The cd turns 25

[yoda313]

http://news.yahoo.com/s/ap/20070817/ap_on_hi_te/compact_disc_anniversary

Wow doesn't that make you feel old??

Of course its talking about the demise of the AUDIO CD in the article but it never mentions is use as a computer distribution model. Sure more and more software titles are being released in dvd format for sheer size but would you ever get a mouse or a joystick with a dvd rom instead of a cdrom? Only if they threw on a ton of "shareware" to get you to buy something else.

Now CD-R'S will be around for ever in the computer world. The convenience is too much to disapear.

[Wile_E]

I have questions for Pieter Kramer, lead engineer of the CD. Why did they design it with such a big center hub? What a waste of space. Why no data section for lyrics and titles embedded into the disc data? Couldn't they have used the CD-G section for this info? Why 44.1KHz instead of the studio standard of 48KHz?

I still have an old Radio Shack portable CD player made in about 1985. It came with an external battery caddy that held 4AA batts. The batteries only lasted about 2-1/2 hours of continuous playback! I was changing batteries all the time!

I also don't believe MP3's and other lossy formats will replace it. There is a part of the community that wants better audio quality and lossless formats. Most kids and adults with Ipods don't understand that MP3's/AAC are lossy formats.

[Midzuki]

Why 44.1KHz instead of the studio standard of 48KHz?

http://en.wikipedia.org/wiki/Compact_disc#Audio_format says:

The sampling rate of 44.1 kHz is inherited from a method of converting digital audio into an analog video signal for storage on video tape, which was the most affordable way to get the data from the recording studio to the CD manufacturer at the time the CD specification was being developed. A device that turns an analog audio signal into PCM audio, which in turn is changed into an analog video signal is called a PCM adaptor. This technology could store six samples (three samples per each stereo channel) in a single horizontal line. A standard NTSC video signal has 245 usable lines per field, and 59.94 fields/s, which works out at 44,056 samples/s/stereo channel. Similarly, PAL has 294 lines and 50 fields, which gives 44,100 samples/s/stereo channel. This system could either store 14-bit samples with some error correction, or 16-bit samples with almost no error correction.

There was a long debate over whether to use 14- or 16-bit samples, and 44,056 or 44,100 samples/s, when the Sony/Philips task force designed the Compact Disc; Philips had already developed a 14 bit D/A converter, but Sony insisted on 16 bit. In the end, 16 bits and 44.1 kilosamples per second prevailed. Philips found a way to produce 16-bit quality using their 14-bit DAC by using four times oversampling.

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[Cornucopia]

Not sure if Peter will be answering you, but I'll put in my 2cents:

44.1kHz--Midzuki summed it up well, but note that the PCM adapter was used to master to U-matic (3/4") videotapes (as that was one of the few inexpensive and common high-bandwidth formats available at the time) for shipment to the pressing plant. Laserdisk used a similar setup. BTW, 44,056 is also 44,100 with drop-frame pulldown, so it all works out quite nicely.

Data sections--Sections of the subcode were available for "future use". This turned out to include: CD+G lyrics/subs/pix data, CD+Midi data and/or CD+Text data. It also followed that CD-ROM data discs would develop, and later CD-Extra/Enhanced CDs (which are Audio+Data hybrids). It just didn't all happen at once. At the time, just the plain CD technology was really "pushing the envelope". Took some years for extra uses to catch up.

Center hub size--still quite needed to provide enough gripping (clamping) strength to hold disc for the torque required with CD/DVD speeds.

Scott

[redwudz]

I still have a portable CD player that isn't much bigger than a CD in diameter, but uses a lead acid battery and weights abut 4 pounds. Now with MP3 and flash drive players, it seems we've came a long ways.

And though 'we' seem to use mostly DVDs for video, there's still a lot of the world where the CD format is the only affordable option for video storage in a small package. I think it will be around a few years yet. Happy Birthday, CD.