BTSC ENCODER
The disclosed BTSC encoder includes a left high pass filter means; a right 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 method of digitally encoding left and right channel audio signals in accordance with the BTSC standard, comprising:
providing digital left and digital right channel audio signals;
combining the digital left and digital right channel audio signals to form a digital sum signal and a digital difference signal; and
encoding the digital sum signal and the digital difference signal according to the BTSC standard so as to produce a digital BTSC signal weighted by a frequency response in the digital domain that is substantially equal to the analog frequency response specified by the BTSC standard.
2 . A method of digitally encoding left and right channel audio signals according to claim 1 , wherein providing digital left and digital right channel audio signals includes receiving analog left and right channel audio signals and digitizing the analog left and right channel audio signals so as to produce the digital left and right channel audio signals.
3 . A method of digitally encoding left and right channel audio signals according to claim 1 , wherein encoding the digital sum signal and the digital difference signal according to the BTSC standard includes encoding the digital sum channel with an applied 75 μs preemphasis.
4 . A method of digitally encoding left and right channel audio signals according to claim 1 , wherein encoding the digital sum signal and the digital difference signal according to the BTSC standard includes encoding the digital difference signal with an adaptive signal weighting system.
5 . A method of generating digital audio signals according to the BTSC standard comprising:
accepting one or more digital audio input signals,
performing a frequency translation of at least one digital audio signal to form at least one modified digital audio signal, and
modifying the amplitude and phase of at least one of the digital audio signals according to the BTSC standard so as to create one or more corresponding digital audio output signals weighted by a frequency response in the digital domain that is substantially equal to the analog frequency response specified by the BTSC standard.
6 . A method of generating digital audio signals according to claim 5 , wherein performing the frequency translation of the least one digital audio signal includes performing the frequency translation by substantially 31.468 kHz.
7 . A method of generating one or more digital output signals according to the BTSC standard, comprising:
filtering a digital signal including sum-channel information so as to create a digital sum-channel signal weighted by a frequency response in the digital domain that is substantially equal to the analog frequency response specified by the BTSC standard;
filtering a digital signal including difference-channel information so as to create a digital difference-channel signal weighted by a frequency response in the digital domain that is substantially equal to the analog frequency response specified by the BTSC standard; and
combining the sum-channel signal and the difference-channel signal so as to form one or more digital output signals according to the BTSC standard.