On scalability in CELP coding systems
Rakesh Taori, R.J. Sluijter, A.J. Gerrits · 2002
We propose methods to achieve bit-rate and complexity scalability in CELP coders/decoders. These methods can be implemented as plug-ins or add-ons to existing CELP systems. The associated scale factors can be readjusted even during run-time. In particular, using the proposed methods, a wideband (sampling rate 16 kHz) coder/decoder has been developed that is capable of reconstructing good to high quality speech at bit rates ranging from 14 to 24 kbit/s. The possible complexity range of the decoder can amount to a factor of 2 or more, depending on the constitution of the transmitted bitstream. Although the system also incorporates a complexity scalable encoder, it is not discussed in this paper. This system has been submitted to MPEG-4, where it has been incorporated in the MPEG-4 Audio Verification Model.