Reducing signal delay in multipulse coding at 16kb/s

Block-band coders typically impose a signal delay of about 60 ms. This paper reports on multipulse-LPC coding structures which reduce signal delay to 2 ms. The proposed structures are based on I) a high update rate for LPC side-information, and II) the use of very short duration intervals for the placement of pulses. The low delay structure imposes a relatively more uniform distribution of pulses in time. The addition of pitch prediction, over very short blocks, is observed to overcome the degradation due to the uniform pulse distribution. An efficient pitch prediction approach and the use of a forward-adaptive lattice filter contribute to maintaining computational requirements within the reach of modem DSP chips.