通过ByteArray来播放MP3

在Actionscript3中，由于没有Sound.loadBytes()方法，所以无法通过ByteArray来直接播放MP3。SWF和图片文件（JPEG，GIF和PNG）可以通过Loader.loadBytes加载，并不需要太多的操作就可以使用,而原始的声音数据可以通过Sound对象的SampleDataEvent来播放。现在事情有点棘手，如果你的MP3数据在ByteArray中，如何播放它呢。as3swf库可以帮助你解决这个问题。
我们要做以下几步：
  1.创建一个嵌入了MP3的SWF。
  2.通过LoaderoadBytes导入SWF。
  3.实例化绑定的类。
显然，最麻烦的差事是创建嵌入了MP3的SWF。刚开始，我们要创建一个嵌入了虚拟MP3的虚拟SWF，来看看里面有什么，然后再动态创建这个结构。（We’ll just start by creating a dummy SWF using a dummy MP3 to see how it has to look like, in order to recreate the structure dynamically later.）

1. package
   
2. {
   
3.    import flash.display.Sprite;
   
4. 
   
5.    public class MP3Wrapper extends Sprite
   
6.    {
   
7.       [Embed(source="test.mp3")]
   
8.       public var soundClass:Class;
   
9.    }
   
10. }

复制代码

这段代码我们只是嵌入进来了MP3，并且把它绑定到一个叫Sound类上。当我们把这个SWF导入到主SWF上的时候，我们可以声明这个类的实例，然后我们得到了一个包含该MP3的声音对象，这时就可以播放它了。
上面的代码就像这样创建SWF的：

1. [69:FileAttributes] AS3: true, HasMetadata: false, UseDirectBlit: false, UseGPU: false, UseNetwork: false
   
2. [09:SetBackgroundColor] Color: ffffffff
   
3. [86:DefineSceneAndFrameLabelData]
   
4.    Scenes:
   
5.       [0] Offset: 0, Name: Scene 1
   
6. [14:DefineSound] SoundID: 1, Format: 2, Rate: 44kHz, Size: 16bit, Type: stereo, Samples: 6867072
   
7. [82:DoABC] Lazy: true, Length: 767
   
8. [76:SymbolClass]
   
9.    Symbols:
   
10.       [0] TagID: 1, Name: MP3Wrapper_soundClass
    
11.       [1] TagID: 0, Name: MP3Wrapper
    
12. [01:ShowFrame]
    
13. [00:End]

复制代码

这里面有三个有用的标签：
1.DefineSound：包含了嵌入的MP3.我们所用的MP3是44kHz，16bit,立体声，包含了6867072声音采样。它属于SWF的内部资源，ID为1.
2.DoABC：包含所有的Actionscript字节，这里是文档类和定义的声音类。
3.SymbolClass：把Actionscript类文件绑定到库资源上，在我们的例子里，文档类是MP3Wrapper，这里

最重要的，是被绑定到库资源里的ID为1的MP3Wrapper_soundClass类。

我们刚刚重用了包括DoABC和SymboClass的所有标签，留下了DefineSound标签，需要我们去动态创建。DefineSound包括了原始的声音数据（这里是MP3），这里面包含了一些标签，它们告诉Flash Player数据的规格数等，比如声音采样的数量、采样率、采样大小、是单声道还是立体声播放，还有库ID等（通常是1，因为我们只有一个库资源）

TagDefineSound的有一个非常方便的工厂方法，用来从MP3创建自己，这个方法叫做createWithMP3。这个方法自动去扫描MP3，来确定MP3里包含的采样数量，还有采样率等：

1. var defineSound:TagDefineSound = TagDefineSound.createWithMP3(1, mp3);

复制代码

这里代码展示了在运行时创建包含MP3文件的SWF，并开始播放它:

1. package
   
2. {
   
3. import flash.display.Loader;
   
4. import flash.display.LoaderInfo;
   
5. import flash.display.Sprite;
   
6. import flash.events.Event;
   
7. import flash.media.Sound;
   
8. import flash.net.URLLoader;
   
9. import flash.net.URLLoaderDataFormat;
   
10. import flash.net.URLRequest;
    
11. import flash.utils.ByteArray;
    
12. 
    
