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Trashed the old pre-accurate-clocking STEP based sample averaging scheme from sn76489 and friends, vastly simplifying the code. Made the output bipolar rather than only above the 0 line.

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Added missing statement to the get_safe_token function for the recently added SN94624
This commit is contained in:
Jonathan Gevaryahu 2009-11-15 03:59:28 +00:00
parent 8be9626ae2
commit 6371d8dc1c
1 changed files with 44 additions and 97 deletions
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141
src/emu/sound/sn76496.c
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@ -65,8 +65,7 @@
#include "sn76496.h"
#define MAX_OUTPUT 0x7fff
#define STEP 0x10000
#define MAX_OUTPUT 0x3fff
#define NOISEMODE (R->Register[6]&4)?1:0
@ -99,6 +98,7 @@ INLINE sn76496_state *get_safe_token(const device_config *device)
sound_get_type(device) == SOUND_SN76489 ||
sound_get_type(device) == SOUND_SN76489A ||
sound_get_type(device) == SOUND_SN76494 ||
sound_get_type(device) == SOUND_SN94624 ||
sound_get_type(device) == SOUND_GAMEGEAR ||
sound_get_type(device) == SOUND_SMSIII);
return (sn76496_state *)device->token;
@ -148,8 +148,7 @@ WRITE8_DEVICE_HANDLER( sn76496_w )
case 2: /* tone 1 : frequency */
case 4: /* tone 2 : frequency */
if ((data & 0x80) == 0) R->Register[r] = (R->Register[r] & 0x0f) | ((data & 0x3f) << 4);
R->Period[c] = STEP * R->Register[r];
if (R->Period[c] == 0) R->Period[c] = STEP;
R->Period[c] = R->Register[r];
if (r == 4)
{
/* update noise shift frequency */
@ -169,7 +168,7 @@ WRITE8_DEVICE_HANDLER( sn76496_w )
if ((data & 0x80) == 0) R->Register[r] = (R->Register[r] & 0x3f0) | (data & 0x0f);
n = R->Register[6];
/* N/512,N/1024,N/2048,Tone #3 output */
R->Period[3] = ((n&3) == 3) ? 2 * R->Period[2] : (STEP << (5+(n&3)));
R->Period[3] = ((n&3) == 3) ? 2 * R->Period[2] : (1 << (5+(n&3)));
/* Reset noise shifter */
R->RNG = R->FeedbackMask;
R->OldNoise = 0;
@ -180,8 +179,6 @@ WRITE8_DEVICE_HANDLER( sn76496_w )
}
}
static STREAM_UPDATE( SN76496Update )
{
int i;
@ -189,113 +186,64 @@ static STREAM_UPDATE( SN76496Update )
stream_sample_t *buffer = outputs[0];
/* If the volume is 0, increase the counter; this is more or less
a speedup hack for when silence is to be output */
for (i = 0;i < 4;i++)
{
if (R->Volume[i] == 0)
{
/* note that I do count += samples, NOT count = samples + 1.
You might think it's the same since the volume is 0, but doing
the latter could cause interferencies when the program is
rapidly modulating the volume. */
if (R->Count[i] <= samples*STEP) R->Count[i] += samples*STEP;
}
}
while (samples > 0)
{
int vol[4];
unsigned int out;
int left;
// clock chip once
INT16 out;
/* decrement Cycles to READY by one */
if (R->CyclestoREADY >0) R->CyclestoREADY--;
/* vol[] keeps track of how long each square wave stays */
/* in the 1 position during the sample period. */
vol[0] = vol[1] = vol[2] = vol[3] = 0;
// handle channels 0,1,2
for (i = 0;i < 3;i++)
{
if (R->Output[i]) vol[i] += R->Count[i];
R->Count[i] -= STEP;
/* Period[i] is the half period of the square wave. Here, in each
loop I add Period[i] twice, so that at the end of the loop the
square wave is in the same status (0 or 1) it was at the start.
vol[i] is also incremented by Period[i], since the wave has been 1
exactly half of the time, regardless of the initial position.
If we exit the loop in the middle, Output[i] has to be inverted
and vol[i] incremented only if the exit status of the square
wave is 1. */
while (R->Count[i] <= 0)
R->Count[i]--;
if (R->Count[i] < 0)
{
R->Count[i] += R->Period[i];
if (R->Count[i] > 0)
{
R->Output[i] ^= 1;
if (R->Output[i]) vol[i] += R->Period[i];
break;
}
R->Count[i] += R->Period[i];
vol[i] += R->Period[i];
R->Output[i] ^= 1;
R->Count[i] = R->Period[i];
}
if (R->Output[i]) vol[i] -= R->Count[i];
}
left = STEP;
do
// handle channel 3
R->Count[3]--;
if (R->Count[3] <= 0)
{
int nextevent;
if (R->Count[3] < left) nextevent = R->Count[3];
else nextevent = left;
if (R->Output[3]) vol[3] += R->Count[3];
R->Count[3] -= nextevent;
if (R->Count[3] <= 0)
if (NOISEMODE == 1) /* White Noise Mode */
{
if (NOISEMODE == 1) /* White Noise Mode */
{
if ((((R->RNG & R->WhitenoiseTaps) != R->WhitenoiseTaps) && ((R->RNG & R->WhitenoiseTaps) != 0)) ^ R->FeedbackInvert ) /* XOR or XNOR */
{
R->RNG >>= 1;
R->RNG |= R->FeedbackMask;
}
else
{
R->RNG >>= 1;
}
}
else /* Periodic noise mode */
if ((((R->RNG & R->WhitenoiseTaps) != R->WhitenoiseTaps) && ((R->RNG & R->WhitenoiseTaps) != 0)) ^ R->FeedbackInvert ) /* XOR or XNOR */
{
if (R->RNG & 1)
{
R->RNG >>= 1;
R->RNG |= R->FeedbackMask;
}
else
{
R->RNG >>= 1;
}
R->RNG >>= 1;
R->RNG |= R->FeedbackMask;
}
else
{
R->RNG >>= 1;
}
R->Output[3] = R->OldNoise;
R->OldNoise = R->RNG & 1;
R->Count[3] += R->Period[3];
if (R->Output[3]) vol[3] += R->Period[3];
}
if (R->Output[3]) vol[3] -= R->Count[3];
else /* Periodic noise mode */
{
if (R->RNG & 1)
{
R->RNG >>= 1;
R->RNG |= R->FeedbackMask;
}
else
{
R->RNG >>= 1;
}
}
R->Output[3] = R->OldNoise;
R->OldNoise = R->RNG & 1;
R->Count[3] = R->Period[3];
}
left -= nextevent;
} while (left > 0);
out = (R->Output[0]?R->Volume[0]:(0-R->Volume[0]))
+(R->Output[1]?R->Volume[1]:(0-R->Volume[1]))
+(R->Output[2]?R->Volume[2]:(0-R->Volume[2]))
+(R->Output[3]?R->Volume[3]:(0-R->Volume[3]));
out = vol[0] * R->Volume[0] + vol[1] * R->Volume[1] +
vol[2] * R->Volume[2] + vol[3] * R->Volume[3];
if (out > MAX_OUTPUT * STEP) out = MAX_OUTPUT * STEP;
*(buffer++) = out / STEP;
*(buffer++) = out;
samples--;
}
@ -348,8 +296,7 @@ static int SN76496_init(const device_config *device, sn76496_state *R)
for (i = 0;i < 4;i++)
{
R->Output[i] = 0;
R->Period[i] = R->Count[i] = STEP;
R->Output[i] = R->Period[i] = R->Count[i] = 0;
}
/* Default is SN76489 non-A */