Add tremolo effect

index.html

@@ -72,8 +72,7 @@
 code: <a href="http://github.com/a1k0n/jsxm/">github.com/a1k0n/jsxm</a>
 todo:
  - missing XM effects:
-   - E3x, E6x, E7x, E9x, EDx, EEx
-   - 7xy - tremolo
+   - E3x, E6x, E9x, EDx, EEx
    - Kxx, Lxx, Pxy, Txy
  - render pattern with the wider fonts for fewer channels
  - fix occasional rendering/audio hiccups when switching songs

test/effects.js

@@ -505,6 +505,29 @@ exports['test E5x finetune override'] = function(assert) {
   assert.equal(f2.toFixed(2), "131.00", "E5f finetune +127");
 };
 
+exports['test E7x set tremolo waveform'] = function(assert) {
+  var xm = testdata.resetXMData();
+  xm.patterns = [
+    [
+      [[48, 1, -1,  0, 0x00]], // C-4  1 -- ---  (default waveform - sine)
+      [[48, 1, -1, 14, 0x71]], // C-4  1 -- E71  (saw, ramp-down)
+      [[48, 1, -1, 14, 0x72]], // C-4  1 -- E72  (square)
+      [[48, 1, -1, 14, 0x73]]  // C-4  1 -- E73  (random)
+    ]
+  ];
+  xm.tempo = 1;
+  var ch = xm.channelinfo[0];
+  XMPlayer.nextTick();
+  assert.equal(ch.tremolotype, 0, 'row 0 tick 0 tremolotype=0');
+  XMPlayer.nextTick();
+  assert.equal(ch.tremolotype, 1, 'row 1 tick 0 tremolotype=1');
+  XMPlayer.nextTick();
+  assert.equal(ch.tremolotype, 2, 'row 2 tick 0 tremolotype=2');
+  XMPlayer.nextTick();
+  assert.equal(ch.tremolotype, 3, 'row 3 tick 0 tremolotype=3');
+};
+
+
 exports['test E60 loop twice with set beginning'] = function(assert) {
   var xm = testdata.resetXMData(2);
 

test/testdata.js

@@ -28,6 +28,7 @@ exports.resetXMData = function(channels) {
       vibratodepth: 1,
       vibratospeed: 1,
       vibratotype: 0,
+      tremolotype: 0,
     });
   }
   xm.songpats = [0];

xm.js

@@ -335,6 +335,7 @@ function nextTick() {
   for (j = 0; j < player.xm.nchan; j++) {
     ch = player.xm.channelinfo[j];
     ch.periodoffset = 0;
+    ch.voloffset = 0;
   }
   if (player.cur_tick >= player.xm.tempo) {
     player.cur_tick = 0;
@@ -414,8 +415,8 @@ function MixChannelIntoBuf(ch, start, end, dataL, dataR) {
   var volE = ch.volE / 64.0;    // current volume envelope
   var panE = 4*(ch.panE - 32);  // current panning envelope
   var p = panE + ch.pan - 128;  // final pan
-  var volL = player.xm.global_volume * volE * (128 - p) * ch.vol / (64 * 128 * 128);
-  var volR = player.xm.global_volume * volE * (128 + p) * ch.vol / (64 * 128 * 128);
+  var volL = player.xm.global_volume * volE * (128 - p) * (ch.vol + ch.voloffset) / (64 * 128 * 128);
+  var volR = player.xm.global_volume * volE * (128 + p) * (ch.vol + ch.voloffset) / (64 * 128 * 128);
   if (volL < 0) volL = 0;
   if (volR < 0) volR = 0;
   if (volR === 0 && volL === 0)
@@ -710,6 +711,10 @@ function load(arrayBuf) {
       vibratodepth: 1,
       vibratospeed: 1,
       vibratotype: 0,
+      tremolopos: 0,
+      tremolodepth: 1,
+      tremolospeed: 1,
+      tremolotype: 0,
     });
   }
   console.log("header len " + hlen);

xmeffects.js

@@ -106,6 +106,50 @@ function eff_t1_6(ch) {  // vibrato + volume slide
   eff_t1_4(ch);
 }
 
+function eff_t0_7(ch, data) {  // tremolo
+  if (data & 0x0f) {
+    ch.tremolodepth = (data & 0x0f) * 2;
+  }
+  if (data >> 4) {
+    ch.tremolospeed = data >> 4;
+  }
+  eff_t1_7(ch);
+}
+
+function eff_t1_7(ch) {  // tremolo
+  ch.voloffset =
+    getTremoloDelta(ch.tremolotype, ch.tremolopos) * ch.tremolodepth;
+  if (isNaN(ch.voloffset)) {
+    console.log("tremolo voloffset NaN?",
+        ch.tremolopos, ch.tremolospeed, ch.tremolodepth);
+    ch.voloffset = 0;
+  }
+  // only updates on non-first ticks
+  if (player.cur_tick > 0) {
+    ch.tremolopos += ch.tremolospeed;
+    ch.tremolopos &= 63;
+  }
+}
+
+function getTremoloDelta(type, x) {
+  var delta = 0;
+  switch (type & 0x03) {
+    case 1: // sawtooth (ramp-down)
+      delta = ((1 + x * 2 / 64) % 2) - 1;
+      break;
+    case 2: // square
+    case 3: // random (in FT2 these two are the same)
+      delta = x < 32 ? 1 : -1;
+      break;
+    case 0:
+    default: // sine
+      delta = Math.sin(x * Math.PI / 32);
+      break;
+  }
+  return delta;
+}
+
+
 function eff_t0_8(ch, data) {  // set panning
   ch.pan = data;
 }
@@ -179,6 +223,9 @@ function eff_t0_e(ch, data) {  // extended effects!
         }
       }
       break;
+    case 7:  // set tremolo waveform
+      ch.tremolotype = data & 0x07;
+      break;
     case 8:  // panning
       ch.pan = data * 0x11;
       break;
@@ -290,7 +337,7 @@ player.effects_t0 = [  // effect functions on tick 0
   eff_t0_4,  // 4
   eff_t0_a,  // 5, same as A on first tick
   eff_t0_a,  // 6, same as A on first tick
-  eff_unimplemented_t0,  // 7
+  eff_t0_7,  // 7
   eff_t0_8,  // 8
   eff_t0_9,  // 9
   eff_t0_a,  // a
@@ -329,7 +376,7 @@ player.effects_t1 = [  // effect functions on tick 1+
   eff_t1_4,
   eff_t1_5,  // 5
   eff_t1_6,  // 6
-  eff_unimplemented,  // 7
+  eff_t1_7,  // 7
   null,   // 8
   null,   // 9
   eff_t1_a,  // a