我正在尝试非常精确地定时发出声音。我使用这段代码来创建计时器:timer=dispatch_source_create(DISPATCH_SOURCE_TYPE_TIMER,0,0,dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_HIGH,0));dispatch_source_set_timer(timer,DISPATCH_TIME_NOW,1ull*500000000,5000ull);dispatch_source_set_event_handler(timer,^{[myAVAudioPlayerplay];});dispa