Tech > ZX-SPECTRUM SCREEN LOADER 2

Is it possible to use the scanline trick in sound RAM?

Would've been nice to hear the actual sonification.

StinkerB06, anastasiadunbar - i think it's possible, but I have not realized it yet =)

4-bit PCM (Pulse Code Modulation) trick:

1. Use waveform FFFFFFFFFFFFFFFFFFFFFFFFFFFFFFFF with plain instrument.
2. Call the DC Offset instrument using SFX API command.
3. Use POKE4 API command to poke the high nibble of the second register of a channel. This is the volume register.

For the ZX Spectrum screen loader program we see here, the scanline trick should also manipulate the sound volume of the inaudible waveform, alternating between 0 volume and 15 volume.

It's literally voltage change to your speakers, and with the scanline trick, you could have a rate up to 8160Hz. The program would be 4080Hz, as it takes two scanlines to update the border color.

Also, 4-bit means there is a 4-bit integer of the sample's amplitude levels, making 16 amplitudes possible.

Learn more at Wikipedia: https://en.wikipedia.org/wiki/Pulse-code_modulation

Also, one thing I forgot:
There might be a way to read a table from the cartridge memory or the RAM, called by the scanline effect. We can get something like a realistic voice or explosion coming out of my TIC-80 then!

I'm sorry to answer so late.
Thank you for such detailed information, but I probably will not be able to implement it.