
Extracting Audio from Pictures of Gramophone Recordings - gbaygon
https://mediapreservation.wordpress.com/2012/06/20/extracting-audio-from-pictures/
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guylhem
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/>)

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!

~~~
klodolph
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.)

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auctiontheory
Mind-blowing.

It does give me pause to wonder how much of the movie of our day-to-day lives
future generations will be able to replay, via goodness knows what mechanism.
(DNA testing of blood and hair is another example of this theme.)

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tokenadult
Following along while listening by looking at the linked German text of "Der
Handschuh"

<http://www.has.vcu.edu/for/schiller/handschuh_dual.html>

helps immensely in sorting out the speech from the noise (at least for me,
with my beginner's knowledge of German). It's amazing to hear the inventor's
poetry reading diction from so long ago.

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lcrs
related, render an audio file as an photoreal image of a vinyl record, then
recover the audio from that image:
[http://www.renderman.org/RMR/Examples/srt2011/audiblyPlausib...](http://www.renderman.org/RMR/Examples/srt2011/audiblyPlausibleRendering.pdf)

~~~
dmacedo
This looks interesting

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wazoox
Someone at the French National Audiovisual Archive ( <http://www.ina.fr/> )
showed me that they have been doing about the same thing for years to get the
sound back from heaps of broken records of various origins, mostly radio
recording from the 30s and 40s -- nothing nearly as old as this. IIRC they
even almost completely automated the process, including matching the groove
across missing bits in the high resolution picture from the scanner.

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kybernetikos
Reminds me of 'Digital Needle'
<http://www.phys.huji.ac.il/~springer/DigitalNeedle/>

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_pferreir_
Great work!

It reminds me of an X-files episode where Mulder and Scully find a first
century ceramic cup that supposedly contains a "phonograph" recording of Jesus
Christ's words during the last supper.

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ck2
Certainly that circular whumping noise can be digitally removed to allow the
voice to be heard more clearly?

It seems to be a precisely repeating pattern, prime for filtering?

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petsounds
Sadly, it seems that all of the audio samples are dead

~~~
SeanDav
worked for me, just took a long time to load the first time. Quality is really
lousy , though still a minor technological miracle.

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teeja
Works for Berliner-style lateral-cut grooves, wouldn't work at all with
vertical-cut records like Edison's!

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justincormack
Reminds me of Godel, Escher, Bach.

~~~
keithpeter
How? Serious question, I'm not challenging!

This work reminds me of what 'analogue' means. There is no _coding_ of the
sound, each stage in the analogue process represents the varying intensities
of the various pitches as some _variation_ in a property of the storage
medium.

Any form of digital representation (CD, mp3 whatever) requires a _convention_
to interpret the raw stream of numbers. If you don't know the convention then
you have a string of numbers.

~~~
klodolph
Analogue signals do have encodings and conventions, and the information is
incorrect or possibly mangled unless you decode in the same way.

So you're recording on a record. How fast does the record spin? Do you want a
constant angular velocity or constant linear velocity? At what angle does the
stylus move? Is there equalization that must be removed afterwards? Is there
some kind of modulation?

The convention for LP is 33⅓ RPM constant angular velocity, with two channels
each cut at 45° from vertical, the groove moving from the outside in, and the
RIAA equalization curve. If you don't know that the audio modulates the groove
position, then you just have an oversized coaster.

Digital conventions are just a little more demanding. However, PCM is quite
simple and you can dig it out of unknown file formats with relative ease.

~~~
keithpeter
" _So you're recording on a record. How fast does the record spin? Do you want
a constant angular velocity or constant linear velocity? At what angle does
the stylus move? Is there equalization that must be removed afterwards? Is
there some kind of modulation?_ "

Fair points. A possible elaboration is that analogue encoding is
_discoverable_ from the medium. _If_ we know that a recording is of a voice,
then we can recover the amplitude signal and speed up/slow down until it
sounds right or until the spectrum matches what we know of the source. Digital
encoding is not discoverable from the medium in quite the same way...

~~~
klodolph
Well, no, it's not that easy. You can't always just speed things up or slow
them down.

For example, try to extract audio from a CD-4 / Quadradisc record. Two of the
channels are modulated with a 30 kHz carrier using something called FM-PM-
SSBFM, and they won't be audible unless you demodulate them properly. You
won't get anything resembling music unless you know exactly what you're doing.

By comparison, I've recovered audio from undocumented proprietary PCM-based
formats from video games made in the 90s. It was no problem.

So I think the distinction between analogue and digital is not as important as
the distinction between simple formats (mono/stereo records, linear PCM) and
complex formats (FM-PM-SSBFM, MP3).

