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Re: [Qemu-devel] [PATCH] PC speaker emulation (fixed point)

From: Sebastian Kaliszewski
Subject: Re: [Qemu-devel] [PATCH] PC speaker emulation (fixed point)
Date: Wed, 25 Jan 2006 01:38:39 +0100
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On Tuesday 24 January 2006 22:45, Fabrice Bellard wrote:
> If you want to model the real PC speaker, the best to do is to generate
> a square signal and to pass it thru a low pass filter with a cut off
> frequency of a few kHz. Then you could even be able to play samples thru
> the simulated PC speaker using the tricks used in old MSDOS programs,
> provided QEMU implements a precise cycle counter (it will come someday
> !).

Change that few to 15 [kHz] and that would be what some PC-speaker hooking 
SB-clones did. But there were PCs with piezoelectric speakers, and those 
could genereate sounds well above 20kHz. But yes, typically 12-15kHz cutoff 
with 1st or 2nd order filter would do the trick.

And if someone wants full reality one would also need some not-too-strong 
(1st order, 6dB/oct) hi-pass filter around 80-120Hz -- as those tiny 
PC-speakers are unable to emit bass.

Sebastian Kaliszewski

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