Title :
Removal of sparse-excitation artifacts in CELP
Author :
Hagen, Roar ; Ekudden, Erik ; Johansson, Bjorn ; Kleijn, W. Bastiaan
Author_Institution :
Speech Coding Res., Ericsson Radio Syst. AB, Stockholm, Sweden
Abstract :
In CELP, the use of codebooks with entries with only a few non-zero samples provides high speech quality and facilitates fast computation. With decreasing bit-rate, the intervals between the pulses increase, and the quality of the reconstructed signal begins to suffer from a particular type of artifact, which is strongest for noise-like segments. In this paper we describe experiments which show that the perceived artifacts are mainly concentrated at frequencies above 3 kHz, and this is consistent with our understanding of auditory theory. Our analysis leads to simple strategies to eliminate the artifacts, even at lower bit rates. We describe both a non-adaptive and an adaptive post-processing method to remove the artifacts. The methods are demonstrated to be efficient when used in the ACELP algorithm. A closed-loop method for ACELP is also described
Keywords :
adaptive signal processing; linear predictive coding; speech coding; 6.4 kbit/s; ACELP; CELP; adaptive post-processing method; auditory theory; closed-loop method; high speech quality; noise-like segments; non-adaptive post-processing method; sparse codebooks; sparse-excitation artifacts removal; speech coding; Auditory system; Background noise; Bit rate; Computational complexity; Frequency; GSM; Linear predictive coding; Speech coding; Speech enhancement; Speech recognition;
Conference_Titel :
Acoustics, Speech and Signal Processing, 1998. Proceedings of the 1998 IEEE International Conference on
Conference_Location :
Seattle, WA
Print_ISBN :
0-7803-4428-6
DOI :
10.1109/ICASSP.1998.674388