An efficient, low-complexity audio coder delivering multiple levels of quality for interactive applications

This paper proposes an e cient rate scalable low complexity audio coder based on the SPIHT set partitioning in hierarchical trees coding algorithm which has achieved notable success in still image coding A wavelet packet transform is used to decompose the audio signal into frequency subbands corresponding roughly to the critical subbands of the human auditory system A psychoacustic model which for simplicity is based on MPEG model I is used to calculate the signal to mask ratio and then calculate the bit rate allocation among subbands We distinguish the subbands into two groups the low frequency group which contains the rst subbands corresponding to KHz and the high frequency group which contains the remaining high frequency subbands The SPIHT algorithm is used to encoder and decode the low frequency group and a reverse sorting process plus arithmetic coding algorithm is used to encode and decode the high frequency group The experiment shows that this coder yields nearly transparent quality at bit rates Kbits second and and degrades only gradually at lower rates The low complexity of this coding system shows its potential for interactive applications with levels of quality from good to perceptually transparent