feeling there should be a relatively simple signal processing version of this, basically a spatiotemporal Fourier transform, that should solve it.

I would go with something like sift features (or a non patented variant thereof if you plan commercial usage). You analyze a first picture and extract the center part. You run a feature detector on each image and the can cheaply match (scale and rotation invariant) against each other - this gives rotation and scaling.

Yea that's precisely what I ended up doing, but the frame extraction was quite finicky.

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

#205

Post by Aldipower »

egypturnash wrote: post #68

All the turntables in my life as a kid had built-in calibration, in the form of four rows of repeating black/silver squares on the side of the wheel, a light flickering at the mains frequency, and a little dial to adjust the turning speed until the row of squares corresponding to your current combination of 50/60 hz DC and 33/45 RPM appeared to stop moving. It was a very clever trick.

My Dual turntable from the 80ties is regulated by a quartz crystal. This thing calibrates itself. :-)

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

#207

Post by lightedman »

kazinator wrote: post #171
criddell wrote: post #168

Earlier quoted context omitted.

How did you determine 7 cents was the correct amount?

Trial and error. Guitar meticulously tuned to concert pitch, with attention to the 12-15 fret area, then compare against versions of the track slowed down by all available factors in audacity from around 0.993 to 0.998. (The stretch tool doesn't take more digits, stupidly.)

"Guitar meticulously tuned to concert pitch, with attention to the 12-15 fret area"

When you need to pay attention to anything outside of open string, fretted 12th, open harmonic 12th fret (and fretted 24th if you have a 24+ fret guitar) for intonation, it's time to get the guitar to a luthier for setup maintenance. Something else is drastically wrong in the setup.

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

#208

Post by bitnasty »

jiayo wrote: post #150
BuildTheRobots wrote: post #143

Earlier quoted context omitted.

I'd be curious to know _why_ your wife felt it was playing too fast. Was it out of tune, out of tempo or something else?

When US (NTSC) shows are aired in Europe (PAL), the framerate difference necessitates a small speed-up. It's barely noticeable, except when music is playing, at which point it is very, very noticeable. Yes, it's a little higher pitched, but it just feels wrong and is immediately noticeable. I think it's about 3% speed up, which is exactly what's being described here.

NTSC is 29.97 fps and PAL is 25. That’s almost 20%!

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

#209

Post by dmd »

okatbest wrote: post #175
dmd wrote: post #118

Earlier quoted context omitted.

Yep, voice memo works fine, not on lockdown (not sure what that is).

Very strange... Best I can offer is to delete and reinstall the app to reset the microphone permissions, or if you'd like you can send me an email via my website (okat.best) and we can try to troubleshoot it

OK, deleting and reinstalling works, and now it works.

I'm concerned that the app does not work at all in airplane mode - like, even navigating between pages ("return to home" from a failure).

It also doesn't work (even without airplane mode) for songs that Shazam fails on - so I guess we've confirmed that that's how this works!

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

#210

Post by [deleted] »

lightedman wrote: post #207
kazinator wrote: post #171

Earlier quoted context omitted.

Trial and error. Guitar meticulously tuned to concert pitch, with attention to the 12-15 fret area, then compare against versions of the track slowed down by all available factors in audacity from around 0.993 to 0.998. (The stretch tool doesn't take more digits, stupidly.)

"Guitar meticulously tuned to concert pitch, with attention to the 12-15 fret area" When you need to pay attention to anything outside of open string, fretted 12th, open harmonic 12th fret (and fretted 24th if you have a 24+ fret guitar) for intonation, it's time to get the guitar to a luthier for setup maintenance. Something else is drastically wrong in the setup.

[deleted]
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