Scalable audio coding based on hierarchical transform coding modules

We propose a method that hierarchically quantizes wideband Modified Discret e Cosine Transform (MDCT) coefficients by developing a module that has a tr ansform coding method primarily for audio as the basic structural unit and freely using this module multiple times at the desired frequencies. The maj or feature of this method is to implement a simple structure having a high degree of freedom in scalable coding to hierarchically quantize MDCT coeffi cients over a wide band of frequencies by sharing the proposed module and u sing it multiple times. This paper presents examples using combinations of the module operating at a sampling frequency of 48 kHz and a bit rate of at least 8 kbit/s. In this example, a bit rate of at least 8 kbit/s and a rec onstructed frequency band of at least 4 kHz can de selected as the objectiv e. Subjective evaluation tests are performed to verify the effectiveness of t he proposed method. (C) 2001 Scripta Technica