add symmetric option (#10)

mohayonao · Aug 11, 2017 · e3f63d1 · e3f63d1
1 parent 5a30197
commit e3f63d1
Show file tree

Hide file tree

Showing 2 changed files with 77 additions and 12 deletions.
diff --git a/index.js b/index.js
@@ -26,7 +26,7 @@ function encodeSync(audioData, opts) {
 
   writeHeader(writer, format, dataView.buffer.byteLength - 8);
 
-  var err = writeData(writer, format, length, audioData);
+  var err = writeData(writer, format, length, audioData, opts);
 
   if (err instanceof Error) {
     throw err;
@@ -79,10 +79,10 @@ function writeHeader(writer, format, length) {
   writer.uint16(format.bitDepth);
 }
 
-function writeData(writer, format, length, audioData) {
+function writeData(writer, format, length, audioData, opts) {
   var bitDepth = format.bitDepth;
-  var floatingPoint = format.floatingPoint ? "f" : "";
-  var methodName = "pcm" + bitDepth + floatingPoint;
+  var encoderOption = format.floatingPoint ? "f" : opts.symmetric ? "s" : "";
+  var methodName = "pcm" + bitDepth + encoderOption;
 
   if (!writer[methodName]) {
     return new TypeError("Not supported bit depth: " + bitDepth);
@@ -130,13 +130,25 @@ function createWriter(dataView) {
       dataView.setUint8(pos, value, true);
       pos += 1;
     },
+    pcm8s: function(value) {
+      value = Math.round(value * 128) + 128;
+      value = Math.max(0, Math.min(value, 255));
+      dataView.setUint8(pos, value, true);
+      pos += 1;
+    },
     pcm16: function(value) {
       value = Math.max(-1, Math.min(value, +1));
       value = value < 0 ? value * 32768 : value * 32767;
       value = Math.round(value)|0;
       dataView.setInt16(pos, value, true);
       pos += 2;
     },
+    pcm16s: function(value) {
+      value = Math.round(value * 32768);
+      value = Math.max(-32768, Math.min(value, 32767));
+      dataView.setInt16(pos, value, true);
+      pos += 2;
+    },
     pcm24: function(value) {
       value = Math.max(-1, Math.min(value, +1));
       value = value < 0 ? 0x1000000 + value * 8388608 : value * 8388607;
@@ -151,13 +163,32 @@ function createWriter(dataView) {
       dataView.setUint8(pos + 2, x2);
       pos += 3;
     },
+    pcm24s: function(value) {
+      value = Math.round(value * 8388608);
+      value = Math.max(-8388608, Math.min(value, 8388607));
+
+      var x0 = (value >>  0) & 0xFF;
+      var x1 = (value >>  8) & 0xFF;
+      var x2 = (value >> 16) & 0xFF;
+
+      dataView.setUint8(pos + 0, x0);
+      dataView.setUint8(pos + 1, x1);
+      dataView.setUint8(pos + 2, x2);
+      pos += 3;
+    },
     pcm32: function(value) {
       value = Math.max(-1, Math.min(value, +1));
       value = value < 0 ? value * 2147483648 : value * 2147483647;
       value = Math.round(value)|0;
       dataView.setInt32(pos, value, true);
       pos += 4;
     },
+    pcm32s: function(value) {
+      value = Math.round(value * 2147483648);
+      value = Math.max(-2147483648, Math.min(value, +2147483647));
+      dataView.setInt32(pos, value, true);
+      pos += 4;
+    },
     pcm32f: function(value) {
       dataView.setFloat32(pos, value, true);
       pos += 4;

diff --git a/test/encoding.js b/test/encoding.js
@@ -2,14 +2,48 @@ const assert = require("assert");
 const encoder = require("..");
 
 const testSpec = [
-  { opts: { bitDepth:  8 }, TypedArray: Uint8Array,
-    data: [ -1, -0.5, 0, 0.5, 1 ], expected: [ 0, 64, 128, 191, 255 ] },
-  { opts: { bitDepth: 16 }, TypedArray: Int16Array,
-    data: [ -1, -0.5, 0, 0.5, 1 ], expected: [ -32768, -16384, 0, 16384, 32767 ] },
-  { opts: { bitDepth: 32 }, TypedArray: Int32Array,
-    data: [ -1, -0.5, 0, 0.5, 1 ], expected: [ -2147483648, -1073741824, 0, 1073741824, 2147483647 ] },
-  { opts: { bitDepth: 32, float: true }, TypedArray: Float32Array,
-    data: [ -1, -0.5, 0, 0.5, 1 ], expected: [ -1, -0.5, 0, 0.5, 1 ] },
+  {
+    opts: { bitDepth: 8 },
+    TypedArray: Uint8Array,
+    data: [ -1, -0.75, -0.5, 0, 0.5, 0.75, 1 ],
+    expected: [ 0, 32, 64, 128, 191, 223, 255 ],
+  },
+  {
+    opts: { bitDepth: 8, symmetric: true },
+    TypedArray: Uint8Array,
+    data: [ -1, -0.75, -0.5, 0, 0.5, 0.75, 1 ],
+    expected: [ 0, 32, 64, 128, 192, 224, 255 ],
+  },
+  {
+    opts: { bitDepth: 16 },
+    TypedArray: Int16Array,
+    data: [ -1, -0.75, -0.5, 0, 0.5, 0.75, 1 ],
+    expected: [ -32768, -24576 , -16384, 0, 16384, 24575, 32767 ],
+  },
+  {
+    opts: { bitDepth: 16, symmetric: true },
+    TypedArray: Int16Array,
+    data: [ -1, -0.75, -0.5, 0, 0.5, 0.75, 1 ],
+    expected: [ -32768, -24576, -16384, 0, 16384, 24576, 32767 ],
+  },
+  {
+    opts: { bitDepth: 32 },
+    TypedArray: Int32Array,
+    data: [ -1, -0.75, -0.5, 0, 0.5, 0.75, 1 ],
+    expected: [ -2147483648, -1610612736, -1073741824, 0, 1073741824, 1610612735, 2147483647 ],
+  },
+  {
+    opts: { bitDepth: 32, symmetric: true },
+    TypedArray: Int32Array,
+    data: [ -1, -0.75, -0.5, 0, 0.5, 0.75, 1 ],
+    expected: [ -2147483648, -1610612736, -1073741824, 0, 1073741824, 1610612736, 2147483647 ],
+  },
+  {
+    opts: { bitDepth: 32, float: true },
+    TypedArray: Float32Array,
+    data: [ -1, -0.5, 0, 0.5, 1 ],
+    expected: [ -1, -0.5, 0, 0.5, 1 ],
+  },
 ];
 
 describe("encoding", () => {