Compatible digital audio for NTSC television
AssigneeDolby Laboratories Licensing Corporation
InventorCraig C. Todd
Life of this patent
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Abstract
A method and apparatus for transmitting a digitally modulated Quadrature Phase Keyed (QPSK) audio carrier signal, or a digitally modulated Quadrature Partial Response System (QPRS) audio carrier signal, wherein the audio carrier signal is located 1.2 MHz below the video carrier of an NTSC signal. This places the digital audio signal 300 KHz above the analog FM sound center frequency of the NTSC signal in the adjacent lower channel, 4.8 MHz above the video carrier of the adjacent lower channel NTSC signal and at the edge of the lower vestigal video sideband components of the NTSC signal with which the digital audio signal is associated.
Claims50
Apparatus for transmitting digitally encoded sound signals on a modulated carrier associated with a standard NTSC color television broadcast signal, wherein the signal components of the NTSC signal are contained within an RF bandwidth of nominally 6 MHz, the FM sound signal carrier frequency is nominally 4.5 NHz above the vision carrier frequency, the NTSC color subcarrier frequency is nominally 3.579545 MHz above the vision carrier frequency, and in the RF spectrum of broadcast and cable systems the standard spacing between the vision carrier frequencies of adjacent channel NTSC signals is 6 MHz, and wherein the standard NTSC color television signal may have its FM sound carrier modulated in accordance with the BTSC multi-channel television sound system, comprising
- modulated carrier signal generation means for receiving sound signals and for generating in response thereto a digitally modulated Quadrature Phase Shift Keyed (QPSK) carrier signal, and
- carrier frequency setting means for setting the frequency of said digitally modulated carrier signal with respect to the components of said NTSC television broadcast signal and for setting the level of said digitally modulated carrier signal, wherein aid carrier signal is set at a frequency about 1.2 MHz below the vision carrier frequency of the NTSC signal and the level of said carrier signal is set at about -23 dB relative tot he peak vision carrier level.
Apparatus for transmitting digitally encoded sound signals on a modulated carrier associated with a standard NTSC color television broadcast signal, wherein the signal components of the NTSC signal are contained within an RF bandwidth of nominally 6 MHz, the FM sound signal carrier frequency is nominally 4.5 MHz above the vision carrier frequency, the NTSC color subcarrier frequency is nominally 3.579545 MHz above the vision carrier frequency, and in the RF spectrum of broadcast and cable systems the standard spacing between the vision carrier frequencies of adjacent channel NTSC signals is 6 MHz, and wherein the standard NTSC color television signal may have its FM sound carrier modulated in accordance with the BTSC multi-channel television sound system, comprising
- modulated carrier signal generation means for receiving sound signals and for generating in response thereto a digitally modulated carrier signal, said modulated carrier signal generation means including Quadrature Partial Response Signaling (QPRS) modulator means for generating a digitally modulated carrier signal, and
- carrier frequency setting means for setting the frequency of said digitally modulated carrier signal with respect to the components of said NTSC television broadcast signal and for setting the level of said digitally modulated carrier signal, wherein said carrier signal is set at a frequency about 1.2 MHz below the vision carrier frequency of the NTSC signal and the level of said carrier signal is set at about -20 dB relative to the peak vision carrier level.
Method for transmitting digitally encoded sound signals on a modulated carrier associated with a standard NTSC color television broadcast signal, wherein the signal components of the NTSC signal are contained within an RF bandwidth of nominally 6 MHz, the FM sound signal carrier frequency is nominally 4.5 MHz above the vision carrier frequency, the NTSC color subcarrier frequency is nominally 3.579545 MHz above the vision carrier frequency, and in the RF spectrum of broadcast and cable systems the standard spacing between the vision carrier frequencies of adjacent channel NTSC signals is 6 MHz, and wherein the standard NTSC color television signal may have its FM sound carrier modulated in accordance with the BTSC multi-channel television sound system, comprising
- receiving sound signals and generating in response thereto a digitally modulated Quadrature Phase Shift Keyed (QPSK) carrier signal,
- setting the frequency of said digitally modulated carrier signal with respect to the components of said NTSC television broadcast signal at a frequency about 1.2 MHz below the vision carrier frequency of the NTSC signal, and
- setting the level of said digitally modulated carrier signal at about -23 dB relative to the peak vision carrier level.
