Graphics display system with video synchronization feature
First Claim
1. A video synchronizing mechanism comprising:
- a first sample rate converter for converting a sampling rate of a stream of video samples from a first sample rate to a first converted rate, said first sample rate converter comprising;
a chroma tracker capable of tracking phase and frequency of chroma bursts, comparing them against a predetermined pattern and generating an error signal based on the result of the comparison; and
a low pass filter for receiving and filtering the error signal from the chroma tracker to generate an adjustment value, wherein the adjustment value is used to adjust the first sample rate or a first down-sampling ratio, which is a ratio between the first sample rate and the first converted rate;
a filter for processing at least some of the video samples having the first converted rate; and
a second sample rate converter for converting the sampling rate from the first converted rate to a second converted rate.
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Accused Products
Abstract
A graphics integrated circuit chip is used in a set-top box for controlling a television display. The graphics chip processes analog video input, digital video input, graphics input and audio input simultaneously. The system includes a video decoder having a chroma-locked sample rate converter. The chroma-locked sample rate converter converts the samples to those taken at a sample rate that is a multiple of the chroma subcarrier frequency and that is locked to chroma bursts of the analog video signal in a control loop. The video decoder also includes a line-locked sample rate converter that receives samples at a multiple of the chroma subcarrier frequency and converts the samples to samples with a sample frequency that is a multiple of the horizontal line rate of the video input. The line-locked sample rate converter measures the horizontal line rate to an accuracy of a fraction of a pixel and adjusts the sample rate and phase of the line-locked sample rate converter to produce accurate line-locked samples. The time base corrector receives samples at the output of the line-locked sample rate converter and provides samples synchronized to the display clock for reducing undesirable artifacts such as jitter.
249 Citations
68 Claims
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1. A video synchronizing mechanism comprising:
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a first sample rate converter for converting a sampling rate of a stream of video samples from a first sample rate to a first converted rate, said first sample rate converter comprising;
a chroma tracker capable of tracking phase and frequency of chroma bursts, comparing them against a predetermined pattern and generating an error signal based on the result of the comparison; and
a low pass filter for receiving and filtering the error signal from the chroma tracker to generate an adjustment value, wherein the adjustment value is used to adjust the first sample rate or a first down-sampling ratio, which is a ratio between the first sample rate and the first converted rate;
a filter for processing at least some of the video samples having the first converted rate; and
a second sample rate converter for converting the sampling rate from the first converted rate to a second converted rate. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
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19. A video synchronizing mechanism comprising:
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a first sample rate converter for converting a sampling rate of a stream of video samples from a first sample rate to a first converted rate;
a filter for processing at least some of the video samples having the first converted rate; and
a second sample rate converter for converting the sampling rate from the first converted rate to a second converted rate, wherein the first sample rate of the stream of video samples is fixed, and the stream of video samples is generated using a free-running input sample clock, and wherein the first sample rate converter comprises a sample rate converter for down-sampling the stream of video samples, and a chroma tracker for tracking phase and frequency of chroma bursts and comparing them against an expected pattern, and the chroma tracker generates an error signal based on the result of the comparison, and wherein the first sample rate converter further comprises a low pass filter for filtering the error signal of the chroma tracker and providing a first adjustment value to the sample rate converter to adjust a first down-sampling ratio, which is a ratio between the first sample rate and the first converted rate. - View Dependent Claims (20, 21, 22, 23, 24)
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25. A video synchronizing mechanism comprising:
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a first sample rate converter for converting a sampling rate of a stream of video samples from a first sample rate to a first converted rate;
a filter for processing at least some of the video samples having the first converted rate; and
a second sample rate converter for converting the sampling rate from the first converted rate to a second converted rate, wherein the first sample rate of the stream of video samples is variable, and wherein the first sample rate converter comprises;
a sample rate converter for down-sampling the stream of video samples, a chroma tracker for tracking phase and frequency of chroma bursts and comparing them against an expected pattern, wherein the chroma tracker generates an error signal based on the result of the comparison, and a low pass filter for filtering the error signal of the chroma tracker and generates an output, which is used to adjust the first sample rate.
