HDMI Audio Clock Correlation for Lower Jitter Transmission
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Solution Overview
Problem
HDMI transmission systems suffer from inferior sound quality due to variations in audio and pixel clocks generated by independent reference clock generators, leading to increased jitter and reduced audio quality compared to IEC60958 specifications.
Innovation Solution
A transmission device that includes a selection arrangement to choose parameters for lowering the frequency of the second clock, a correlation detection mechanism to transmit correlation information, and an information acquisition mechanism to adjust parameters based on allowable ranges, ensuring stable clock generation at the reception device, thereby reducing playback audio clock frequency variation and improving sound quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If independent reference clock generators are used for audio clock and pixel clock, then device complexity is reduced, but audio quality deteriorates due to clock frequency variations and jitter
Solution Approach 1:
The patent changes the parameter of clock frequency relationship by introducing correlation information between audio clock and pixel clock. Instead of using completely independent clock generators, the system transmits correlation data that allows the receiver to adjust the audio clock frequency to maintain a stable relationship with the pixel clock, thereby reducing jitter while keeping the independent generator configuration.
Solution Approach 2:
The patent implements a feedback mechanism where correlation information about the relationship between audio clock and pixel clock is transmitted from the sender to the receiver. The receiver uses this feedback to adjust its audio clock generation, creating a closed-loop system that compensates for frequency variations and maintains audio quality without requiring complex synchronized hardware.
2Reliability
If audio clock frequency is lowered to reduce jitter, then audio quality improves, but clock generation complexity increases
Solution Approach 1:
The patent introduces correlation information as an intermediary element that mediates between the audio clock and pixel clock. This intermediary data allows the system to achieve stable audio clock generation without directly complexifying the clock generation hardware. The correlation information acts as a communication bridge that simplifies the overall system architecture while improving audio quality.
3Reliability
If correlation information is transmitted between audio clock and pixel clock, then jitter is reduced, but transmission data volume increases
Solution Approach 1:
The patent optimizes the correlation information transmission by carefully selecting which parameters to transmit. Instead of transmitting complete clock waveforms or detailed timing information, the system transmits condensed correlation data that captures the essential relationship between audio clock and pixel clock frequencies, minimizing data volume while achieving jitter reduction.
Data Source
AI summary
The identification information processing unit receives identification information identifying the reception device from a reception device, and generates decoded identification information indicating the decoded value of the received identification information. The parameter value selection unit selects the first parameter value when the decoded identification information includes an information representing a television, selects a second parameter value that is less than the first parameter value when the decoded identification information includes an information representing an audio device, and generates a selected parameter value. The frequency divider frequency divides the audio clock using the selected parameter value, and generates a frequency division signal. The counter counts one period of the frequency division signal using the pixel clock and generates the cycle time stamp. The transmission device then sends the selected parameter value and cycle time stamp to the reception device.