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An Investigation into Embedded Audio Coding Using An AAC Perceptually Lossless Base Layer

Embedded lossless audio coding attempts to combine the higher compression ratios of perceptual coding with the perfect reconstruction of the original signal provided by lossless coding. This paper examines the residual signal of a perceptual audio coding base layer and considers its usage as an embedded bitstream for an embedded lossless coder. It is shown that the residual signal of a lossy perceptual audio coder retains correlation that can be exploited in lossless compression. This allows an embedded stream to be provided in a lossless coder with approximately 6% overhead over pure lossless audio coding. A 6% overhead appears to be a minimal cost for the backward compatibility and scalability afforded by embedded streams.