port: revert multithreaded audio experiments

until I can figure out how to fix all the funny concurrency issues that cropped up

port/src/pdsched.c

@@ -242,6 +242,18 @@ void schedStartFrame(OSSched *sc)
 	videoStartFrame();
 }
 
+void schedAudioFrame(OSSched *sc)
+{
+	s32 i;
+
+	if (!g_SndDisabled) {
+		for (i = 0; i < g_Vars.diffframe60; i++) {
+			amgrFrame();
+			audioEndFrame();
+		}
+	}
+}
+
 /**
  * Handle a retrace (vsync) event.
  *
@@ -260,6 +272,18 @@ void schedEndFrame(OSSched *sc)
 {
 	sc->frameCount++;
 
+#if PAL
+	if (!g_Resetting && (sc->frameCount & 1)) {
+		// osStopTimer(&g_SchedRspTimer);
+		// osSetTimer(&g_SchedRspTimer, 280000, 0, amgrGetFrameMesgQueue(), &g_SchedRspMsg);
+	}
+#else
+	if (!g_Resetting && ((sc->frameCount & 1) || IS4MB())) {
+		// osStopTimer(&g_SchedRspTimer);
+		// osSetTimer(&g_SchedRspTimer, 280000, 0, amgrGetFrameMesgQueue(), &g_SchedRspMsg);
+	}
+#endif
+
 	if (!g_Resetting) {
 		viHandleRetrace();
 	}
@@ -271,6 +295,7 @@ void schedEndFrame(OSSched *sc)
 	joy00014238();
 
 	sndHandleRetrace();
+	schedAudioFrame(sc);
 	schedRenderCrashPeriodically(sc->frameCount);
 	videoEndFrame();