High-quality sound coding within 2×64 kbit/s using instantaneous dynamic bit-allocation

A subband ADPCM (adaptive differential pulse-code modulation) algorithm to encode 15 kHz signals is given. It features dynamic bit allocation based on the log scale factors of the adaptive embedded quantizers and on the roughly quantized instantaneous values of the subband difference signals. Bit allocation is performed for frame lengths equal to one sample interval of the narrowest channel. Side information is transmitted only to maintain octet-sequence integrity and channel synchronization. The receiver can switch dynamically between decoding either 1 or 2×64 kb/s. The algorithm was implemented using three TI 32010 digital signal processors. Results of formal subjective tests are given