BTSC ENCODER
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 digital signal processor arrangement for use in generating a broadcast television BTSC encoded stereo signal from a left-channel signal and a right-channel signal, comprising:
a signal generator arrangement configured so as to generate a digital summation signal as a function of the sum of the left-channel and right-channel signals, and a digital difference signal as a function of the difference between the left-channel and right-channel signals;
a summation signal processing arrangement including a filter arrangement configured to filter the digital summation signal so as to produce a conditioned digital summation signal;
a difference signal processing arrangement including a pre-emphasis filter arrangement and a signal compressor arrangement, the filter and compressor arrangements being configured so as to condition and compress the digital difference signal so as to produce a conditioned digital difference signal;
a signal combiner arrangement configured so as to combine the conditioned digital summation signal with a modulated version of the conditioned digital difference signal so as to generate a composite modulated signal; and
a digital-to-analog converter arrangement for converting the composite modulated signal to an analog output signal;
wherein the digital signal processor is configured to provide a frequency response in the digital domain that is substantially equal to the corresponding analog frequency response specified by the BTSC standard.
2 . An arrangement in accordance with claim 1 , wherein the filter arrangement of the summation signal processing arrangement is configured so as to filter the digital summation signal with a 75 μs pre-emphasis so as to produce a conditioned digital summation signal.
3 . The arrangement according to claim 1 , wherein the pre-emphasis filter arrangement comprises a fixed and variable pre-emphasis network.
4 . A digital signal processor arrangement for use in generating a broadcast television BTSC encoded stereo signal from a left-channel signal and a right-channel signal, comprising:
a signal generator arrangement configured so as to generate a digital summation signal as a function of the sum of the left-channel and right-channel signals, and a digital difference signal as a function of the difference between the left-channel and right-channel signals;
a summation signal processing arrangement including a filter arrangement configured to filter the digital summation signal so as to produce a conditioned digital summation signal;
a difference signal processing arrangement including a pre-emphasis filter arrangement and a signal compressor arrangement, the filter and compressor arrangements being configured so as to condition and compress the digital difference signal so as to produce a conditioned digital difference signal;
a signal combiner arrangement configured so as to combine the conditioned digital summation signal with a modulated version of the conditioned digital difference signal so as to generate a composite modulated signal, wherein the difference between the conditioned digital summation signal and the conditioned digital difference signal, for a given frequency and level, conforms substantially with the difference specified by the BTSC standard; and
a digital-to-analog converter arrangement for converting the composite modulated signal to an analog output signal.
5 . An arrangement in accordance with claim 4 , wherein the filter arrangement of the summation signal processing arrangement is configured so as to filter the digital summation signal with a 75 μs pre-emphasis so as to produce a conditioned digital summation signal.
6 . The arrangement according to claim 4 , wherein the pre-emphasis filter arrangement comprises a fixed and variable pre-emphasis network.