Android AudioTrack Mixing的示例代碼

Question

我在資源文件夾中有兩個PCM聲音文件。我使用inputstream並將它們轉換爲bytearray。

然後我通過規範化處理它們並添加music1和music2並輸出到字節數組輸出。最後，將輸出數組放入AudioTrack中。

顯然，我沒有聽到任何聲音，有什麼不對。

private void mixSound() throws IOException { 

    InputStream in1=getResources().openRawResource(R.raw.cheerapp2);  
    InputStream in2=getResources().openRawResource(R.raw.buzzer2); 

    byte[] music1 = null; 
    music1= new byte[in1.available()]; 
    music1=convertStreamToByteArray(in1); 
    in1.close(); 


    byte[] music2 = null; 
    music2= new byte[in2.available()]; 
    music2=convertStreamToByteArray(in2); 
    in2.close(); 

    byte[] output = new byte[music1.length]; 

    audioTrack.play(); 

    for(int i=0; i < output.length; i++){ 

     float samplef1 = music1[i]/128.0f;  //  2^7=128 
     float samplef2 = music2[i]/128.0f; 


     float mixed = samplef1 + samplef2; 
     // reduce the volume a bit: 
     mixed *= 0.8; 
     // hard clipping 
     if (mixed > 1.0f) mixed = 1.0f; 
     if (mixed < -1.0f) mixed = -1.0f; 
     byte outputSample = (byte)(mixed * 128.0f); 
     output[i] = outputSample; 
     audioTrack.write(output, 0, i); 
     } //for loop 


     public static byte[] convertStreamToByteArray(InputStream is) throws IOException { 



    ByteArrayOutputStream baos = new ByteArrayOutputStream(); 
    byte[] buff = new byte[10240]; 
    int i = Integer.MAX_VALUE; 
    while ((i = is.read(buff, 0, buff.length)) > 0) { 
     baos.write(buff, 0, i); 
    } 

    return baos.toByteArray(); // be sure to close InputStream in calling function 

} 

Answer 1

我試過你的代碼（代替我自己的一些音頻文件）。我初始化了一個像這樣的AudioTrack實例，希望這與你的做法類似：

AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, 44100, AudioFormat.CHANNEL_OUT_STEREO, AudioFormat.ENCODING_PCM_16BIT, 44100, AudioTrack.MODE_STREAM); 

並嘗試運行它。它發出了高調的噪音，隨着時間的推移而降低。我檢查了代碼，問題在於你正在將mixSound（）方法的每個循環迭代中的整個輸出字節數組寫入audioTrack。

行

audioTrack.write(output, 0, i); 

需求外循環，搬到改爲

audioTrack.write(output, 0, output.length); 

所以你這兩個文件一起拌勻成輸出字節數組，然後寫了整個事情一次。

所以對於工作mixSound方法的代碼如下所示：

private void mixSound() throws IOException { 
    AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, 44100, AudioFormat.CHANNEL_OUT_STEREO, AudioFormat.ENCODING_PCM_16BIT, 44100, AudioTrack.MODE_STREAM); 

    InputStream in1=getResources().openRawResource(R.raw.track1);  
    InputStream in2=getResources().openRawResource(R.raw.track2); 

    byte[] music1 = null; 
    music1= new byte[in1.available()]; 
    music1=convertStreamToByteArray(in1); 
    in1.close(); 


    byte[] music2 = null; 
    music2= new byte[in2.available()]; 
    music2=convertStreamToByteArray(in2); 
    in2.close(); 

    byte[] output = new byte[music1.length]; 

    audioTrack.play(); 

    for(int i=0; i < output.length; i++){ 

     float samplef1 = music1[i]/128.0f;  //  2^7=128 
     float samplef2 = music2[i]/128.0f; 


     float mixed = samplef1 + samplef2; 
     // reduce the volume a bit: 
     mixed *= 0.8; 
     // hard clipping 
     if (mixed > 1.0f) mixed = 1.0f; 

     if (mixed < -1.0f) mixed = -1.0f; 

     byte outputSample = (byte)(mixed * 128.0f); 
     output[i] = outputSample; 

    } //for loop 
    audioTrack.write(output, 0, output.length); 

}