We describe a systematic procedure to replace vector quantization (VQ) with trellis-coded vector quantization (TCVQ) in existing CELP coders. Following this procedure, we design an 8/16 kbit/s TCVQ CELP coder. We analyze the performance of this method in terms of quality and complexity. Our results show that a CELP coder using TCVQ produces significantly better quality than the same coder using VQ, with reasonable complexity. By modifying the TCVQ CELP coder parameters one can favorably trade coding quality against complexity and/or delay.

We analyze the performance of a CELP coder where the vector quantization (VQ) of the excitation is replaced with trellis-coded vector quantization (TCVQ). Our results show that TCVQ performs significantly better than VQ, with reasonable complexity. This makes TCVQ a fair choice for trading quality against complexity and/or delay. We describe a systematic procedure to replace VQ with TCVQ for existing CELP coders. We propose an optimization algorithm to appropriately populate the trellis. We show how pseudo-Gray coding can be applied to the TCVQ codebook to improve intrinsic coder robustness to channel errors. Finally, we evaluate the complexity and performance of the method.