The CD is 40 years old and he's dead (is it?)
Philips Player Prototype, Elektuur Magazine No. 188, June 1979, Public domain mark 1.0
The CD is 40 years old, and for those of us who remember how it started, it remains the mysterious achievement of high technology even now when this media had to make room for the onslaught of streaming services.
If you set out to identify the moment when digital storage of data began to supplant analog in consumer electronics, the appearance of a CD can be considered as such. In the mid-seventies, the most coveted electronic gadgets were an analog video recorder and a CB radio station, but with the release of the first home computers and laser players, dreams of striving to be “on the crest of a wave” suddenly changed. The CD-player also turned out to be the first (in fact, the second after the LD-player) consumer electronic device containing a small but real laser, which then seemed something fantastic, but simply unrealistic. Today, new technologies, entering the market, do not produce such an effect: they are considered as something appearing and disappearing "in its own way."
Where did he come from?
The “legs” of the format grow from the latest video recording methods of the time, which the developers also sought to adapt for high-quality sound recording. Sony tried to adapt a VCR for digital sound recording, while Philips tried to record analogue sound on optical discs similar to those that were already used to store video. Then the engineers of both corporations came to the conclusion that it is better to record on an optical disc, but in digital form. Today this “but” seems to be taken for granted, but then they did not immediately come to it. After developing two incompatible, but very similar formats, Sony and Philips began to cooperate, and by 1979 they presented prototypes of a player and a 120-mm disc that can hold more than an hour of 16-bit stereo audio with a sampling frequency of 44.1 kHz. In popular science literature and periodicals, incredible futurism was attributed to new technology, exaggerating its capabilities. In television programs, they promised that these discs would be “indestructible” compared to vinyl records, which further fueled interest in them. The top-loading Philips player, sparkling with a silver case, looked amazing, but the first models of these devices hit the store shelves only in 1982.
How does he work?
Although it seemed to users that the principle of operation of the CD-player is overly complicated and incomprehensible, in fact everything is surprisingly simple and understandable there. Especially compared to analog VCRs, next to which were many of these players. By the end of the eighties, on the example of a PCD device, even a wide variety of topics were explained to future electronic engineers. Then many already knew what kind of format it was, but not everyone could afford to buy such a player.
The read head of the CD drive contains surprisingly few moving parts. The module, which includes both the source and the radiation receiver, is moved by a small electric motor through the worm gear. The IR laser shines in a prism reflecting the beam at an angle of 90 °. The lens focuses it, and then, reflected from the disk, through the same lens it falls back into the prism, but this time does not change its direction and reaches an array of four photodiodes. The focusing mechanism consists of a magnet and windings. With proper tracking and focusing, the highest radiation intensity is achieved in the center of the array, tracking violation causes a spot shift, and focus violation - its expansion. Automation adjusts the position of the read head, focus and speed so that an analog signal is output,
Reading head device with explanations, CC BY-SA 3.0 The
bits are combined into frames to which EFM (eight-to-fourteen modulation) modulation is used even when writing , avoiding single zeros and ones, for example, the sequence 000100010010000100100 turns into 111000011100000111. After skipping frames through the search table, a stream of 16-bit data is obtained, passing the Reed-Solomon correction and arriving at the DAC. Although different manufacturers over the years of the format's existence introduced various improvements to this system, the main part of the device remained a very simple optical-electronic unit.
What happened to him afterwards?
In the nineties, the format from a fantastic and prestigious one turned into a mass one. Players have become much cheaper, portable models have entered the market. Disc players began to crowd out cassette pockets. The same thing happened with the CD-ROM, and in the second half of the nineties it was difficult to imagine a new PC without a CD-drive and a multimedia encyclopedia in the kit. The Vist 1000HM is no exception - a stylish computer with speakers integrated in the monitor, a VHF receiver and a compact IR keyboard with a built-in joystick that resembles a huge remote from the music center. In general, he shouted with all his appearance that his place was not in the office, but in the living room, and he claims to be the place occupied by the music center. The disc of the Nautilus Pompilius band with compositions in four-bit monophonic WAV files was attached to it, which took up little space. There was also a more specialized technique, using CDs, for example, Philips CD-i and Commodore Amiga CDTV, as well as Video CD players, a Sega Mega CD device for Mega Drive / Genesis consoles, 3DO and Play Station consoles (the very first) ...
Commodore Amiga CDTV, CC BY-SA 3.0
Computer Vist Black Jack II, apparently not different from Vist 1000HM, itWeek, (163) 39`1998
And while after the rich the others mastered all this, there was a new topic on the agenda: the ability to record CDs at home. It smelled of fantasy again. Few happy owners of recording drives tried to recoup them by sticking ads: "I will backup your hard disk to CD, inexpensively." This coincided with the advent of compressed MP3 audio format, the first MPMan and Diamond Rio players were released. But they used then still expensive flash memory, but the Lenoxx MP-786 compact disk became a real hit - and he read perfectly both self-written and ready-made disks with MP3 files. Napster and similar resources soon fell victim to record companies, which, however, were simultaneously eyeing the new format. One of the first licensed MP3 discs was released by the Crematorium group, and most often they listened to him on this player. And the translator even once had a chance to get inside one of these players and eliminate the defect causing the disk to touch the cover. Apple’s release of the first iPods to buy albums through a convenient interface on a computer screen prompted music publishers to finally move from combating compressed audio formats to commercialization. Then the smartphone almost completely discontinued individual MP3 players even faster than they had previously squeezed the CD. Lasers in modern consumer electronics are either absent or stand idle most of the time, but vinyl and cassettes are now being reborn. Is the CD dead? Probably not, because the production of both drives and media has not been completely discontinued. And it is possible