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40 years later, a game for the ZX Spectrum will be again broadcast over FM radio

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Re: 40 years later, a game for the ZX Spectrum will be again broadcast over FM radio

#81

Post by gorkish »

rightbyte wrote: post #72
bronikowski wrote: post #12

I sometimes mention that our radio used to broadcast games you could tape off the air to young people and they fail to grasp the futuristic glory I experienced when I explained to myself it's like one-way modem.

Honestly, I miss teletext so much. I was my primary news source until it was in practice abandoned. It was so nice. No pictures at all. Just text of different sizes and block art. And the wait time made you read in order once and not 'doomscrool'. The limited text length forced the writers to keep it short. My point being, one way coms are underrated.

If you are so inclined, ARRL transmits amateur radio news bulletins daily on a regular schedule[1] in the USA. The bulletins can be received with any shortwave radio that supports SSB (single sideband modulation) and decoded with a soundcard and appropriate software. Obviously, it's considerably different content, but if you are looking more for the experience of receiving and decoding a radio text bulletin, you can certainly have it! Many other teletext services[2] exist as well.

[1] https://www.arrl.org/digital-transmissions

[2] https://en.wikipedia.org/wiki/List_of_teletext_services

Re: 40 years later, a game for the ZX Spectrum will be again broadcast over FM radio

#82

Post by anthk »

As a silly test, I encoded the Spanish versions of the Sherlock Holmes' volumes (XZ compressed each one) to FLAC with minimodem --tx 300, and later I converted them to Opus at 64 Kbps.

Each file weighted less than 30MB, not bad at all. The raw WAV files were around 400MB each.

The files were re-read back with minimodem --rx at the same rate and dumped back to an XZ file, the sha512sum matched the originals.

Re: 40 years later, a game for the ZX Spectrum will be again broadcast over FM radio

#83

Post by anthk »

Bene592 wrote: post #66
tombert wrote: post #50

It's a bit before my time, and tape based games never really caught on in the US as far as I'm aware, but I've always been kind of fascinated by storing programs in audio. There's something bizarrely cool about the idea of taking something designed for an analog medium and using it for something sort of definitionally not analog. It was traditionally cassette tapes, but I saw a YouTube video where some companies dist…

Both the CD and the ZX Spectrum came out in 1982

If you had a CD playing device at home by 1982, it would be like having an 8K 60" TV today.

Or, as a better match, a high end VR device able to push 4k games to each eye at 120FPS.

Everyone and his grandma used tapes/cassetes until mid 90's.

Re: 40 years later, a game for the ZX Spectrum will be again broadcast over FM radio

#84

Post by anthk »

rwmj wrote: post #77
Bene592 wrote: post #76

Earlier quoted context omitted.

How well does this work with lossy compression? I would trust only lossless formats and analog with digital data encoded as audio, but I have zero hands-on experience with this

The bit rate of a speccy tape recording was only about 1500 bps, and we routinely recorded on the cheapest tapes, and tape machines that were little better. I'm sure it'll be fine. Technical details for those interested: https://sinclair.wiki.zxnet.co.uk/wiki/Spectrum_tape_interfa...

Minimodem at 300BPS with the audio encoded to OPUS at 64 KBPS makes pretty reliable dumps with a relative small space per hour (~30MB).

Re: 40 years later, a game for the ZX Spectrum will be again broadcast over FM radio

#85

Post by tombert »

anthk wrote: post #83
Bene592 wrote: post #66

Earlier quoted context omitted.

Both the CD and the ZX Spectrum came out in 1982

If you had a CD playing device at home by 1982, it would be like having an 8K 60" TV today. Or, as a better match, a high end VR device able to push 4k games to each eye at 120FPS. Everyone and his grandma used tapes/cassetes until mid 90's.

Yeah, I was about to respond with something like this. I knew that CDs came out in the early 80's, but I still more or less associate them with the 90's; it wasn't expected that you bought a CD for music until then. As a very little kid I had cassettes for my sing-along tunes, by the time 6 or 7 (1997-1998), it feels like pretty much everyone had made the jump to CDs.

