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

[Joachim Henke]

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.

Regards
Jo.

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
http://he-jo.net/

pcspk.diff.gz
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