Annex B describes a scalable superwideband (SWB, 50‑14000 Hz) speech and audio coding algorithm operating at 64, 80 and 96 kbit/s. The ITU-T G.722 superwideband extension codec is interoperable with ITU-T G.722.
The output of the ITU-T G.722 SWB coder has a bandwidth of 50-14000 Hz. The coder operates with 5 ms frames, has an algorithmic delay of 12.3125 ms and a worst case complexity of 22.76 WMOPS. By default, the encoder input and decoder output are sampled at 32 kHz.
The superwideband encoder for improved ITU-T G.722 64 kbit/s core produces an embedded bitstream structured in two layers corresponding to two available bit rates from 80 to 96 kbit/s. The superwideband encoder for improved ITU-T G.722 56 kbit/s core produces an embedded bitstream structured in one layer corresponding to one available bit rate of 64 kbit/s. This 64 kbit/s mode is also scalable with the 80 kbit/s and 96 kbit/s modes. 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 (96 kbit/sà 80 kbit/sà 64 kbit/s) with no need for out-of-band signalling.
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 B contains an electronic attachment with the ANSI C source code, which is an integral part of this annex.