Bluetooth Earphone Adaptive Playback Speed Control
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Solution Overview
Problem
Delays and interruptions in content playback occur due to differences in playback speed between a host device and an accessory, leading to unsynchronized audio and video experiences, particularly noticeable in paired devices like earbuds where one earbud may play faster than the other, causing frustrating discrepancies in audio output.
Innovation Solution
An accessory with processing devices that monitor buffer levels and adjust playback speed based on buffer level thresholds, using linear least square fits to determine speed adjustments, ensuring synchronized playback by transmitting instructions to adjust playback speed at a predetermined time, thus maintaining a consistent user experience.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the playback speed is increased to deliver content faster to the user, then the productivity of content delivery is improved, but the reliability of synchronized playback deteriorates due to buffer underruns and playback interruptions
Solution Approach 1:
The system continuously monitors the buffer level and uses this feedback to dynamically adjust the playback speed. When the buffer level indicates sufficient content, the playback speed is increased; when the buffer level drops, the playback speed is reduced to prevent interruptions. This closed-loop feedback mechanism resolves the contradiction by making playback speed adaptive rather than fixed.
Solution Approach 2:
The playback speed is made dynamic rather than static. The system adjusts the playback speed in real-time based on buffer conditions, transitioning between different speed states. This dynamic adjustment allows the system to optimize content delivery speed while maintaining reliable synchronized playback, directly resolving the technical contradiction.
2Reliability
If the buffer is filled to ensure sufficient content for faster playback, then the reliability of continuous playback is improved, but the loss of time due to initial buffering and delays increases
Solution Approach 1:
The system performs preliminary buffering to a moderate level to ensure continuous playback reliability, but then immediately begins dynamic speed adjustment to compensate for the initial delay. The preliminary action is minimized and followed by active management that recovers time loss through accelerated playback when buffer conditions permit.
Solution Approach 2:
The system changes the playback speed parameter dynamically based on buffer level. Instead of maintaining a constant high buffer level to ensure continuous playback, the system adjusts the playback speed parameter in response to buffer conditions, allowing it to recover from initial buffering delays while maintaining reliability.
3Reliability
If the playback speed is adjusted dynamically based on buffer level, then the reliability of synchronized playback is improved, but the device complexity increases due to buffer monitoring and speed adjustment mechanisms
Solution Approach 1:
The system uses the existing buffer infrastructure to monitor its own state and automatically adjusts its own playback speed without requiring external control. The buffer level information, already available as part of normal operation, is used to self-regulate the playback speed, minimizing additional complexity while improving reliability.
4Productivity
If the content is transmitted faster from the host device to the accessory, then the productivity of content transfer is improved, but the loss of time due to buffer synchronization issues and data drops increases
Solution Approach 1:
The system implements periodic monitoring of buffer levels and periodic adjustment of playback speed. This periodic action allows the system to maintain high content transfer speeds while regularly checking and correcting synchronization issues, preventing buffer overflow and data drops that would cause time loss.
Data Source
AI summary
The present disclosure provides systems and methods for adjusting the playback speed of accessories based on the buffer level of the received content. The accessories may receive content from a host device at a certain speed. The incoming speed of the content may be different than the playback speed of the content. Therefore, a buffer level of the received content may be determined using a linear least square (“LLS”) fit of the buffer level, the average of the buffer level, or a phased locked loop (“PLL”) approach. Based on a difference between the buffer level and the playback speed, a speed adjustment may be determined. Instructions may be transmitted from a primary accessory to a secondary accessory to adjust the playback speed by a certain amount at a certain time. This may ensure that the accessories remain in sync. The accessories may then adjust their respective playback speeds.