Question

How does CMTimeCompare work? Apple seems to have left out the return values from their documentation.

https://developer.apple.com/library/mac/#documentation/CoreMedia/Reference/CMTime/Reference/reference.html

I assume if the times are equal it returns zero and return positive or negative 1 based on which is greater?

Answer 1

From 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.

EDIT:

Please note that:

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, equal to itself,
and greater than any other CMTime. Negative infinity is considered to be equal to itself,
and less than any other CMTime.