US4964162A — Secure television signal encoding and decoding sy…

Claim 1

Independent Claim 195 words

A television signal encoding apparatus, comprising: a video encoder for generating a line-spin scrambled video signal having minimized amplitude gaps, a line-spin scrambled video signal being generated by dividing the active portion of each line of a video signal into at least two segments and then interchanging the segments, an amplitude gap being formed between each of the interchanged segments, the video encoder including: an analog-to-digital converter for digitizing a video signal; and means for selectively applying a line spin scrambling transform to each line of the digitized video signal, the line spin scrambling transform being applied to a line of the digitized video signal only if the amplitude gap between each of the interchanged segments is less than or equal to a preselected value, the preselected value being less than 100 IRE units; and an audio encoder for generating a digitally-encrypted audio signal capable of being transmitted within the bandwidth limitations of a conventional television transmission system, the audio encoder including: an analog-to-digital converter for digitizing an audio signal; means for encrypting the digitized audio signal; and a three-level, partial response modulator for modulating the encrypted audio signal with a three-level, partial response waveform.

Claim 2

Dependent Claim 195 words

A television signal encoding apparatus, comprising: a video encoder for generating a line-spin scrambled video signal having minimized amplitude gaps, a line-spin scrambled video signal being generated by dividing the active portion of each line of a video signal into at least two segments and then interchanging the segments, an amplitude gap being formed between each of the interchanged segments, the video encoder including: an analog-to-digital converter for digitizing a video signal; and means for selectively applying a line spin scrambling transform to each line of the digitized video signal, the line spin scrambling transform being applied to a line of the digitized video signal only if the amplitude gap between each of the interchanged segments is less than or equal to a preselected value, the preselected value being less than 100 IRE units; and an audio encoder for generating a digitally-encrypted audio signal capable of being transmitted within the bandwidth limitations of a conventional television transmission system, the audio encoder including: an analog-to-digital converter for digitizing an audio signal; means for encrypting the digitized audio signal; and a three-level, partial response modulator for modulating the encrypted audio signal with a three-level, partial response waveform.

Claim 3

Dependent Claim 195 words

The television signal encoding apparatus as set forth in claim 1, wherein the means for selectively applying a line spin transform further includes: means for selectively applying a line spin scrambling transform to each line of the digitized video signal and a reverse transform to a segment of the scrambled video line, the line spin scrambling and reverse transforms being applied to a line of the digitized video signal only if the amplitude gap between each of the interchanged and reversed segments is less than or equal to the preselected value; means for selectively applying a line spin scrambling transform to each line of the digitized video signal, an inverse transform to a segment of the scrambled video line, and a reverse transform to another segment of the scrambled video line, the line spin scrambling, reverse and inverse transforms being applied to a line of the digitized video signal only if the amplitude gap between each of the interchanged, reversed and inverted segments is less than or equal to the preselected value; and means for selectively applying a reverse transform to each line of the digitized video signal that has not been line spin scrambled.

Claim 4

Dependent Claim 93 words

The television signal encoding apparatus as set forth in claim 1, wherein the means for selectively applying a line spin scrambling transform further includes: means for selectively applying a line spin scrambling transform to each line of the digitized video signal and an inverse transform to a segment of the line-spin scrambled video line, the line spin scrambling and inverse transforms being applied to a line of the digitized video signal only if the amplitude gap between each of the interchanged and inverted segments is less than or equal to the preselected value.

Claim 5

Dependent Claim 88 words

The television signal encoding apparatus as set forth in claim 1, wherein the audio encoder includes: a pair of analog-to-digital converters for digitizing the left and right channels of a stereo audio signal; means for multiplexing the left and right digitized stereo audio samples to form a serial bit stream of stereo audio samples; means for encrypting the serial bit stream of stereo audio samples; and a three-level, partial response modulator for modulating the serial bit stream of encrypted stereo audio samples with a three-level, partial response waveform.

Claim 6

Dependent Claim 136 words

The television signal encoding apparatus as set forth in claim wherein the video encoder further includes means for accurately synchronizing digital timing signals with the digitized video signal, the synchronizing means including: means for generating a controllable master sampling clock signal; means for generating a color-burst-frequency signal from the master sampling clock signal, the generating means including a counter driven by the master sampling clock signal; a phase error detector for measuring the phase error between the color-burst-frequency signal and a color burst signal in the digitized video signal; and means for controlling the frequency of the master sampling clock signal with the measured phase error; wherein the video signal is digitized at a sampling rate controlled by the master sampling clock signal, thereby synchronizing the master sampling clock signal with the video color burst signal.

