5 ms·

Well that's a good hack!! that's why I read HN, not for some Arrington story. I wouldn't have guessed there was enough data left in the picture of the gramopho

by guylhem 14y ago

Well that's a good hack!! that's why I read HN, not for some Arrington story. I wouldn't have guessed there was enough data left in the picture of the gramophone track to recreate audio from it. Which makes me think about Shannon theorem - my guesses would have been wrong, so I wonder just "how wrong". What would the minimal resolution (dpi) be to store say 1 minute of audio at 8Hz? Would there be an easy way to calculate that (just a back of the envelope calculation, to get a rough idea) What was the resolution of the printing press ca 1880, to know how much audio could have been "stored" in a single page for posterity? In the picture there is a lot of text, so obviously a lot of lost space. And I wonder how we could make 2d barcodes to store uncompressed wav audio, which might be more resistant to noise, but only because it'll be like a "lower resolution", ie less easily disruptible. Which leads me back to Shannon. I'm not into audio processing but that raises a lot of questions I'll be pondering over with some coffee tonight (obligatory xkcd reference- http://xkcd.com/356/ http://xkcd.com/356/) That's the kind of article I love :-) EDIT: downvotes, whatever. Haters gonna hate. I'll have some hours of fun thanks to this article anyway!

kyrias 14y ago
> "I wouldn't have guessed there was enough data left in the picture of the > gramophone track to recreate audio from it." Ah, well the thing is that the needle isn't straight, it has an angle i.e. as the tracks get deeper they also get wider, so you only need to be able to see how wide the track is. http://www.vinylrecorder.com/stereo.html http://www.vinylrecorder.com/stereo.html
klodolph 14y ago
Twibright Optar stores 200kB per A4 sheet, or 25 seconds at 64kbits/s. 64kbits/s is high quality stereo audio if compressed using Opus. Most music sounds great at this bit rate. 64kbits/s is also 8kHz µ-law PCM, which is the standard for telephone lines in North America--so, terrible but intelligible. Opus can be turned down to 6kbits/s, which gives you about 4.4 minutes of muddy but intelligible speech per page. By extrapolation, we can calculate density for microfiche. Assuming a resolution of 120 lp/mm, microfiche has about 5 times the resolution of the paper used for Optar, and the dimensions are exactly half. This means that microfiche has 6.3 times the density of A4 paper, measured in bytes per sheet. This gives us one high quality, durable recording of "Ring of Fire" on a single sheet of microfiche. I wouldn't bother with uncompressed PCM. (You use the term "wav audio", but WAV is a file format.)
caseysoftware 14y ago
"I wouldn't have guessed there was enough data left in the picture of the gramophone track to recreate audio from it." I'd bet it's almost the other way around.. the information density would be so low because the information itself is relatively low resolution* that it makes the analysis that much easier. * "Resolution" in the detail sense of the word, not the visual.
InclinedPlane 14y ago
Consider that the outer rim of a 45 rpm vinyl record moves at only about 16.5 inches per second. This means that the effective sampling frequency is equal to 16.5 * dpi, so even at a relatively modest (for film anyway) 300 dpi you'll get 5,000 Hz sampling, enough to reproduce many sounds moderately well.
w1ntermute 14y ago
> not for some Arrington story For those missing the reference: https://news.ycombinator.com/item?id=5501832 https://news.ycombinator.com/item?id=5501832

by guylhem 14y ago

kyrias 14y ago

> "I wouldn't have guessed there was enough data left in the picture of the > gramophone track to recreate audio from it." Ah, well the thing is that the needle isn't straight, it has an angle i.e. as the tracks get deeper they also get wider, so you only need to be able to see how wide the track is. http://www.vinylrecorder.com/stereo.html http://www.vinylrecorder.com/stereo.html

klodolph 14y ago

Twibright Optar stores 200kB per A4 sheet, or 25 seconds at 64kbits/s. 64kbits/s is high quality stereo audio if compressed using Opus. Most music sounds great at this bit rate. 64kbits/s is also 8kHz µ-law PCM, which is the standard for telephone lines in North America--so, terrible but intelligible. Opus can be turned down to 6kbits/s, which gives you about 4.4 minutes of muddy but intelligible speech per page. By extrapolation, we can calculate density for microfiche. Assuming a resolution of 120 lp/mm, microfiche has about 5 times the resolution of the paper used for Optar, and the dimensions are exactly half. This means that microfiche has 6.3 times the density of A4 paper, measured in bytes per sheet. This gives us one high quality, durable recording of "Ring of Fire" on a single sheet of microfiche. I wouldn't bother with uncompressed PCM. (You use the term "wav audio", but WAV is a file format.)

caseysoftware 14y ago

"I wouldn't have guessed there was enough data left in the picture of the gramophone track to recreate audio from it." I'd bet it's almost the other way around.. the information density would be so low because the information itself is relatively low resolution* that it makes the analysis that much easier. * "Resolution" in the detail sense of the word, not the visual.

InclinedPlane 14y ago

Consider that the outer rim of a 45 rpm vinyl record moves at only about 16.5 inches per second. This means that the effective sampling frequency is equal to 16.5 * dpi, so even at a relatively modest (for film anyway) 300 dpi you'll get 5,000 Hz sampling, enough to reproduce many sounds moderately well.

w1ntermute 14y ago

> not for some Arrington story For those missing the reference: https://news.ycombinator.com/item?id=5501832 https://news.ycombinator.com/item?id=5501832