Digital Compact Cassette (DCC) is a discontinued magnetic tape sound recording format introduced by Philips and Matsushita Electric in late 1992 and marketed as the successor to the standard analog Compact Cassette. It was also a direct competitor to Sony's MiniDisc (MD), but neither format toppled the then-ubiquitous analog cassette despite their technical superiority, and DCC was discontinued after four years in the marketplace. Another competing format, Digital Audio Tape (DAT), had by 1992 also failed to sell in large quantities to consumers, although it was popular as a professional digital audio storage format.
The DCC form factor is similar to the analog compact cassette (CC), and DCC recorders and players can play back either type: analog as well as DCC. This backward compatibility was intended to allow users to adopt digital recording without rendering their existing tape collections obsolete, but because DCC recorders couldn't record (only play back) analog cassettes, it effectively forced consumers to either replace their cassette deck with a DCC recorder and give up analog recording, or keep the existing cassette deck and make space to add the DCC recorder to their setup.
History
DCC signaled the parting of ways of Philips and Sony, which had previously worked together successfully on the audio CD, CD-ROM, and CD-i. The companies had also worked together on the Digital Audio Tape which was successful in professional environments, but was perceived as too expensive and fragile for consumers. Furthermore, the recording industry had been fighting against digital recording in court, resulting in the Audio Home Recording Act and SCMS.
Philips had developed the Compact Cassette in 1963 and allowed companies to use the format royalty-free, which made it hugely successful but not a significant money-maker. The company saw a market for a digital version of the cassette, and expected that the product would be popular if it could be made compatible with the analog cassette.
Around 1988, Philips participated in the Eureka 147 project that eventually produced the DAB standard. For this, it cooperated with the Institute for Perception Research of the Eindhoven University of Technology to create the PASC compression algorithm based on psychoacoustics.
On 8 October 1990, Philips made the first formal announcement of DCC. Tandy Corporation announced at the same time that it would distribute the recorders and tapes through its Tandy and RadioShack stores. It was expected at the time that DCC recorders would be available in the beginning of 1992 and would cost several hundred dollars less than DAT recorders. Even though this first announcement already used the term "digital compact cassette" (without capitalization), some publications around this time also referred to it as S-DAT (Stationary-Head Digital Audio Tape), to distinguish it from R-DAT (Rotary-Head Digital Audio Tape).
On 5 July 1991, Philips announced that it had joined forces with Matsushita to develop DCC.
The first DCC recorders were introduced at the CES in Chicago in May 1992 and at the Firato consumer electronics show in Amsterdam in September 1992. At that time, not only Philips and Technics (a brand of Matsushita) announced DCC recorders but also other brands such as Grundig and Marantz, which were both related to Philips at the time. Around the same time, Sony introduced the MiniDisc.
More recorders and players were introduced by Philips and other manufacturers in the following years, including some portable players and recorders as well as in-dash DCC/radio combinations for use in vehicles.
At the "HCC-dagen" computer fair in Utrecht, Netherlands, between 24 and 26 November 1995, Philips presented the DCC-175 portable recorder that can be connected to an IBM-compatible PC using the "PC-link" cable. This was the only DCC recorder that can be connected to, and controlled by a computer, and it was only ever available in the Netherlands.
Philips marketed the DCC format mostly in Europe, the United States and Japan. According to the newspaper article that announced the demise of DCC, DCC was more popular than MiniDisc in Europe, especially in the Netherlands.
DCC was quietly discontinued in October 1996 after Philips admitted it had failed at achieving any significant market penetration with the format, and unofficially conceded victory to Sony. However, the MiniDisc format had not done very well either; the price of both systems had been too high for the younger market, while audiophiles rejected MD and DCC because they felt the lossy compression degraded the audio quality too much.
Technology
Magneto-resistive stationary heads
Unlike helical scan systems such as DAT or VHS, the head is stationary and the tape moves in linear direction relative to the head. Like analog audio tapes, the heads use half of the tape width in each direction. There are nine tracks per side: eight tracks for the audio, and one track for auxiliary information. The track pitch is 195 μm. The head assembly has what Philips called "Fixed Azimuth Tape Guidance" (FATG) pins, which work together with the "Azimuth Locking Pins System" (ALPS) in the cassette to guide the tape.
DCC used magneto-resistive (MR) heads 70 μm wide for playback, and miniaturized coils 185 μm wide for recording. The heads were produced using photolithography. Some DCC head assemblies had separate MR heads to play analog tapes, others re-used two DCC heads to pick up the left and right analog audio tracks from the tape.