Claim 7

Dependent Claim 99 words

The television signal encoding apparatus as set forth in claim 5, wherein the synchronizing means further includes: a horizontal synch signal separator for separating a horizontal synch signal from the digitized video signal; means for generating a reference horizontal synch signal; a phase error detector for measuring the phase error between the video horizontal synch signal and the reference horizontal synch signal; and a horizontal counter clocked by the master sampling clock signal, the horizontal counter being loaded with the phase error measured between the horizontal synch signals, thereby synchronizing the horizontal counter with the video horizontal synch signal.

Claim 8

Dependent Claim 62 words

The television signal encoding apparatus as set forth in claim 6, wherein the means for generating a reference horizontal synch signal includes: memory means programmed with a horizontal synch signal, the horizontal synch signal being read from the memory means when addressed by the horizontal counter, thereby generating a reference horizontal synch signal that is synchronized with the video horizontal synch signal.

Claim 9

Dependent Claim 48 words

The television signal encoding apparatus as set forth in claim 6, wherein the phase error detector for measuring the phase error between the horizontal synch signals includes: means for measuring the number of sampling clock pulses between the video horizontal synch signal and the reference horizontal synch signal.

Claim 10

Dependent Claim 76 words

The television signal encoding apparatus as set forth in claim 6, wherein the synchronizing means further includes: a vertical synch signal separator for separating a vertical synch signal from the digitized video signal; means for generating a reference vertical synch signal; and a vertical counter, the vertical counter being loaded with the line number of the horizontal video line having the video vertical synch signal, thereby synchronizing the vertical counter with the video vertical synch signal.

Claim 11

Dependent Claim 62 words

The television signal encoding apparatus as set forth in claim 9, wherein the means for generating a reference vertical synch signal includes: memory means programmed with a vertical synch signal, the vertical synch signal being read from the memory means when addressed by the vertical counter, thereby generating a reference vertical synch signal that is synchronized with the video vertical synch signal.

Claim 12

Dependent Claim 35 words

The television encoding apparatus as set forth in claim 9, wherein the vertical counter is clocked at the rate that the horizontal counter is loaded with the phase error measured between the horizontal synch signals.

Claim 13

Dependent Claim 100 words

The television signal encoding apparatus as set forth in claim 4, wherein the means for encrypting the serial bit stream of audio samples further includes: means for bursting out the serial bit stream of encrypted stereo audio samples at a higher data rate to allow for the insertion of other data into the serial bit stream; means for encoding the serial bit stream of encrypted stereo audio samples for error correction; and means for randomizing the serial bit stream of encrypted stereo audio samples, the randomizing means including means for multiplying the serial bit stream by a pseudorandom bit stream.

Claim 14

Dependent Claim 41 words

The television signal encoding apparatus as set forth in claim 4, wherein the means for encrypting the serial bit stream of audio samples includes: means for adding each bit of every stereo audio sample to a pseudorandom number generator seed value.

Claim 15

Dependent Claim 44 words

The television signal encoding apparatus as set forth in claim 4, wherein the modulator includes: memory means for storing amplitude samples from a plurality of three-level, partial response waveforms, the memory means being addressed by a plurality of bits from the serial bit stream.

Claim 16

Dependent Claim 72 words

The television signal encoding apparatus as set forth in claim 14, wherein the means for encrypting the serial bit stream of stereo audio samples further includes: means for differentially encoding each bit in the serial bit stream with a state opposite that of the immediately preceding differentially-encoded bit when the bit is a one and with a state equal that of the immediately preceding differentially-encoded bit when the bit is a zero.

Claim 17

Dependent Claim 135 words

The television signal encoding apparatus as set forth in claim 4, wherein the modulator includes: a pair of flip-flops for converting the serial bit stream of encrypted stereo audio samples into parallel in-phase and staggered quadrature-phase symbol streams and for differentially encoding each symbol in each of the in-phase and staggered quadrature-phase symbol streams with a state opposite that of the immediately preceding differentially-encoded symbol when the symbol is a one and with a state equal that of the immediately preceding differentially-encoded symbol when the symbol is a zero; memory means for storing amplitude samples from a plurality of three-level, partial response waveforms, the memory means being addressed by a plurality of symbols from the in-phase and the staggered quadrature-phase symbol streams; and means for multiplexing the in-phase and staggered quadrature-phase partial response amplitude samples.

Claim 18

Dependent Claim 29 words

The television signal encoding apparatus as set forth in claim 4, wherein the modulator further includes: means for up-converting the modulated stereo audio signal to a video subcarrier frequency.

