gemini://zaibatsu.circumlunar.space/~solderpunk/gemlog/digital-audio-on-tape.gmi

I'm still on a little bit of a dead media kick, so here's a follow up to my earlier post on helical scan videotapes. I promise this will be the last tape related post for a while. Not because I don't find this stuff fascinating, but because if I delve any deeper there will be a very real risk of me actually buying hardware, and I need that like the proverbial hole in my head...

Compact Discs appeared on the scene in 1982, and were an undeniable success, with CD sales surpasing vinyl sales for the first time in 1986 and casette tape sales in 1992. This is unsurprising, as they offered objectively superior sound quality and increased physical durability compared to either of these analogue formats. However, from the point of view of consumers, they were effectively a read-only format. Record companies could mass-produce pre-recorded content on CD, but ordinary people couldn't. Yes, CD burners eventually became a thing, but they weren't widespread until literally decades after CDs were, and they were tethered to big, heavy, expensive personal computers. So for a very long time there was a gap in the market, with no medium offering the advantages of digital audio like the CD with the easy, cheap, portable recordability (and re-recordability) of the cassette. To my knowledge, there were three serious attempts to close this gap, one of which was Sony's MiniDisc format, which I've written about previously and am currently a fan and daily user of. This post is about the other two, both of which were tape-based. Ultimately, all three of these formats failed to achieve anything like the success of either CDs or cassettes. Easy, portable digital recording for the masses didn't really become a thing until MP3 players came along.

The earliest of these three formats was, like the MiniDisc, a product of Sony in Japan. That would be the straightforwardly-named Digital Audio Tape, or DAT, released in 1987. Like the videotape formats I wrote about recently, DAT used a helical scan method, with a rotating head which passed across the tape at an angle. This design allows a high rate of information transfer, and DAT took full advantage of this by storing 16-bit samples of uncompressed audio at rates of 32 kHz, 44.1 kHz (i.e. identical to CD audio) or even 48 kHz (superior to CD!). Obviously the technically superior of the three options, DAT never became successful as a consumer product due primarily to the high cost of the mechanically complex decks, but it was successful in professional recording studios, which could afford the gear.

The other was by Philips in the Netherlands and went by the name of Digital Compact Cassette, or DCC, released in 1992 - the same year as the MiniDisc and hence much more of a direct competitor. Philips were convinced that a successful digital successor to the cassette tape had to be backward compatible with the established analogue cassettes. Owing to this, DCC was in a lot of ways technically similar to familiar cassettes, with the result that DCC players could also play (but not record to) analogue tapes, so you could sell your tape deck and buy a DCC deck without having to re-purchase your existing music collection. One thing DCC inherited from analogue tapes is the simpler, stationary head design, which made the hardware a lot cheaper than DAT, but also meant that it was working with a considerably lower bitrate than DAT. As a consequence, DCC, like MD, used a lossy compression scheme to fit a practical length of audio (up to 2 hours, at least in theory) into a practically sized cassette. The scheme used was called Precision Adaptive Sub-band Coding, or PASC, which would later be standardised as MP1 (as in, the thing before the thing before MP3!). Wikipedia says that DCC was more successful than MD in Europe, especially in its native Netherlands, but used DCC gear and tapes are much scarcer and more expensive here on sites like eBay. This might reflect the difference in lifetime: Philips called it quits pretty early when it was clear that DCC wasn't taking off, and discontinued the format in 1996, after only four years. In contrast, Sony kept shipping MD players until 2011, for a total life of nearly two decades. Even if DCC outsold MD for the four years they were both around, MD had plenty of time to catch up in the long run.

I should note that there *were* digital audio tape formats which used simple stationary heads but still stored full-quality uncompressed audio. As an inevitable consequence, the tapes were very long and were hence stored on large reels rather than in compact cassettes, limiting then, once again, to professional studio contexts. In fact, this seems to be the oldest form of digital audio tape: one example, Sony's Digital Audio Stationary Head, or DASH, format is from 1982. I guess DAT and DCC represent two alternative strategies at miniaturising the DASH design - DAT by increasing hardware complexity, and DCC by increasing software complexity.

Digital audio on tape