We used to put digital sound on videotape - and the history here is wild!

I found this book https://archive.org/details/digitalaudiocomp0000unse_y6f6/ and it talks about what differs between 14 & 16 bit. Also I think the digital format of the time was the video signal, what else could you store the data on, at a reasonable price?

MrSVCD

This episode needs to be submitted somewhere for an award of excellence. This was great. Thank you!

I remember when WGBX 44 in Boston (a PBS UHF station that was part of WGBH) experimented for a while in the mid 80's with PCM Audio broadcasts over their TV channel. Viewers could use a Hi8 deck to play the digital audio stream.

Here is a diagram of how the 14 bit and 16 bit formats are laid out on the video signal. TL;DR is that 16 bit format "steals" half of the error correcting space for the extra 2 bits per sample. See the previous and next page of the manual for more detail. You'll also notice a "copy prohibiting" bit in the signal, which I thought was interesting... https://www.manualslib.com/manual/466194/Sony-Pcm-F1.html?page=26

John Hiesey

Somebody wrote software to convert captured SD video back into audio again https://youtu.be/beZCRdq2Nt4 There's a github repo of it. In the 80s, the BBC provided 'telesoftware' for their computers over the teletext lines of a TV signal, and even now there are loads of home recordings out there (especially any made off air to SVHS tapes) that hold a time capsule of teletext data from when they were recorded.

John Terry

Here is a recording of what it looked like (warning, flickering/flashing images): https://www.youtube.com/watch?v=VfUgT2YoPzI

Nick Loh

The video output on the TV reminds me of a video I once saw that showed how TiVo DVRs got their program guide data if they weren't hooked up to a phone line. The company bought infomercial slots on certain stations and transmitted data over the video signal. The DVR knew to tune to that channel at the given time and decode the data, and what you would see looked kind of like what the TV in your video is showing (except for a scrolling "there is nothing wrong with your TV" marquee in the center of the screen - they also had a voiceover to that effect, interspersed with some muzak). I never saw this with our family's TiVo because we did have a phone line going to it, but I imagine me from that time would have been equal parts fascinated and terrified by it if I did. It makes sense that it looks similar to your device's output, since they're kind of doing the same thing (just with program data instead of digital audio)...

Nick Loh

I do appreciate the irony of the flashing 12:00

Jon Adams

Very very interesting

Donald J Arndt

I can't post this on YouTube because it gets filtered out. But during the "event" I've created a program which can in real time play out WAV files into this encoded image over the composite output of a Raspberry Pi Zero (PiCM). I was bored. There's a demo video on my YouTube channel of it in action, decoded back via a software decoder (unfortunately I don't have any original hardware to test with). It's not totally faithful as the Raspi can't draw outside the visible region and the PCM format spans a bit over that, but the error correction able to fill-in the missing lines, so it still works. Also, there's a video called "[PCM Video Course] Digital Audio on Video Tape - Part 1: EIAJ STC-007 PCM Structure" on YouTube which explains the structure of the video signal very nicely. The 14bit format does have a bit more error correction, the 16bit format is kind of a retro fit and sacrifices some of the error correction bits for the extra resolution.

István Nagy

Aw man, the closing mention that "digital audio data is still data" reminded me of a funny thing that happened at the local university, a couple of years ago. Basically whenever old offices & storage-rooms get cleaned out, students get to see pieces of obsolete hardware (like hard-drives from the '70s, the size of a washing machine, and the cost of a car at that time - no-one dares to throw them away because half a century ago those were really expensive). One such device was an eastern-european clone of the ZX-Spectrum computer, from the '80s (from when our professors were starting their careers). ZX-Spectrum, being intended for home/hobby use, didn't have a hard-drive (too expensive), but loaded data from an audio-jack (the user was expected to already have a casette deck & tapes laying around, and reuse those). While the students were looking around to see who had access to a cassette-deck, an older professors saw them, and was like "wait, no, let me show you how it's done!". The prof then took his iPhone, an audio patch-cable, downloaded some WAV files to the smartphone, and played those audio-files back using the headphone-port & the patch-cable into '80s computer. It was really fun to see the prof grinning while transferring files from a brand-new smartphone into an "ancient" computer. Digital data-> Audio Signal -> Digital data... because "data is still data", even when presented in the form of an audio signal.

As for storing computer data on video tape: Many years ago (1979-1988) I worked at Corvus Systems, which was the first company to make hard drive systems for the Apple II, and later, many other microcomputers. It was a 10MB, 8-inch drive and cost $5350.00. In November '79 they introduced the Mirror, which could back up your hard drive to VHS tape. Capacity was 100MB but I don't remember at what tape size/speed. If you had the very expensive Panasonic NV-8208 VCR you could connect the Mirror to the VCR's remote inteface and control it with the backup software. I still have a binder full of Corvus brochures, company newsletters, articles, etc. And here's a video about the company from 1982: https://www.youtube.com/watch?v=arkgOkjDagk.

Mark Johansson