Re: Re: [hatari-devel] YM2149 + C10 lowpass filter mapping

[David Savinkoff <dsavnkff@xxxxxxxxx>]

Hi Nicolas,

I've pondered over these patches for a couple of days and and
believe the C10 capacitor filter is ready for inclusion in Hatari.

The audio.c patch is the same as before, and the sound.c
patch has prettier comments.

This filter is better than the previous (unused) filter, so at least
sound.c should be patched (if the filter selecting method in
audio.c is unacceptable).

I've listened to the mad_plus demo, sh11inv demo, blubber demo
and key clicks to hear the theoretical sound difference between
the ST and the STe (I don't have an STe). I think the demos
sound better with some of the dry harmonics filtered.

A two-channel bank-switched IIR filter is now used to model the
YM2149 + C10 components. This is faster and way better than before.

The YM2149 is filtered at 7.7 KHz when it charges capacitor C10,
and filtered at 2.1 KHz when R8 discharges C10. This is exactly
what happens on a real ST.

David

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