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Preserve fractional part of sample offset when looping, fixes remaining pitch stability problems.

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This commit is contained in:
R. Belmont 2008-01-19 17:10:10 +00:00
parent 0818e4793b
commit 797d75363b
1 changed files with 21 additions and 10 deletions
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31
src/emu/sound/scsp.c
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@ -40,8 +40,9 @@
#define EG_SHIFT 16 #define EG_SHIFT 16
#define FM_DELAY 4 // delay in number of slots processed before samples are written to the FM ring buffer #define FM_DELAY 0 // delay in number of slots processed before samples are written to the FM ring buffer
// driver code indicates should be 4, but sounds distorted then
// include the LFO handling code // include the LFO handling code
#include "scsplfo.c" #include "scsplfo.c"
@ -1009,7 +1010,8 @@ INLINE INT32 SCSP_UpdateSlot(struct _SCSP *SCSP, struct _SLOT *slot)
} }
for (addr_select=0;addr_select<2;addr_select++) for (addr_select=0;addr_select<2;addr_select++)
{ {
INT32 rem_addr;
switch(LPCTL(slot)) switch(LPCTL(slot))
{ {
case 0: //no loop case 0: //no loop
@ -1021,26 +1023,35 @@ INLINE INT32 SCSP_UpdateSlot(struct _SCSP *SCSP, struct _SLOT *slot)
break; break;
case 1: //normal loop case 1: //normal loop
if(*addr[addr_select]>=LEA(slot)) if(*addr[addr_select]>=LEA(slot))
*slot_addr[addr_select]=LSA(slot)<<SHIFT; {
rem_addr = *slot_addr[addr_select] - (LEA(slot)<<SHIFT);
*slot_addr[addr_select]=(LSA(slot)<<SHIFT) + rem_addr;
}
break; break;
case 2: //reverse loop case 2: //reverse loop
if((*addr[addr_select]>=LSA(slot)) && !(slot->Backwards)) if((*addr[addr_select]>=LSA(slot)) && !(slot->Backwards))
{ {
*slot_addr[addr_select]=LEA(slot)<<SHIFT; rem_addr = *slot_addr[addr_select] - (LSA(slot)<<SHIFT);
*slot_addr[addr_select]=(LEA(slot)<<SHIFT) - rem_addr;
slot->Backwards=1; slot->Backwards=1;
} }
if((*addr[addr_select]<=LSA(slot) || (*slot_addr[addr_select]&0x80000000)) && slot->Backwards) else if((*addr[addr_select]<LSA(slot) || (*slot_addr[addr_select]&0x80000000)) && slot->Backwards)
*slot_addr[addr_select]=LEA(slot)<<SHIFT; {
rem_addr = (LSA(slot)<<SHIFT) - *slot_addr[addr_select];
*slot_addr[addr_select]=(LEA(slot)<<SHIFT) - rem_addr;
}
break; break;
case 3: //ping-pong case 3: //ping-pong
if(*addr[addr_select]>=LEA(slot)) //reached end, reverse till start if(*addr[addr_select]>=LEA(slot)) //reached end, reverse till start
{ {
*slot_addr[addr_select]=LEA(slot)<<SHIFT; rem_addr = *slot_addr[addr_select] - (LEA(slot)<<SHIFT);
*slot_addr[addr_select]=(LEA(slot)<<SHIFT) - rem_addr;
slot->Backwards=1; slot->Backwards=1;
} }
if((*addr[addr_select]<=LSA(slot) || (*slot_addr[addr_select]&0x80000000)) && slot->Backwards)//reached start or negative else if((*addr[addr_select]<LSA(slot) || (*slot_addr[addr_select]&0x80000000)) && slot->Backwards)//reached start or negative
{ {
*slot_addr[addr_select]=LSA(slot)<<SHIFT; rem_addr = (LSA(slot)<<SHIFT) - *slot_addr[addr_select];
*slot_addr[addr_select]=(LSA(slot)<<SHIFT) + rem_addr;
slot->Backwards=0; slot->Backwards=0;
} }
break; break;