Multiple description transform coding of audio using optimal transforms of arbitrary dimension

Abstract

A multiple description (MD) joint source-channel (JSC) encoder in accordance with the invention encodes n components of an audio signal for transmission over m channels of a communication medium, where n and m may take on any desired values. In an illustrative embodiment, the encoder combines a multiple description transform coder with elements of a perceptual audio coder (PAC). The encoder is configured to select one or more transform parameters for a multiple description transform, based on a characteristic of the audio signal to be encoded. For example, the transform parameters may be selected such that the resulting transformed coefficients have a variance distribution of a type expected by a subsequent entropy coding operation. The components of the audio signal may be quantized coefficients separated into a number of factor bands, and the transform parameter for a given factor band may be set to a value determined based on a transform parameter from at least one other factor band, e.g., the previous factor band. As another example, the transform parameter for one or more of the factor bands may be selected based on a determination as to whether the audio signal to be encoded is of a particular predetermined type. A desired variance distribution may also be obtained for the transformed coefficients by, e.g., pairing or otherwise grouping coefficients such that the coefficients of each pair or group are required to be in the same factor band.