Tree-Encoding of Speech Using the (M, L)-Algorithm and Adaptive Quantization

This paper shows the utility of using adaptive quantizers in the tree-encoding of speech waveforms based on the (M, L) algorithm [1]. Resulting adaptive differential PCM (ADPCM) and adaptive delta modulation (ADM) encoders, with time-invariant prediction networks, can provide useful speech outputs at bit rates in the order of 24 kbits/s; at 16 kbits/s, on the other hand, the encoders exhibit clearly perceptible amounts of quantization noise.