将CMTime值转换为swift

Question

I have the following 2 lines of code that I am moving to Swift but I am a little stuck.

CMTime trimmingTime = CMTimeMake(lround(videoAsset.naturalTimeScale / videoAsset.nominalFrameRate), videoAsset.naturalTimeScale);
CMTimeRange timeRange = CMTimeRangeMake(trimmingTime, CMTimeSubtract(videoAsset.timeRange.duration, trimmingTime));

When converting the below line to begin with I get the following error.

var trimmingTime: CMTime
trimmingTime = CMTimeMake(value: lround(videoAsset.naturalTimeScale / videoAsset.nominalFrameRate), timescale: videoAsset.naturalTimeScale)

Binary operator '/' cannot be applied to operands of type 'CMTimeScale' (aka 'Int32') and 'Float'

I have tried a few different approaches but nothing seems to work.

Answer 1

Binary operator '/' cannot be applied to operands of type 'CMTimeScale' (aka 'Int32') and 'Float' so you need forecast CMTimeScale into Float.

You need to convert CMTimeScale into Float :

trimmingTime = CMTimeMake(value: lround(Float(videoAsset.naturalTimeScale) / videoAsset.nominalFrameRate), timescale: videoAsset.naturalTimeScale)

Answer 2

You can not simply perform mathematically operation with different type of operands in swift like other languages. You need to type-cast manually.

Here you should cast videoAsset.naturalTimeScale ( which is CMTimeScale and CMTimeScale is of type Int32 ) to Float to get it work.

Float(videoAsset.naturalTimeScale)

But CMTimeMake 's value key will accept value CMTimeValue type value. So use it like:

trimmingTime = CMTimeMake(value: CMTimeValue(Float(videoAsset.naturalTimeScale) / videoAsset.nominalFrameRate), timescale: videoAsset.naturalTimeScale)

Again to make you code more Swifty use CMTime rather CMTimeMake as:

trimmingTime = CMTime(value: CMTimeValue(Float(videoAsset.naturalTimeScale) / videoAsset.nominalFrameRate), timescale: videoAsset.naturalTimeScale)