Claim 19

Dependent Claim 26 words

The television signal encoding apparatus as set forth in claim 17, wherein the means for up-converting includes: means for digitally complementing the modulated stereo audio signal.

Claim 20

Dependent Claim 33 words

The television signal encoding apparatus as set forth in claim 4, wherein the modulator further includes: means for multiplexing the modulated stereo audio signal into the horizontal blanking interval of the video signal.

Claim 21

Independent Claim 183 words

A method for encoding a television signal, comprising the steps of: generating a line-spin scrambled video signal having minimized amplitude gaps, a line-spin scrambled video signal being generated by dividing the active portion of each line of a video signal into at least two segments and then interchanging the segments, an amplitude gap being formed between each of the interchanged segments, the step of generating including the steps of: digitizing a video signal; and selectively applying a line spin scrambling transform to each line of the digitized video signal, the line spin scrambling transform being applied to a line of the digitized video signal only if the amplitude gap between each of the interchanged segments is less than or equal to a preselected value, the preselected value being less than 100 IRE units; and generating a digitally encrypted audio signal capable of being transmitted within the bandwidth limitations of a conventional television transmission system, the step of generating including the steps of: digitizing an audio signal; encrypting the digitized audio signal; and modulating the encrypted audio signal with a three-level, partial response waveform.

Claim 22

Independent Claim 183 words

A method for encoding a television signal, comprising the steps of: generating a line-spin scrambled video signal having minimized amplitude gaps, a line-spin scrambled video signal being generated by dividing the active portion of each line of a video signal into at least two segments and then interchanging the segments, an amplitude gap being formed between each of the interchanged segments, the step of generating including the steps of: digitizing a video signal; and selectively applying a line spin scrambling transform to each line of the digitized video signal, the line spin scrambling transform being applied to a line of the digitized video signal only if the amplitude gap between each of the interchanged segments is less than or equal to a preselected value, the preselected value being less than 100 IRE units; and generating a digitally encrypted audio signal capable of being transmitted within the bandwidth limitations of a conventional television transmission system, the step of generating including the steps of: digitizing an audio signal; encrypting the digitized audio signal; and modulating the encrypted audio signal with a three-level, partial response waveform.

Claim 23

Dependent Claim 66 words

The encoding method as set forth in claim 20, wherein the step of selectively applying a line spin scrambling transform further includes the step of: selectively applying a reverse transform to each line of the digitized video signal that has not been line spin scrambled, the reverse transform being applied to a line of the digitized video signal only if the previous line was not reversed.

Claim 24

Dependent Claim 139 words

The encoding method as set forth in claim 20, wherein the step of selectively applying a line spin scrambling transform further includes the step of: selectively applying a line spin scrambling transform to each line of the digitized video signal and a reverse transform to a segment of the scrambled video line, the line spin scrambling and reverse transforms being applied to a line of the digitized video signal only if the amplitude gap between each of the interchanged and reversed segments is less than or equal to the preselected value, and if the amplitude at the beginning and the amplitude at the end of the active portion of the video line prior to line spin scrambling are both greater than or less than a reference value, and if the video line has not previously been line spin scrambled.

Claim 25

Dependent Claim 115 words

The encoding method as set forth in claim 22, wherein the step of selectively applying a line spin scrambling transform further includes the step of: selectively applying a line spin scrambling transform to each line of the digitized video signal, an inverse transform to a segment of the scrambled video line, and a reverse transform to another segment of the scrambled video, the line spin scrambling, reverse and inverse transforms being applied to a line of the digitized video signal only if the amplitude gap between each of the interchanged, reversed and inverted segments is less than or equal to the preselected value and if the video line has not previously been line spin scrambled.

Claim 26

Dependent Claim 66 words

The encoding method as set forth in claim 23, wherein the step of selectively applying a line spin scrambling transform further includes the step of: selectively applying a reverse transform to each line of the digitized video signal that has not been line spin scrambled, the reverse transform being applied to a line of the digitized video signal only if the previous line was not reversed.

Claim 27

Dependent Claim 86 words

The encoding method as set forth in claim 20, wherein the step of selectively applying a line spin scrambling transform includes the steps of: applying a line spin scrambling transform to each line of the digitized video signal; and selectively applying an inverse transform to a segment of each line-spin scrambled video line, the inverse transform being applied to a line-spin scrambled video line only if the amplitude gap between each of the interchanged and inverted segments is less than or equal to 50 IRE units.

