Multi-channel transcoder rate adapter having low delay and integral echo cancellation
AssigneeDSC/Celcore, Inc.
InventorsJames M. Davis, James D. Pruett
Life of this patent
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Abstract
A multi-channel transcoder with rate adapter converts the data rate of GSM and PSTN network data in a multi-channel network. A transcoder having echo-cancellation features uses the robust voice activity detection functions of the GSM transcoder functions to enhance the accuracy of echo-cancellation of near-end signals. A method for decoding a GSM signal in which the transmission of the audio data over the network is commenced prior to the completing of the decoding process. A transcoder unit having rate adaption and echo-cancellation with improved decoding is implemented in a single DSP and processes multiple traffic channels simultaneously.
Claims10
A transcoder unit having a rate adaption function and an echo-cancellation function, comprising:
- a single digital signal processor integrated circuit chip (DSP), the DSP having at least one input connected to at least one of a multi-channel near-end transmission line and a multi-channel far-end transmission line, and at least one output connected to at least one of the multi-channel far-end transmission line and the multi-channel near-end transmission line, wherein the DSP
- receives far-end input data from the multi-channel far-end transmission line at a first data rate,
- receives near-end input data from the multi-channel near-end transmission line at a second data rate,
- decodes the far-end input data to produce decoded far-end input data,
- performs an echo-cancellation operation on the near-end input data to produce echo-cancelled near-end input data,
- encodes the echo-cancelled near-end input data to produce encoded near-end input data,
- performs a near-end speech detection operation on the near-end input data and produces a first value (HCNTR) as a function of the presence of speech in the near-end input data,
- calculates a second value (INHIBIT) as a function of the far-end input data and the encoded near-end input data,
- performs training functions using the decoded far-end input data when the first value (HCNTR) is a first predetermined level and the second value (INHIBIT) is a second predetermined level,
- transmits the decoded far-end input data over the multi-channel near-end transmission line at the second data rate, and
- transmits the encoded near-end input data over the multi-channel far-end transmission line at the first data rate.
Dependencies are inferred from the claim text.