FM/HD1 Diversity Delay Synchronization With Buffered ASRC
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Solution Overview
Problem
Maintaining consistent audio timing across diverse audio paths for FM and HD1 signals in HD Radio broadcasting is challenging, leading to comb filter effects and blend artifacts due to varying delay differences, which existing methods struggle to address effectively.
Innovation Solution
Implementing a synchronous audio processing system with a single ASRC to sample the audio feed, splitting it into synchronized FM and HD paths, and using a buffer to control the input rate of the ASRC, ensuring no samples are added or removed, and employing a sync handler to manage buffer states for precise timing alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If separate audio processors are used for FM and HD1 audio paths, then processing flexibility is improved, but timing consistency deteriorates due to varying delay elements
Solution Approach 1:
The patent merges the timing control function into a centralized synchronization system that coordinates both FM and HD1 audio processors. A master clock and buffer management system统一管理 the timing of both separate processing paths, ensuring consistent throughput delay while maintaining the flexibility benefits of separate processors.
Solution Approach 2:
The patent implements feedback mechanisms through buffer state monitoring and adaptive rate control. The system continuously monitors buffer levels and adjusts the ASRC input rate accordingly, creating a closed-loop control system that maintains timing consistency despite variations in processing delays across separate audio paths.
2Adaptability or versatility
If ASRC rate conversion is applied in separate audio paths, then sample rate adaptability is improved, but differential delay increases due to independent rate conversion
Solution Approach 1:
The patent makes the ASRC operation universal by coordinating both FM and HD1 audio paths through a single master clock reference. The ASRC in each path operates adaptively but is synchronized to the same timing基准, allowing sample rate conversion flexibility while minimizing differential delay between paths.
Solution Approach 2:
The patent introduces a buffer management system as an intermediary between the ASRC operations and final audio output. This buffer acts as a mediator that absorbs timing variations from independent rate conversions and smooths out differential delays before signals are combined.
3Manufacturing precision
If audio encoders are co-located to maintain timing sync, then timing precision is improved, but system complexity and cost increase
Solution Approach 1:
The patent enables audio encoders to be distributed while maintaining timing synchronization through self-service mechanisms. Each encoder independently monitors buffer states and adjusts its own ASRC input rate based on feedback from the synchronization system, eliminating the need for centralized co-location while maintaining timing precision.
Data Source
AI summary
A broadcast system may have less restrictive timing constraints by providing synchronous processing chains for the HD audio portion and the FM audio portion so that no samples are added or removed from when the input audio is first sampled at an input rate and when the signals are combined and output by a digital analog converter operating at an output rate. The signals can be buffered within the synchronous processing paths and the state of the buffer can be used to control the input rate of the sampler. Graceful change over across multiple input sources can be achieved provided all input source input rates are controlled to by the overall output rate and all input sources are phase aligned to produce output symbols at the same time.