Comment by Annatar
4 years ago
This works on the same principle as the video backup system (VBS) which we used in the 1980's and the early 1990's on our Commodore Amigas: if I remember correctly, one three hour PAL/SECAM VHS tape had a capacity of 130 MB. The entire hardware fit into a DB 25 parallel port connector and was easily made by oneself with a soldering iron and a few cheap parts.
https://www.youtube.com/watch?v=VcBY6PMH0Kg
SGI IRIX also had something conceptually similar to this "YouTubeDrive" called HFS, the hierarchical filesystem, whose storage was backed by tape rather than disk, but to the OS it was just a regular filesystem like any other: applications like ls(1), cp(1), rm(1) or any other saw no difference, but the latency was high of course.
That's how digital audio was originally recorded to tape back in the 1970s and 80s: encode the data into a broadcast video signal and record it using a VCR.
In the age of $5000 10 MB hard drives, this was the only sensible way to work with the 600+ MB of data needed to master a compact disc.
That's also where the ubiquitous 44.1 kHz sample rate comes from. It was the fastest data rate could be reliably encoded into both NTSC and PAL broadcast signals. (For NTSC: 3 samples per scan line, 245 scan lines per frame, 60 frames per second = 44100 samples per second.)
130 MB for the whole tape is not a lot. It equals to a floppy disk throughput, which is probably not a coincidence. However, basic soldering implies that the rest of the system acts like a big software-defined DAC/ADC.
Dedicated controller could pack a lot more data, as in hobo tape storage system: https://en.wikipedia.org/wiki/ArVid
Dedicated controllers were absolutely out of the question because nobody could afford them, which is why Amigas were so popular: a fully multitasking, multimedia computer for 450 DM. That's 225 EUR! Somebody that cost sensitive won't even consider a dedicated controller; back then wasn't like it's today.
This was at a time when 3.5" floppy disks were expensive (and hard to come by), and hard drives were between 40 - 60 MB, so 130 MB was quite practical. The floppy drive in the Amiga read and wrote at 11 KB / s.
And yes, this was a DAC and an ADC in software, with added Reed-Solomon error correction encoding and CRC32. The goal was to be economical. The end price was everything; it had to be as cheap as possible.
"one three hour PAL/SECAM VHS tape had a capacity of 130 MB"
This reminds me of the Danmere Backer.
"The entire hardware fit into a DB 25 parallel port connector and was easily made by oneself with a soldering iron and a few cheap parts."
This reminds me of the DIY versions of the Covox Speech Thing: https://hackaday.com/2014/09/29/the-lpt-dac/