Transmission system comprising a sub-band echo canceller which includes a sub-band coding arrangement
First Claim
1. A transmission system for transmitting signals between at least two transceiver stations, each said transceiver station comprising:
- (a) at least one sub-band encoding-decoding arrangement for multi-sub-band encoded signals including a sub-band decoder and a sub-band encoder,(b) at least one sub-band echo canceller coupled to the sub-band encoding-decoding arrangement,(c) said sub-band encoding-decoding arrangement comprising;
(i) at least one synthesis filter bank for receiving a decoded sub-band signal from the sub-band decoder and forming a full-band speech signal,(ii) at least one analysis filter bank for analysing a full-band speech signal and forming therefrom a sub-band signal to be sent to the sub-band encoder,(d) the synthesis filter bank and the analysis filter bank being connected for processing signals of the sub-band encoding-decoding arrangement,(e) the synthesis filter bank and the analysis filter bank also being connected for processing signals of the sub-band echo canceller.
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Abstract
Transmission system comprising a sub-band echo canceller which includes a sub-band coding arrangement.
The invention relates to a transmission system comprising a sub-band echo canceller which includes a canceller that can be switched between a receive path (r) and a send path (s).
To reduce the computational complexity as well as the signal delays also with sub-band coding or sub-band decoding, the sub-band coding arrangement comprises a synthesis filter bank and an analysis filter bank which are provided for sub-band coding and also for sub-band echo cancellation.
Advantageous applications for the echo canceller are subscriber terminal units, for example, hands-free facilities for car telephones, videophones or video conference units which have an echo path formed by at least one microphone and at least one loudspeaker.
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Citations
20 Claims
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1. A transmission system for transmitting signals between at least two transceiver stations, each said transceiver station comprising:
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(a) at least one sub-band encoding-decoding arrangement for multi-sub-band encoded signals including a sub-band decoder and a sub-band encoder, (b) at least one sub-band echo canceller coupled to the sub-band encoding-decoding arrangement, (c) said sub-band encoding-decoding arrangement comprising; (i) at least one synthesis filter bank for receiving a decoded sub-band signal from the sub-band decoder and forming a full-band speech signal, (ii) at least one analysis filter bank for analysing a full-band speech signal and forming therefrom a sub-band signal to be sent to the sub-band encoder, (d) the synthesis filter bank and the analysis filter bank being connected for processing signals of the sub-band encoding-decoding arrangement, (e) the synthesis filter bank and the analysis filter bank also being connected for processing signals of the sub-band echo canceller. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A subscriber terminal unit comprising:
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(a) at least one microphone, (b) at least one loudspeaker forming with the microphone an echo path, (c) at least one sub-band encoding-decoding arrangement multi-sub-band encoded signals including a sub-band decoder and a sub-band encoder, (d) at least one sub-band echo canceller coupled to the sub-band encoding-decoding arrangement, (e) said sub-band encoding-decoding arrangement comprising; (i) at least one synthesis filter bank for receiving a decoded sub-band signal from the sub-band decoder and forming a full-band speech (ii) at least one analysis filter bank for analysing a full-band speech signal and forming therefrom a sub-band signal to be sent to the sub-band encoder, (f) the synthesis filter bank and the analysis filter bank being connected for processing signals of the sub-band encoding-decoding arrangement, (g) the synthesis filter bank and the analysis filter bank also being connected for processing signals of the sub-band echo canceller.
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20. A subscriber terminal unit comprising:
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(a) at least one microphone, (b) at least one loudspeaker forming with the microphone an echo path, (c) a sub-band decoder for receiving a full-band signal and forming sub-band signals along a receive path, (d) a sub-band encoder for receiving sub-band signals from a send path and forming full-band signals, (e) a synthesis filter bank connecting the receive path to the loudspeaker and forming full-band signals, (e) an analysis filter bank connected to the microphone and forming sub-band signals, (f) a subtracter, (g) a sub-band echo canceller connected to receive sub-band signals from the receive and from the send path, (e) said subtracter having inputs connected to receive sub-band signals from the sub-band echo canceller and from the analysis filter and having an output connected to the send path.
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Specification