Using AudioTrack in Android to play a WAV file

I'm working with Android, trying to make my AudioTrack application play a Windows .开发者_运维问答wav file (Tada.wav). Frankly, it shouldn't be this hard, but I'm hearing a lot of strange stuff. The file is saved on my phone's mini SD card and reading the contents doesn't seem to be a problem, but when I play the file (with parameters I'm only PRETTY SURE are right), I get a few seconds of white noise before the sound seems to resolve itself into something that just may be right.

I have successfully recorded and played my own voice back on the phone -- I created a .pcm file according to the directions in this example:

http://emeadev.blogspot.com/2009/09/raw-audio-manipulation-in-android.html

(without the backwards masking)...

Anybody got some suggestions or awareness of an example on the web for playing a .wav file on an Android??

Thanks, R.

---

I stumbled on the answer (frankly, by trying &^@! I didn't think would work), in case anybody's interested... In my original code (which is derived from the example in the link in the original post), the data is read from the file like so:

    InputStream             is  = new FileInputStream       (file);
    BufferedInputStream     bis = new BufferedInputStream   (is, 8000);
    DataInputStream         dis = new DataInputStream       (bis);      //  Create a DataInputStream to read the audio data from the saved file

    int i = 0;                                                          //  Read the file into the "music" array
    while (dis.available() > 0)
    {
        music[i] = dis.readShort();                                     //  This assignment does not reverse the order
        i++;
    }

    dis.close();                                                        //  Close the input stream

In this version, music[] is array of SHORTS. So, the readShort() method would seem to make sense here, since the data is 16-bit PCM... However, on the Android that seems to be the problem. I changed that code to the following:

     music=new byte[(int) file.length()];//size & length of the file
    InputStream             is  = new FileInputStream       (file);
    BufferedInputStream     bis = new BufferedInputStream   (is, 8000);
    DataInputStream         dis = new DataInputStream       (bis);      //  Create a DataInputStream to read the audio data from the saved file

    int i = 0;                                                          //  Read the file into the "music" array
    while (dis.available() > 0)
    {
        music[i] = dis.readByte();                                      //  This assignment does not reverse the order
        i++;
    }

    dis.close();                                                        //  Close the input stream

In this version, music[] is an array of BYTES. I'm still telling the AudioTrack that it's 16-bit PCM data, and my Android doesn't seem to have a problem with writing an array of bytes into an AudioTrack thus configured... Anyway, it finally sounds right, so if anyone else wants to play Windows sounds on their Android, for some reason, that's the solution. Ah, Endianness......

R.

---

I found a lot of long answers to this question. My final solution, which given all the cutting and pasting is hardly mine, comes down to:

public boolean play() {

    int i = 0;
    byte[] music = null;
    InputStream is = mContext.getResources().openRawResource(R.raw.noise);

    at = new AudioTrack(AudioManager.STREAM_MUSIC, 44100,
        AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT,
        minBufferSize, AudioTrack.MODE_STREAM);

    try{
        music = new byte[512];
        at.play();

        while((i = is.read(music)) != -1)
            at.write(music, 0, i);

    } catch (IOException e) {
        e.printStackTrace();
    }

    at.stop();
    at.release();
    return STOPPED;
}

STOPPED is just a "true" sent back as a signal to reset the pause/play button. And in the class initializer:

public Mp3Track(Context context) {
    mContext = context;
    minBufferSize = AudioTrack.getMinBufferSize(44100,
        AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT);
}

Context is just "this" from the calling activity. You can use a FileInputStream on the sdcard, etc. My files are in res/raw

---

Are you skipping the first 44 bytes of the file before you dump the rest of the file's data into the buffer? The first 44 bytes are the WAVE header and they would sound like random noise if you tried to play them.

Also, are you sure you are creating the AudioTrack with the same properties as the WAVE you are trying to play (sample rate, bit rate, number of channels, etc)? Windows actually does a good job of giving this information to you in the File Properties page:

---

As said by Aaron C, you have to skip initial 44 bytes or (as I prefer) read first 44 bytes that are the WAVE header. In this way you know how many channels, bits per sample, length, etc... the WAVE contains.

Here you can find a good implementation of a WAVE header parser/writer.

---

Please don't perpetuate terrible parsing code. WAV parsing is trivial to implement http://soundfile.sapp.org/doc/WaveFormat/ and you will thank yourself by being able to parse things such as the sampling rate, bit depth, and number of channels.

Also x86 and ARM (at least by default) are both little endian , so native-endian WAV files should be fine without any shuffling.

---

Just confirm if you have AudioTrack.MODE_STREAM and not AudioTrack.MODE_STATIC in the AudioTrack constructor:

AudioTrack at = new AudioTrack(
  AudioManager.STREAM_MUSIC,
  sampleRate,
  AudioFormat.CHANNEL_IN_STEREO,
  AudioFormat.ENCODING_PCM_16BIT,
  // buffer length in bytes
  outputBufferSize,
  AudioTrack.MODE_STREAM
);

---

Sample wav file:
http://www.mauvecloud.net/sounds/pcm1644m.wav

Sample Code:

public class AudioTrackPlayer {
    Context mContext;
    int minBufferSize;
    AudioTrack at;
    boolean STOPPED;

    public AudioTrackPlayer(Context context) {
        Log.d("------","init");
        mContext = context;
        minBufferSize = AudioTrack.getMinBufferSize(44100,
                AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT);
    }

    public boolean play() {
        Log.d("------","play");
        int i = 0;
        byte[] music = null;
        InputStream is = mContext.getResources().openRawResource(R.raw.pcm1644m);

        at = new AudioTrack(AudioManager.STREAM_MUSIC, 44100,
                AudioFormat.CHANNEL_CONFIGURATION_MONO, AudioFormat.ENCODING_PCM_16BIT,
                minBufferSize, AudioTrack.MODE_STREAM);
        try {
            music = new byte[512];
            at.play();

            while ((i = is.read(music)) != -1)
                at.write(music, 0, i);

        } catch (IOException e) {
            e.printStackTrace();
        }
        at.stop();
        at.release();
        return STOPPED;
    }
}