Security and Communication Networks

Research Article

Feature Extraction Method for Hidden Information in Audio Streams Based on HM-EMD

Empirical mode decomposition.

	Input: original signal x (t), supposed IMF number i
	Output: intrinsic mode functions, IMF
(1)	i = 1, = x (t).
(2)	Get the extremum points of signal , calculate the upper and lower envelope by cubic spline interpolation with the maximum and minimum points as control points, and get the average value of upper and lower envelope at every points.
(3)	. If satisfies formulas (1) and (2), then is taken as the ith IMF signal , i = i + 1; if not, repeat step 2 and 3 for signal .
(4)	. Return to step 1 until the termination condition is satisfied.