CMFormatDescription to CMVideoFormatDescription - swift

Question

I'm trying to get the resolution of the camera of a device using swift.
I'm using CMVideoFormatDescriptionGetDimensions which requires a CMVideoFormatDescription, but AVCaptureDevice.formatDescription returns a CMFormatDescription. I've tried a multitude of ways to cast CMFormatDescription to CMVideoFormatDescription and can't seem to get it working.
Below is a sample of the code that I'm using:
for format in device.formats as [AVCaptureDeviceFormat] {
let videoDimensions = CMVideoFormatDescriptionGetDimensions(format.formatDescription)
}

Answer 1

This doesn't seem possible in Swift at the moment. One solution then would be to write a helper function in objective-c, such as:
CMVideoDimensions CMFormatDescriptionGetDimensions(CMFormatDescriptionRef formatDescription)
{
if (CMFormatDescriptionGetMediaType(formatDescription) == kCMMediaType_Video)
return CMVideoFormatDescriptionGetDimensions(formatDescription);
else
return (CMVideoDimensions) {
.width = 0,
.height = 0
};
}
Include the header with the function prototype in the Swift bridging header so that it will be accessible as a global function from your Swift code.

Answer 2

I was able to get the resolution using the swift method below:
let captureDevice = AVCaptureDevice.defaultDeviceWithMediaType(AVMediaTypeVideo) as AVCaptureDevice
let formatDesc = captureDevice.activeFormat.formatDescription
let dimensions = CMVideoFormatDescriptionGetDimensions(formatDesc)

Answer 3

Here's a solution in pure Swift, really only usable for logging purposes and such. Paste the following function in your class or somewhere else:
func widthAndHeightFromTrack(track: AVAssetTrack) -> CGSize {
let str = track.formatDescriptions.description
let regex = try! NSRegularExpression(pattern: "[0-9]{2,4} x [0-9]{2,4}", options: [])
if let result = regex.firstMatchInString(str, options: [], range: NSMakeRange(0, str.characters.count)) {
let dimensionString = (str as NSString).substringWithRange(result.range)
let dimensionArray = dimensionString.componentsSeparatedByString(" x ")
let width = Int(dimensionArray[0])
let height = Int(dimensionArray[1])
return CGSize(width: width!, height: height!)
}
return CGSizeZero
}
Example usage:
let allTracks: AVAsset = someAVAsset.tracksWithMediaType(AVMediaTypeVideo)
let videoTrack = allTracks[0]
let videoTrackDimensions = widthAndHeightFromTrack(videoTrack)
// You now have a CGSize, print it
print("Dimensions: \(videoTrackDimensions)")
Of course, the above solution will completely break whenever Apple changes something in the string representation of the CMFormatDescription. But it's useful for logging the dimensions.

Answer 4

Maybe, question is too old, but the Swift issue is still not fixed.
public extension AVURLAsset {
var audioFormatDescription: CMAudioFormatDescription? {
if let track = self.tracks(withMediaType: .audio).first,
let untypedDescription = track.formatDescriptions.first {
// hacks, warnings, disablings of swiftlint below are wrork-around of
// Swift bug: it fails converting 'Any as CMFormatDescription'
let forceTyped: CMFormatDescription?
//swiftlint:disable force_cast
= untypedDescription as! CMAudioFormatDescription
//swiftlint:enable force_cast
if let description = forceTyped {
return description
} else {
return nil
}
} else {
return nil
}
}
}