Claim 28

Dependent Claim 85 words

The encoding method as set forth in claim 20, wherein the step of generating a digitally encrypted audio signal includes the steps of: digitizing the left and right channels of a stereo audio signal; multiplexing the left and right digitized audio samples to form a serial bit: stream of stereo audio samples; encrypting the serial bit stream of stereo audio samples; and modulating the serial bit stream of encrypted stereo audio samples with a three-level, partial response waveform to form a modulated stereo audio signal.

Claim 29

Dependent Claim 132 words

The encoding method as set forth in claim 20, wherein the step of generating a line-spin scrambled video signal further includes the step of accurately synchronizing digital timing signals with the digitized video signal, the step of synchronizing including the steps of: generating a controllable master sampling clock signal; generating a color-burst-frequency signal from the master sampling clock signal by driving a counter with the master sampling clock signal; measuring the phase error between the color-burst-frequency signal and a color burst signal in the digitized video signal; and controlling the frequency of the master sampling clock signal with the measured phase error; wherein the video signal is digitized at a sampling rate controlled by the master sampling clock signal, thereby synchronizing the master sampling clock signal with the video color burst signal.

Claim 30

Dependent Claim 84 words

The encoding method as set forth in claim 27, wherein the step of synchronizing further includes the steps of: separating a horizontal synch signal from the digitized video signal; generating a reference horizontal synch signal; measuring the phase error between the video horizontal synch signal and the reference horizontal synch signal; and loading a horizontal counter clocked by the master sampling clock signal with the phase error measured between the horizontal synch signals, thereby synchronizing the horizontal counter with the video horizontal synch signal.

Claim 31

Dependent Claim 52 words

The encoding method as set forth in claim 28, wherein the step of generating a reference horizontal synch signal includes the step of reading a horizontal synch signal from memory when addressed by the horizontal counter, thereby generating a reference horizontal synch signal that is synchronized with the video horizontal synch signal.

Claim 32

Dependent Claim 45 words

The encoding method as set forth in claim 28, wherein the step of measuring the phase error between the horizontal synch signals includes the step of measuring the number of sampling clock pulses between the video horizontal synch signal and the reference horizontal synch signal.

Claim 33

Dependent Claim 65 words

The encoding method as set forth in claim 28, wherein the step of synchronizing further includes the steps of: separating a vertical synch signal from the digitized video signal; generating a reference vertical synch signal; and loading a vertical counter with the line number of the horizontal video line having the vertical synch signal, thereby synchronizing the vertical counter with the video vertical synch signal.

Claim 34

Dependent Claim 52 words

The encoding method as set forth in claim 31, wherein the step of generating a reference vertical synch signal includes the step of: reading a vertical synch signal from memory when addressed by the vertical counter, thereby generating a reference vertical synch signal that is synchronized with the video vertical synch signal.

Claim 35

Dependent Claim 44 words

The encoding method as set forth in claim 31, wherein the step of loading a vertical counter includes the step of clocking the vertical counter at the rate that the horizontal counter is loaded with the phase error measured between the horizontal synch signals.

Claim 36

Dependent Claim 86 words

The encoding method as set forth in claim 26, wherein the step of encrypting the serial bit stream includes the steps of: bursting out the serial bit stream of encrypted stereo audio samples at a higher data rate to allow for the insertion of other data into the serial bit stream; encoding the serial bit stream of encrypted stereo audio samples for error correction; and randomizing the serial bit stream of encrypted stereo audio samples by multiplying the serial bit stream by a pseudorandom bit stream.

Claim 37

Dependent Claim 37 words

The encoding method as set forth in claim 26, wherein the step of encrypting the serial bit stream includes the step of: adding each bit of every stereo audio sample to a pseudorandom number generator seed value.

Claim 38

Dependent Claim 51 words

The encoding method as set forth in claim 26, wherein the step of modulating the serial bit stream includes the steps of: addressing memory locations with a plurality of bits from the serial bit stream; and reading from the memory locations amplitude samples from a plurality of three-level, partial response waveforms.

Claim 39

Dependent Claim 66 words

The encoding method as set forth in claim 36, wherein the step of encrypting the serial bit stream includes the step of: differentially encoding each bit in the serial bit stream with a state opposite that of the immediately preceding differentially-encoded bit when the bit is a one and with a state equal that of the immediately preceding differentially-encoded bit when the bit is a zero.

Claim 40

Dependent Claim 82 words

The encoding method as set forth in claim 26, wherein the step of modulating the serial bit stream includes the steps of: converting the serial bit stream of encrypted stereo audio samples into parallel in-phase and staggered quadrature-phase symbol streams; addressing memory locations with a plurality of the symbols from the in-phase and the staggered quadrature-phase symbol streams; reading from the memory locations amplitude samples from a plurality of three-level, partial response waveforms; and multiplexing the in-phase and staggered quadrature-phase amplitude samples.

