Huffman Code Based Error Screening and Channel Code Optimization for Error Concealment in Perceptual Audio Coding (PAC) Algorithms

The class of Perceptual Audio Coding (PAC) algorithms yields efficient and high-quality stereo digital audio bit streams at rates from 16 kb/sec up to 128 kb/sec (and even higher bit rates). To avoid "pops and clicks" in the decoded audio signals after transmission over unreliable channels, e.g., in the context of digital audio broadcasting (DAB), channel error detection combined with source error concealment, or source error mitigation, techniques are preferred to pure channel error correction. One simple and efficient way of doing channel error detection is to use a high-reate block code; for example, the preferred solution for hybrid in-band on-channel (HIBOC) DAB in the FM band employs a cyclic redundancy check (CRC) code. Several joint source-channel coding issues arise in this framework because PAC contains a fixed-to-variable source coding component in the form of Huffman codes, so that the output packets are of varying length.