NSTimer help solve the problem caused by the collapse of

My source projects https://github.com/midfar/ios-media
When finished audio loaded when playing long (duration) If you specify a broadcast, the program will crash.
NSTimer result looks like a problem, do not know how to change the trouble to help me see, Thank you very much.
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I also encountered
So, I do not let timer stops, instead of using the calculation of the long way around
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Has been in use, never had
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If possible, minimize the use of timers! ! ! !
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Have found a reason not NSTimer problem. Thank you reply, though did not give solutions.
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I had a go