Patent ID: 6424936
Filing Date: 2002-07-23
Classification: G10L,H04B

Abstract:
A method for identifying and categorizing an audio signal into subclasses to determine a subframe block size of a transform coder, comprising:detecting a number of block sizes available for the transform coder; sampling an input audio signal at predetermined time intervals into samples, and grouping said samples into frames each having an equal number of samples; analyzing the frames in time domain to produce at least one comparison index by: extending each frame in accordance with a window function used in the transform coder; subdividing the extended frame containing the audio samples into smaller subframes, the number of smaller subframes being determined by a time interval determined by temporal hearing characteristics of a human ear; identifying a peak value within each subframe based on an amplitude of the samples within the subframe; computing a difference between the peak value of adjacent subframes and the peak value of two subframes which are separated by a subframe time interval, the difference being used as the comparison index; and comparing the index with a predetermined threshold value, such that a smaller block size is invoked when the index is greater than the predetermined threshold value, and a larger block size is invoked when the index is not greater than the predetermined threshold value; and selecting an appropriate block size for the transform coder.