Claim 41

Dependent Claim 71 words

The encoding method as set forth in claim 38, wherein the step of converting the serial bit stream includes the step of: differentially encoding each symbol in each of the in-phase and staggered quadrature-phase symbol streams with a state opposite that of the immediately preceding differentially-encoded symbol when the symbol is a one and with a state equal that of the immediately preceding differentially-encoded symbol when the symbol is a zero.

Claim 42

Dependent Claim 34 words

The encoding method as set forth in claim 26, wherein the step of modulating the serial bit stream further includes the step of: up-converting the modulated stereo audio signal to a video subcarrier frequency.

Claim 43

Dependent Claim 30 words

The encoding method as set forth in claim 40, wherein the step of up-converting the modulated stereo audio signal includes the step of: digitally complementing the modulated stereo audio signal.

Claim 44

Dependent Claim 38 words

The encoding method as set forth in claim 26, wherein the step of modulating the serial bit stream further includes the step of: multiplexing the modulated stereo audio signal into the horizontal blanking interval of the video signal.

Claim 45

Dependent Claim 135 words

A television signal decoding apparatus, comprising a video decoder that applies line tilt compensation to a line-spin scrambled video signal, the video decoder including an analog-to-digital converter for digitizing the line-spin scrambled video signal; means for measuring the amplitude of the line tilt in the digitized scrambled video signal; means for generating a complementary ramp based on the measured amplitude; and means for summing the complementary ramp with each line of the digitized scrambled video signal; and an audio decoder that recovers an audio signal modulated with a three-level, partial response waveform, the audio decoder including: an analog-to-digital converter for digitizing the modulated audio signal; a three-level, partial response demodulator for recovering a serial bit stream of audio samples from the digitized audio signal; and means for decrypting the serial bit stream of audio samples.

Claim 46

Dependent Claim 135 words

A television signal decoding apparatus, comprising a video decoder that applies line tilt compensation to a line-spin scrambled video signal, the video decoder including an analog-to-digital converter for digitizing the line-spin scrambled video signal; means for measuring the amplitude of the line tilt in the digitized scrambled video signal; means for generating a complementary ramp based on the measured amplitude; and means for summing the complementary ramp with each line of the digitized scrambled video signal; and an audio decoder that recovers an audio signal modulated with a three-level, partial response waveform, the audio decoder including: an analog-to-digital converter for digitizing the modulated audio signal; a three-level, partial response demodulator for recovering a serial bit stream of audio samples from the digitized audio signal; and means for decrypting the serial bit stream of audio samples.

Claim 47

Dependent Claim 81 words

The television decoding apparatus as set forth in claim 43, and further including means for applying an unscrambling transform to each line-spin scrambled line of the compensated scrambled video signal, the means for applying an unscrambling transform including: means for applying a reverse transform to each reversed video segment or reversed video line of the compensated scrambled video signal; and means for applying an inverse transform to each inverted video segment or inverted video line of the compensated scrambled video signal.

Claim 48

Dependent Claim 44 words

The television decoding apparatus as set forth in claim 43, wherein the means for measuring the line tilt amplitude includes: means for measuring the amplitude differential between the ends of the active portion of a dummy video line transmitted with a constant-amplitude active portion.

Claim 49

Dependent Claim 44 words

The television decoding apparatus as set forth in claim 45, wherein the means for measuring the line tilt amplitude further includes: means for replacing the dummy video line with a previous video line for display of the unscrambled video signal on a television monitor.

Claim 50

Dependent Claim 37 words

The television decoding apparatus as set forth in claim 45, wherein the dummy video line is transmitted at the bottom of each video field with a constant-amplitude active portion in the gray region of the luminance scale.

Claim 51

Dependent Claim 45 words

The television decoding apparatus as set forth in claim 45, wherein the means for measuring the amplitude differential includes: means for measuring the amplitude differential between adjacent points sampled across the active portion of the dummy video line; and means for accumulating the amplitude differentials.

Claim 52

Dependent Claim 58 words

The television decoding apparatus as set forth in claim 43, wherein the audio decoder includes: an analog-to-digital converter for digitizing a modulated stereo audio signal; a three-level, partial response demodulator for recovering a serial bit stream of stereo audio samples from the digitized stereo audio signal; and means for decrypting the serial bit stream of stereo audio samples.

