Patent ID: 7403624

Claim:
A BTSC (Broadcast Television Systems Committee) encoder, comprising: a dual-channel sigma-delta analog-to-digital converter (ADC) having a left (L) audio input adapted for receiving a left (L) audio signal and a right (R) audio input adapted for receiving a right (R) audio signal, wherein responsive to L audio and R audio input signals, said dual-channel sigma-delta ADC converts the input signals into left and right digital audio output signals, respectively, and outputs the left and right digital audio output signals onto left and right digital audio outputs, respectively; a sync separator having a composite video input adapted for receiving a composite video signal, wherein responsive to the composite video input signal, said sync separator separates a horizontal synchronization signal from the composite video input signal and outputs the synchronization signal on a synchronization output; an audio processor having left and right digital audio inputs coupled to the left and right digital audio outputs of said dual-channel sigma-delta ADC and having a synchronization signal input coupled to the synchronization output of said sync separator, wherein responsive to left and right digital audio input signals and a synchronization signal, said audio processor processes the input and synchronization signals into a left+right (L+R) signal, a modulated left−right (L−R) signal, and a pilot tone signal, further wherein said audio processor outputs the L+R, modulated L−R, and pilot tone signals on a L+R output, a modulated L−R output, and a pilot tone output, respectively; filtering means coupled to the L+R output, the modulated L−R output, and the pilot tone output of said audio processor, said filtering means including a first filter for providing a filtered L+R signal, and a second filter for providing at least one of: i) a filtered and combined pilot and modulated L−R signal and ii) separately filtered pilot and modulated L−R signals, further wherein said filtering means outputs the filtered L+R signal on a first output, and outputs one of i) the filtered and combined pilot and modulated L−R signal on a second output and ii) the separately filtered pilot and modulated L−R signals on a second and a third output, respectively; and composite audio signal generating means coupled to the first output and one of i) the second output and ii) the second and third outputs, wherein responsive to the filtered L+R signal, and at least one of i) the filtered and combined pilot and modulated L−R signal and ii) the separately filtered pilot and modulated L−R signals, said composite audio signal generating means generating a composite analog audio signal, further wherein said composite signal generating means outputs the composite analog audio signal on a composite analog audio signal output of said composite audio signal generating means.