公开(公告)号：BR9606800A

公开(公告)日：1997-12-30

申请号：BR9606800

申请日：1996-01-25

Applicant: QUALCOMM INC

Inventor： WEARVER LINDSAY A JR ,  SIH GILBERT C ,  JACOBS PAUL E ,  GARDNER WILLIAM R ,  LAM S KATHERINE ,  DEJACO ANDREW P

IPC: G10L11/02 ,  G10L19/00 ,  G10L19/14 ,  H04B7/26 ,  H04B14/04 ,  H04Q11/04 ,  H04W88/18 ,  G10L5/00 ,  H04Q7/24

Abstract: When one vocoding system is coupled to another vocoding system, a tandem arrangement results. The tandem configuration results in voice quality degradation as speech is encoded and decoded, then encoded and decoded again. One reason for the degradation is that postfiltering performed at the output of the speech decoding process introduces distortions in the spectral content of the reconstructed speech as compared to the original speech. The present invention prevents the degradation due to the use of postfilters by modifying the postfiltering within the vocoders where a tandem configuration exists. A detection code is embedded within the data signal to indicate the existence of a tandem configuration. If the detection code is received at a vocoder, modified vocoding is established within the vocoders to prevent the degradation due to the postfiltering.