Transform predictive coding of wideband speech signals

This paper presents a novel wideband speech coding algorithm called transform predictive coding (TPC). The main emphasis is on low complexity. TPC uses short-term and long-term prediction to remove the redundancy in speech. The prediction residual is quantized in the frequency domain based on a calculated noise masking threshold. In its simplest form, the TPC coder uses only open-loop quantization and therefore has a low complexity. A 16 kb/s full-duplex, open-loop TPC coder takes only 22% of the CPU load on a 150 MHz SGI Indy workstation and about 34% on a 90 MHz Pentium PC. The speech quality of TPC is almost transparent at 32 kb/s, very good at 24 kb/s, and acceptable at 16 kb/s. In the second half of the paper, we report our recent progress in using closed-loop quantization techniques to improve TPC output speech quality