Ripping Vinyl Via Your Scanner?

An anonymous reader writes "This site describes a method of extracting audio off of scanned images of vinyl records. Kazaa vinyl swapping is on it's way!" While this method creates exceptionally noisy samples, you can definitely hear the underlying music.

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looks possible

[alizard]

These numbers are EXTREMELY approximate, I just wanted to see if his claims are possible. They are.

Standard rotational speed = 33 1/3 RPM

12" record

Circumference = pi * D

33.3RPM /60 ~ 0.5 R/second

12" * pi ~ 37" circumference.

0.5 * 37" = 18.5"

18.5 * 600dpi = 11,100 samples per inch, which gives a Nyquist limit of 5550Hz... a 2400 dpi or better might actually give full audio bandwidth, though in this case, the higher the better, since the area available for sampling decreases towards the center of the record, and for really high fidelity sound, more than 2 samples at 20K are necessary.

His model for how the record was encoded is *wrong*. The RIAA method of stereo modulation (back when they were mostly a standards organization) places the amplitude information on each wall of the V-shaped groove. It is intended to be picked up with a stylus connected to a something in the form of an Y , with channel information picked up by coil or magnet or other means attached to each upper leg of the Y.

Fixing his model should result in drastically improved performance if he's extracting stereo information. Cleaning the record would also help a lot.

His project actually *is* worth doing. An optimized algorithm should allow anyone or a museum with a good scanner to turn his vinyl (SPELLED CORRECTLY) collection into decent quality Red Book or MP3 tracks without any further damage to the records. The basic problem is to linearize the relationship between 16-24 bit gray scale information of reflected light and the depth modulation in each groove.

The suggestion of using software to extract 3D information from the grooves posted elsewhere is a good idea, but this is a good start.

Cool hack.

You want to try this at home?

[alizard]

http://www.aardvarkmastering.com/riaa.htm contains the physical dimensional specifications for 33 1/3, 45, 78 RPM records.

http://arts.ucsc.edu/ems/music/tech_background/TE- 19/teces_19.html contains basic information on how the LP record works. I think the most important thing for the experimenter is called RIAA equalization, in order to limit the physical motion of the recording stylus that cut the record, bass was reduced and treble increased in a very precise way, in order to reproduce the original sound, the opposite must be done.

The RIAA equalization curve is a plot of amplitude boost/cut vs. frequency. Apply its inverse to the raw analog signal(s) that come out of your signal processing.

You can find it at http://www.tanker.se/lidstrom/riaa.htm.

Oh, and CLEAN THE RECORD BEFORE DOING THIS. The info in Part 14 of the rec.audio.* FAQ is as good a place to start to find out how as any.

Have fun and feel free to let me know if you get anywhere.

You might also want a look at my other post to this thread.

Re:Of course it's a hoax

[Draoi]

Like I just pointed out on another thread, the source has been posted here.

The guy goes on to say;

Woke up, fell out of bed... rampaged by a slashdot horde.

Some clarifications to the slashdot crowd:

I am sorry so many of you thought this page was a hoax only because no source code was supplied (I'm sure you'll all agree, now that you can see the code, that it is both straightforward and crappy).