A new 2-kbit/s speech coder based on normalized pitch waveform

Speech coding at very low bit-rate is useful for purposes such as voice communication over computer networks. However speech coding at around 2.0 kbit/s is difficult for CELP coders while maintaining a high quality. In this paper, a speech coding model called `normalized pitch waveform´ and its quantization scheme are presented, aiming for effective compression coding of the `voiced´ speech. Listening tests have proven that an efficient and high quality coding has been achieved at 2.0 kbit/s, less than half of the FS1016. Furthermore this paper discusses the disadvantage of the normalized pitch waveform and presents an alternative method of using non-normalized pitch waveform. Encoding of a transitional `mixed´ state between the `voiced´ and the `unvoiced´ state is discussed for further improvements