Btsc encoder

Abstract

The disclosed BTSC encoder includes a left high pass filter means; a matrix means for receiving the digital left and digital right filtered signals, and including means for summing the digital left and digital right filtered signals and thereby generating a digital sum signal, and including means for subtracting one of the digital left and digital right filtered signals from the other of the digital left and digital right filtered signals and thereby generating a digital difference signal; a difference channel processing means for digitally processing the digital difference signal; and a sum channel processing means for digitally processing the digital sum signal.

1 . A circuit for encoding digital left and digital right audio signals according to the BTSC standard, comprising:
 a digital matrix unit configured to generate a digital sum channel signal and a digital difference channel signal;   a sum channel processing unit having a frequency response in the digital domain that is substantially equal to the corresponding analog frequency response specified by the BTSC standard; and   a difference channel processing unit having a frequency response in the digital domain that is substantially equal to the corresponding analog frequency response specified by the BTSC standard;   wherein the sum channel processing unit is configured to produce a conditioned digital sum channel signal in response to the digital sum channel signal, and the difference channel processing unit is configured to produce an encoded digital difference channel signal in response to the digital difference channel signal.   
     
     
         2 . A circuit for encoding digital left and digital right audio signals according to  claim 1 , wherein the digital matrix unit, the difference channel processing unit, and the sum channel processing unit are included on a single integrated circuit. 
     
     
         3 . A circuit for encoding digital left and digital right audio signals according to  claim 1 , wherein the digital matrix unit, the difference channel processing unit, and the sum channel processing unit are implemented by a digital signal processor. 
     
     
         4 . A system for generating a broadcast television stereo signal from a left-channel signal and a right-channel signal, comprising:
 a signal combiner arrangement configured so as to generate a summation signal comprising the sum of a right digital signal and a left digital signal, and generate a difference signal comprising the difference between the right digital signal and the left digital signal;   a sum and difference signal generator arrangement configured so as to generate a first pre-emphasized digital signal as a function of the summation signal, and a second pre-emphasized digital signal as a function of the difference signal;   a signal transformation arrangement configured so as to transform the first pre-emphasized digital signal to a digital BTSC compliant L+R signal, and transform the second pre-emphasized digital signal to a digital BTSC compliant L−R signal, wherein the signal transformation arrangement is configured and arranged to have a frequency response in the digital domain that is substantially equal to the analog frequency response specified by the BTSC standard; and   a composite signal generator arrangement configured so as to generate a digital composite signal as a function of the combination of the digital BTSC compliant L+R signal and a modulated version of the digital BTSC compliant L−R signal.   
     
     
         5 . The system of  claim 4 , wherein the sum and difference signal generator arrangement comprises a fixed and variable pre-emphasis network. 
     
     
         6 . A circuit for encoding digital left and digital right audio signals according to the BTSC standard, comprising:
 a digital matrix unit configured to generate a digital sum channel signal and a digital difference channel signal;   a sum channel processing unit; and   a difference channel processing unit;   wherein the sum channel processing unit is configured to produce a conditioned digital sum channel signal in response to the digital sum channel signal, and the difference channel processing unit is configured to produce an encoded digital difference channel signal in response to the digital difference channel signal, and wherein the difference between the conditioned digital sum channel signal and the encoded digital difference channel signal, for a given frequency and level, conforms substantially with the difference specified by the BTSC standard.   
     
     
         7 . A circuit for encoding digital left and digital right audio signals according to  claim 6 , wherein the digital matrix unit, the difference channel processing unit, and the sum channel processing unit are included on a single integrated circuit. 
     
     
         8 . A circuit for encoding digital left and digital right audio signals according to  claim 6 , wherein the digital matrix unit, the difference channel processing unit, and the sum channel processing unit are implemented by a digital signal processor. 
     
     
         9 . A system for generating a broadcast television stereo signal from a left-channel signal and a right-channel signal, comprising:
 a signal combiner arrangement configured so as to generate a summation signal comprising the sum of a right digital signal and a left digital signal, and generate a difference signal comprising the difference between the right digital signal and the left digital signal;   a sum and difference signal generator arrangement configured so as to generate a first pre-emphasized digital signal as a function of the summation signal, and a second pre-emphasized digital signal as a function of the difference signal;   a signal transformation arrangement configured so as to transform the first pre-emphasized digital signal to a digital BTSC compliant L+R signal, and transform the second pre-emphasized digital signal to a digital BTSC compliant L−R signal; and   a composite signal generator arrangement configured so as to generate a digital composite signal as a function of the combination of the digital BTSC compliant L+R signal and a modulated version of the digital BTSC compliant L−R signal, wherein the difference between the digital BTSC compliant L+R signal and the digital BTSC compliant L−R signal, for a given frequency and level, conforms substantially with the difference specified by the BTSC standard.   
     
     
         10 . The system of  claim 9 , wherein the sum and difference signal generator arrangement comprises a fixed and variable pre-emphasis network.