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[YM2612] fixed LFO AM modulation waveform (California Games)

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EkeEke 2012-08-02 23:14:08 +02:00
parent 737fcd116c
commit 02999945ea
1 changed files with 11 additions and 16 deletions
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27
source/sound/ym2612.c
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@ -27,7 +27,7 @@
** - added YM2612 Context external access functions
** - fixed LFO implementation:
** .added support for CH3 special mode: fixes various sound effects (birds in Warlock, bug sound in Aladdin...)
** .modified LFO behavior when switched off (AM/PM current level is held) and on (LFO step is reseted): fixes intro in Spider-Man & Venom : Separation Anxiety
** .inverted LFO AM waveform: fixes Spider-Man & Venom : Separation Anxiety (intro), California Games (surfing event)
** .improved LFO timing accuracy: now updated AFTER sample output, like EG/PG updates, and without any precision loss anymore.
** - improved internal timers emulation
** - adjusted lowest EG rates increment values
@ -1041,12 +1041,12 @@ INLINE void advance_lfo()
/* There are 128 LFO steps */
ym2612.OPN.lfo_cnt = ( ym2612.OPN.lfo_cnt + 1 ) & 127;
/* triangle */
/* AM: 0 to 126 step +2, 126 to 0 step -2 */
/* triangle (inverted) */
/* AM: from 126 to 0 step -2, 0 to 126 step +2 */
if (ym2612.OPN.lfo_cnt<64)
ym2612.OPN.LFO_AM = ym2612.OPN.lfo_cnt * 2;
ym2612.OPN.LFO_AM = (ym2612.OPN.lfo_cnt ^ 63) << 1;
else
ym2612.OPN.LFO_AM = 126 - ((ym2612.OPN.lfo_cnt&63) * 2);
ym2612.OPN.LFO_AM = (ym2612.OPN.lfo_cnt & 63) << 1;
/* PM works with 4 times slower clock */
ym2612.OPN.LFO_PM = ym2612.OPN.lfo_cnt >> 2;
@ -1506,22 +1506,17 @@ INLINE void OPNWriteMode(int r, int v)
case 0x22: /* LFO FREQ (YM2608/YM2610/YM2610B/ym2612) */
if (v&8) /* LFO enabled ? */
{
if (!ym2612.OPN.lfo_timer_overflow)
{
/* restart LFO */
ym2612.OPN.lfo_cnt = 0;
ym2612.OPN.lfo_timer = 0;
ym2612.OPN.LFO_AM = 0;
ym2612.OPN.LFO_PM = 0;
}
ym2612.OPN.lfo_timer_overflow = lfo_samples_per_step[v&7] << LFO_SH;
}
else
{
/* hold LFO waveform in reset state */
ym2612.OPN.lfo_timer_overflow = 0;
ym2612.OPN.lfo_timer = 0;
ym2612.OPN.lfo_cnt = 0;
ym2612.OPN.LFO_PM = 0;
ym2612.OPN.LFO_AM = 126;
}
break;
case 0x24: /* timer A High 8*/
ym2612.OPN.ST.TA = (ym2612.OPN.ST.TA & 0x03)|(((int)v)<<2);
@ -1954,7 +1949,7 @@ void YM2612ResetChip(void)
ym2612.OPN.lfo_timer_overflow = 0;
ym2612.OPN.lfo_timer = 0;
ym2612.OPN.lfo_cnt = 0;
ym2612.OPN.LFO_AM = 0;
ym2612.OPN.LFO_AM = 126;
ym2612.OPN.LFO_PM = 0;
ym2612.OPN.ST.TAC = 0;