Claim 53

Dependent Claim 140 words

The television decoding apparatus as set forth in claim 43, wherein the video decoder further includes means for accurately synchronizing digital timing signals with the digitized scrambled video signal, the synchronizing means including: means for generating a controllable master sampling clock signal; means for generating a color-burst-frequency signal from the master sampling clock signal, the generating means including a counter driven by the master sampling clock signal; a phase error detector for measuring the phase error between the color-burst-frequency signal and a color burst signal in the digitized scrambled video signal; and means for controlling the frequency of the master sampling clock signal with the measured phase error; wherein the line-spin scrambled video signal is digitized at a sampling rate controlled by the master sampling clock signal, thereby synchronizing the master sampling clock signal with the video color burst signal.

Claim 54

Dependent Claim 99 words

The television decoding apparatus as set forth in claim 50, wherein the synchronizing means further includes: a horizontal synch signal separator for separating a horizontal synch signal from the digitized scrambled video signal; means for generating a reference horizontal synch signal; a phase error detector for measuring the phase error between the video horizontal synch signal and the reference horizontal synch signal; and a horizontal counter clocked by the master sampling clock signal, the horizontal counter being loaded with the phase error measured between the horizontal synch signals, thereby synchronizing the horizontal counter with the video horizontal synch signal.

Claim 55

Dependent Claim 61 words

The television decoding apparatus as set forth in claim 51, wherein the means for generating a reference horizontal synch signal includes: memory means programmed with a horizontal synch signal, the horizontal synch signal being read from the memory means when addressed by the horizontal counter, thereby generating a reference horizontal synch signal that is synchronized with the video horizontal synch signal.

Claim 56

Dependent Claim 47 words

The television decoding apparatus as set forth in claim 51, wherein the phase error detector for measuring the phase error between the horizontal synch signals includes: means for measuring the number of sampling clock pulses between the video horizontal synch signal and the reference horizontal synch signal.

Claim 57

Dependent Claim 76 words

The television decoding apparatus as set forth in claim 51, wherein the synchronizing means further includes: a vertical synch signal separator for separating a vertical synch signal from the digitized scrambled video signal; means for generating a reference vertical synch signal; and a vertical counter, the vertical counter being loaded with the line number of the horizontal video line having the video vertical synch signal, thereby synchronizing the vertical counter with the video vertical synch signal.

Claim 58

Dependent Claim 61 words

The television decoding apparatus as set forth in claim 54, wherein the means for generating a reference vertical synch signal includes: memory means programmed with a vertical synch signal, the vertical synch signal being read from the memory means when addressed by the vertical counter, thereby generating a reference vertical synch signal that is synchronized with the video vertical synch signal.

Claim 59

Dependent Claim 35 words

The television decoding apparatus as set forth in claim 54, wherein the vertical counter is clocked at the rate that the horizontal counter is loaded with the phase error measured between the horizontal synch signals.

Claim 60

Dependent Claim 89 words

The television decoding apparatus as set forth in claim 49, wherein the means for decrypting the serial bit stream further includes: means for randomizing the serial bit stream of stereo audio samples to remove randomization applied to the stereo audio signal during modulation; means for correcting the serial bit stream for errors present in the modulated stereo audio signal; a serial-to-parallel converter for separating the left and right stereo audio samples; and a pair of digital-to-analog converters for converting the left and right stereo audio samples to analog signals.

Claim 61

Dependent Claim 49 words

The television decoding apparatus as set forth in claim 49, wherein the three-level, partial response demodulator includes: means for recovering a stream of on-symbol audio samples from the digitized stereo audio signal; and means for converting the on-symbol audio samples into a serial bit stream of stereo audio samples.

Claim 62

Dependent Claim 61 words

The television decoding apparatus as set forth in claim 49, wherein the three-level, partial response demodulator includes: means for recovering a stream of alternating in-phase and staggered quadrature-phase on-symbol audio samples from the digitized stereo audio signal; and means for converting the stream of alternating in-phase and staggered quadrature-phase on-symbol audio samples into a serial bit stream of stereo audio samples.

Claim 63

Dependent Claim 32 words

The television decoding apparatus as set forth in claim 58, wherein the means for recovering includes: means for generating an on-symbol clock signal; and a latch clocked by the on-symbol clock signal.

Claim 64

Dependent Claim 32 words

The television decoding apparatus as set forth in claim 59, wherein the means for recovering includes: means for generating an on-symbol clock signal; and a latch clocked by the on-symbol clock signal.

Claim 65

Dependent Claim 24 words

The television decoding apparatus as set forth in claim 58, wherein the means for converting includes: a half amplitude threshold detector; and an inverter.

