Audio Wake-Up Latency Reduction via Encoded Fast Mode Signals
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Solution Overview
Problem
Current SOUNDWIRE audio systems experience latency due to the slow activation mode during wake-up, which affects the user's audio experience as they transition through a safe, slow mode before reaching an active mode.
Innovation Solution
The system introduces a negative differential line with an encoded signal during the check PHY_Num phase to indicate a fast mode speed, allowing capable slaves to start in an active mode without passing through the safe mode, thereby reducing latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the system uses the traditional safe mode activation during wake-up, then the slave devices can reliably establish communication, but the activation latency increases due to transitioning through slow safe mode first
Solution Approach 1:
The master device performs preliminary actions during the check PHY_Num phase by encoding and transmitting fast mode capability indication signals before the actual wake-up activation. This allows slave devices to pre-prepare for fast mode operation, eliminating the need to transition through safe mode later and reducing activation latency while maintaining reliable communication establishment.
Solution Approach 2:
The system changes the communication rate parameter dynamically by introducing encoded signals that indicate fast mode capability. During the check PHY_Num phase, the master device transmits encoded signals on the differential audio bus that convey communication rate information, allowing slave devices to adjust their activation parameters and skip the slow safe mode transition, thus reducing activation latency while ensuring reliable communication.
2Loss of time
If the system transitions directly to fast mode during wake-up, then the activation latency is reduced, but the risk of communication errors increases without proper capability verification
Solution Approach 1:
The system implements feedback by having slave devices monitor and decode the encoded signals transmitted by the master device during the check PHY_Num phase. The encoded signals contain fast mode capability indication information that provides feedback to slave devices about whether fast mode activation is appropriate. This feedback mechanism ensures that direct fast mode transition only occurs when both master and slave devices are capable, maintaining communication reliability while reducing activation latency.
Solution Approach 2:
The capability verification is performed as a preliminary action during the check PHY_Num phase through encoded signal transmission. The master device encodes and transmits fast mode capability indication signals before the actual wake-up activation, allowing slave devices to verify compatibility in advance. This preliminary verification ensures that direct fast mode transition is safe and reliable, eliminating communication errors while maintaining low activation latency.
3Speed
If the system uses encoded signals during check PHY_Num phase, then fast mode activation is enabled, but the protocol complexity increases
Solution Approach 1:
The encoded signals transmitted during the check PHY_Num phase serve multiple functions: they convey fast mode capability indication information, maintain protocol compatibility with existing SOUNDWIRE devices, and enable future extensions. By designing the encoding scheme to be multi-functional and compatible with the existing protocol framework, the system achieves fast mode activation without significantly increasing overall protocol complexity, as the same signal mechanism serves multiple purposes.
Data Source
AI summary
Systems and methods for fast activation of slaves during wake up in an audio system allow a master device in an audio system such as a SOUNDWIRE audio system to send system and/or topology information to capable slave devices during a wake up window so that the slaves may start in an active mode rather than a safe mode. In the most recent proposed versions of SOUNDWIRE, there is a check PHY_Num phase. The systems for fast activation of slaves cause a negative differential line to be driven with an encoded signal by the master during a check PHY_Num phase where the encoded signal indicates a fast mode speed. Capable slaves may then begin in a fast mode rather than a safe (and slow) mode. Latency may be reduced by starting in a fast mode, which may improve the user's audio experience.