Skeptoid: Digital vs Vinyl, Podcast casts its skeptical eye on digital audio Options

[rick.hughes]

Skeptoid: Digital vs Vinyl

[pdq]

@splice: That's an awful lot of conjecture, and frankly I see almost nothing that I would agree with.

[splice]

@splice: That's an awful lot of conjecture, and frankly I see almost nothing that I would agree with.

We were indeed making great strides in vinyl technology in the 80s, and the Soundstream system was real. The remaining candidates for conjecture are my musings on sample depth and rate, and the possible physical carrier form. I look forward to hearing your reasons for disagreement. You can PM me if you prefer, and if it has legs we can open a thread for it.

[pdq]

@splice: That's an awful lot of conjecture, and frankly I see almost nothing that I would agree with.

We were indeed making great strides in vinyl technology in the 80s, and the Soundstream system was real.

I don't have any details on the Soundstream system of recording audio data optically on a card, but let's muse on that a little.

A CD has a data track that is over 5,000 meters long by 1.6 micrometers wide. It is scanned at a rate of about 1.2 meters per second. The disc is about 1 mm thick so that a lens that is almost in contact with it can have a very short focal length and very small f/ number. Without that it would not have enough resolution at the wavelength available in early 1980's diode lasers to resolve 1.6 micron details.

Now what would be the equivalent in a "card"? To have the same storage area as a CD it would need to be about 8x10 cm. To be able to read the data with the same inexpensive diode laser you would still need to have the lens almost in contact with the card, but now you are scanning the data rectilinearly, i.e. scan one axis very rapidly while tracking the other axis within 1.6 microns. To achieve 1.2 meters per second scanning you would need to scan the long axis 12 times per second back and forth. Does any of this actually sound like a viable alternative to CD?

If someone has real information on how the Soundstream system worked I would love to hear it. Perhaps they had some approach that I have not thought of that made it all practical, but after all, their product was never introduced and shortly after they went out of business.

Edit: I searched for Soundstream's patents, and none that I found related to optical storage of audio data. Apparently they didn't value the idea very highly.


This post has been edited by pdq: Apr 10 2012, 16:43