Processing in AudioRecord thread

Question

I am processing audio recorded by AudioRecord in a thread, but if I run the processing in the recorder thread, some frames get dropped. According to android, AudioRecord.read() --> bufferoverflow, how to handle the buffer?, I need to run the processing in a separate thread, but how? Do I need to create a new thread for every single frame (2-3 per second)?

Here is my current solution but I am wondering if there is a better way to do this?

//in the AudioRecord thread
while (!break_condition) {
    int num_read = recorder.read(buffer, 0, buffer.length);
    HeavyProcessingRunnable myRunnable = new HeavyProcessingRunnable(buffer);
    Thread t = new Thread(myRunnable)
    t.start();
}

The runnable for the heavy processing

public class HeavyProcessingRunnable implements Runnable {
    private byte[] var;
    public HeavyProcessingRunnable(byte[] var) {
        this.var = var;
    }
    public void run() {
        //if this is executed in audio recorder thread, frames get dropped
        someHeavyProcessing(var);
    }
}

How did you finally solve this problem? Can you give an example? — DuosDuo, Feb 27 '19 at 18:21

score 1 · Accepted Answer · edited May 23 '17 at 12:18

Creating a new thread everytime is somewhat expensive (discussion). It would be better to create the heavy processing thread only once and feed it with audio samples. Here's an example:

// Do it only once.

HandlerThread myHandlerThread = new HandlerThread("my-handler-thread");
myHandlerThread.start();

Handler myHandler = new Handler(myHandlerThread.getLooper(), new Handler.Callback() {
    @Override
    public boolean handleMessage(Message msg) {
        someHeavyProcessing((byte[]) msg.obj, msg.arg1);
        return true;
    }
});

// In audio recorder thread.
// Mind the handler reference.

while (!break_condition) {
    int num_read = recorder.read(buffer, 0, buffer.length);
    Message message = myHandler.obtainMessage();
    message.obj = buffer;
    message.arg1 = num_read;
    message.sendToTarget();
}

By the way, it's important to provide num_read along with the audio samples.

@user09123789542 for checking the number of bytes read (>= 0) or any error code (< 0). `read()` may read less bytes than the buffer size [(documentation)](https://developer.android.com/reference/android/media/AudioRecord.html#read(byte[],%20int,%20int)). — nandsito, Nov 07 '16 at 16:15

Processing in AudioRecord thread

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