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Re: Fixing PPU Audio Buzz

Posted: Tue Mar 12, 2013 1:40 pm
by Septr
So Blargg, is there nothing I can do to solve my problem? I'm beginning to think My initial success was just a false positive. Though, it sounded just like B00DaW's example in his post:
B00daW wrote: Edit: Here is an amplified clip of a blank NSF. At around 4 seconds I turn the PPU off. There is a marginable amount of difference, but there is still a lot of buzz that I cannot account for. Any ideas?
He says he 'turned the PPU off, but did he do that with code or something hardware side?

Re: Fixing PPU Audio Buzz

Posted: Tue Mar 12, 2013 1:51 pm
by blargg
Is there any kind of hardware quantizer device? Or one that refuses to change the output signal until the input signal is sufficiently different from it? That'd clean up things like this amazingly well.

Re: Fixing PPU Audio Buzz

Posted: Tue Mar 12, 2013 3:25 pm
by rainwarrior
Only if the noise floor was low enough to be smaller than your smallest quantization step / threshold, which it might be, depending on the situation. High frequency stuff being filtered before sampling is also a problem, since this ruins the original quantization (you'd need to work at high frequency).

In a really ideal case maybe you'd tap a device that outputs via PWM and just reverse the PWM encoding to get back the digital signal.

Re: Fixing PPU Audio Buzz

Posted: Tue Mar 12, 2013 7:38 pm
by tepples
rainwarrior wrote:In a really ideal case maybe you'd tap a device that outputs via PWM and just reverse the PWM encoding to get back the digital signal.
And now you know part of why Sony used PDM encoding for SACD.