XGM PCM crackle question

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cero
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Joined: Mon Nov 30, 2015 1:55 pm

XGM PCM crackle question

Post by cero » Tue Sep 13, 2016 11:19 am

I have some PCM sound (voice recording) that crackles when played. The frequency is not the issue, nor is wavtoraw's 16-to-14 kHz conversion - the converted file sounds fine when played in Audacity.

I would appreciate if someone could check this, is it still the ladder effect hw bug, or a bug in the XGM driver?

Source, binary:
https://u.pomf.is/uznkzu.zip

It also includes the output from an emulator.

Stef
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Re: XGM PCM crackle question

Post by Stef » Tue Sep 13, 2016 12:59 pm

Can't download your file...
Does the crackle happens in emulators as well or only on real hardware ?
Are you interrupting Z80 for a long time ? or hogging main BUS for too long (DMA exceeding VBlank period) ?

cero
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Posts: 259
Joined: Mon Nov 30, 2015 1:55 pm

Re: XGM PCM crackle question

Post by cero » Tue Sep 13, 2016 4:57 pm

Blocked by your ISP? That's been quite a reliable host, what download service works for you?

I still can't test on hw, so just in multiple emulators. (Got a Genny, but no flashcart yet)

Here's the full source:

Code: Select all

#include <genesis.h>
#include "files.h"

int main() {

        Z80_init();
        Z80_loadDriver(Z80_DRIVER_XGM, 1);

        SND_setPCM_XGM(64, snd_you, sizeof(snd_you));
        SND_startPlayPCM_XGM(64, 0, 0);

        VDP_drawText("Hello Genny World!", 10, 13);

        while (1);

        return 0;
}

Stef
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Re: XGM PCM crackle question

Post by Stef » Tue Sep 13, 2016 7:09 pm

Definitely the emulator, without any doubt. In fact depending the emulator the DAC is sampled at different rate which create the aliasing your hear. But you may also use a 14 Khz resampled sample for better result as the internal rescomp resampler sucks ;)

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