This paper examines enhancement to ITU-T Recommendation G.711.1 PCM wideband extension speech coder. To further improve the core lower-band coding performance the use of vector quantization and delayed decision coding is studied. A particular case of delayed decision coding, tree encoding, is implemented in the above standard. The bitstream is compatible with both the legacy G.711 and the G.711.1 decoder. PESQ (ITU-T P.862, Perceptual Evaluation of Speech Quality) is used to evaluate the performance. Both the vector quantizer and tree encoder have better performance than the original core layer encoder.
Bibliographic reference. Khan, Abdul Hannan / Kabal, Peter (2011): "Tree encoding for the ITU-t g.711.1 speech coder", In INTERSPEECH-2011, 2553-2556.