Android AudioTrack does not play all samples

Question

I'm using AudioTrack to play a sequence of sine waves, but when I run it on my HTC M9, it plays only part of the samples, and how long it will play is random. e. g. I have 20 tones to play, but it only plays like 2 to 17.5 tones of them. And yes it even will stop in middle of a tone.

Here is my code, from another answer:

    ArrayList<double[]> samples = new ArrayList<>();
    int numSamples = 0;
    for (final ToneSegment seg : sequence) {
        int num =  seg.getDuration() * sampleRate / 1000;
        double[] sample = new double[num];
        for (int i = 0; i < num; ++i) {
            sample[i] = Math.sin(2 * Math.PI * i * seg.getPitch() / sampleRate);
        }
        samples.add(sample);
        numSamples += num;
    }

    byte generatedSnd[] = new byte[2 * numSamples];
    int idx = 0;
    for (double[] sample : samples) {
        for (final double dVal : sample) {
            final short val = (short) ((dVal * 32767));
            generatedSnd[idx++] = (byte) (val & 0x00ff);
            generatedSnd[idx++] = (byte) ((val & 0xff00) >>> 8);
        }
    }

    audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
            sampleRate, AudioFormat.CHANNEL_OUT_MONO,
            AudioFormat.ENCODING_PCM_16BIT, generatedSnd.length,
            AudioTrack.MODE_STATIC);
    audioTrack.write(generatedSnd, 0, generatedSnd.length);
    audioTrack.play();

Does anyone have any idea? Thanks!

Answer 1

You are using AudioTrack.MODE_STATIC that is meant for short sounds and low-latency requirements while you should use AudioTrack.MODE_STREAM. AudioTrack.MODE_STREAM is meant for longer streams, but I do not know how long your samples are. So you can try and change AudioTrack:

audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
        sampleRate, AudioFormat.CHANNEL_OUT_MONO,
        AudioFormat.ENCODING_PCM_16BIT, generatedSnd.length,
        AudioTrack.MODE_STREAM);

Also The AudioTrack requires the buffer size in bytes, a short needs to be multiplied by two to calculate the correct amount of required bytes. You could hack it in like this :

audioTrack = new AudioTrack(AudioManager.STREAM_MUSIC,
        sampleRate, AudioFormat.CHANNEL_OUT_MONO,
        AudioFormat.ENCODING_PCM_16BIT, generatedSnd.length*2,
        AudioTrack.MODE_STREAM);