1) CMTimeMake(1,10)
actually means a value of 1 and a timescale of 10. They are a numerator and denominator, so it is 1/10 of a second, not 1 second.
2) The result will be like CMTimeMake(2, 10)
, which is 2/10ths of a second.
Peter is right. The following code makes the concept more clear:
1)
Float64 seconds = 5;
int32_t preferredTimeScale = 600;
CMTime inTime = CMTimeMakeWithSeconds(seconds, preferredTimeScale);
CMTimeShow(inTime);
The above code gives: {3000/600 = 5.000}
Which means a total duration of 5 seconds, with 3000 frames with a timescale of 600 frames per second.
2)
int64_t value = 10000;
int32_t preferredTimeScale = 600;
CMTime inTime = CMTimeMake(value, preferredTimeScale);
CMTimeShow(inTime);
This one gives {10000/600 = 16.667}
Which means a total duration of 16.667 seconds, with 10000 frames with a timescale of 600 frames per second.
Notice the difference between CMTimeMake(int64_t value, int32_t timescale) and CMTimeMakeWithSeconds(Float64 seconds, int32_t preferredTimeScale)
Hope this explanation helps. For further clarifications, please don't hesitate to post further questions on this post.
With CMTimeMake(A, B)
you store a rational number, an exact fraction A / B
seconds
CMTimeMake(1, 4)
-> the time interval 0.25 secondsWith CMTimeMakeWithSeconds(A, B)
you store A
seconds to a resolution of B
steps
CMTimeMakeWithSeconds(0.25, ...)
-> the time interval 0.25 secondsYou commonly see CMTimeMakeWithSeconds(time, NSEC_PER_SEC)
. The NSEC_PER_SEC
effectively means "max resolution".
If you only want to know how to make an interval for 1 second (like me), this is your answer:
int seconds = 1;
CMTime interval = CMTimeMakeWithSeconds(seconds, NSEC_PER_SEC);
A CMTime struct represents a length of time that is stored as rational number.
CMTime has a value and a timescale field, and represents the time value/timescale seconds .
See See this SO Answer which is clear
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