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[Qemu-devel] [PATCH] PC speaker emulation (square wave)

From: Joachim Henke
Subject: [Qemu-devel] [PATCH] PC speaker emulation (square wave)
Date: Wed, 25 Jan 2006 22:54:53 +0100

Ok, I simplified my patch to generate just plain square waves. Indeed, its sound is much closer to a real PC speaker now.

Does "cut off frequency" mean, that we have silence above that specific frequency? I changed my patch to go this way. Before, it always played the highest possible frequency for that case (f > 16 kHz).

This emulation should be sufficient for now. I'm not sure, if it's worth to add more overhead to emulate every possible shortcoming of an original PC speaker. We can go ahead, when we have realtime PIT emulation.


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 !).

Joachim Henke

Attachment: pcspk.diff.gz
Description: GNU Zip compressed data

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