Bandwidth scalable speech coding and rate switching

Bit rate scalability in speech coders can be used to achieve SNR scalable speech coding or bandwidth scalable coding of speech and audio. While SNR scalability has been studied theoretically and practically, the fundamental limits of bandwidth scalability have received substantially less attention. We utilize classical rate distortion theory subject to a weighted squared error fidelity criterion to analyze the performance of subband structured bandwidth scalable coders. We propose the application of bandwidth scalable speech coding for rate switching in wireless environments and develop a bandwidth scalable coder that builds upon narrowband adaptive multirate speech coders. The bandwidth scalable coders exhibit performance competitive with wideband speech coders at the same rates.