setMaxFps.swift

func setMaxFps(device: AVCaptureDevice) {
    var minFPS = 0.0
    var maxFPS = 0.0
    var maxWidth:Int32 = 0
    var selectedFormat:AVCaptureDevice.Format? = nil

    for format in device.formats {
        for range in format.videoSupportedFrameRateRanges {
            let desc = format.formatDescription
            let dimentions = CMVideoFormatDescriptionGetDimensions(desc)

            if(minFPS <= range.minFrameRate && maxFPS <= range.maxFrameRate && maxWidth <= dimentions.width){
                minFPS = range.minFrameRate
                maxFPS = range.maxFrameRate
                maxWidth = dimentions.width
                selectedFormat = format
            }
        }
    }

    do {
        try device.lockForConfiguration()
        device.activeFormat = selectedFormat!
        device.activeVideoMinFrameDuration = CMTimeMake(value: 1, timescale: Int32(minFPS))
        // Set lowest frame rate to reduce memory
        device.activeVideoMaxFrameDuration = CMTimeMake(value: 1, timescale: Int32(minFPS))
        device.unlockForConfiguration()

    } catch {

    }
}