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26. A video synchronizing mechanism comprising:
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a first sample rate converter for converting a sampling rate of a stream of video samples from a first sample rate to a first converted rate;
a filter for processing at least some of the video samples having the first converted rate; and
a second sample rate converter for converting the sampling rate from the first converted rate to a second converted rate, wherein the first sample rate of the stream of video samples is variable, and wherein the first sample rate converter comprises a sample rate converter for down-sampling the stream of video samples, and a chroma tracker for tracking phase and frequency of chroma bursts and comparing them against an expected pattern, wherein the chroma tracker generates an error signal based on the result of the comparison, and wherein the first sample rate converter further comprises a low pass filter for filtering the error signal of the chroma tracker and generates an output, and wherein the first sample rate converter further comprises a voltage controlled oscillator, wherein the first sample rate is an oscillation frequency of the voltage controlled oscillator, and the voltage controlled oscillator receives the output of the low pass filter and uses it to adjust the oscillating frequency. - View Dependent Claims (27, 28, 29, 30)
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31. A video synchronizing mechanism comprising:
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a first sample rate converter for converting a sampling rate of a stream of video samples to a first converted rate;
a filter for processing at least some of the video samples having the first converted rate; and
a second sample rate converter for converting the sampling rate from the first converted rate to a second converted rate, wherein the second sample rate converter comprises a sample rate converter module for down-sampling the video samples having the first converted rate, and a horizontal sync tracker for detecting horizontal syncs and counting the number of samples between the horizontal syncs to a sub-sample accuracy, and the horizontal sync tracker provides a second adjustment value to the sample rate converter module to adjust a second down-sampling ratio, which is the ratio between the first converted rate and the second converted rate. - View Dependent Claims (32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43)
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44. A method of synchronizing video comprising the steps of:
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converting a sampling rate of a stream of video samples from a first sample rate to a first converted rate, comprising;
tracking phase and frequency of chroma bursts;
comparing said phase and frequency against a predetermined pattern;
generating an error signal based on the result of the comparison;
filtering the error signal to generate an adjustment value; and
adjusting, using the adjustment value, the first sample rate or a first down-sampling ratio, which is a ratio between the first sample rate and the first converted rate;
processing at least some of the video samples having the first converted rate; and
converting the sampling rate from the first converted rate to a second converted rate. - View Dependent Claims (45, 46, 47, 48, 49, 50, 51, 52, 53, 54)
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55. A method of synchronizing video comprising the steps of:
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converting a sampling rate of a stream of video samples from a first sample rate to a first converted rate;
processing at least some of the video samples having the first converted rate; and
converting the sampling rate from the first converted rate to a second converted rate, wherein the step of converting the sampling rate of the stream of video samples from the first sample rate to the first converted rate comprises the steps of tracking phase and frequency of chroma bursts, comparing them against an expected pattern, generating an error signal based on the result of the comparison, low pass filtering the error signal, and providing the filtered error signal as a first adjustment value to a sample rate converter to adjust a first down-sampling ratio, which is the ratio between the first sample rate and the first converted rate.
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56. A method of synchronizing video comprising the steps of:
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converting a sampling rate of a stream of video samples from a first sample rate to a first converted rate;
processing at least some of the video samples having the first converted rate; and
converting the first converted rate to a second converted rate, wherein the step of converting the sampling rate of the stream of video samples from the first sample rate to the first converted rate comprises the steps of tracking phase and frequency of chroma bursts, comparing them against an expected pattern, and generating an error signal based on the result of the comparison, low pass filtering the error signal, and providing the filtered error signal to a voltage controlled oscillator to adjust the first sample rate.
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57. A method of synchronizing video comprising the steps of:
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converting a sampling rate of a stream of video samples to a first converted rate;
processing at least some of the video samples having the first converted rate; and
converting the sampling rate from the first converted rate to a second converted rate, wherein the step of converting the first converted rate to the second converted rate comprises the steps of detecting horizontal syncs to a sub-sample accuracy, counting the number of samples between the horizontal syncs, generating a second adjustment value, and using the second adjustment value to adjust a second down-sampling ratio, which is a ratio between the first converted rate and the second converted rate. - View Dependent Claims (58)
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59. A video synchronizing mechanism comprising:
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a first sample rate converter for converting a sampling rate of a stream of video samples to a first converted rate, the first sample rate converter comprising;
a chroma tracker for tracking phase and frequency of chroma bursts, comparing them against a predetermined pattern and generating an error signal based on the result of the comparision; and
a low pass filter for receiving and filtering the error signal from the chroma tracker to generate an adjustment value, wherein the adjustment value is used to adjust the first sample rate or a first down-sampling ratio, which is a ratio between the first sample rate and the first converted rate;
a filter for processing at least some of the video samples having the first converted rate;
a second sample rate converter for converting the sampling rate from the first converted rate to a second converted rate; and
a time base corrector for synchronizing the output of the second sample rate converter to a display clock, wherein the display clock runs at a display clock rate that differs from the second converted rate, wherein the time base corrector comprises a FIFO for receiving an output of the second sample rate converter as an input and providing an output that is synchronous to the display clock. - View Dependent Claims (60, 61, 62, 63, 64, 65, 66, 67, 68)
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Specification