Digital compact cassette

The digital compact cassette, or Digital Compact Cassette in English (DCC), was a magnetic audio tape format, cassette compact, chromium oxide-based, used as a medium for digital magnetic recording and sound reproduction introduced by the companies Philips and Matsushita at the end of 1992 and marketed as the successor to the conventional analog cassette. It was also a competitor to Sony's MiniDisc format. Another competing format, digital audio tape (DAT), had failed in 1992 to sell in large quantities. DCC shared a similar form factor to analog cassettes, and DCC equipment could play any type of cassette. This compatibility allowed users to adopt digital recording without needing to build up their existing obsolete tape collections.

History

Philips' objective when launching the DCC was to replace the analog cassette (CC), which this same company had launched on the market in 1963. Philips had already launched, shortly before (1986), together with Sony, the so-called Digital Audio Tape (DAT). However, as more than 80 companies continued to develop the DAT format, of which a split had been created between R-DAT (rotating head) and S-DAT (stationary head), Philips decided to launch a new cassette format on its own. digital audio for home environments.

Philips did not achieve its objective and the DCC was a short-lived format. Its drawbacks outweighed its advantages and the format was a failure, being withdrawn from the market in 1996, that is, 5 years after its launch. Philips made the announcement public on October 31, 1996, when it also announced its intention to manufacture discs in Minidisc format, paying the corresponding royalties to Sony Corporation, developer of the format.

Philips reassured DCC users by establishing a 10-year term, ending in 2006, in which it would maintain tape production and technical support for the equipment that had been acquired.

DCC format

The DCC format cassette shares physical characteristics of the conventional audio cassette:

• Cartridge size: 100 x 65 x 12 mm
• Ribbon length: 60,35m (60 minutes).
• Width of the tape: 3,81 mm

DCCs were recorded with a sample rate of 44.1 kHz and a resolution of 16 bits, although sample rates of 32 and 48 kHz were also supported. Based on Nyquist's theorem, if the lowest sampling frequency (32 kHz) was used, the frequency response dropped to 16,000 Hz (16x2=32). The data transmission speed of the DCC was 1.54 Mbps, higher than that of the CD which is 1.4 Mbps.

The DCC, like the S-DAT format, is a multitrack recording system with a stationary head since the only thing that moves is the tape. In video tapes and R-DATs, the heads rotate on a drum and the tape also moves. The tape travel speed is 4.75 cm/s like the analog Compact Cassettes and the two DAT formats.

As DCC is a multitrack format, since it allows 16 audio tracks (8 per side), it has several playback and recording heads that can be synchronized. The tracks are recorded helically and it is the width of the tracks (185 nanometers) that determines the distance between the heads. S-DAT tape tracks are wider. Consequently, the information storage capacity of a DCC is much smaller than that of a DAT. The width of the track passage is 10 nanometers. In addition to the 16 tracks indicated, the DCC on each side introduces an auxiliary track in which an inaudible control signal is recorded that allows, among other things:

• Indicate the start of the tape.
• Facilitate the location of contents by introducing brands.
• Point out the end of the recording and the end of the tape itself, allowing you to know the recording time available.

The DCC uses the PASC (Precision Adaptive Sub-band Coding) data compression algorithm developed by Philips which divides each of the 16 audio tracks into two sub-bands, analyzing a total of 32 sub-bands. PASC like Sony's ATRAC also eliminates sounds that cannot be perceived by humans. However, the PASC offers better "quality" than ATRAC, since it performs a 4:1 compression similar to MPEG-audio level 1, while the MiniDisc's ATRAC compression was 5:1, making the quality poorer.

Although PASC is a lossy encoding system, DCC systems could allow unlimited multigeneration, since when the contents of one DCC tape are copied to another, the PASC signal is decrypted by the PCM codec, another algorithm lossless compression. Theoretically, DCC allows unlimited multi-generation, but in practice this was not allowed as manufacturers introduced an anti-piracy system (copy management system) called SCMS (Serial Copy Management System).. This system attempted to avoid unlimited digital copying of CDs and other pre-recorded commercial media (DAT, MD or any analog source). Among other things, the SCMC reads the original source codes and prevents DCC teams from making more than one copy of an original prerecorded source.

Advantages of the format

1. Compatible with the compact case. All DCC equipment allows to reproduce, although not to record, the contents of analog case tapes.
2. Higher quality than the MiniDisc when offering lower compression. However, its quality is lower than that of the CD-Audio, which uses the PCM system which is a lossless compression system.

Disadvantages

1. High cost of manufacturing and marketing. In December 1992, DCC teams cost on average approximately 600 current Euros and each tape (which could only be recorded) around 15 current Euros. In recent times, DCC teams were more affordable. Mechanical components were simplified, including the Turbodrive fast track search system, which would improve DCC performance. The price had been reduced to 240 euros today, but it was already late to stimulate sales profitably.
2. Only 1st generation digital copy (in 44.1 kHz) was allowed once to avoid illegal copies. Unspoilt tapes allowed multiple records, but the overlap of digital information (especially in recordings made between different players), could cause collapse in the data track, a fact that produced reading errors of meter and cutting tracks. The consumer was not profitable as they were very expensive.
3. Increased acceptance of the DAT format at the professional level, the Minidisc (basically in Japan and the United States) and the CDR at the domestic level (although it was quickly supplanted by the recording on PCs), which prevented the DCC from obtaining a level of sales that would allow the recording producers to be held and attractive.
4. Sequential access of musical tracks in front of random access that allow CD-Audio, DVD-Audio and Minidisc. Although DCC systems had automated programming for editing, it was very simple and manual, and errors could occur during the recording process. The latest models allowed the insertion of titles, but it was only reproducible in these models, the oldest only reproduced titles of study.
5. It wears off the support in front of optical digital formats, except the magnetic head of the Minidisc registry. The DCC, although protected, had the same maintenance problems as conventional tapes, as magnetic fields, thermal foci and humidity could damage them. DAT tapes have the same problem, although quality and manufacturing design makes them more protected.
6. DCC recorders could only play analog cassettes. This made the DCC impractical by removing the user's freedom to choose in which format to record, analogue or digital, and precipitated the decay of it. Although it is a misleading commercial criterion that also followed the Philips partners (Marantz, Grundig and Panasonic), it also lengthened the useful life of the head of the players, whose wear gave evidence of precise maintenance if its use was as an analog tape player.
7. The static and self-reverse head produced filth recording errors and misadjustments in the quality of the components. The recording requires greater contact accuracy and calibrated with the magnetic tape, and if it is dirty or unchecked, the result is negative, with data loss cuts. Digital reading was not so problematic, even in different players. The dual (analogue and digital) use of tapes led to greater wear of the head caused by the poor quality of iron oxide tapes and metal particle tapes (unseen in most first-generation DCC heads), so only chromium dioxide tapes could be reproduced without these damaging the heads. In the latest players manufactured by Philips (series 951 and 730), the compatibility and mechanical problems in the head and SMD components would be considerably improved, while analogue reproduction was of better sound quality. The head will be subject to an approximate duration of about 1000 hours as your DAT counterpart.
8. The duration of the head and the surface assembly capacitors of the equipment plates was the main problem of obsolescence of these breeders-grabbers, whose spare parts were already scarce at the time and currently nonexistent. Such capacitors tend to swell and release their acid content that corrodes and crosses the tracks, leaving the plates unused. The damaged head is irreparable and has caused, after two decades of existence in the domestic market, great movements of resale of defective items for this reason, which only favors those who need less obsolete spare parts.

Comparison of digital cassette formats