I remember data storage on regular cassette tapes was painfully slow.
Audio tape interface revives microcassettes as storage medium
11–20 of 37 posts
Re: Audio tape interface revives microcassettes as storage medium
#12I wonder what the maximum bitrate of an audio cassette is, using modern encoding techniques like OFDM with error correction? I searched once, and saw estimates in the 25 kbps range, but no usable implementation.
The sound quality of an audio cassette is at least as good, and almost certainly better, than the quality of an analogue telephone line. So I bet you could set a lower bound of at least 33.6kbit/s, since that was as fast as telephone modems went. 56k modems relied on your phone line being digital after the switchboard, but I would imagine that 56k should be doable as well.
Not sure it's directly comparable. When modem flips one bit, the CRC checksum in IP packet becomes incorrect, someone drops the IP packet, the condition is detected and the packet is re-transmitted. This slows down things substantially but user still gets their data. I think tapes need more reliability because there's only 1 try.
Re: Audio tape interface revives microcassettes as storage medium
#13I wonder what the maximum bitrate of an audio cassette is, using modern encoding techniques like OFDM with error correction? I searched once, and saw estimates in the 25 kbps range, but no usable implementation.
I was able to fit about 60 MB per channel on a 90 min audio cassette [1]. The bias frequency of that particular deck was about 60 kHz. This means bypassing the recording circuitry could lead to much higher data rates.
Re: Audio tape interface revives microcassettes as storage medium
#14I did something similar in the early nineties by using the venerable AM7910, an old modem chip often used in vintage computer and Ham Radio gear, to make an interface to store and retrieve data on tape from my Amiga 500.
I used a normal cassette deck for storing, but the chip was really slow at 1200 bps, even for an old system like AmigaOS, and per data sheet it didn't offer higher speeds, however I tried anyway to change its clock frequency by testing a few Xtals in place of its 2.4576 MHz standard one, and eventually settled to an old PAL color TV Xtal (4.433619 MHz) that would nearly double the speed without introducing errors. Good old times...
Re: Audio tape interface revives microcassettes as storage medium
#15I remember data storage on regular cassette tapes was painfully slow.
I used audio cassette for a few years (1978-1979) on my home-built Z-80 system.
Upgraded to a wacky cassette transport called a Phi-Deck. It was faster and had automated head control and seek; you could do a real file system on it. 9600 baud equivalent, for the setup I used; could get 100K or so on a cassette if you were patient.
Re: Audio tape interface revives microcassettes as storage medium
#16Earlier quoted context omitted.
The sound quality of an audio cassette is at least as good, and almost certainly better, than the quality of an analogue telephone line. So I bet you could set a lower bound of at least 33.6kbit/s, since that was as fast as telephone modems went. 56k modems relied on your phone line being digital after the switchboard, but I would imagine that 56k should be doable as well.
Not sure it's directly comparable. When modem flips one bit, the CRC checksum in IP packet becomes incorrect, someone drops the IP packet, the condition is detected and the packet is re-transmitted. This slows down things substantially but user still gets their data. I think tapes need more reliability because there's only 1 try.
I remember back in the 80s when my BBC Micro would miss a bit it would just beep and tell you to "Rewind tape", which meant, go back about 10 seconds. And then it would figure it out from there.
Re: Audio tape interface revives microcassettes as storage medium
#17>common disturbances like speed variations (which cause wow and flutter)
Had to look that up. What they call "slow wow" that is common in turntable records makes sense though as onomatopoeia.
Re: Audio tape interface revives microcassettes as storage medium
#18I remember 6/7-year-old me begging my father for a tape deck to use with CoCo3. He refused, saying they were too expensive. Were they really in the early 90s? I doubt it. I lost interest in writing basic on that thing since I couldn't save programs. Anyway, I fully intend to try this out if only to close that loop.
No one here can tell you whether your father was right or wrong. A tape deck and connection cable would have cost $35-$60 in the early 90s, which your father might have seen as closer to:
A) A week's groceries for the whole family, or
B) A single evening's entertainment for one person.
Re: Audio tape interface revives microcassettes as storage medium
#19Earlier quoted context omitted.
The sound quality of an audio cassette is at least as good, and almost certainly better, than the quality of an analogue telephone line. So I bet you could set a lower bound of at least 33.6kbit/s, since that was as fast as telephone modems went. 56k modems relied on your phone line being digital after the switchboard, but I would imagine that 56k should be doable as well.
Not sure it's directly comparable. When modem flips one bit, the CRC checksum in IP packet becomes incorrect, someone drops the IP packet, the condition is detected and the packet is re-transmitted. This slows down things substantially but user still gets their data. I think tapes need more reliability because there's only 1 try.
The Commodore 64 (and possibly earlier Commodore systems such as the PET and VIC20) actually recorded each "block" twice on the tape, and could correct up to 31 errors per block as long as an error didn't affect the same exact byte in each block (it didn't do anything like ECC).
This also made loading/saving from tape really slow - 50bps.
Re: Audio tape interface revives microcassettes as storage medium
#20I wonder what the maximum bitrate of an audio cassette is, using modern encoding techniques like OFDM with error correction? I searched once, and saw estimates in the 25 kbps range, but no usable implementation.
They were getting 33.6kbps out of a fully analog phone line with 300Hz-4Khz usable frequency range. Depends on the equipment and tape, but I imagine even cheapish equipment would have at least twice that amount of bandwidth to work with, maybe even up to 10-12kHz instead of a 4kHz top end.
High end equipment and high end tape shows up to ~20kHz or so: https://audiochrome.blogspot.com/2019/12/cassette-tape-compa...