Video Sampling Clock Verification Using Frame Difference Ratios
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Solution Overview
Problem
Existing methods for determining the sampling frequency and phase in analog-to-digital conversion for digital video devices are imprecise and unreliable, often relying on noisy clocks, test patterns, or static tables, which fail to accurately convert analog signals to digital format, especially when dealing with wide-mode analog graphics sources and images with blanked regions.
Innovation Solution
A method and apparatus that use a controllable frequency and selectable phase clock to convert analog signals into digital signals by computing the difference between successive frames, verifying the frequency based on a characteristic measure such as the ratio of maximum to minimum frame differences, allowing for accurate sampling frequency selection without predefining signal properties or excluding images with blanked areas.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional methods using noisy clocks, test patterns, or static tables are used to determine sampling frequency, then the conversion process is simple, but the measurement precision and reliability of frequency determination deteriorates
Solution Approach 1:
The patent replaces traditional mechanical/clock-based frequency determination methods with a computational approach. Instead of relying on noisy clocks, test patterns, or static lookup tables, the system uses frame difference computation between successive video frames to automatically determine the sampling frequency. This substitution of computational methods for mechanical/time-based methods improves precision without requiring complex additional hardware.
Solution Approach 2:
The system performs self-calibration by automatically computing frame differences between successive frames and using this information to determine the correct sampling frequency. The conversion process itself generates the data needed for frequency determination, eliminating the need for external test patterns or pre-configured tables. The system serves its own calibration needs through normal operation.
2Measurement precision
If precise predefinition of signal properties is required for accurate conversion, then the conversion accuracy improves, but the adaptability to different input sources and aspect ratios deteriorates
Solution Approach 1:
The patent implements a dynamic frequency determination method that adapts to different input sources and video modes. Instead of using static lookup tables or predefined signal properties, the system continuously computes frame differences and determines sampling frequency based on the actual input signal characteristics. This dynamic approach maintains high conversion accuracy while automatically adapting to various aspect ratios, resolutions, and video standards without requiring manual configuration.
Solution Approach 2:
The system changes its operational parameters dynamically based on the input signal. By computing frame differences and analyzing the temporal characteristics of the video signal, the system automatically adjusts the sampling frequency determination process to match the specific characteristics of each input source. This allows accurate conversion across different video modes, aspect ratios, and signal types without requiring precise predefinition of signal properties.
3Measurement precision
If methods excluding images with blanked regions are used, then the measurement precision for active video regions improves, but the versatility to handle various image formats deteriorates
Solution Approach 1:
The patent creates a universal frequency determination method that works for all types of video inputs, including images with blanked regions, black borders, and various aspect ratios. The frame difference computation approach naturally handles different image formats by focusing on temporal changes rather than spatial position. This universal method maintains measurement precision while accommodating wide-mode analog graphics sources, 4:3, and other formats without requiring separate processing paths or exclusions.
Data Source
AI summary
A method and apparatus for an analog-to-digital video signal converter. The converter is controlled by a clock with controllable frequency and phase for sampling an analog signal. A measure of the difference between successive frames of the image is computed for a sequence of clock phases. The measure can be a count taken over pixels of the magnitude of the difference between a pixel in one frame and the corresponding pixel in a following frame exceeding a threshold value. The frequency of the clock is verified using a characteristic of the frame difference. The characteristic can be the ratio of the maximum measure to the minimum measure over the selected clock phases. Other characteristics can be used such as a difference of a maximum and a minimum measure.