Identification of a valid set of parameters for the creation of an AudioRecord

Question

I am working on Audiorecorder to send and receive audio over UDP. I am getting null pointer exception error. After some research, I found that some devices might not support all the sampling rates. With help of this example AudioRecord object not initializing. I have even added a class to check the possible combinations of sampling rates too. I am looking for valid set of paramters that could possibly accepted on all devices.

public class audioCall {

private static final int SAMPLE_RATE = 16000;

public audioCall throws Exception {

    new Thread(){
        @Override
        public void run() {
            int bytes_read = 0;
            int bytes_sent = 0;
            byte[] buf = new byte[1600];

     try {
            // creating socket and start recording

             DatagramSocket clientSocket = new DatagramSocket();
             AudioRecord audioRecorder = findAudioRecord();
             audioRecorder.startRecording();

             while (true){

                 bytes_read = audioRecorder.read(pcm_data,0,1600);
                 DatagramPacket sendPacket = new DatagramPacket(buf, bytes_read, serverAddress, serverPort);
                 Socket.send(sendPacket);
                 bytes_sent += bytes_read;
                 Thread.sleep(20,0);
              }
                 audioRecorder.stop();
                 audioRecorder.release();
                 Socket.disconnect();
                 Socket.close();
                 return;
    }
}.start();

//check for the valid sample rates

private static int[] mSampleRates = new int[] { 8000, 11025, 22050, 44100 };
public AudioRecord findAudioRecord() {
    for (int rate : mSampleRates) {
        for (short audioFormat : new short[] { AudioFormat.ENCODING_PCM_8BIT, AudioFormat.ENCODING_PCM_16BIT }) {
            for (short channelConfig : new short[] { AudioFormat.CHANNEL_IN_MONO, AudioFormat.CHANNEL_IN_STEREO }) {
                try {
                    Log.d(LOG_TAG, "Attempting rate " + rate + "Hz, bits: " + audioFormat + ", channel: "
                            + channelConfig);
                    int bufferSize = AudioRecord.getMinBufferSize(rate, channelConfig, audioFormat);

                    if (bufferSize != AudioRecord.ERROR_BAD_VALUE && buffersize != AudioRecord.ERROR) {
                        // check if we can instantiate and have a success
                        AudioRecord recorder = new AudioRecord(MediaRecorder.AudioSource.DEFAULT, rate, channelConfig, audioFormat, bufferSize);

                        if (recorder.getState() == AudioRecord.STATE_INITIALIZED)
                            return recorder;
                    }
                } catch (Exception e) {
                    Log.e(LOG_TAG, rate + "Exception, keep trying.",e);
                }
            }
        }
    }
    return null;
}

}

here is my Log cat error report:

FATAL EXCEPTION: Thread-5
Process: com.example.app, PID: 27780
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.media.AudioRecord.startRecording()' on a null object reference
    at com.example.th1go_app.ControlConnection.UDPClient$2.run(Client.java:161)

How can I proceed?

You question is still not on point, as what you are trying to solve is not the NPE, but the identification of a valid set of parameters for the creation of an `AudioRecord`. Presumably on all devices. — second, Jul 22 '19 at 15:52
Also consider adding the `&& bufferSize != AudioRecord.ERROR` to the `bufferSize check`, as suggested in the comments of the linked answer. — second, Jul 22 '19 at 15:55
Thanks dude. I have made the necessary changes. Hopefully I will be able to solve it — cantona_7, Jul 23 '19 at 06:54

Identification of a valid set of parameters for the creation of an AudioRecord

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