Application of quadrature mirror filters to split band voice coding schemes

This paper deals with applications of Quadrature Mirror Filters (QMF) to coding of voice signal in sub-bands. Use of QMF´s enables to avoid the aliasing effects due to samples decimation when signal is split into sub-bands. Each sub-band is then coded independently with use of Block Companded PCM (BCPCM) quantizers. Then a variable number of bits is allocated to each sub-band quantizer in order to take advantage of the relative perceptual effect of the quantizing error. The paper is organized as follows: - First, splitting in two sub-bands with QMF´s is analysed. -Then, a general description of a splitband voice coding scheme using QMF´s is made. -Finally, two coding schemes are considered, operating respectively at 16 KBps and 32 KBps. Averaged values of S/N performances are given when encoding both male and female voices. Comparisons are made with conventional BCPCM and CCITT A-Law. Taped results will be played at the conference.