Reference-Clock Audio Timing for HDMI Jitter Isolation
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Solution Overview
Problem
The conventional method for generating an audio clock in high definition multimedia interface (HDMI) systems faces challenges due to video clock jitter and noise interference, requiring high-sensitivity components and resulting in poor audio clock quality.
Innovation Solution
A method and apparatus that utilize a reference clock and video clock to determine a ratio signal, allowing the generation of an output clock that is more stable by multiplying the reference clock frequency through a phase-locked loop, independent of video clock jitter and noise, using either clock to count the other and calculate the audio clock frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the conventional HDMI method uses video frequency and audio information frame parameters (N and CTS) to generate audio clock, then the audio clock can be obtained indirectly, but the audio clock quality deteriorates due to video clock jitter and noise interference
Solution Approach 1:
The patent extracts the audio clock generation process from the video clock signal path by using a separate reference clock source. Instead of deriving audio clock indirectly from video frequency through parameters N and CTS, the system extracts and uses a dedicated reference clock that is independent of video signal transmission, thereby eliminating the harmful effects of video clock jitter and noise on audio clock quality
Solution Approach 2:
The patent introduces a reference clock as an intermediary element between the video signal and audio clock generation. This reference clock acts as a mediator that provides a stable timing source for audio sampling without being affected by video signal variations. The reference clock decouples the audio clock generation from video clock instability, allowing high-quality audio sampling independent of video transmission issues
2Reliability
If the conventional method uses large parameters N and CTS for audio clock generation, then the audio clock can be calculated according to HDMI specification, but the PLL requires high-sensitivity components increasing device complexity
Solution Approach 1:
The patent changes the fundamental parameter used for audio clock generation from the HDMI specification method (using large integers N and CTS with video frequency) to using a reference clock with a different frequency relationship. By changing the timing reference from video-derived clocks to a separate reference clock, the system achieves accurate audio sampling without requiring high-sensitivity PLL components, thereby reducing device complexity while maintaining generation accuracy
3Ease of manufacture
If the video clock is used directly for audio clock generation, then the process is simplified, but the audio clock inherits video clock instability and noise
Solution Approach 1:
The patent segments the clock signal system into independent functional parts: video signal processing uses video clock, while audio signal processing uses a separate reference clock. This segmentation allows each subsystem to have its own optimal timing source, preventing video clock instability from affecting audio clock stability while keeping the overall system design relatively simple and modular
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach generates a more stable audio clock by decoupling it from video clock jitter and noise, improving the accuracy and reliability of the audio clock generation process.
Implementation Method 1
generating an output clock according to the ratio signal and the reference clock
Data Source
AI summary
A method for generating an audio clock includes: receiving a reference clock; receiving a received signal from a multimedia interface of a receiver, wherein the received signal comprises a video signal and an audio signal; utilizing one of the reference clock and a video clock of the video signal to count the other of the reference clock and the video clock and determining a ratio signal; and generating an output clock according to the ratio signal and the reference clock.