使用NSTimer可以显示每秒的时间码帧

    - (void) viewDidLoad {
        // Start the Timer method for here to start it when the view loads.
            runTimer = [NSTimer scheduledTimerWithTimeInterval: .01 target: self selector: @selector(updateDisplay) userInfo: nil repeats: YES];
    }

- (void)updateDisplay {
        NSDateFormatter *formatter = [[NSDateFormatter alloc] init];
        NSDate *date = [NSDate date];

        // Display each hour, minute, second and frame.
        [formatter setDateFormat:@\"hh\"];
        [timecodeHourLabel setText:[formatter stringFromDate:date]];

        [formatter setDateFormat:@\"mm\"];
        [timecodeMinuteLabel setText:[formatter stringFromDate:date]];

        [formatter setDateFormat:@\"ss\"];
        [timecodeSecondLabel setText:[formatter stringFromDate:date]];
}

1/24 * 1000

NSDate

NSTimer

UILabel