Btsc encoder

Abstract

The disclosed BTSC encoder includes a left high pass filter means for receiving a digital left channel audio signal and for digitally high pass filtering the digital left channel audio signal and thereby generating a digital left filtered signal; a right high pass filter means for receiving a digital right channel audio signal and for digitally high pass filtering the digital right channel audio signal and thereby generating a digital right filtered signal; 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 system for producing a digital composite modulated BTSC signal, comprising a digital BTSC encoder arranged so as to generate a digital BTSC encoded signal, wherein the digital BTSC encoder is configured to have a frequency response in the digital domain that is substantially equal to the corresponding analog frequency response specified by the BTSC standard, and a digital composite modulator. 
     
     
         2 . A circuit for producing a digital composite modulated BTSC signal, comprising a matrix unit configured to produce a digital sum signal and a digital difference signal, a digital sum channel processing unit configured to produce a conditioned digital sum signal in response to the digital sum signal, and a digital difference channel processing unit configured to produce an encoded digital difference signal in response to the digital difference signal, and a digital modulator unit configured to produce a composite modulated signal in response to the encoded digital difference signal and the conditioned digital sum signal, wherein the circuit is configured to have a frequency response in the digital domain that is substantially equal to the corresponding analog frequency response specified by the BTSC standard. 
     
     
         3 . A circuit for producing a digital composite modulated BTSC signal according to  claim 2 , wherein the digital modulator unit is configured to modulate the encoded digital difference signal at a frequency substantially equal to 31,468 Hz. 
     
     
         4 . A circuit for producing a digital composite modulated BTSC signal, comprising a matrix unit configured to produce a digital sum signal and a digital difference signal, a digital sum channel processing unit configured to produce a conditioned digital sum signal in response to the digital sum signal, and a digital difference channel processing unit configured to produce a conditioned digital difference signal in response to the digital difference signal, and a digital modulator unit configured to produce a composite modulated signal in response to the encoded digital difference signal and the conditioned digital sum signal, wherein the difference between the conditioned digital sum signal and conditioned digital difference signal, for a given frequency and level, conforms substantially with the difference specified by the BTSC standard. 
     
     
         5 . A circuit for producing a digital composite modulated BTSC signal according to  claim 4 , wherein the digital modulator unit is configured to modulate the encoded digital difference signal at a frequency substantially equal to 31,468 Hz.