4800 and 7200 bit/sec hybrid codebook multipulse coding

The authors describe a low-complexity coding technique that combines multipulse and stochastic excitation. The system, known as hybrid multipulse coding (HMC), provides good quality at 4.8 and 7.2 kb/s. HMC uses efficient pulse excitation for voiced speech and stochastic excitation for unvoiced speech. For the best speech quality, HMC uses an optimization algorithm for simultaneous solution of pitch predictor and excitation parameters, producing a higher signal-to-noise ratio than CELP (code-excited linear prediction) in the 4.8-kb/s configuration. At 7.2 kb/sec, CELP and HMC give diagnostic acceptability measure (DAM) scores close enough so that their standard error limits overlap. In all configurations, HMC requires from 5 to 14 times fewer multiply/accumulate operations than CELP for similarly sized codebooks