U.S. Philips Corporation

Marc E Groenewegen

Robbert G Van Der Waal

Arnoldus W Oomen

Raymond N Veldhuis

A transmitter provided with a subband coder is disclosed. The transmitter receives a wideband digital information at an input 1 and provides an output signal for transmission at an output (30). The input signal may have a varying sampling frequency (f.sub.g). The bitrate of the output signal is substantially constant. In order to compensate for the varying sampling frequency of the input signal, the transmitter is provided with a buffer memory (8) and a detector (18) for determining the filling degree of the memory (8). The control signal so derived, which is representative of the filing degree, is supplied to the bitallocation information generation unit (10). The bitpool B is varied in response to the control signal so as to control the filling degree to a nominal value, such as half full (FIG. 1). Further a receiver is disclosed for receiving the transmitted wideband digital information signal.

Transmitter for and method of transmitting a wideband digital

For encoding sound received as a stream of multibit input sample, from a finite length sequence of input samples, an instantaneous audibility threshold characteristic is determined. Next, a shaped, dither determined, signal is subtracted from the input samples to produce processing samples. Subtracting a dither signal dynamically ignores processing sample bits below the threshold. Next, quantization by a variable number of bits below the threshold is performed, while retaining all sample bits above the threshold. The ignored bits are replaced by the dither signal as buried channel bits at an adjustable number of bits per sample. Therefore, upgraded samples have non-ignored bits and buried channel bits are obtained and outputted. The noise is shaped through shape-filtering a difference between the upgraded samples and the processing samples, which shape-filtering may amend a received white-noise-like signal towards an actual threshold-versus-frequency characteristic.

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Eindhoven, Netherlands

Marc E Groenewegen