13. import com.codeazur.as3swf.SWF;
    
14. import com.codeazur.as3swf.SWFData;
    
15. import com.codeazur.as3swf.data.SWFScene;
    
16. import com.codeazur.as3swf.data.SWFSymbol;
    
17. import com.codeazur.as3swf.data.consts.SoundCompression;
    
18. import com.codeazur.as3swf.data.consts.SoundRate;
    
19. import com.codeazur.as3swf.data.consts.SoundSize;
    
20. import com.codeazur.as3swf.data.consts.SoundType;
    
21. import com.codeazur.as3swf.tags.TagDefineSceneAndFrameLabelData;
    
22. import com.codeazur.as3swf.tags.TagDefineSound;
    
23. import com.codeazur.as3swf.tags.TagDoABC;
    
24. import com.codeazur.as3swf.tags.TagEnd;
    
25. import com.codeazur.as3swf.tags.TagFileAttributes;
    
26. import com.codeazur.as3swf.tags.TagSetBackgroundColor;
    
27. import com.codeazur.as3swf.tags.TagShowFrame;
    
28. import com.codeazur.as3swf.tags.TagSymbolClass;
    
29. 
    
30. public class MP3Player extends Sprite
    
31. {
    
32. public function MP3Player()
    
33. {
    
34. // Load the mp3 into a ByteArray
    
35. var request:URLRequest = new URLRequest("test.mp3");
    
36. var loader:URLLoader = new URLLoader();
    
37. loader.dataFormat = URLLoaderDataFormat.BINARY;
    
38. loader.addEventListener(Event.COMPLETE, completeHandler);
    
39. loader.load(request);
    
40. }
    
41. 
    
42. protected function completeHandler(e:Event):void {
    
43. var mp3:ByteArray = URLLoader(e.target).data as ByteArray;
    
44. // Wrap the MP3 with a SWF
    
45. var swf:ByteArray = createSWFFromMP3(mp3);
    
46. // Load the SWF with Loader::loadBytes()
    
47. var loader:Loader = new Loader();
    
48. loader.contentLoaderInfo.addEventListener(Event.INIT, initHandler);
    
49. loader.loadBytes(swf);
    
50. }
    
51. 
    
52. protected function initHandler(e:Event):void {
    
53. // Get the sound class definition
    
54. var SoundClass:Class = LoaderInfo(e.currentTarget).applicationDomain.getDefinition("MP3Wrapper_soundClass") as Class;
    
55. // Instantiate the sound class
    
56. var sound:Sound = new SoundClass() as Sound;
    
57. // Play the sound
    
58. sound.play();
    
59. }
    
60. 
    
61. protected function createSWFFromMP3(mp3:ByteArray):ByteArray
    
62. {
    
63. // Create an empty SWF
    
64. // Defaults to v10, 550x400px, 50fps, one frame (works fine for us)
    
65. var swf:SWF = new SWF();
    
66. 
    
67. // Add FileAttributes tag
    
68. // Defaults: as3 true, all other flags false (works fine for us)
    
69. swf.tags.push(new TagFileAttributes());
    
70. 
    
71. // Add SetBackgroundColor tag
    
72. // Default: white background (works fine for us)
    
73. swf.tags.push(new TagSetBackgroundColor());
    
74. 
    
75. // Add DefineSceneAndFrameLabelData tag
    
76. // (with the only entry being "Scene 1" at offset 0)
    
77. var defineSceneAndFrameLabelData:TagDefineSceneAndFrameLabelData = new TagDefineSceneAndFrameLabelData();
    
78. defineSceneAndFrameLabelData.scenes.push(new SWFScene(0, "Scene 1"));
    
79. swf.tags.push(defineSceneAndFrameLabelData);
    
80. 
    
81. // Add DefineSound tag
    
82. // The ID is 1, all other parameters are automatically
    
83. // determined from the mp3 itself.
    
84. swf.tags.push(TagDefineSound.createWithMP3(1, mp3));
    
85. 
    
86. // Add DoABC tag
    
87. // Contains the AS3 byte code for the document class and the
    
88. // class definition for the embedded sound
    
89. swf.tags.push(TagDoABC.create(abc));
    
90. 
    
91. // Add SymbolClass tag
    
92. // Specifies the document class and binds the sound class
    
93. // definition to the embedded sound
    
94. var symbolClass:TagSymbolClass = new TagSymbolClass();
    
95. symbolClass.symbols.push(SWFSymbol.create(1, "MP3Wrapper_soundClass"));
    
96. symbolClass.symbols.push(SWFSymbol.create(0, "MP3Wrapper"));
    
97. swf.tags.push(symbolClass);
    
98. 
    
99. // Add ShowFrame tag
    
100. swf.tags.push(new TagShowFrame());
     
101. 
     
102. // Add End tag
     
103. swf.tags.push(new TagEnd());
     
104. 
     
105. // Publish the SWF
     
106. var swfData:SWFData = new SWFData();
     
107. swf.publish(swfData);
     
108. 
     
109. return swfData;
     
110. }
     
111. 
     
