Audio Output Filtering With Variable Group Delay for Low Latency
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Solution Overview
Problem
Existing audio output systems in personal devices face challenges in achieving low latency and minimizing out-of-band noise while maintaining a high dynamic range, as out-of-band filtering often introduces undesirable delay.
Innovation Solution
A system with a filter configured to receive digital audio signals, perform filtering with a selectable variable group delay, and convert the signal to an analog output, ensuring a low-pass filtered signal with minimal latency and effective noise reduction, utilizing a digital-to-analog converter and a driver to maintain low power consumption and dynamic range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If out-of-band filtering is applied to reduce noise, then noise reduction is improved, but latency increases
Solution Approach 1:
The filter implements variable group delay that dynamically adjusts based on operating conditions. The filter can switch between different delay modes (first mode with higher group delay for low signal levels, second mode with lower group delay for high signal levels) to optimize the trade-off between noise reduction and latency depending on the current audio signal characteristics
Solution Approach 2:
The filter changes its group delay parameter dynamically based on signal level conditions. By adjusting the group delay parameter according to whether the audio signal level is above or below a threshold, the system optimizes noise filtering effectiveness while minimizing latency impact on the audio path
2Reliability
If filtering is applied to maximize dynamic range, then dynamic range is improved, but power consumption increases
Solution Approach 1:
The filter operates in different modes depending on the audio signal level. For high signal levels where noise is less problematic, the filter uses a mode with lower power consumption and reduced filtering. For low signal levels where noise reduction is more critical, the filter switches to a mode with higher power consumption but better noise performance, thus optimizing the overall dynamic range while managing power consumption
Solution Approach 2:
The filter adjusts its operating parameters (group delay, filtering strength) based on signal level conditions. This parameter adjustment allows the system to achieve maximum dynamic range when needed while reducing power consumption during conditions where aggressive filtering is less necessary
Data Source
AI summary
A system may include an input configured to receive a digital audio input signal having at least four and fewer than 65,000 quantization levels and sampled at at least 500 kilohertz, a low-pass filter configured to receive the digital audio input signal and perform filtering on the digital audio input signal to generate a filtered digital audio input signal having a bandwidth of between approximately 100 hertz and 10 kilohertz, a digital-to-analog converter configured to receive the filtered digital audio input signal and convert the filtered digital audio input signal into an equivalent analog audio input signal, and a driver configured to receive the equivalent analog audio input signal and drive an analog audio output signal to a transducer, wherein a group delay from the input to an output of the driver is less than 50 microseconds.