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-rw-r--r--src/m4a.c109
1 files changed, 49 insertions, 60 deletions
diff --git a/src/m4a.c b/src/m4a.c
index 3d564a5a1..99feeadd7 100644
--- a/src/m4a.c
+++ b/src/m4a.c
@@ -911,7 +911,7 @@ void CgbSound(void)
{
s32 ch;
struct CgbChannel *channels;
- s32 evAdd;
+ s32 envelopeStepTimeAndDir;
s32 prevC15;
struct SoundInfo *soundInfo = SOUND_INFO_PTR;
vu8 *nrx0ptr;
@@ -933,6 +933,7 @@ void CgbSound(void)
if (!(channels->statusFlags & SOUND_CHANNEL_SF_ON))
continue;
+ /* 1. determine hardware channel registers */
switch (ch)
{
case 1:
@@ -966,8 +967,9 @@ void CgbSound(void)
}
prevC15 = soundInfo->c15;
- evAdd = *nrx2ptr;
+ envelopeStepTimeAndDir = *nrx2ptr;
+ /* 2. calculate envelope volume */
if (channels->statusFlags & SOUND_CHANNEL_SF_START)
{
if (!(channels->statusFlags & SOUND_CHANNEL_SF_STOP))
@@ -982,7 +984,7 @@ void CgbSound(void)
// fallthrough
case 2:
*nrx1ptr = ((u32)channels->wavePointer << 6) + channels->length;
- goto loc_82E0E30;
+ goto init_env_step_time_dir;
case 3:
if (channels->wavePointer != channels->currentPointer)
{
@@ -1003,8 +1005,8 @@ void CgbSound(void)
default:
*nrx1ptr = channels->length;
*nrx3ptr = (u32)channels->wavePointer << 3;
- loc_82E0E30:
- evAdd = channels->attack + 8;
+ init_env_step_time_dir:
+ envelopeStepTimeAndDir = channels->attack + CGB_NRx2_ENV_DIR_INC;
if (channels->length)
channels->n4 = 0x40;
else
@@ -1015,16 +1017,17 @@ void CgbSound(void)
if ((s8)(channels->attack & mask))
{
channels->envelopeVolume = 0;
- goto EC_MINUS;
+ goto envelope_step_complete;
}
else
{
- goto loc_82E0F96;
+ // skip attack phase if attack is instantaneous (=0)
+ goto envelope_decay_start;
}
}
else
{
- goto loc_82E0E82;
+ goto oscillator_off;
}
}
else if (channels->statusFlags & SOUND_CHANNEL_SF_IEC)
@@ -1032,12 +1035,12 @@ void CgbSound(void)
channels->pseudoEchoLength--;
if ((s8)(channels->pseudoEchoLength & mask) <= 0)
{
- loc_82E0E82:
+ oscillator_off:
CgbOscOff(ch);
channels->statusFlags = 0;
- goto LAST_LABEL;
+ goto channel_complete;
}
- goto loc_82E0FD6;
+ goto envelope_complete;
}
else if ((channels->statusFlags & SOUND_CHANNEL_SF_STOP) && (channels->statusFlags & SOUND_CHANNEL_SF_ENV))
{
@@ -1047,46 +1050,41 @@ void CgbSound(void)
{
channels->modify |= CGB_CHANNEL_MO_VOL;
if (ch != 3)
- {
- evAdd = channels->release;
- }
- goto EC_MINUS;
+ envelopeStepTimeAndDir = channels->release | CGB_NRx2_ENV_DIR_DEC;
+ goto envelope_step_complete;
}
else
{
- goto loc_82E0F02;
+ goto envelope_pseudoecho_start;
}
}
else
{
- loc_82E0ED0:
+ envelope_step_repeat:
if (channels->envelopeCounter == 0)
{
if (ch == 3)
- {
channels->modify |= CGB_CHANNEL_MO_VOL;
- }
+
CgbModVol(channels);
- if ((channels->statusFlags & SOUND_CHANNEL_SF_ENV) == 0)
+ if ((channels->statusFlags & SOUND_CHANNEL_SF_ENV) == SOUND_CHANNEL_SF_ENV_RELEASE)
{
channels->envelopeVolume--;
if ((s8)(channels->envelopeVolume & mask) <= 0)
{
- loc_82E0F02:
+ envelope_pseudoecho_start:
channels->envelopeVolume = ((channels->envelopeGoal * channels->pseudoEchoVolume) + 0xFF) >> 8;
if (channels->envelopeVolume)
{
channels->statusFlags |= SOUND_CHANNEL_SF_IEC;
channels->modify |= CGB_CHANNEL_MO_VOL;
if (ch != 3)
- {
- evAdd = 8;
- }
- goto loc_82E0FD6;
+ envelopeStepTimeAndDir = 0 | CGB_NRx2_ENV_DIR_INC;
+ goto envelope_complete;
}
else
{
- goto loc_82E0E82;
+ goto oscillator_off;
}
}
else
@@ -1094,13 +1092,13 @@ void CgbSound(void)
