Ninth International Conference on Spoken Language Processing

Pittsburgh, PA, USA
September 17-21, 2006

An Unified Unit-Selection Framework for Ultra Low Bit-Rate Speech Coding

V. Ramasubramanian (1), D. Harish (2)

(1) Siemens Information Systems Ltd., India; (2) International Institute of Information Technology, India

We propose a unified framework for segment quantization of speech at ultra low bit-rates of 150 bits/sec based on unit-selection principle using a modified one-pass dynamic programming algorithm. The algorithm handles both fixed- and variable- length units in a unified manner, thereby providing a generalization over two existing unit selection methods, which deal with ‘single-frame’ and ‘segmental’ units differently. The proposed algorithm performs unit-selection based quantization directly on the units of a continuous codebook, thereby not incurring any of the sub-optimalities of the existing ‘segmental’ algorithm. Moreover, the existing ‘single-frame’ algorithm becomes a special case of the proposed algorithm. Based on the rate-distortion performance on a multi-speaker database, we show that fixed length units of 6-8 frames perform significantly better than single-frame units and offer similar spectral distortions as variable-length phonetic units, thereby circumventing expensive segmentation and labeling of a continuous database for unit selection based low bit-rate coding.

Full Paper

Bibliographic reference.  Ramasubramanian, V. / Harish, D. (2006): "An unified unit-selection framework for ultra low bit-rate speech coding", In INTERSPEECH-2006, paper 2028-Mon1FoP.4.