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 . An adaptive digital signal weighting system for processing a digital information signal representing the difference between left and right stereophonic audio signals, the system comprising: 
 a digital filter arrangement constructed and arranged so as to digitally vary the gain impressed on the portion of said digital information signal within a first select spectral region within a predetermined bandwidth by a first variable gain factor, said first variable gain factor varying in response to and as a function of a first digital control signal;    a first digital control signal generator constructed and arranged so as to digitally generate said first digital control signal only in response to and in accordance with the signal energy of said digital information signal within a second select spectral region including at least a part of said first select spectral region;    a digital gain controller, coupled to said digital filter arrangement and constructed and arranged so as to digitally vary the signal gain impressed on the digital information signal substantially throughout said predetermined bandwidth by a second variable gain factor, said second variable gain factor varying in response to and as a function of a second digital control signal; and    a second digital control signal generator constructed and arranged so as to digitally generate said second control signal in response to and as a function of the signal energy of said digital information signal substantially within a third select spectral region within said predetermined bandwidth;    wherein the digital filter arrangement, first control signal generator, digital gain controller, and the second control signal generator each operate at a predetermined sample rate so as to preserve the signal content of the information signal.