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POAccurate repeating iPhone sounds
 

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  1. POAccurate repeating iPhone sounds
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    <p>I am working with an app that needs to play a sound "tap" at 60 ms intervals (making for 1000 taps per minute). When I get past about 120 ms intervals (500 taps per minute), the sounds become very erratic and seem to be piling up on one another.</p> <p>The sound byte that I'm using is 10 ms long, and I have a thread timer that is running at 20 ms intervals. I am using AVAudioPlayer to play the sound, and have tried formats of wav, caf and m4a. I have tested with NSLog outputs to see when the AVAudioPlayer is being fired off, and when the timer loop is polling...and all the times seem accurate enough.</p> <p>I have added Audio Session handling in my viewDidLoad() method as follows:</p> <pre><code> [[AVAudioSession sharedInstance] setCategory: AVAudioSessionCategoryPlayback error: &amp;setCategoryError]; </code></pre> <p>Here is my timer loop that is running in it's own thread:</p> <pre><code>NSAutoreleasePool *pool = [[NSAutoreleasePool alloc] init]; // Give the sound thread high priority to keep the timing steady. [NSThread setThreadPriority:1.0]; while (running) { // loop until stopped. [self performSelectorOnMainThread:@selector(playOutput) withObject:nil waitUntilDone:NO]; // An autorelease pool to prevent the build-up of temporary objects. NSAutoreleasePool *loopPool = [[NSAutoreleasePool alloc] init]; NSDate *curtainTime = [[NSDate alloc] initWithTimeIntervalSinceNow:sleepValue]; NSDate *currentTime = [[NSDate alloc] init]; // Wake up periodically to see if we've been cancelled. while (running &amp;&amp; ([currentTime compare:curtainTime] == NSOrderedAscending)) { [NSThread sleepForTimeInterval:0.015]; [currentTime release]; currentTime = [[NSDate alloc] init]; } [curtainTime release]; [currentTime release]; [loopPool drain]; } [pool drain]; </code></pre> <p>Here is how I am initializing my AVAudioPlayer:</p> <pre><code>NSString *beatOne = @"3h"; NSString *beatOneSoundFile = [[NSBundle mainBundle] pathForResource:beatOne ofType:@"caf"]; NSURL *beatOneURL = [[NSURL alloc] initFileURLWithPath:beatOneSoundFile]; beatPlayerOne = [[AVAudioPlayer alloc]initWithContentsOfURL:beatOneURL error:nil]; beatPlayerOne.delegate = self; beatPlayerOne.currentTime = 0; [beatPlayerOne prepareToPlay]; [beatOneURL release]; </code></pre> <p>And here is where the audio player is played:</p> <pre><code>[beatPlayerOne pause]; beatPlayerOne.currentTime = 0; [beatPlayerOne play]; </code></pre> <p>Thanks in advance for any help...</p>
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    1. COperhaps you could think of playing audio files containing say ten taps?
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      1. USamergin
    2. COUltimately, the interval between taps will be adjustable. It needs to be able to handle a max of 1000 taps per minute (higher if possible), but eventually, you approach a "quantum" issue of the wait time is too close to the smallest discernable amount of time (i.e. the millisecond).
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