Method and apparatus that generates VBI data coding waveforms
First Claim
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1. An apparatus for generating VBI data coding waveforms and color burst waveforms comprising:
- a first selection circuit for receiving a color burst data signal, a VBI data signal, and a color burst period signal, and generates an address based thereon;
a second selection circuit for receiving a color burst scalar signal, a VBI scalar signal, and the color burst period signal, and generating one of the color burst scalar signal and the VBI scalar signal based on the color burst period signal; and
a waveform look-up table coupled to the first selection circuit for receiving the address and providing a waveform output corresponding to the address.
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Abstract
An apparatus and method is provided for generating VBI data coding waveforms. The present invention utilizes a single look-up table that stores sampled values of sine waves in direct waveform synthesis for both color burst processing and VBI data coding processing. Furthermore, the present invention utilizes a 2T pulse as a signalling waveform in direct synthesis to overcome the problem of overlap for conventional unit pulse durations.
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Citations
15 Claims
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1. An apparatus for generating VBI data coding waveforms and color burst waveforms comprising:
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a first selection circuit for receiving a color burst data signal, a VBI data signal, and a color burst period signal, and generates an address based thereon;
a second selection circuit for receiving a color burst scalar signal, a VBI scalar signal, and the color burst period signal, and generating one of the color burst scalar signal and the VBI scalar signal based on the color burst period signal; and
a waveform look-up table coupled to the first selection circuit for receiving the address and providing a waveform output corresponding to the address. - View Dependent Claims (2, 3, 4, 5)
a third selection circuit for receiving a color burst sign control signal, a VBI sign control signal, and the color burst period signal, and generating one of the color burst sign control signal and the VBI sign control signal as a sign signal based on the color burst period signal; and
a sign determination circuit coupled to the look-up table and the multiplier for receiving a value from the look-up table and multiplying the value with either a one or a negative one based on the sign signal.
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5. The apparatus of claim 1, wherein said waveform look-up table includes sampled values of a sine wave.
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6. A video play-back system comprising:
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(a) a video source for providing video information;
(b) a display for viewing the video information; and
(c) a video encoder for generating VBI data coding waveforms and color burst waveforms, said video encoder including a waveform generator having;
(i) a first selection circuit for receiving a color burst data signal, a VBI data signal, and a color burst period signal, and generates an address based thereon;
(ii) a second selection circuit for receiving a color burst scalar signal, a VBI scalar signal, and the color burst period signal, and generating one of the color burst scalar signal and the VBI scalar signal based on the color burst period signal; and
(iii) a waveform look-up table coupled to the first selection circuit for receiving the address and providing a waveform output corresponding to the address. - View Dependent Claims (7, 8, 9, 10, 11, 12)
a third selection circuit for receiving a color burst sign control signal, a VBI sign control signal, and the color burst period signal, and generating one of the color burst sign control signal and the VBI sign control signal as a sign signal based on the color burst period signal; and
a sign determination circuit coupled to the look-up table and the multiplier for receiving a value from the look-up table and multiplying the value with either a one or a negative one based on the sign signal.
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10. The system of claim 6, wherein the waveform look-up table includes sampled values of a sine wave.
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11. The system of claim 7, wherein the video encoder further includes:
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a processor that receives video data representing the video information from the video source, and receives VBI data bits, and in response thereto provides chrominance signals to the waveform generator; and
a digital to analog converter coupled to the waveform generator to receive the waveform output and to convert the output waveform into analog form.
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12. The system of claim 11, wherein the processor generates luminance signals, and wherein the video encoder further includes:
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a luminance signal generator coupled to the processor to receive luminance signals; and
an adder having inputs coupled to the luminance signal generator and the waveform generator, and an output coupled to the digital to analog converter.
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13. A method of shaping a waveform for VBI data coding comprising:
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a. using a 2T pulse signal as a unit pulse, where T is a bit interval;
b. determining the current and previous VBI data bits from a stream of VBI data bits; and
c. using a waveform look-up table to provide VBI coding waveform values for a duration of T based on VBI phase data, which includes;
if a current VBI data bit is one, and the previous VBI data bit is one, providing a one for a duration of T;
if a current VBI data bit is zero, and the previous VBI data bit is zero, providing a zero for a duration of T; and
if a current VBI data bit is zero and the previous VBI data bit is one, or if a current VBI data bit is one and the previous VBI data bit is zero, then using the waveform look-up table to provide VBI coding waveform values for a duration of T based on VBI phase data.
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14. A method of shaping a waveform in an encoder for VBI data coding comprising:
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a. using a 2T pulse signal as a unit pulse, where T is a bit interval;
b. determining the current and previous VBI data bits from a stream of VBI data bits; and
c. using a color sub-carrier waveform look-up table to provide VBI coding waveform values for a duration of T based on VBI phase data.
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15. A method of shaping a waveform for VBI data coding comprising:
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a. using a 2T pulse signal as a unit pulse, where T is a bit interval, the 2T pulse generated by squaring a half-cycle of a sine wave;
b. determining the current and previous VBI data bits from a stream of VBI data bits; and
c. using a waveform look-up table to provide VBI coding waveform values for a duration of T based on VBI phase data;
wherein the 2T pulse is equal to cos2[(t/2T)pi] for −
T≧
t≧
T.
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Specification