How to convert CMSampleBuffer to Data for video in Swift?

Question

I have downloaded a source code from here. I am getting CMSampleBuffer for video from the camera in the following function.

public func captureOutput(_ captureOutput: AVCaptureOutput, didOutput sampleBuffer: CMSampleBuffer, from connection: AVCaptureConnection) {
        do {
            var textures: [MTLTexture]!

            switch pixelFormat {
            case .rgb:
                let textureRGB = try texture(sampleBuffer: sampleBuffer, textureCache: textureCache)
                textures = [textureRGB]
            case .yCbCr:
                let textureY = try texture(sampleBuffer: sampleBuffer, textureCache: textureCache, planeIndex: 0, pixelFormat: .r8Unorm)
                let textureCbCr = try texture(sampleBuffer: sampleBuffer, textureCache: textureCache, planeIndex: 1, pixelFormat: .rg8Unorm)
                textures = [textureY, textureCbCr]
            }

            let timestamp = try self.timestamp(sampleBuffer: sampleBuffer)

            delegate?.metalCameraSession(self, didReceiveFrameAsTextures: textures, withTimestamp: timestamp)

        }
        catch let error as MetalCameraSessionError {
            self.handleError(error)
        }
        catch {
            /**
             * We only throw `MetalCameraSessionError` errors.
             */
        }
    }

How can I convert sampleBuffer to Data using Swift 4?

I have tried this. But it is creating another issue instead with iPhone not simulator.