channels->envelopeCounter = channels->release;
}
}
- else if ((channels->statusFlags & SOUND_CHANNEL_SF_ENV) == 1)
+ else if ((channels->statusFlags & SOUND_CHANNEL_SF_ENV) == SOUND_CHANNEL_SF_ENV_SUSTAIN)
{
- loc_82E0F3A:
+ envelope_sustain:
channels->envelopeVolume = channels->sustainGoal;
channels->envelopeCounter = 7;
}
- else if ((channels->statusFlags & SOUND_CHANNEL_SF_ENV) == 2)
+ else if ((channels->statusFlags & SOUND_CHANNEL_SF_ENV) == SOUND_CHANNEL_SF_ENV_DECAY)
{
int envelopeVolume, sustainGoal;
@@ -1109,21 +1107,19 @@ void CgbSound(void)
sustainGoal = (s8)(channels->sustainGoal);
if (envelopeVolume <= sustainGoal)
{
- loc_82E0F5A:
+ envelope_sustain_start:
if (channels->sustain == 0)
{
channels->statusFlags &= ~SOUND_CHANNEL_SF_ENV;
- goto loc_82E0F02;
+ goto envelope_pseudoecho_start;
}
else
{
channels->statusFlags--;
channels->modify |= CGB_CHANNEL_MO_VOL;
if (ch != 3)
- {
- evAdd = 8;
- }
- goto loc_82E0F3A;
+ envelopeStepTimeAndDir = 0 | CGB_NRx2_ENV_DIR_INC;
+ goto envelope_sustain;
}
}
else
@@ -1136,7 +1132,7 @@ void CgbSound(void)
channels->envelopeVolume++;
if ((u8)(channels->envelopeVolume & mask) >= channels->envelopeGoal)
{
- loc_82E0F96:
+ envelope_decay_start:
channels->statusFlags--;
channels->envelopeCounter = channels->decay;
if ((u8)(channels->envelopeCounter & mask))
@@ -1144,13 +1140,11 @@ void CgbSound(void)
channels->modify |= CGB_CHANNEL_MO_VOL;
channels->envelopeVolume = channels->envelopeGoal;
if (ch != 3)
- {
- evAdd = channels->decay;
- }
+ envelopeStepTimeAndDir = channels->decay | CGB_NRx2_ENV_DIR_DEC;
}
else
{
- goto loc_82E0F5A;
+ goto envelope_sustain_start;
}
}
else
@@ -1161,43 +1155,40 @@ void CgbSound(void)
}
}
- EC_MINUS:
+ envelope_step_complete:
+ // every 15 frames, envelope calculation has to be done twice
+ // to keep up with the hardware envelope rate (1/64 s)
channels->envelopeCounter--;
if (prevC15 == 0)
{
prevC15--;
- goto loc_82E0ED0;
+ goto envelope_step_repeat;
}
- loc_82E0FD6:
+ envelope_complete:
+ /* 3. apply pitch to HW registers */
if (channels->modify & CGB_CHANNEL_MO_PIT)
{
if (ch < 4 && (channels->type & TONEDATA_TYPE_FIX))
{
- int biasH = REG_SOUNDBIAS_H;
+ int dac_pwm_rate = REG_SOUNDBIAS_H;
- if (biasH < 64)
- {
+ if (dac_pwm_rate < 0x40) // if PWM rate = 32768 Hz
channels->frequency = (channels->frequency + 2) & 0x7fc;
- }
- else if (biasH < 128)
- {
+ else if (dac_pwm_rate < 0x80) // if PWM rate = 65536 Hz
channels->frequency = (channels->frequency + 1) & 0x7fe;
- }
}
+
if (ch != 4)
- {
*nrx3ptr = channels->frequency;
- }
else
- {
*nrx3ptr = (*nrx3ptr & 0x08) | channels->frequency;
- }
channels->n4 = (channels->n4 & 0xC0) + (*((u8*)(&channels->frequency) + 1));
*nrx4ptr = (s8)(channels->n4 & mask);
}
- if (channels->modify & 1)
+ /* 4. apply envelope & volume to HW registers */
+ if (channels->modify & CGB_CHANNEL_MO_VOL )
{
REG_NR51 = (REG_NR51 & ~channels->panMask) | channels->pan;
if (ch == 3)
@@ -1212,17 +1203,15 @@ void CgbSound(void)
}
else
{
- evAdd &= 0xf;
- *nrx2ptr = (channels->envelopeVolume << 4) + evAdd;
+ envelopeStepTimeAndDir &= 0xf;
+ *nrx2ptr = (channels->envelopeVolume << 4) + envelopeStepTimeAndDir;
*nrx4ptr = channels->n4 | 0x80;
if (ch == 1 && !(*nrx0ptr & 0x08))
- {
*nrx4ptr = channels->n4 | 0x80;
- }
}
}
- LAST_LABEL:
+ channel_complete:
channels->modify = 0;
}
}
generated by cgit v1.2.3 (git 2.25.1) at 2025-05-10 07:49:31 +0000