112. private static var abcData:Array = [
     
113. 0x10, 0x00, 0x2e, 0x00, 0x00, 0x00, 0x00, 0x19, 0x07, 0x6d, 0x78, 0x2e, 0x63, 0x6f, 0x72, 0x65,
     
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142. 0x04, 0x05, 0x00, 0x05, 0x02, 0x09, 0x05, 0x00, 0x08, 0x00, 0x06, 0x07, 0x09, 0x07, 0x00, 0x0b,
     
143. 0x01, 0x08, 0x00, 0x00, 0x09, 0x00, 0x01, 0x00, 0x04, 0x01, 0x0a, 0x06, 0x01, 0x0b, 0x11, 0x01,
     
144. 0x07, 0x00, 0x0a, 0x00, 0x05, 0x00, 0x01, 0x0c, 0x06, 0x00, 0x00, 0x08, 0x08, 0x03, 0x01, 0x01,
     
145. 0x04, 0x00, 0x00, 0x06, 0x01, 0x02, 0x04, 0x00, 0x01, 0x09, 0x01, 0x05, 0x04, 0x00, 0x02, 0x0c,
     
146. 0x01, 0x06, 0x04, 0x01, 0x03, 0x0c, 0x00, 0x01, 0x01, 0x01, 0x02, 0x03, 0xd0, 0x30, 0x47, 0x00,
     
147. 0x00, 0x01, 0x00, 0x01, 0x03, 0x03, 0x01, 0x47, 0x00, 0x00, 0x03, 0x02, 0x01, 0x01, 0x02, 0x0a,
     
148. 0xd0, 0x30, 0x5d, 0x04, 0x20, 0x58, 0x00, 0x68, 0x01, 0x47, 0x00, 0x00, 0x04, 0x02, 0x01, 0x05,
     
149. 0x06, 0x09, 0xd0, 0x30, 0x5e, 0x0a, 0x2c, 0x11, 0x68, 0x0a, 0x47, 0x00, 0x00, 0x05, 0x01, 0x01,
     
150. 0x06, 0x07, 0x06, 0xd0, 0x30, 0xd0, 0x49, 0x00, 0x47, 0x00, 0x00, 0x06, 0x02, 0x01, 0x01, 0x05,
     
151. 0x17, 0xd0, 0x30, 0x5d, 0x0d, 0x60, 0x0e, 0x30, 0x60, 0x0f, 0x30, 0x60, 0x03, 0x30, 0x60, 0x03,
     
152. 0x58, 0x01, 0x1d, 0x1d, 0x1d, 0x68, 0x02, 0x47, 0x00, 0x00, 0x07, 0x01, 0x01, 0x06, 0x07, 0x03,
     
153. 0xd0, 0x30, 0x47, 0x00, 0x00, 0x08, 0x01, 0x01, 0x07, 0x08, 0x06, 0xd0, 0x30, 0xd0, 0x49, 0x00,
     
154. 0x47, 0x00, 0x00, 0x09, 0x02, 0x01, 0x01, 0x06, 0x1b, 0xd0, 0x30, 0x5d, 0x10, 0x60, 0x0e, 0x30,
     
155. 0x60, 0x0f, 0x30, 0x60, 0x03, 0x30, 0x60, 0x02, 0x30, 0x60, 0x02, 0x58, 0x02, 0x1d, 0x1d, 0x1d,
     
156. 0x1d, 0x68, 0x05, 0x47, 0x00, 0x00, 0x0a, 0x01, 0x01, 0x08, 0x09, 0x03, 0xd0, 0x30, 0x47, 0x00,
     
157. 0x00, 0x0b, 0x02, 0x01, 0x09, 0x0a, 0x0b, 0xd0, 0x30, 0xd0, 0x60, 0x05, 0x68, 0x08, 0xd0, 0x49,
     
158. 0x00, 0x47, 0x00, 0x00, 0x0c, 0x02, 0x01, 0x01, 0x08, 0x23, 0xd0, 0x30, 0x65, 0x00, 0x60, 0x0e,
     
159. 0x30, 0x60, 0x0f, 0x30, 0x60, 0x11, 0x30, 0x60, 0x12, 0x30, 0x60, 0x13, 0x30, 0x60, 0x07, 0x30,
     
160. 0x60, 0x07, 0x58, 0x03, 0x1d, 0x1d, 0x1d, 0x1d, 0x1d, 0x1d, 0x68, 0x06, 0x47, 0x00, 0x00
     
161. ];
     
162. 
     
163. private static function abcDataToByteArray():ByteArray {
     
164. var ba:ByteArray = new ByteArray();
     
165. for (var i:uint = 0; i < abcData.length; i++) {
     
166. ba.writeByte(abcData[i]);
     
167. }
     
168. return ba;
     
169. }
     
170. 
     
171. private static var abc:ByteArray = abcDataToByteArray();
     
172. }
     
173. }