Nortel Networks Corporation

David G Sloan

Chung Cheung C Chu

Rafi Rabipour

The invention relates to a method and apparatus for controlling the transition of a bypass capable codec between operative modes, based on a certain characteristic of the audio data signal processed by the codec. The apparatus relies on a control signal to determine when the codec will switch from one mode to another. This control signal reflects a characteristic of the audio data signal received at the apparatus, such as the type of speech activity or the format of the audio data signal. When in the active (non-bypass) mode, the apparatus relies on an additional control signal to switch to the inactive (bypass) mode. This additional control signal is received from a control unit at a remote codec that indicates that the remote codec is also bypass capable, hence the decoder at the first codec and the encoder at the remote codec can switch to the inactive mode to pass between them the compressed data frames.

Method and apparatus for controlling the transition of an audio signal converter between two operative modes based on a certain characteristic of the audio input signal

A signal processor for effecting the conversion of an audio data signal from one format to another. The signal processor has a signal converter that can selectively acquire two operative modes, namely a first operative mode and a second operative mode. In the first operative mode, the signal converter transforms the audio data signal from one format to another and releases the converted audio data signal from the output of the signal processor. In the second operative mode, the signal converter is disabled and permits passage of the audio data signal to the output without conversion. The signal processor has a control unit for controlling the transition of the signal converter between operative modes. The control unit enables the signal converter to pass from the first operative mode to the second operative mode when at least one operating condition has been satisfied. The control unit reacts to a link impairment occurring on the data communication channel to alter the operating condition to be satisfied to enable passage from the first operative mode to the second operative mode. In a specific example of implementation, the modification to the operating condition can be such as to &ldquo;tighten&rdquo; the requirements to be met for switching from the first to the second operative mode.

Method and apparatus for controlling the transition of an audio converter between two operative modes in the presence of link impairments in a data communication channel

The invention relates to a method and apparatus for transmitting control information over an audio data stream, such as PCM coded speech information. The device comprises a control unit having two inputs receiving the PCM speech samples and control information signal. Each PCM sample is made up of a plurality of bits arranged according to different significance positions, such as position _N, where N&plus;1 is the number of bits in the sample. The control unit receives a selected sample and shifts a bit at a selected significance position to a lower significance position. The empty slot at the predetermined significance position is used to receive a bit from the control information signal. The compound signal thus obtained is then released over a transport path, such as a T link, for transmission to a remote location. At the receiver, the control information bit is extracted from the selected sample at the predetermined significance position, and the PCM speech sample is recovered by shifting upwardly at least one bit at a significance position lower than the selected significance position.

Growing community of inventors

Verdun, Canada

David G Sloan