ITU-T Recommendations

Annex D describes a scalable superwideband (SWB, 50-14000 Hz) speech and audio coding algorithm operating from 96 to 112 kbit/s for G.711.1 80 kbit/s core, and operating from 112 to 128 kbit/s for G.711.1 96 kbit/s core. The G.711.1 superwideband extension codec is interoperable with both G.711 and G.711.1.The output of the G.711.1 SWB coder has a bandwidth of 50-14000 Hz. The coder operates with 5 ms frames, has an algorithmic delay of 12.8125 ms and a worst case complexity of 21.498 WMOPS. By default, the encoder input and decoder output are sampled at 32 kHz.The superwideband encoder produces an embedded bitstream structured in two layers corresponding to two available bit rates from 96 to 112 kbit/s or from 112 to 128 kbit/s with a step size of 16 kbit/s depending on the chosen G.711.1 core. The bitstream can be truncated at the decoder side or by any component of the communication system to instantaneously adjust the bit rate to the desired value with no need for out-of-band signalling. At G.711.1 80 kbit/s mode or 96 kbit/s mode, G.711.1 SWB is fully interoperable with G.711.1.The underlying algorithm includes three main parts: higher band enhancements, bandwidth extension (BWE) and transform coding in modified discrete cosine transform (MDCT) domain based on algebraic vector quantization (AVQ).Annex D contains an electronic attachment with the ANSI C source code, which is an integral part of this Annex.