Adaptive Isochronous USB Audio to RF Synchronization
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Solution Overview
Problem
The communication of audio data between a USB interface and a wireless RF hub is challenging, especially for low latency applications like telephony, due to issues with complex frequency synthesizers and data loss during signal conversion, and existing methods are not universally compatible with different operating systems.
Innovation Solution
A method and system that synchronize isochronous audio data frames between a USB interface and a wireless RF communication device using a serial audio link, with an adaptive streaming controller that counts start-of-frame pulses and compares them to the wireless RF communication device clock to determine a clock difference signal, triggering a synchronization event code for rate matching, thus avoiding delays and system-specific signal requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an adaptive mode with frequency synthesizer is used to control audio transfer rate, then the audio synchronization can be maintained, but the device complexity increases and compatibility across different operating systems deteriorates
Solution Approach 1:
The patent extracts the clock synchronization function from the complex frequency synthesizer and implements it separately using a USB interface clock signal. The USB interface provides the master clock that directly controls the audio data transfer rate, eliminating the need for a complex adaptive frequency synthesizer while maintaining synchronization reliability.
Solution Approach 2:
The USB interface serves multiple functions: it provides both the data transfer pathway and the master clock signal for synchronization. This multi-functional approach eliminates the need for separate frequency control mechanisms, improving compatibility across different operating systems that all support USB isochronous transfers with standardized clock signaling.
2Reliability
If a buffer is used to synchronize data streams with different sample rates, then rate matching is achieved, but the latency increases which is unacceptable for low latency applications
Solution Approach 1:
The patent implements dynamic rate matching by using a variable transfer rate mechanism controlled by the USB interface clock. Instead of using a fixed buffer to absorb rate differences, the system dynamically adjusts the audio data transfer rate to match the USB clock, eliminating buffer delay while maintaining synchronization for low latency applications.
3Adaptability or versatility
If digital signal is converted to analog and then to digital via ND converter, then signal adaptation is achieved, but data loss occurs and device complexity increases
Solution Approach 1:
The patent replaces the mechanical/electrical conversion process (D/A and A/D conversion) with a digital-only solution. The USB interface directly transfers digital audio data with digital clock synchronization, eliminating the need for analog conversion stages. This maintains signal integrity without data loss while reducing device complexity.
Data Source
AI summary
A method of and a system for synchronizing isochronous audio data frames provided by a USB interface to a clock of a wireless RF communication device is provided. The USB interface and the wireless RF communication device are connected via an I2S link, the method comprising receiving the isochronous audio data frames and the wireless RF communication device clock in a streaming controller, phase locking the isochronous audio data frames to a USB interface clock, counting start-of-frame pulses of the phase locked isochronous audio data frames, comparing the counted start-of-frame pulses with the wireless RF communication device clock to determine a difference signal, the difference signal triggering a synchronization event code when a threshold difference has been reached, rate matching the isochronous audio data frames to the wireless RF communication device clock upon receiving the synchronization event code.