From 0502eead9a85b477e0b569e12e9c44cd24ec88df Mon Sep 17 00:00:00 2001
From: Lars Brinkhoff <lars@nocrew.org>
Date: Thu, 2 Apr 2020 12:23:03 +0200
Subject: [PATCH] Support for playing music.

---
 emu/Makefile     |  4 +--
 emu/apr.c        |  1 +
 emu/main_panel.c |  2 ++
 emu/music.c      | 72 ++++++++++++++++++++++++++++++++++++++++++++++++
 emu/pdp6.h       |  3 ++
 5 files changed, 80 insertions(+), 2 deletions(-)
 create mode 100644 emu/music.c

diff --git a/emu/Makefile b/emu/Makefile
index 37b9d06..f91e745 100644
--- a/emu/Makefile
+++ b/emu/Makefile
@@ -12,8 +12,8 @@ LIBS=-lpthread -lm
 SDLLIBS=`sdl2-config --libs` `pkg-config SDL2_image --libs`
 
 
-pdp6: main_panel.c dis340.c chargen.inc joy.c $(SRC) $(H)
-	$(CC) -o $@ $(CFLAGS) $(SDLFLAGS) main_panel.c dis340.c joy.c $(SRC) $(LIBS) $(SDLLIBS)
+pdp6: main_panel.c dis340.c chargen.inc joy.c music.c $(SRC) $(H)
+	$(CC) -o $@ $(CFLAGS) $(SDLFLAGS) main_panel.c dis340.c joy.c music.c $(SRC) $(LIBS) $(SDLLIBS)
 pdp6_s: main_serial.c $(SRC) $(H)
 	$(CC) -o $@ $(CFLAGS) main_serial.c $(SRC) $(LIBS)
 
diff --git a/emu/apr.c b/emu/apr.c
index c0e191d..39617d2 100644
--- a/emu/apr.c
+++ b/emu/apr.c
@@ -3109,6 +3109,7 @@ defpulse(mi_fm_mb)
 {
 	// 7-7
 	apr->mi |= apr->c.mb;
+	music_sample(apr->mi);
 }
 
 defpulse(mi_clr)
diff --git a/emu/main_panel.c b/emu/main_panel.c
index 253feaa..9fe8b82 100644
--- a/emu/main_panel.c
+++ b/emu/main_panel.c
@@ -1259,6 +1259,8 @@ void main340(void);
 	if(apr == nil || tty == nil || ptr == nil || ptp == nil)
 		err("need APR, TTY, PTR and PTP");
 
+	music_init(apr);
+
 	while(awaitinit);
 
 	cmdchans[0] = chancreate(sizeof(char*), 1);
diff --git a/emu/music.c b/emu/music.c
new file mode 100644
index 0000000..c4a20ac
--- /dev/null
+++ b/emu/music.c
@@ -0,0 +1,72 @@
+#include "pdp6.h"
+#include <SDL2/SDL.h>
+
+/* Number of samples in audio buffer. */
+#define AUDIO_SAMPLES (4*4096)
+/* Number of samples in MI buffer. */
+#define MI_SAMPLES (100*1024)
+
+static Uint8 buffer[MI_SAMPLES];
+static Uint8 audio[2*AUDIO_SAMPLES];
+
+int samples = 0;
+int refill = 1;
+
+void music_sample(word mi)
+{
+	Uint8 x = 0;
+        int i;
+	if(samples == MI_SAMPLES)
+		return;
+        for(i = 0; i < 6; i++) {
+          if(mi & (1 << i))
+            x+= 40;
+        }
+        buffer[samples++] = x;
+
+        if(refill) {
+          int i, j;
+          fprintf (stderr, "[%d]", samples);
+          for(i = 0; i < 2*AUDIO_SAMPLES; i++) {
+            j = (int)((float)i * (float)MI_SAMPLES / (float)(2*AUDIO_SAMPLES) + .5);
+            audio[i] = buffer[j];
+          }
+          samples = 0;
+          refill = 0;
+        }
+}
+
+static void callback(void *data, Uint8 *stream, int len)
+{
+	if (refill)
+		memset(stream, 0, len);
+	else
+		memcpy(stream, audio, len);
+	refill = 1;
+}
+
+void music_init(Apr *apr)
+{
+	SDL_AudioSpec want, have;
+	SDL_AudioDeviceID dev;
+
+	SDL_memset(&want, 0, sizeof want);
+	want.freq = 48000;
+	want.format = AUDIO_U8;
+	want.channels = 1;
+	want.samples = AUDIO_SAMPLES;
+	want.callback = callback;
+	want.userdata = apr;
+
+	dev = SDL_OpenAudioDevice(NULL, 0, &want, &have, SDL_AUDIO_ALLOW_FORMAT_CHANGE);
+	if (dev == 0)
+		SDL_Log("Failed to open audio: %s", SDL_GetError());
+	else {
+		if (have.format != want.format)
+			SDL_Log("We didn't get Float32 audio format.");
+                fprintf(stderr, "Frequency: %d\n", have.freq);
+                fprintf(stderr, "Channels: %d\n", have.channels);
+                fprintf(stderr, "Samples: %d\n", have.samples);
+		SDL_PauseAudioDevice(dev, 0);
+	}
+}
diff --git a/emu/pdp6.h b/emu/pdp6.h
index 0a42210..6891710 100644
--- a/emu/pdp6.h
+++ b/emu/pdp6.h
@@ -704,3 +704,6 @@ Device *makenetcons(int argc, char *argv[]);
 
 void writeconsreg(Apr *apr, u32 addr, u32 data);
 u32 readconsreg(Apr *apr, u32 addr);
+
+void music_init(Apr *apr);
+void music_sample(word mi);