How to program a real-time accurate audio sequencer on the iphone?

Question

I want to program a simple audio sequencer on the iphone but I can\'t get accurate timing. The last days I tried all possible audio techniques on the iphone, starting from Audio

Answer 1

By measuring the time elapsed for the "Do some work" part in the loop and subtracting this duration from the nextTime greatly improves accuracy:

while (loop == YES)
{
    timerInterval = adjustedTimerInterval ;

    startTime = CFAbsoluteTimeGetCurrent() ;

    if (delegate != nil)
    {
        [delegate timerFired] ; // do some work
    }

    endTime = CFAbsoluteTimeGetCurrent() ;

    diffTime = endTime - startTime ; // measure how long the call took. This result has to be subtracted from the interval!

    endTime = CFAbsoluteTimeGetCurrent() + timerInterval-diffTime ;

    while (CFAbsoluteTimeGetCurrent() < endTime)
    {
        // wait until the waiting interval has elapsed
    }
}