Fix PCM34 read accuracy on CGB-C and older

LIJI32 · LIJI32 · commit 10801af8e3d6 · 2025-10-16T00:23:28.000+03:00
diff --git a/Core/apu.c b/Core/apu.c
@@ -568,7 +568,7 @@ static void tick_noise_envelope(GB_gameboy_t *gb)
     if (!(nr42 & 7)) return;
 
     if (gb->cgb_double_speed) {
-        gb->apu.pcm_mask[0] &= (gb->apu.noise_channel.current_volume << 4) | (gb->model == GB_MODEL_CGB_0? 0x3F : 0x1F);
+        gb->apu.pcm_mask[1] &= (gb->apu.noise_channel.current_volume << 4) | 0x1F;
     }
     
     if (nr42 & 8) {
@@ -1023,7 +1023,7 @@ restart:;
 
                 /* Step LFSR */
                 if (new_bit && !old_bit) {
-                    if (cycles_left == 0 && gb->apu.samples[GB_NOISE] == 0) {
+                    if (cycles_left == 0 && gb->apu.samples[GB_NOISE] == 0 && !gb->cgb_double_speed) {
                         gb->apu.pcm_mask[1] &= 0x0F;
                     }
                     step_lfsr(gb, cycles - cycles_left);

Original file line number	Diff line number	Diff line change
`@@ -568,7 +568,7 @@ static void tick_noise_envelope(GB_gameboy_t *gb)`
`568`	`568`	`if (!(nr42 & 7)) return;`
`569`	`569`
`570`	`570`	`if (gb->cgb_double_speed) {`
`571`		`- gb->apu.pcm_mask[0] &= (gb->apu.noise_channel.current_volume << 4) \| (gb->model == GB_MODEL_CGB_0? 0x3F : 0x1F);`
	`571`	`+ gb->apu.pcm_mask[1] &= (gb->apu.noise_channel.current_volume << 4) \| 0x1F;`
`572`	`572`	`}`
`573`	`573`
`574`	`574`	`if (nr42 & 8) {`
`@@ -1023,7 +1023,7 @@ restart:;`
`1023`	`1023`
`1024`	`1024`	`/* Step LFSR */`
`1025`	`1025`	`if (new_bit && !old_bit) {`
`1026`		`- if (cycles_left == 0 && gb->apu.samples[GB_NOISE] == 0) {`
	`1026`	`+ if (cycles_left == 0 && gb->apu.samples[GB_NOISE] == 0 && !gb->cgb_double_speed) {`
`1027`	`1027`	`gb->apu.pcm_mask[1] &= 0x0F;`
`1028`	`1028`	`}`
`1029`	`1029`	`step_lfsr(gb, cycles - cycles_left);`