公开(公告)号：EP1697925A4

公开(公告)日：2009-07-08

申请号：EP04814785

申请日：2004-12-17

Applicant: MOTOROLA INC

Inventor： JASIUK MARK A ,  RAMABADRAN TENKASI V ,  MITTAL UDAR ,  ASHLEY JAMES P ,  MCLAUGHLIN MICHAEL J

IPC: G10L11/04 ,  G10L19/00 ,  G10L19/04 ,  G10L19/08 ,  G10L19/10 ,  G10L19/12

CPC classification number: G10L19/09

Abstract: A method (Fig. 9) and apparatus (500, 600) for prediction in a speech-coding system extends a 1st order long-term predictor (LTP) filter, using a sub-sample resolution delay, to a multi-tap LTP filter (504, 604). From another perspective, a conventional integer-sample resolution multi-tap LTP filter is extended to use sub-sample resolution delay. Such a multi-tap LTP filter offers a number of advantages over the prior-art. Particularly, defining the lag with sub-sample resolution makes it possible to explicitly model the delay values that have a fractional component, within the limits of resolution of the over-sampling factor used by the interpolation filter. The coefficients (ßi's) of the multi-tap LTP filter are thus largely freed from modeling the effect of delays that have a fractional component. Consequently their main function is to maximize the prediction gain of the LTP filter via modeling the degree of periodicity that is present and by imposing spectral shaping.

公开(公告)号：EP1238479A4

公开(公告)日：2005-07-27

申请号：EP00980890

申请日：2000-11-30

Applicant: MOTOROLA INC

Inventor： RAMABADRAN TENKASI V ,  ASHLEY JAMES P

IPC: H04B3/06 ,  G10L21/02 ,  H04B15/00 ,  H04S1/00

CPC classification number: H04S1/007

Abstract: A method and apparatus for suppressing acoustic background noise in a communication system. An operating signal-to-noise ratio (SNR) level is reliably evaluated from channel energy (293) and background noise energy (294) values by a SNR level estimator (295). A minimum gain factor and a gain slope are adapted (290) depending on the operating SNR level. Using these adapted values and the channel SNR, the channel gain is selected (233). When the channel SNR is below a certain threshold, the channel is completely noise-like and the gain factor selected is minimum so that the channel is maximally attenuated. When the channel SNR is fairly high, the channel gain selected is 0 dB. For intermediate values of channel SNR, the gain factor selected lies between minimum and 0 dB.