PCT No. PCT / SE96 / 00128 Sec. 371 Date Aug. 4, 1997 Sec. 102(e) Date Aug. 4, 1997 PCT Filed Feb. 2, 1996 PCT Pub. No. WO96 / 24926 PCT Pub. Date Aug. 15, 1996A speech
encoder (100) receives speech signals (S) which are encoded and transmitted on a
communication channel (120).
Silence in the speech is utilized by a data
encoder (101) to transmit data on the speech
frequency band via the channel (120). A
signal classifier (103) switches between the encoders (100, 101). The speech
encoder has synthesis filter (115) with state variables in a
delay line, predictor adaptor (116),
gain predictor (113, 114) and excitation
codebook (112). The data encoder (101) has
delay line with state variables stored and updated in a buffer (192). On switching (103, 102, 193) from data to speech, the buffer state variables are fed into the synthesis filter
delay line via an input (144) for smooth transition in the speech encoding. Coefficient values in the synthesis filter (115) and an
excitation signal (ET(1 . . . 5)) are generated. Thereby a buffer in the
gain predictor (113, 114) is preset and its predictor coefficients and
gain are generated. The incoming speech
signal (S) newly detected is encoded (CW) by the values generated in the speech encoder (100), which is successively adapted. The
receiver side has corresponding speech and data decoders.