Adaptive Audio Synchronization via Embedded Sync Signal
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Solution Overview
Problem
In adaptive audio systems, the non-deterministic nature of Ethernet-based audio stream transmission poses challenges for precise audio-video synchronization, as existing methods rely on real-time interfaces that are not applicable to bursty, non-real-time transmission mediums like Ethernet, leading to potential desynchronization issues.
Innovation Solution
A synchronization signal is embedded in the multi-channel audio stream, containing track identifier and frame count information to align the adaptive audio content with the video signal, enabling proper synchronization and a switchover process that fades out adaptive audio and fades in multi-channel audio if synchronization is lost, ensuring continuous playback.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If Ethernet-based adaptive audio stream transmission is used, then bandwidth and capacity are improved, but transmission determinism and synchronization precision deteriorate
Solution Approach 1:
The system embeds synchronization information (PTP timestamps, frame numbers) in advance within the audio data packets before transmission. This preliminary embedding of timing references allows the receiver to pre-calculate and adjust playback timing, compensating for Ethernet's non-deterministic transmission characteristics and maintaining precise synchronization with video.
Solution Approach 2:
The system implements a feedback mechanism where synchronization status is continuously monitored by comparing audio and video timing references. When desynchronization is detected, the system adjusts the audio playback rate or timing in real-time to re-synchronize with the video stream, ensuring continuous synchronization despite Ethernet transmission variability.
2Quantity of substance
If Ethernet-based adaptive audio stream transmission is used, then audio channel capacity is improved, but transmission reliability and synchronization stability worsen
Solution Approach 1:
The system employs buffering mechanisms that store audio packets in advance before playback. This buffer acts as a cushion against transmission variability, allowing the system to absorb timing jitter and packet arrival variations inherent in Ethernet transmission, thereby maintaining stable synchronization without requiring real-time transmission perfection.
Solution Approach 2:
Continuous synchronization monitoring with automatic corrective adjustments ensures that any drift or instability in the Ethernet transmission is compensated in real-time, maintaining reliable synchronization throughout playback.
3Measurement precision
If explicit synchronization functions are added to Ethernet audio transmission, then synchronization capability is improved, but system complexity increases
Solution Approach 1:
The synchronization information is merged directly into the existing audio data packet structure rather than requiring separate synchronization channels or protocols. PTP timestamps and frame number information are embedded within the audio packets themselves, allowing synchronization functionality to be added without significantly increasing system complexity while still achieving precise synchronization.
4Measurement precision
If deterministic latency is implemented for audio-video synchronization, then synchronization accuracy is improved, but adaptability to variable network conditions deteriorates
Solution Approach 1:
The system implements dynamic synchronization adjustment where the audio playback timing is continuously adapted based on actual network conditions and synchronization status. Rather than using fixed deterministic latency, the system dynamically modifies playback rate and timing to maintain synchronization accuracy while adapting to variable Ethernet transmission conditions.
Data Source
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AI summary
Embodiments are described for a synchronization and switchover mechanism for an adaptive audio system in which multi-channel (e.g., surround sound) audio is provided along with object-based adaptive audio content. A synchronization signal is embedded in the multi-channel audio stream and contains a track identifier and frame count for the adaptive audio stream to play out. The track identifier and frame count of a received adaptive audio frame is compared to the track identifier and frame count contained in the synchronization signal. If either the track identifier or frame count does not match the synchronization signal, a switchover process fades out the adaptive audio track and fades in the multi-channel audio track. The system plays the multi-channel audio track until the synchronization signal track identifier and frame count and adaptive audio track identifier and frame count match, at which point the adaptive audio content will be faded back in.