Synchronizing Mobile Audio Playback Using FIFO Fill Level Feedback
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Solution Overview
Problem
Binaural hearing aids face synchronization challenges in playing back digital audio signals due to internal timer differences, leading to perceived sound shifts, as they lack wired connections and wireless synchronization is battery-intensive.
Innovation Solution
A method synchronizes digital signal playback across mobile audio terminals by using constant data rate packets, generating a time reference signal from received data packets to maintain a constant FIFO memory fill level, adjusting playback speed based on this signal to compensate for timer discrepancies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If wireless synchronization is used between binaural hearing aids, then synchronization accuracy is improved, but battery consumption increases
Solution Approach 1:
The patent uses the transmitted audio signal itself as an intermediary carrier to embed timing information. Instead of establishing a separate wireless communication channel between hearing aids for synchronization, the timing data is conveyed through the audio signal packets from the transmitter. This allows synchronization without additional battery-consuming wireless communication between the hearing aids.
Solution Approach 2:
Each hearing aid independently extracts timing information from the received audio packets and autonomously adjusts its playback timing. The system does not require active communication or coordination between the hearing aids themselves - each device self-regulates its synchronization based on the embedded timing markers in the audio stream, eliminating the need for inter-device wireless synchronization.
2Device complexity
If internal timers with manufacturing tolerances are used in hearing aids, then device complexity is reduced, but playback synchronization deteriorates
Solution Approach 1:
The patent embeds timing reference markers within the audio data packets transmitted from the transmitter. Each hearing aid continuously monitors these timing markers and adjusts its playback timing accordingly. This feedback mechanism compensates for timer drift and manufacturing tolerances without requiring complex synchronization protocols or additional hardware between devices.
Solution Approach 2:
The transmitter pre-embeds timing synchronization information within the audio data packets before transmission. This preliminary action ensures that each hearing aid receives not only audio data but also reference timing information needed to synchronize playback, eliminating the need for post-reception synchronization adjustments between devices.
3Stability of the object's composition
If data packets are buffered in FIFO memory for non-real-time transmission, then data rate stability is improved, but timing synchronization becomes dependent on internal timers
Solution Approach 1:
The transmitted audio signal serves multiple functions simultaneously: it carries the audio data for playback and embeds timing synchronization information within the same data stream. This multi-functionality allows the system to maintain stable data buffering while the embedded timing markers provide reference points for synchronization, making the timing independent of individual device timer accuracy.
Data Source
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AI summary
The invention describes a method (40) for synchronizing the playback of a digital signal (16) sent by a transmitter (18) to a plurality of mobile audio terminals (4), wherein the mobile audio terminals (4) each have a signal receiving unit (14), a first-in-first-out memory (45) connected to the signal receiving unit (14) and an audio playback unit (10) connected to the first-in-first-out memory (45), and wherein the transmitter (18) sends the digital signal (16) as a plurality of data packets (20) with a time-averaged constant data rate (34).It is provided that each mobile audio terminal (4) receives at least a subset of the multitude of data packets (20) in the same way by the signal receiving unit (14), the signal receiving unit (14) generates a time reference signal (48) based on the received data packets (20), a FIFO signal (50) is generated by the first-in-first-out memory (45) which contains information on the fill level of the first-in-first-out memory (45) at certain times, an instantaneous playback speed (64) is set based on the time reference signal (48) and the FIFO signal (50), the audio playback unit (4) reproduces samples (62) corresponding to the digital signal (16) at the instantaneous playback speed (64), and thereby the fill level of the first-in-first-out memory (45) is kept constant on average over time.