Re: 40 years later, a game for the ZX Spectrum will be again broadcast over FM radio

#86

Post by ansible »

dingaling wrote: post #67
theblazehen wrote: post #23

Earlier quoted context omitted.

For those curious: https://www.youtube.com/watch?v=YhKQy580STQ

Fascinating, here's the story from the programmer: http://www.headen.com/XL1.htm I'm not sure why he felt he had to write it all in machine code though, sadly he doesn't discuss that decision. Perhaps it was due to the time-dependency of the lyrics?

Without knowing the specifics of that platform, it is likely that the BASIC interpreter was not fast enough to generate the desired effects and animations.

Re: 40 years later, a game for the ZX Spectrum will be again broadcast over FM radio

#87

Post by anthk »

chairleader wrote: post #43

Out of curiosity, are there Linux tools to go from binary files to audio and back again? i.e `cat archive.zip | faxify -wav > archive.zip.wav`

Minimodem

Encode to opus:

      cat foo.zip | minimodem --tx -r 300 -f out.flac

      opusenc --bitrate 64 out.flac out.opus
Decode from opus:

       minimodem --rx -r 300 -f out.opus > foo2.zip

Re: 40 years later, a game for the ZX Spectrum will be again broadcast over FM radio

#88

Post by RetroTechie »

sdwr wrote: post #30
Waterluvian wrote: post #9

What I'm most curious about is if this was always just a happy side-effect of cassette-based data storage, or if they put specific effort into making this work. Ie. by being resilient to noise before and after a broadcast, having error correction, etc.

I'm curious how the timing worked - what happened if you were a few seconds early to record? Was the first part of the broadcast filled with noops?

ZX Spectrum tapes use a lead-in tone which the ROM code locks onto.

Random noise (and data! from a previous block) before that is ignored.

Zooming out, the format is:

  Lead-in (~4..5s usually), followed by a short header with program name & type of data that follows.
  A short pause.
  A shorter lead-in (~2s), followed by the data/program itself.
Most software uses several of such blocks. Eg. a short BASIC loader, followed by a loading screen, followed by a # of KB's machine code.

As far as audio tape storage goes, the ZX Spectrum system was fairly reliable & user-friendly.

That's ignoring headerless blocks, speedloaders, and the many copy-protection schemes...

Re: 40 years later, a game for the ZX Spectrum will be again broadcast over FM radio

#89

Post by chairleader »

anthk wrote: post #87
chairleader wrote: post #43

Out of curiosity, are there Linux tools to go from binary files to audio and back again? i.e `cat archive.zip | faxify -wav > archive.zip.wav`

Minimodem Encode to opus: cat foo.zip | minimodem --tx -r 300 -f out.flac opusenc --bitrate 64 out.flac out.opus Decode from opus: minimodem --rx -r 300 -f out.opus > foo2.zip

fantastic, thanks!

Re: 40 years later, a game for the ZX Spectrum will be again broadcast over FM radio

#90

Post by bcrl »

SillyUsername wrote: post #53
tombert wrote: post #50

It's a bit before my time, and tape based games never really caught on in the US as far as I'm aware, but I've always been kind of fascinated by storing programs in audio. There's something bizarrely cool about the idea of taking something designed for an analog medium and using it for something sort of definitionally not analog. It was traditionally cassette tapes, but I saw a YouTube video where some companies dist…

Dialup modem did the same thing but with more efficient protocol and error control via a network stack. ADSL also took a step further and used the shielding on copper cables to attain higher (inaudible) frequencies. The tech in some form is still about this is just the granddaddy version :D

ADSL does not depend on shielding of copper. It uses Discrete Multi Tone modulation which modulates many subcarriers to be able to compensate for channel distortion as the characteristics of each phone line are rather different in the frequency domain. This same technology underlies many modern wireless protocols as well.
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