AVB Talker Timestamp Validation via Modulus Operation
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Solution Overview
Problem
In AVB systems, determining valid presentation times for audio/video data packets is challenging, leading to potential synchronization issues among listeners, as not all packets include valid presentation times, which can result in incorrect playback timing.
Innovation Solution
A method and system where a talker device determines valid presentation times by performing a modulus operation on the number of data blocks since the last valid presentation time stamped data block and the number of data blocks in a sample, setting a timestamp_valid field in the packet header to indicate whether a packet includes a valid presentation time, ensuring synchronized playback across listeners.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If presentation times are included in every audio/video data packet, then synchronization accuracy among listeners is improved, but device complexity and processing overhead increase
Solution Approach 1:
The patent segments the audio/video data stream into fixed-size samples, with each sample containing a specific number of data blocks. By performing modulus operations on sample indices rather than individual packets, the system reduces processing complexity while maintaining synchronization accuracy at the sample level.
Solution Approach 2:
Instead of timestamping every single packet, the patent applies timestamping selectively to specific samples based on the modulus operation result. This partial action approach provides sufficient synchronization information for listeners while reducing the computational burden on talker devices.
2Manufacturing precision
If presentation times are calculated for all data packets, then playback timing accuracy is improved, but computational resources and processing time are consumed
Solution Approach 1:
The patent implements periodic timestamping by calculating the modulus of the cumulative data block count against the syt_interval value. This creates a periodic pattern where timestamps are generated at regular intervals (every syt_interval blocks) rather than continuously for every packet, reducing processing time while maintaining timing accuracy.
Solution Approach 2:
The talker device pre-calculates and sets the timestamp_valid field based on the modulus operation result before packet transmission. This preliminary action allows listener devices to efficiently identify valid timestamp packets without performing complex calculations, reducing overall processing time across the network.
3Reliability
If timestamp validation is performed on every packet at the listener device, then synchronization reliability is improved, but processing load and energy consumption increase
Solution Approach 1:
The patent extracts the timestamp validation logic into a simple field check (timestamp_valid) that is easily evaluable at the listener device. By separating the complex modulus calculation (performed only at the talker) from the simple validation check (performed at all listeners), the system maintains synchronization reliability while minimizing energy consumption at listener devices.
Solution Approach 2:
Each listener device independently evaluates the timestamp_valid field for received packets and autonomously determines which packets contain valid presentation times. This self-service approach eliminates the need for centralized validation coordination, reducing communication overhead and energy consumption while maintaining synchronization reliability.
Data Source
AI summary
Embodiments are disclosed for a device for determining which packets of an audio/video stream include a valid presentation time. In some embodiments, a device comprises a communication interface communicatively connectable to another device and configured to transmit data, a processor, and a storage device that stores instructions executable by the processor to designate a sample of an audio/video stream as including a valid presentation time responsive to a sum of a number of data blocks that have been sampled since a last valid presentation time stamped data block and a number of data blocks in the sample being greater than or equal to a threshold value.