digital sound program

[dr. kwack]

Back in the mid 90's I found an old program in BASIC for the C-64 that would enable your computer to capture sound samples via the tape drive.

 

It was crude, but was fun to play around with.

 

I believe it was an issue of Compute! or Compute's Gazette for the Commodore.

 

Would this be possible on an 800XL? If so is there a similar program listing somewhere?

[Rybags]

The Atari has audio-in via the SIO port (which the cassette drive supplies an output to).

 

The only problem is that the sound is just mixed with what POKEY/GTIA generates and there is no way to either sample or alter that sound.

 

I'm fairly sure though that there are simple electonics projects around which hook up to the paddle input of a joystick port.

 

It would be a simple case of scanning the paddles in fast POTGO mode, but the sample rate would not be so great since it takes 2 scanlines for the hardware to generate a value.

[MaPa]

It is possible on ATARI. I remember we had such a small program. You just put audio cassete in tape drive start the program and it recorder around 20-30s of music to the memory and then replayed it back via POKEY (volume only mode of course).

[dr. kwack]

MaPa,

 

Was that a public domain program or something you had typed in? Just curious...

[ijor]

There was no such a program, because as Rybags pointed out, the CPU has no access whatsoever to the audio input coming from the tape at the SIO connector.

[Rybags]

These days, such a program is not needed anyway. Even a '386 running a sound card can capture audio just fine.

 

The Atari can only play 4-bit samples, but you can save memory and use 2-bit samples which are still distinguishable.

 

There are also tricks to use multiple voices to get better than 4-bit samples.

 

Writing a player program is fairly simple, just a couple of dozen lines of Assembler.

[pseudografx]

There was no such a program, because as Rybags pointed out, the CPU has no access whatsoever to the audio input coming from the tape at the SIO connector.

1009063[/snapback]

Actually, there was one, but I'm afraid it only worked with tape recorders that had TURBO expansion built in. Unfortunately I can't remember its name, but it was probably made by some Czech programmer.

[MaPa]

Maybe TURBO expansion was needed I don't know. We just had that soft at home and I tried it a little, using some audio cassetes and replayed it back... IIRC I looked into the code of that small program and it used only 1bit sampling.. reads 0 or 1 from SIO and then replayed it back.. zero volume or full volume, nothing more. With 15,6kHz (change every line... 312x50) it's almost 2kB per second so as I said before, it played around 20+ sec of music.

[pirx]

It would be a simple case of scanning the paddles in fast POTGO mode, but the sample rate would not be so great since it takes 2 scanlines for the hardware to generate a value.

 

I did once such a device but it was sampling very low quality - with SKCTL bit 2 set the values returned by POTG0 were very inconsistent, I mean sound was hardly recognizable and close to random. With SKCTL bit 2 cleared the values were beautifully rendered, but 50/60Hz was way too low for any sound

 

It is possible though, that my audio-to-resistance converter was just poorly designed.