Two-channel coding of digital signals
First Claim
1. Signal processing apparatus comprising an encoder for encoding an analog signal (V) to produce a coded signal, said encoder comprising:
- analog to digital encoder means (10) for sampling the analog signal (V) to provide a digitally encoded signal (S);
coding means (12) responsive to the output of said encoder means (10) for providing two distinct subsampled digital signals (E, P);
said coding means (12) including subsampling means (56) for subsampling said digitally encoded signal (S) to provide a subsampled digital signal (P) corresponding to the input signal, and also including filtering and subsampling means (50,52,54) for filtering and subsampling said digitally encoded signal (S) to provide a complementary subsampled signal (E) corresponding to the difference between the digitally encoded signal (S) and a filtered signal derived by filtering the signal (S); and
first and second coding means (14,15,16;
20,22, 24,26,28,30) for encoding said two distinct signals (E, P) to provide two coded distinct signals (EI, Ep) respectively, each of said first and second coding means being operative to encode in a different way to that in which the other encodes.
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Accused Products
Abstract
A video codec is used to reduce the bandwidth of a video signal for storage and/or transmission. To transmit an uncoded quality color NTSC television signal is digitized form requires channel bandwidth typically 90-120 Mb/s for the signal in the composite format and 216 Mb/s for the signal in the component format. The proposed video codec achieves a reduction of the required transmission bandwidth by a factor of 2-3 by splitting the imput signal into two channels, a main and a complementary channel, and by applying different coding techniques in each. In the main channel the input signal is subsampled and DPCM encoded using a fixed-rate companded quantization, whereas VWL and block coding is used to encode the complementary channel carrying the interpolation error signal. This arrangement seeks to ensure high picture quality while being easily adaptable to different transmission rates and signal formats. In bandwidth-on-demand applications the main channel cna be used alone to provide a lesser quality signal, for example CATV quality at 35 Md/s, with an attendant reduction in system complexity.
136 Citations
44 Claims
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1. Signal processing apparatus comprising an encoder for encoding an analog signal (V) to produce a coded signal, said encoder comprising:
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analog to digital encoder means (10) for sampling the analog signal (V) to provide a digitally encoded signal (S); coding means (12) responsive to the output of said encoder means (10) for providing two distinct subsampled digital signals (E, P); said coding means (12) including subsampling means (56) for subsampling said digitally encoded signal (S) to provide a subsampled digital signal (P) corresponding to the input signal, and also including filtering and subsampling means (50,52,54) for filtering and subsampling said digitally encoded signal (S) to provide a complementary subsampled signal (E) corresponding to the difference between the digitally encoded signal (S) and a filtered signal derived by filtering the signal (S); and first and second coding means (14,15,16;
20,22, 24,26,28,30) for encoding said two distinct signals (E, P) to provide two coded distinct signals (EI, Ep) respectively, each of said first and second coding means being operative to encode in a different way to that in which the other encodes. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26)
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27. A signal processing method for encoding an analog signal (V) to produce a coded signal, comprising the steps of:
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sampling the analog signal (V) to provide a digitally encoded signal (S); providing two distinct subsampled digital signals (E, P) from the digitally encoded signal (S) including; subsampling said digitally encoded signal (S) to provide a subsampled digital signal (P) corresponding to the input signal, and filtering and subsampling said digitally encoded signal (S) to provide a complementary subsampled signal (E) corresponding to the difference between the digitally encoded signal (S) and a filtered signal derived by filtering the signal (S); and encoding said two distinct signals (E, P) differently from each other to provide two coded distinct signals (EI, EP), respectively. - View Dependent Claims (28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44)
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Specification
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- Resources
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Current AssigneeNortel Networks Limited (Nortel Networks Corporation)
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Original AssigneeNorthern Telecom Limited (Nortel Networks Corporation)
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InventorsPrasada, Birendra, Sabri, Mohamed S., Golembiowski, Albert
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Primary Examiner(s)Groody, James J.
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Assistant Examiner(s)Peng, John K.
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Application NumberUS06/939,983Time in Patent Office693 DaysField of Search358/133, 358/138, 358/135, 358/12, 358/136, 375/27, 375/28, 375/33, 340/347 DDUS Class Current375/240.21CPC Class CodesH04N 19/124 QuantisationH04N 19/30 using hierarchical techniqu...H04N 19/50 using predictive coding H04...
