AVB Stream Shaping for Consistent Media Rate
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Solution Overview
Problem
In Audio Video Bridging (AVB) networks, the inconsistent transmission rate of audio/video samples can lead to disruptive issues such as audio distortion and variable playback rates, as the number of samples in packets may not align with the expected media rate, causing skipped or sped-up/slowed-down playback.
Innovation Solution
A method and system to dynamically determine the number of sample chunks to include in each packet based on reserved bandwidth, elapsed time, and available sample blocks, ensuring that the transmission rate matches the media rate by calculating the bandwidth credit and adjusting the sample chunk count for each packet generation interval.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed number of samples are transmitted in each packet, then the transmission structure is simple, but the media rate cannot be maintained when network conditions vary, causing audio distortion and playback rate variability
Solution Approach 1:
The patent applies dynamics by making the number of samples per packet variable rather than fixed. The stream shaper dynamically adjusts the sample count based on elapsed time since the last packet and available bandwidth credit, allowing the transmission rate to adapt to varying network conditions while maintaining the expected media rate at the listener
Solution Approach 2:
The patent implements feedback through the bandwidth credit mechanism. The talker calculates elapsed time since the last packet transmission and uses this feedback to determine how many additional samples can be sent in the current packet. This closed-loop control ensures the media rate is maintained despite network variability
2Productivity
If more samples are transmitted in each packet to increase efficiency, then bandwidth utilization improves, but the risk of audio distortion increases if the transmission rate deviates from the expected media rate
Solution Approach 1:
The patent changes the parameter of sample count per packet from a fixed value to a dynamically calculated value. The stream shaper computes the optimal number of samples based on elapsed time and bandwidth credit, adjusting this parameter in real-time to maximize bandwidth utilization while ensuring the listener receives samples at the correct rate for consistent playback
3Loss of time
If the transmission rate is increased to reduce latency, then real-time playback is improved, but audio distortion occurs when the rate exceeds the expected media rate
Solution Approach 1:
The patent applies preliminary action by having the talker calculate the expected number of samples to send based on elapsed time before actually transmitting the packet. This advance calculation ensures that even when transmission occurs faster or slower than ideal intervals, the listener receives the correct number of samples to maintain the expected media rate and avoid distortion
Data Source
AI summary
Embodiments are disclosed for a device for determining a number of sample blocks to include in a packet. 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 determine a total sample size of samples stored in a transmission buffer. The instructions are further executable to calculate a bandwidth credit based on a reserved bandwidth and an elapsed time since a last sent packet, determine a number of sample blocks to include in a packet based on the total sample size and the bandwidth credit, and generate a packet including the determined number of sample blocks.