Digital Audio Input Clock Validation With Mute During Re-Lock
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Solution Overview
Problem
In digital audio input systems, determining the existence of a valid external clock is challenging, especially when the internal clock is used for other device requirements, leading to potential distortion due to jitter, and existing hardware solutions increase complexity and cost.
Innovation Solution
A method and apparatus that dynamically determine the existence of an external clock by reading and comparing clock parameters, muting audio if the clock changes, and sending lock or relock indications to the audio driver, using periodic polling and a tolerance value to manage clock changes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If hardware solutions are used to determine the existence of a valid external clock, then the reliability of clock detection is improved, but the device complexity and cost increase
Solution Approach 1:
The patent replaces hardware-based clock validation mechanisms with a software driver that reads clock parameters from hardware registers and performs validation through comparison operations. The audio driver reads the clock ratio from a hardware register, compares it against a stored reference value, and determines clock validity through software logic, thereby eliminating the need for complex dedicated hardware validation circuits.
2Adaptability or versatility
If the internal clock is used for other requirements, then the adaptability of the device is improved, but the ability to support external clocking is worsened
Solution Approach 1:
The patent implements a feedback mechanism where the audio driver continuously monitors the clock ratio parameter from the hardware register and compares it against a stored reference value. When the clock becomes invalid (ratio changes beyond tolerance), the driver detects this through the comparison failure and responds by muting the audio output, providing feedback about the clock's validity status and enabling dynamic adaptation to clock changes.
Solution Approach 2:
The system dynamically determines clock validity by comparing the current clock ratio reading against a stored reference value. The audio driver can adapt its behavior based on the comparison result - continuing normal operation when the clock is valid or muting audio when the clock becomes invalid. This dynamic approach allows the system to support external clocking reliably even when the internal clock is repurposed for other functions.
3Device complexity
If software implementation is used for clock determination, then the device complexity is reduced, but the measurement precision of clock validation may be worsened
Solution Approach 1:
The patent replaces complex hardware validation circuits with software-based comparison operations that read clock parameters from hardware registers. The audio driver performs precise numerical comparison of the clock ratio value against a stored reference, achieving accurate clock validation through software logic rather than hardware circuitry, thereby reducing device complexity while maintaining validation precision.
Data Source
AI summary
Methods and apparatus for determining the existence of an external clock over a digital input port on a computer. In one embodiment, the external clock is validated, and a lock is performed when the clock is valid. Whenever a loss of the lock is detected, and, if a re-lock is likely, the apparatus is muted so that audio artifacts that would otherwise be heard are minimized. The methods and apparatus also provide automatic re-locking to the external clock when a sampling rate change is detected.