Claim 66

Dependent Claim 24 words

The television decoding apparatus as set forth in claim 59, wherein the means for converting includes: a half amplitude threshold detector; and an inverter.

Claim 67

Dependent Claim 31 words

The television decoding apparatus as set forth in claim 60, wherein the on-symbol clock signal can be used to derive a video color burst signal and a video horizontal synch signal.

Claim 68

Dependent Claim 31 words

The television decoding apparatus as set forth in claim 61, wherein the on-symbol clock signal can be used to derive a video color burst signal and a video horizontal synch signal.

Claim 69

Independent Claim 121 words

A method for decoding a television signal, comprising the steps of: applying line tilt compensation to a line-spin scrambled video signal, the step of applying line tilt compensation including the steps of: digitizing the line-spin scrambled video signal; measuring the amplitude of the line tilt in the digitized scrambled video signal; generating a complementary ramp based on the measured amplitude; and summing the complementary ramp with each line of the digitized scrambled video signal; and recovering an audio signal modulated with a three-level, partial response waveform, the step of recovering including the steps of; digitizing the modulated audio signal; recovering a serial bit stream of audio samples from the digitized audio signal; and decrypting the serial bit stream of audio samples.

Claim 70

Independent Claim 121 words

A method for decoding a television signal, comprising the steps of: applying line tilt compensation to a line-spin scrambled video signal, the step of applying line tilt compensation including the steps of: digitizing the line-spin scrambled video signal; measuring the amplitude of the line tilt in the digitized scrambled video signal; generating a complementary ramp based on the measured amplitude; and summing the complementary ramp with each line of the digitized scrambled video signal; and recovering an audio signal modulated with a three-level, partial response waveform, the step of recovering including the steps of; digitizing the modulated audio signal; recovering a serial bit stream of audio samples from the digitized audio signal; and decrypting the serial bit stream of audio samples.

Claim 71

Dependent Claim 74 words

The decoding method as set forth in claim 66, and further including the step of unscrambling each line-spin scrambled video line of the compensated scrambled video signal, the step of unscrambling including the steps of: applying a reverse transform to each reversed video segment or reversed video line of the compensated scrambled video signal; and applying an inverse transform to each inverted video segment or inverted video line of the compensated scrambled video signal.

Claim 72

Dependent Claim 44 words

The decoding method as set forth in claim 68, wherein the step of measuring the line tilt amplitude includes the step of: measuring the amplitude differential between the ends of the active portion of a dummy video line transmitted with a constant-amplitude active portion.

Claim 73

Dependent Claim 44 words

The decoding method as set forth in claim 68 wherein the step of measuring the line tilt amplitude further includes the step of: replacing the dummy video line with a previous video line for display of the unscrambled video signal on a television monitor.

Claim 74

Dependent Claim 36 words

The decoding method as set forth in claim 68, wherein the dummy video line is transmitted at the bottom of each video field with a constant-amplitude active portion in the gray region of the luminance scale.

Claim 75

Dependent Claim 43 words

The decoding method as set forth in claim 68, wherein the step of measuring the amplitude differential includes the steps of: measuring the amplitude differential between adjacent points sampled across the active portion of the dummy video line; and accumulating the amplitude differentials.

Claim 76

Dependent Claim 53 words

The decoding method as set forth in claim 66, wherein the step of recovering a modulated audio signal includes the steps of: digitizing a modulated stereo audio signal; recovering a serial bit stream of stereo audio samples from the digitized stereo audio signal; and decrypting the serial bit stream of stereo audio samples.

Claim 77

Dependent Claim 127 words

The decoding method as set forth in claim 66, and further including the step of accurately synchronizing digital timing signals with the digitized scrambled video signal, the step of synchronizing including the steps of: generating a controllable master sampling clock signal; generating a color-burst-frequency signal from the master sampling clock signal by driving a counter with the master sampling clock signal; measuring the phase error between the color-burst-frequency signal and a color burst signal in the digitized scrambled video signal; and controlling the frequency of the master sampling clock signal with the measured phase error; wherein the line-spin scrambled video signal is digitized at a sampling rate controlled by the master sampling clock signal, thereby synchronizing the master sampling clock signal with the video color burst signal.

Claim 78

Dependent Claim 85 words

The decoding method as set forth in claim 73, wherein the step of synchronizing further includes the steps of: separating a horizontal synch signal from the digitized scrambled video signal; generating a reference horizontal synch signal; measuring the phase error between the video horizontal synch signal and the reference horizontal synch signal; and loading a horizontal counter clocked by the master sampling clock signal with the phase error measured between the horizontal synch signals, thereby synchronizing the horizontal counter with the video horizontal synch signal.