All DCC players and recorders are auto-reverse, so every player and recorder must have a way to position the heads for the A-side as well as the B-side of the tape. In stationary recorders, the mechanism switched sides by pivoting the head assembly 180 degrees (Philips used a modified version of an analog auto-reverse cassette deck during development, on which this mechanism was based),Philips Early DCC Deck Prototype, Dutch Audio Classics. but in portable recorders and players, the head assemblies had heads for the tracks on both sides, which saved space in the mechanism, but made the head assembly more complicated:
Pivoting head mechanisms in stationary recorders such as the DCC-900 used a head assembly that had nine (MR) playback heads and nine (coil) recording heads for DCC, plus two (MR) heads for playing analog compact cassettes. The head assembly was mounted on a pivoting mechanism that rotated the head assembly by 180 degrees when it switched from one side of the tape to the other. Playback-only portable players such as the DCC-130 and DCC-134 used head assemblies with 18 MR heads, nine for each side of the tape. When playing analog cassettes, two of the DCC MR heads were used to pick up the analog audio. Portable recorders such as the DCC-170 and DCC-175 used head assemblies with 18 MR heads for DCC playback, 18 coil heads for DCC recording, and 4 MR heads for analog playback (a total of 40 heads in one head assembly).
Magneto-resistive heads do not use iron so they do not build up residual magnetism. They never need to be demagnetized, and if a magnetic field from e.g. a cassette demagnetizer is applied to MR heads, it induces so much current into the heads that they are damaged or destroyed. Also, it is recommended never to use a cleaning cassette as DCC heads are fragile and this operation could ruin them permanently.
Tape specifications and PASC audio compression
DCC tape is the same width as in analog compact cassettes, and operates at the same speed: per second. The tape that was used in production cassettes was chromium dioxide- or cobalt-doped ferric oxide, 3–4 μm thick in a total tape thickness of 12 μm,Philips DCC page preserved as part of the DCC FAQ page identical to the tape that was widely in use for video tapes.
Nine heads are used to read/write half the width of the tape; the other half of the width are used for the B-side. Eight of these tracks contain audio data, the ninth track is used for auxiliary information such as song titles and track markers, as well as markers to make the player switch from side A to side B (with or without winding towards the end of the tape first) and end-of-tape markers.
The (theoretical) maximum capacity of a DCC tape is 120 minutes, compared to 3 hours for DAT; however, no 120-minute tapes were ever produced. Also, because of the time needed for the mechanism to switch direction, there is always a short interruption in the audio between the two sides of the tape. DCC recorders could record from digital sources that used the S/PDIF standard, at sample rates of 32 kHz, 44.1 kHz or 48 kHz, or they could record from analog sources at 44.1 kHz.
Because of the low tape speed, the achievable bit rate of DCC is limited. To compensate, DCC uses Precision Adaptive Sub-band Coding (PASC) for audio data compression. PASC was later integrated into the ISO/IEC 11172-3 standard as MPEG-1 Audio Layer I (MP1). Though MP1 allows various bit rates, PASC is fixed at 384 kilobits per second. The bandwidth of a CD recording of approximately 1.4 megabits per second is reduced to 384 kilobits per second, a compression ratio of around 3.68:1. The difference in quality between PASC and the 5:1 compression used by early versions of ATRAC in the original MiniDisc is largely a subjective matter.
After adding system information (such as emphasis settings, SCMS information, and time code) as well as adding Reed-Solomon error correction bits to the 384 kbit/s data stream, followed by 8b/10b encoding,Method of transmitting information, encoding device for use in the method, and decoding device for use in the method, June 1986. the resulting bit rate on the eight main data tracks tape ends up being twice the rate of the original PASC data: 768 kbit/s, which is recorded onto the eight main data tracks at 96 kbit/s per track in an interleaved pattern.Digital Compact Cassette (DCC) - Matsushita and Philips Develop New Standard. Retrieved 2017-01-16. According to the Philips webpage, it is possible for a DCC player to recover all missing data from a tape, even if one of the 8 audio tracks is completely unreadable, or if all tracks are unreadable for 1.45 mm (about 0.03 seconds).
Auxiliary track
On prerecorded tapes, the information about album artist, album title, and track titles and lengths is recorded on the auxiliary ninth track continuously for the length of the entire tape. This made it possible for players to recognize immediately what the tape position is and how to get to any of the other tracks (including which side of the tape to turn to), as soon as a tape was inserted and playback was started, regardless of whether the tape was rewound before inserting or not.
On user tapes, a track marker was recorded at the beginning of every track, so that it was possible to skip and repeat tracks automatically. The markers were automatically recorded when a silence was detected during an analog recording, or when a track marker was received in the S/PDIF signal of a digital input source (this track marker is automatically generated by CD players). It was possible to remove these markers (to "merge tracks"), or add extra markers (to "split tracks") without rerecording the audio. Furthermore, it was possible to add markers afterwards that would signal the end of the tape or the end of the tape side, so that during playback, the player would stop the mechanism, fast-forward to the end of the A-side, or switch from the A-side to the B-side immediately.
On later generations of recorders, it was possible to enter title information for each track, which was recorded on the auxiliary track after the start-of-track marker. Because the title information was only stored in one place (unlike prerecorded tapes where users could see the names of all tracks on a tape) it was not possible to see tracks names of any other track than the one that is currently playing.