if let asbd = CMAudioFormatDescriptionGetStreamBasicDescription(audioDesc as! CMAudioFormatDescription) {
                let numChannels = asbd.pointee.mChannelsPerFrame

                let sampleRate = asbd.pointee.mSampleRate
                let audioFormat = asbd.pointee.mFormatID

                let formatFlags = asbd.pointee.mFormatFlags
                // What now???