The Adaptive Differential Pulse Code Modulation(ADPCM) algorithm has been used to replace the Adaptive Pulse Code Modulation(APCM) algorithm in the RPE-LTP scheme to quantize the selected RPE sequence.

• 又用自适应差分脉冲编码调制（ADPCM），代替RPE－LTP方案中的自适应脉冲编码调制（APCM）对选择的RPE序列进行的量化编码。