MPEG-4 Audio Lossless Coding (ALS) is a new extension of the MPEG-4 audio coding family. The MPEG-4 ALS codec is based on forward-adaptive linear prediction, which enables remarkable compression even with low predictor orders. However, still better compression can be achieved when high orders are considered as well. This requires efficient quantization of the predictor coefficients together with adaptive block length switching. The paper describes the basic elements of the ALS codec with a focus on high-order prediction. It also presents latest developments during the standardization process and points out the most important applications of this new lossless audio format.
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