Enhanced joint stereo coding method using temporal envelope shaping

Abstract

A method and apparatus for performing joint stereo coding of multi-channel audio signals using intensity stereo coding techniques. In particular, predictive filtering techniques are applied to the spectral coefficient data, thereby preserving the time structure of the output signal of each channel, while maintaining the benefit of the high bit rate savings offered by intensity stereo coding. In one illustrative embodiment of the invention, the input signal is decomposed into spectral coefficients by a high-resolution filterbank/transform; the time-dependent masking threshold of the signal is estimated using a perceptual model; a filter performing linear prediction in frequency is applied at the filterbank outputs for each channel; intensity stereo coding techniques are applied for coding both residual signals into one carrier signal; the spectral values of the carrier signal are quantized and coded according to the precision corresponding to the masking threshold estimate; and all relevant information (i.e., the coded spectral values, intensity scaling data and prediction filter data for each channel, as well as the additional side information) is packed into a bitstream and transmitted to the decoder.