Question

I’m working on creating an app that allows very low bandwidth communication via high frequency sound waves. I’ve gotten to the point where I can create a frequency and do the fourier transform (with the help of Moonblink’s open source code for Audalyzer).

But here’s my problem: I’m unable to get the code to run with the correct timing. Let’s say I want a piece of code to execute every 10ms, how would I go about doing this?

I’ve tried using a TimerTask, but there is a huge delay before the code actually executes, like up to 100ms.

I also tried this method simply by pinging the current time and executing only when that time has elapsed. But there is still a delay problem. Do you guys have any ideas?

Thread analysis = new Thread(new Runnable()
{
    @Override
    public void run()
    {
        android.os.Process.setThreadPriority(android.os.Process.THREAD_PRIORITY_URGENT_DISPLAY);

        long executeTime = System.currentTimeMillis();

        manualAnalyzer.measureStart();
        while (FFTransforming) 
        {          
            if(System.currentTimeMillis() >= executeTime)
            {
                //Reset the timer to execute again in 10ms
                executeTime+=10;

                //Perform Fourier Transform
                manualAnalyzer.doUpdate(0);

                //TODO: Analyze the results of the transform here...

            }
        }
        manualAnalyzer.measureStop();
    }
});
analysis.start();

Answer 1

Your thread/loop strategy is probably roughly as close as you’re going to get. However, 10ms is not a lot of time, most Android devices are not super-powerful, and a Fourier transform is a lot of work to do. I find it unlikely that you’ll be able to fit that much work in 10ms. I suspect you’re going to have to increase that period.