General Category > Emulators

Sound emulation survey

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cpcitor:
Hi! This is a survey to gather some information about behaviors of emulators with regard to sound.

Can you run the BASIC commands below on real CPCs and emulators and tell what you hear?
It's even better if you can post captures of the output.

The first is only to sanity check your setup and make sure you hear a 440Hz basic tone.
The second is the one I'm interested in.


--- Code: ---sound 2,284,50,15 : sound 2,6,50,15
--- End code ---

Here are my samples:

* cpcec or cpcec-plus (Linux): 1 second 440Hz tone, then one second of a different, higher pitch, tone. Attached sound_2_284_50_15_sound_2_6_50_15_cpcec.wav.bin
* caprice32 (Linux): 1 second 440Hz tone, then one second of a different, higher pitch, tone. But different!
* floooh's chips test of the tiny8bits emulator libraries:  1 second 440Hz tone, then one second of a different, higher pitch, tone. But different again! (You can try it live on https://floooh.github.io/tiny8bit/cpc.html?type=cpc464 )
* real CPC... I let you try this one.

You might be wondering why I'm asking this.

If you think you can guess why I'm asking this, your guess is welcome.

Captures from emulators and real CPCs are the most welcome of all.

It's best with attached samples. Since the forum rejects wav files, simply rename to .wav.bin and it passed.

roudoudou:
the crappy high pitch sound is due to aliasing/rounded index for replay

i asked Megachur to let his emulator run at higher replay rate (up to 192KHz) and it solve easily most the high frequencies replay (still not perfect but really better)
a solution for high frequencies replay at 44Khz or 48Khz may be to use sinus instead of squares and let shanon do the rest

cpcitor:

--- Quote from: roudoudou on 23:37, 03 November 21 ---the crappy high pitch sound is due to aliasing/rounded index for replay

i asked Megachur to let his emulator run at higher replay rate (up to 192KHz) and it solve easily most the high frequencies replay (still not perfect but really better)
a solution for high frequencies replay at 44Khz or 48Khz may be to use sinus instead of squares and let shanon do the rest

--- End quote ---

You're right, this is aliasing.

Still, that's not all.

Shannon does not say to replace the square with a sine, and there's no need to deviate from the chip behavior like this.

Is there any emulator out there that has a different result?

eto:

--- Quote from: cpcitor on 23:21, 03 November 21 ---You might be wondering why I'm asking this.
--- End quote ---

Indeed - and knowing it might make help to motivate people to attach cables and record it ;-)

roudoudou:

--- Quote from: cpcitor on 13:57, 04 November 21 ---Shannon does not say to replace the square with a sine, and there's no need to deviate from the chip behavior like this.

--- End quote ---
I never said that  :o
What i mean is using a sinus will keep the high frequencies clean. It's impossible with a square signal and a restitution frequency non multiple of the generator one

Moreover, the AY high frequencies looks like sinus signal because it can't do a clean square so fast  ;D

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