Stereophonic audio signal decompression switching to monaural audio signal

Abstract

A communication system for sending a sequence of symbols on a communication link. The system includes a transmitter for placing information indicative of the sequence of symbols on the communication link and a receiver for receiving the information placed on the communication link by the transmitter. The transmitter includes a clock for defining successive frames, each of the frames including M time intervals, where M is an integer greater than 1. A modulator modulates each of M carrier signals with a signal related to the value of one of the symbols thereby generating a modulated carrier signal corresponding to each of the carrier signals. The modulated carriers are combined into a sum signal which is transmitted on the communication link. The carrier signals include first and second carriers, the first carrier having a different bandwidth than the second carrier. In one embodiment, the modulator includes a tree-structured array of filter banks having M leaf nodes, each of the values related to the symbols forming an input to a corresponding one of the leaf nodes. Each of the nodes includes one of the filter banks. Similarly, the receiver can be constructed of a tree-structured array of sub-band filter banks for converting M time-domain samples received on the communication link to M symbol values.A stereophonic audio signal decompression method that includes decoding, using a decoder, a compressed stereophonic audio signal. A de-quantizer de-quantizes the compressed stereophonic audio signal to generate sets of frequency components for synthesizing left and right audio signals. A controller switches to constructing a single set of frequency components by averaging corresponding frequency components in the left and right audio signals when a computational workload exceeds a capacity of a decompression system and a synthesizer synthesizes a monaural audio time domain signal.

1. A communication system for sending a sequence of symbols on a communication link a sequence of symbols having values representative of said symbols, said communication system comprising a transmitter for placing information indicative of said sequence of symbols on said communication link and a receiver for receiving said information placed on said communication link by said transmitter, said transmitter comprising
 a clock for defining successive frames, each said frame comprising M time intervals, where M is an integer greater than 1;   a modulator modulating each of M carrier signals with a signal related to the value of one of said symbols thereby generating a modulated carrier signal corresponding to each of said carrier signals that is to be modulated and generating a sum signal comprising a sum of said modulated carrier signals, said modulator comprising a tree-structured array of filter banks having nodes, including a root node and M leaf nodes, each of said values related to said symbols forming an input to a corresponding one of said leaf nodes, each of said nodes, other than said leaf nodes, comprising one of said filter banks; and   an output circuit for transmitting said sum signal on said communication link, wherein said carrier signals comprise first and second carriers, said first carrier having a different bandwidth than said second carrier.   
     
     
       2. The communication system of  claim 1  wherein said receiver comprises:
 an input circuit for receiving and storing M time-domain samples transmitted on said communication link; and 
 a decoder for recovering said M symbol values, said decoder comprising a tree-structured array of sub-band filter banks, said received M time-domain samples forming the input of a root node of said tree-structured array of said decoder and said M symbol values being generated by the leaf nodes of said tree-structured array of said decoder, each said sub-band filter bank comprising a plurality of FIR filters having a common input for receiving an input time-domain signal, each said filter generating an output signal representing a symbol value in a corresponding frequency band. 
 
     
     
       3. A communication system for sending a sequence of symbols on a communication link, said communication system comprising a transmitter for placing information indicative of said sequence of symbols on said communication link, said transmitter comprising:
 a clock for defining successive frames, each said frame comprising M time intervals, where M is an integer greater than 1;   a modulator modulating each of M carrier signals with a signal related to the value of one of said symbols thereby generating a modulated carrier signal corresponding to each of said carrier signals that is to be modulated and generating a sum signal comprising a sum of said modulated carrier signals;   an output circuit transmitting said sum signal on said communication link, wherein said carrier signals comprise first and second carriers, said first carrier having a different bandwidth than said second carrier; and   a receiver comprising:
 an input circuit for receiving and storing M time-domain samples transmitted on said communication link; and 
 a decoder for recovering said M symbol values, said decoder comprising a tree-structured array of sub-band filter banks, said received M time-domain samples forming the input of a root node of said tree-structured array said decorder and said M symbol values being generated by the leaf nodes of said tree-structured array decorder, each said sub-band filter bank comprising a plurality of FIR filters having a common input for receiving an input time-domain signal, each said filter generating an output signal representing a symbol value in a corresponding frequency band. 
   
     
     
       4. The communication system of  claim 3  wherein said modulator comprises a tree-structured array of filter banks having nodes, including a root node and M leaf nodes, each of said values related to said symbols forming an input to a corresponding one of said leaf nodes, each of said nodes, other than said leaf nodes, comprising one of said filter banks. 
     
     
       5. A stereophonic audio signal decompression method comprising:
 decoding, using a decoder, a compressed stereophonic audio signal;   de-quantizing, using a de-quantizer, the compressed stereophonic audio signal to generate sets of frequency components for synthesizing left and right audio signals;   switching, using a controller, to constructing a single set of frequency components by averaging corresponding frequency components in the left and right audio signals when a computational workload exceeds a capacity of a decompression system; and   synthesizing, using a synthesizer, a monaural audio time domain signal.