M CHANGES → CHANGES

@@ -2,6 +2,7 @@ 0.9.0: (Future)
 Emulation fixes:
  - ARM: Fix ALU reading PC after shifting
  - ARM: Fix STR storing PC after address calculation
+ - GB Serialize: Fix timing bug loading channel 4 timing
  - GBA DMA: Linger last DMA on bus (fixes mgba.io/i/301 and mgba.io/i/1320)
  - GBA Memory: Misaligned SRAM writes are ignored
  - GBA Memory: Improve gamepak prefetch timing

M src/gb/audio.c → src/gb/audio.c

@@ -1078,9 +1078,13 @@ LOAD_32LE(audio->ch4.lfsr, 0, &state->ch4.lfsr);
 	LOAD_32LE(audio->ch4.lastEvent, 0, &state->ch4.lastEvent);
 	LOAD_32LE(when, 0, &state->ch4.nextEvent);
 	if (audio->ch4.envelope.dead < 2 && audio->playingCh4) {
-		if (when - audio->ch4.lastEvent > (uint32_t) audio->sampleInterval) {
+		if (!audio->ch4.lastEvent) {
 			// Back-compat: fake this value
-			audio->ch4.lastEvent = when - audio->sampleInterval;
+			uint32_t currentTime = mTimingCurrentTime(audio->timing);
+			int32_t cycles = audio->ch4.ratio ? 2 * audio->ch4.ratio : 1;
+			cycles <<= audio->ch4.frequency;
+			cycles *= 8 * audio->timingFactor;
+			audio->ch4.lastEvent = currentTime + (when & (cycles - 1)) - cycles;
 		}
 		mTimingSchedule(audio->timing, &audio->ch4Event, when);
 	}