[hatari-devel] Improved YM2149 cycle accuracy

[Nicolas Pomarède <npomarede@xxxxxxxxxxxx>]

Hi

with the recent release of maxYMiser FM v1.53, it was reported by gwEn 
(author of maxYMiser) that Hatari 2.3 didn't correctly render the new 
"syncsquare" effect.

Thanks to some example files and after rewriting the way internal YM2149 
sound buffer (at 250 kHz) was mixed into the output sound buffer 
(usually at 44.1 kHz), the YM2149 emulation should now be really cycle 
accurate, even in these cases where period registers are changed several 
times at 32 CPU cycles interval to get the correct "sync" between YM's 
clock and MFP timers.

Doing so, I also removed some older parts of sound.c that were not used 
since Hatari 2.1, as there's no need to keep less accurate parts 
compared to the relative small overhead of emulating YM2149 at full 250 
kHz (as more musics might use this syncsquare effect in the future, 
better have a version of Hatari that supports it out of the box)

For the record, I attach the 2 sample SNDH files to use in maxYMiser and 
hear the difference between Hatari 2.3 and this new version.

Nicolas

Attachment: SYSQBELL.SND
Description: Basic audio

Attachment: SYNCSQUA.SND
Description: Basic audio