Method for transmitting digitally encoded sound signals on a modulated carrier associated with a standard NTSC color television broadcast signal, wherein the signal components of the NTSC signal are contained within an RF bandwidth of nominally 6 MHz, the FM sound signal carrier frequency is nominally 3.579545 MHz above the vision carrier frequency, and in the RF spectrum of broadcast and cable systems the standard spacing between the vision carrier frequencies of adjacent channel NTSC signals is 6 MHz, and wherein the standard NTSC color television signal may have its FM sound carrier modulated in accordance with the BTSC multi-channel television sound system, comprising
- receiving sound signals and generating in response thereto a digitally modulated Quadrature Partial Response Signaling (QPRS) carrier signal,
- setting the frequency of said digitally modulated carrier signal with respect to the components of said NTSC television broadcast signal, wherein said carrier signal is set at a frequency about 1.2 MHz below the vision carrier frequency of the NTSC signal and,
- setting the level of said digitally modulated carrier signal at about -20 dB relative to the peak vision carrier level.
Apparatus for receiving a digital audio signal, the signal comprising digitally-encoded audio signals modulated on a suppressed digital audio carrier signal, the carrier signal being associated with a standard NTSC color television broadcast signal, wherein the signal components of the NTSC signal are contained within an RF bandwidth of nominally 6 MHz, the FM sound signal carrier frequency is nominally 4.5 MHz above the vision carrier frequency, the color subcarrier frequency is nominally 3.579545 MHz above the vision carrier frequency, and in the RF spectrum of broadcast and cable systems the standard spacing between the vision carrier frequencies of adjacent channel NTSC signals is 6 MHz, and wherein the standard NTSC color television signal may have its FM sound carrier modulated in accordance with the BTSC multi-channel television sound system, and wherein the frequency of the digital audio carrier signal is about 1.2 MHz below the frequency of the NTSC vision carrier, and the digital audio signal has a nominal bandwidth in the range of 0.5 to 0.7 times the total data rate of the digitally-encoded audio signals, comprising
- digital audio signal demodulating means for receiving the digital audio signal and for generating in response thereto audio signals,
- digital audio carrier signal generating means for generating a carrier reinsertion signal at the frequency of the digital audio carrier signal for reinserting into said digital audio signal as the suppressed carrier thereof.
Method for receiving a digital audio signal, the signal comprising digitally-encoded audio signals modulated on a suppressed digital audio carrier signal, the carrier signal being associated with a standard NTSC color television broadcast signal, wherein the signal components of the NTSC signal are contained within an RF bandwidth of nominally 6 MHz, the FM sound signal carrier frequency is nominally 4.5 MHz above the vision carrier frequency, the color subcarrier frequency is nominally 3.579545 MHz above the vision carrier frequency, and in the RF spectrum of broadcast and cable systems the standard spacing between the vision carrier frequencies of adjacent channel NTSC signals is 6 MHz, and wherein the standard NTSC color television signal may have its FM sound carrier modulated in accordance with the BTSC multi-channel television sound system, and wherein the frequency of the digital audio carrier signal is about 1.2 MHz below the frequency of the NTSC vision carrier, and the digital audio signal has a nominal bandwidth in the range of 0.5 to 0.7 times the total data rate of the digitally-encoded audio signals, comprising
- receiving the digital audio signal and generating in response thereto audio signals,
- generating a carrier reinsertion signal at the frequency of the digital audio carrier signal and reinserting said reinsertion signal into said digital audio signal as the suppressed carrier thereof.
Dependencies are inferred from the claim text.