koomen (03/20/83)
Last night (Fri 3/18) the PBS news show "All Things Considered" broadcast a section on the new Compact Discs. Assuming this has sparked some interest among you, I hereby submit what information I have of the system. When in Holland last august '82 I visited the Firato, one of Europe's largest biannual consumer electronics exhibitions. One of the exciting events was the world's first public demonstration of the Compact Disc System by Philips, the primary developer of CD. With some 250 recordings already in existence at the time, the system became available to the Dutch consumer around Christmas 1982. Audio Specs: Channels: 2 Frequency range: 2 - 20,000 Hz Dynamic range: >90 dB Signal/Noise ratio: >90 dB Channel seperation: >90 dB T.H.D. < 0.005 % Disc specs: diameter: disc: 120 mm (4.7") center hole: 15 mm (0.6") thickness: 1.2 mm (0.05") program diam. 50 - 116 mm single side recording playing time: 60 min. stereo speed: 500-200 rpm 1.2 - 1.4 m/s (47 - 55 ips) scan direction: left-turning, from inside out Optics: track width: 1.6 microns (15,875 tracks/inch) AlGaAs laser wavelength: 0.78 microns focal length: 2 microns beam diam on disc: 1 micron Recording: sample freq: 44.1 KHz quantification: 16 bits linear/channel bit representation: two's complement pre-emphasis: none or 50/15 u/sec Audio bitstream: 1.41 Mbits/sec Channel bitstream: 4.32 Mbits/sec error correction: CIRC (*) (Cross Interleave Reed Solomon Code) Modulation: EFM (**) (Eight-to-Fourteen Modulation) Frame Layout: 2 * 6 audio samples: 192 bits (24 bytes) error correction: 64 bits ( 8 bytes) control/display: 8 bits ( 1 byte) before EFM: 264 bits (33 bytes) after EFM: 462 bits (33 * 14) low freq suppression: 99 bits (3 per 14 bit symbol) synchronization: 27 bits Total frame size: 588 bits frames/second: 7350 total bandwidth: 4.3 Mbits/sec disc capacity: 4800 secs = 35,280,000 frames = 20.7 Gigabits (*) CIRC enables correction of error sequences of upto 4096 bits, corresponding to ~2.5 mm (0.1") track length. Linear interpolation allows masking of error sequences of upto 12,288 bits, or ~7.7 mm (0.3") track length (**) EFM improves timing, increases information density, reduces cross-track interference and low frequency signal components (to eliminate servo system disruption) Enough to make you drool? -- Hans Koomen Arpa: Koomen.Wbst@PARC-MAXC Usenet: ...!allegra!rochester!koomen