CODEWITHSUNDEEP
androidbluetoothstreamingandroid-bluetoothvoice
abrutsze
abrutsze

Reputation: 506

How to play a byte stream ? ( voice call between devices )

The goal is to organize a voice call between two devices. The problem is in reciveing part, I get a very high levl of noise, so it is impossible to understand the speach. Here is my code:

The sending part:

    public void startRecording() {

//  private static final int RECORDER_SAMPLERATE = 44100;
//  private static final int RECORDER_CHANNELS = AudioFormat.CHANNEL_IN_STEREO;
//  private static final int RECORDER_AUDIO_ENCODING = AudioFormat.ENCODING_PCM_16BIT;
//  bufferSize = AudioRecord.getMinBufferSize(8000,
                AudioFormat.CHANNEL_CONFIGURATION_MONO,
                AudioFormat.ENCODING_PCM_16BIT);

    recorder = new AudioRecord(MediaRecorder.AudioSource.MIC,
            RECORDER_SAMPLERATE, RECORDER_CHANNELS, RECORDER_AUDIO_ENCODING, bufferSize);

    int i = recorder.getState();
    if (i == 1)
        recorder.startRecording();
    isRecording = true;
    recordingThread = new Thread(new Runnable() {

        @Override
        public void run() {
            byte data[] = new byte[bufferSize];
            bluetoothCall.sendMessage(data);
        }
    }, "AudioRecorder Thread");
    recordingThread.start();
}

The receiving part ( probably the problem is in this part ) :

    private final Handler mHandler = new Handler() {
    @Override
    public void handleMessage(Message msg) {
        switch (msg.what) {

            case MESSAGE_WRITE:
                 // ...
            case MESSAGE_READ:
                try{

                //  private int sampleRate = 44100 ;
                //  int bufferSize = AudioRecord.getMinBufferSize(8000,
                                     AudioFormat.CHANNEL_CONFIGURATION_MONO,
                                     AudioFormat.ENCODING_PCM_16BIT);

                    byte[] readBuf = (byte[]) msg.obj;

                    mAudioTrack = new AudioTrack(AudioManager.STREAM_MUSIC, sampleRate, AudioFormat.CHANNEL_IN_STEREO, AudioFormat.ENCODING_PCM_16BIT, bufferSize, AudioTrack.PERFORMANCE_MODE_LOW_LATENCY);

                    mAudioTrack.play();

                    mAudioTrack.write(readBuf, 0, readBuf.length);
                    mAudioTrack.release();
                }
                catch (Exception e){
                }
                break;
        }
    }
};

Upvotes: 1

Views: 509

Answers (1)

Mick
Mick

Reputation: 25491

VoIP quality is typically influenced by several factors:

  • latency (end to end time taken for a packet)
  • jitter (variance in latency)
  • packet loss

Most issues in VoIP implementations are usually around latency and jitter, but from your description of noise it sounds more like you might be losing data or having it corrupted somehow.

Either way, unless you are doing this for learning or academic purposes it may be easier to use a VoIP library which will have solved these issues for you - there is quite a lot of complexity in both the signalling and the voice commuicaton for VoIp calls.

Android has a built in SIP library now:

This does require a SIP server of some sort, even if you build it into your client, which may not be what you want.

You can also build your own solution around the RTP, the voice data transfer part, but this will require much more work for discovering IP addresses etc:

You can use SIP clients without a server often but you need to work out the IP address and, more trickily, the port (https://stackoverflow.com/a/44449337/334402).

If you do want to use SIP there are opeusource SIP servers available - e.g.:

Upvotes: 2

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