Claim 79

Dependent Claim 52 words

The decoding method as set forth in claim 74, wherein the step of generating a reference horizontal synch signal includes the step of reading a horizontal synch signal from memory when addressed by the horizontal counter, thereby generating a reference horizontal synch signal that is synchronized with the video horizontal synch signal.

Claim 80

Dependent Claim 45 words

The decoding method as set forth in claim 74, wherein the step of measuring the phase error between the horizontal synch signals includes the step of measuring the number of sampling clock pulses between the video horizontal synch signal and the reference horizontal synch signal.

Claim 81

Dependent Claim 66 words

The decoding method as set forth in claim 74, wherein the step of synchronizing further includes the steps of: separating a vertical synch signal from the digitized scrambled video signal; generating a reference vertical synch signal; and loading a vertical counter with the line number of the horizontal video line having the vertical synch signal, thereby synchronizing the vertical counter with the video vertical synch signal.

Claim 82

Dependent Claim 52 words

The decoding method as set forth in claim 77, wherein the step of generating a reference vertical synch signal includes the step of: reading a vertical synch signal from memory when addressed by the vertical counter, thereby generating a reference vertical synch signal that is synchronized with the video vertical synch signal.

Claim 83

Dependent Claim 44 words

The decoding method as set forth in claim 77, wherein the step of loading a vertical counter includes the step of clocking the vertical counter at the rate that the horizontal counter is loaded with the phase error measured between the horizontal synch signals.

Claim 84

Dependent Claim 77 words

The decoding method as set forth in claim 72, wherein the step of decrypting the serial bit stream further includes the steps of: randomizing the serial bit stream of stereo audio samples to remove randomization applied to the stereo audio signal during modulation; correcting the serial bit stream for errors present in the modulated stereo audio signal; separating the left and right stereo audio samples; and converting the left and right stereo audio samples to analog signals.

Claim 85

Dependent Claim 54 words

The decoding method as set forth in claim 72, wherein the step of recovering a serial bit stream of stereo audio samples includes the steps of: recovering a stream of on-symbol audio samples from the digitized stereo audio signal; and converting the on-symbol audio samples into a serial bit stream of stereo audio samples.

Claim 86

Dependent Claim 66 words

The decoding method as set forth in claim 72, wherein the step of recovering a serial bit stream of stereo audio samples includes the steps of: recovering a stream of alternating in-phase and staggered quadrature-phase on-symbol audio samples from the digitized stereo audio signal; and converting the stream of alternating in-phase and staggered quadrature-phase on-symbol audio samples into a serial bit stream of stereo audio samples.

Claim 87

Dependent Claim 38 words

The decoding method as set forth in claim 81, wherein the step of recovering a stream of on-symbol audio samples includes the steps of: generating an on-symbol clock signal; and clocking a latch with the on-symbol clock signal.

Claim 88

Dependent Claim 39 words

The decoding method as set forth in claim 82, wherein the step of recovering a stream of alternating on-symbol audio samples includes the steps of: generating an on-symbol clock signal; and clocking a latch with the on-symbol clock signal.

Claim 89

Dependent Claim 41 words

The decoding method as set forth in claim 81, wherein the step of converting the on-symbol audio samples includes the steps of: applying each on-symbol audio sample to a half amplitude threshold detector; and inverting the output of the threshold detector.

Claim 90

Dependent Claim 44 words

The decoding method as set forth in claim 82, wherein the step of converting the stream of alternating on-symbol audio samples includes the steps of: applying each on-symbol audio sample to a half amplitude threshold detector; and inverting the output cf the threshold detector.

Claim 91

Dependent Claim 39 words

The decoding method as set forth in claim 83, wherein the step of generating an on-symbol clock signal includes the step of deriving a video color burst signal and a video horizontal synch signal from the on-symbol clock signal.

Claim 92

Dependent Claim 39 words

The decoding method as set forth in claim 84, wherein the step of generating an on-symbol clock signal includes the step of deriving a video color burst signal and a video horizontal synch signal from the on-symbol clock signal.

Annuity Stage	Window Opens	Payment Deadline	Surcharge Period Until	Estimated Fee	Status
3.5 Years (Year 4)	1993-10-15	1994-04-16	1994-10-16	$2000.00	Window Closed / Lapsed
7.5 Years (Year 8)	1997-10-15	1998-04-16	1998-10-16	$3760.00	Window Closed / Lapsed
11.5 Years (Year 12)	2001-10-15	2002-04-16	2002-10-16	$7700.00	Window Closed / Lapsed

Secure television signal encoding and decoding system

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