C# Frame.ToArray方法代码示例

		/**
		 * Calculates FFT of a signal frame using radix-2 algorithm.
		 *
		 * Input data is given as a pointer to Frame object.
		 * Output spectrum is written to the spectrum vector, which must be
		 * initialized prior to the call to fft(). The spectrum is
		 * normalized by N/2, wher N is input frame length (zero-padded).
		 * The method  returns maximum magnitude of the calculated spectrum,
		 * which can be used for example to scale a frequency plot.
		 *
		 * @param frame pointer to Frame object
		 * @param spectrum initialized complex vector of the same length as data
		 * @return maximum magnitude of the spectrum
		 * @since 2.0.1
		 */
		public double Fft(Frame frame, ref Complex[] spectrum)
		{
			// the vector is initialized to zero padded length,
			// what means that it contains default values of contained type
			// (0.0 in case of double); that allows us to loop
			// only to frame length without padding and
			// automatically have zeros at the end of data
			double[] data = new double[zeroPaddedLength];
			int length = frame.GetLength();
			
			short[] frameArray = frame.ToArray();
			
			// first sample does not need preemphasis
			data[0] = frameArray[0];

			double current = 0.0;
			double previous = data[0];
			
			// iterate over all samples of the frame
			// filter the data through preemphasis
			// and apply a chosen window function
			// The goal of pre-emphasis is to compensate the high-frequency part
			// that was suppressed during the sound production mechanism of humans.
			// Moreover, it can also amplify the importance of high-frequency formants.
			// It's not neccesary for only music, but important for speech
			// (Set to 0 if no pre-emphasis should be performed)
			for (int n = 1; n < length; n++)
			{
				current = frameArray[n];
				data[n] = (current - preemphasisFactor * previous) * Window.Apply(winType, n, length);
				previous = current;
			}
			
			return Fft(data, ref spectrum);
		}