CMTimeCompare如何工作？ Apple似乎已经从他们的文档中遗漏了返回值.
我假设如果时间相等则返回零并返回正或负1,基于哪个更大？
解决方法
来自CMTime.h：
Returns the numerical relationship (-1 = less than,1 = greater than,
0 = equal) of two CMTimes.-1 is returned if time1 is less than time2. 0 is returned if they are equal. 1 is returned if time1 is greater than time2.
编辑：
请注意：
Invalid CMTimes are considered to be equal to other invalid CMTimes,and greater than any other CMTime. Positive infinity is considered to be less than any invalid CMTime,equal to itself,and greater than any other CMTime. An indefinite CMTime is considered to be less than any invalid CMTime,less than positive infinity,and greater than any other CMTime. Negative infinity is considered to be equal to itself,and less than any other CMTime.