Overlap two audio files - performance

Question

Please someone tell me how to overlap two Audio files and generate single audio file from them. I am trying the following code but I am unable to open saved file.
package com.example.audiomix;
import java.io.ByteArrayOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStream;
import android.app.Activity;
import android.media.AudioFormat;
import android.media.AudioManager;
import android.media.AudioTrack;
import android.net.Uri;
import android.os.Bundle;
import android.os.Environment;
public class MainActivity extends Activity {
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
// MediaPlayer mediaPlayer=MediaPlayer.create(getApplicationContext(),getAssets()+"")
try {
mixSound();
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
private void mixSound() {
try {
AudioTrack audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, 44100, AudioFormat.CHANNEL_OUT_STEREO, AudioFormat.ENCODING_PCM_16BIT, 44100, AudioTrack.MODE_STREAM);
// Uri url = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.one);
// System.out.println("MainActivity.mixSound() url1"+url.toString());
// File file = new File(url.toString());
// Uri url2 = Uri.parse("android.resource://" + getPackageName() + "/" + R.raw.two);
// System.out.println("MainActivity.mixSound() url1"+url2.toString());
// File file2 = new File(url2.toString());
// InputStream in1=new FileInputStream(file);
// InputStream in2=new FileInputStream(file2);
// int rid = getResources().getIdentifier(getPackageName() + ":raw/one.mp3" , null, null);
// //get the file as a stream
// InputStream in1 = getResources().openRawResource(rid);
//// InputStream in1=new FileInputStream("");
//
// int rid2 = getResources().getIdentifier(getPackageName() + ":raw/two.mp3" , null, null);
// //get the file as a stream
// InputStream in2 = getResources().openRawResource(rid2);
//
//// InputStream in2=new FileInputStream(getResources().openRawResource(R.raw.one).toString());
InputStream in1 = getApplicationContext().getResources().openRawResource(R.raw.media);
InputStream in2 = getApplicationContext().getResources().openRawResource(R.raw.media1);
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[music2.length];
audioTrack.play();
int j=0;
for(int i=0; i < output.length-1; i++){
float mixed;
if(j<music1.length-1){
float samplef1 = music1[j] / 128.0f; // 2^7=128
float samplef2 = music2[i] / 128.0f;
mixed = samplef1 + samplef2;
j++;
}else{
float samplef2 = music2[i] / 128.0f;
mixed = samplef2;
}
float samplef1 = music1[j] / 128.0f; // 2^7=128
float samplef2 = music2[i] / 128.0f;
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);
//convert array of bytes into file
FileOutputStream fileOuputStream =
new FileOutputStream(Environment.getExternalStorageDirectory()+"/abc.wav");
fileOuputStream.write(output);
fileOuputStream.close();
System.out.println("MainActivity.mixSound()==>Done");
System.out.println("Done");
}catch(Exception e){
// e.printStackTrace();
System.out.println("MainActivity.mixSound()==>"+e);
}
}
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
}
}
I have tried to first convert audio file into byte array. Then I am saving it on SD card.
The generated file is saved but when I try to play the saved file it is not playing.

Answer 1

That's because both byte arrays have raw audio bytes and headers, so when you mix them you should get one crappy audio file. But you don't. That means that files you are mixing aren't ones with same properties in other words their formats are different.