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

Post by plastic3169 » Tue, May 28, 2024, 5:51 PM UTC

okatbest wrote: post #93

plastic3169 wrote: post #42

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…

Hey that's very odd, would you mind telling me which country/region you are located in? I actually released the app yesterday but didn't post about it til today because it wasn't being indexed properly on the App Store yet, it's possible that it's still not live everywhere. I have an image link to the listing in the first section of the web page and if on iPhone it should show you the classic "this website has an app…

Post by derefr » Tue, May 28, 2024, 6:00 PM UTC

crazygringo wrote: post #81

derefr wrote: post #47

Earlier quoted context omitted.

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…

There aren't really reference BPM's. Not everything is recorded with a click track, though a lot is. But even so, while it will usually be an integer BPM, it's not always rounded to the nearest 5. 120 might be too fast while 115 is too slow, so you pick 118. For an app that's trying to correct your turntable speed by e.g. 3%, it couldn't even begin to guess the "correct" BPM.

Post by derefr » Tue, May 28, 2024, 6:11 PM UTC

egypturnash wrote: post #96

taylodl wrote: post #90

Earlier quoted context omitted.

You had access to nicer turntables as a kid! That was a distinguishing feature between the more "serious" music hobbyist and the person who just wanted to play some tunes. I haven't messed around with a turntable in over 20 years but these days, only the supposed "serious" music hobbyist would be using a turntable and I'd think anyone making a turntable that didn't have this adjustment would be laughed out of the mar…

My dad was a recording engineer, so he knew where to go to find the sweet spot between "this sounds great" and "this sounds insanely fabulous but requires a second mortgage". And yeah honestly I'm surprised you can get a turntable that isn't made for the audiophile market any more, but the one shown in the video for this app sure does lack any fine speed adjustment. Just a little button labeled 33/45.

Post by crazygringo » Tue, May 28, 2024, 6:19 PM UTC

derefr wrote: post #103

crazygringo wrote: post #81

Earlier quoted context omitted.

There aren't really reference BPM's. Not everything is recorded with a click track, though a lot is. But even so, while it will usually be an integer BPM, it's not always rounded to the nearest 5. 120 might be too fast while 115 is too slow, so you pick 118. For an app that's trying to correct your turntable speed by e.g. 3%, it couldn't even begin to guess the "correct" BPM.

But would a large-enough majority of songs be recorded with a multiple-of-5 BPM, that this app could presume the first record you play has a multiple-of-5 BPM, and be right 80+% of the time? If so, then that could still be how it was done here. It wouldn't always work for the first record, but you'd be highly likely to get a "good reading" by at least the third one you try.

Post by phreeza » Tue, May 28, 2024, 6:20 PM UTC

netsharc wrote: post #41

astral303 wrote: post #23

Earlier quoted context omitted.

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)