PCR Timestamp Extraction for Network Jitter Measurement
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Solution Overview
Problem
Calculating the Media Delivery Index's delay factor (DF) is complex due to the need for extracting the embedded media rate from encoded packets, which requires significant processing and is not accurate as it doesn't include MPEG transport overhead, especially in scalable IPTV networks.
Innovation Solution
Using Program Clock Reference (PCR) timestamps within Transport Stream packets to simplify the calculation of DF by expressing it in terms of PCR differences and packet counts, eliminating the need to determine packet sizes and media rates, and being applicable to both constant and variable bit rate transmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the embedded media rate is extracted from PES packets to calculate DF, then the media rate information is obtained, but significant processing resources and hardware/software complexity are required
Solution Approach 1:
The patent extracts only the necessary PCR timestamp values from the TS packet headers without requiring full PES packet decoding. This selective extraction of critical timing information eliminates the need for complex decoder processing while obtaining sufficient data for DF calculation.
Solution Approach 2:
The patent uses PCR timestamps as a simplified copy/representation of the actual media rate information. Instead of processing the complete media stream to extract embedded rates, it uses the PCR timing copies to calculate DF, achieving equivalent measurement purposes with minimal processing.
2Measurement precision
If the embedded media rate is used for DF calculation, then the rate information is available, but it does not include MPEG transport overhead and is not accurate
Solution Approach 1:
The PCR timestamps inherently contain the complete timing information including all transport overhead. The patent leverages this self-contained timing data to calculate DF directly without needing to add or subtract overhead components manually, achieving both accuracy and simplicity.
3Productivity
If the embedded media rate extraction is performed in scalable fashion across hundreds of video channels, then the measurement can be scaled, but the processing requirements increase significantly
Solution Approach 1:
The patent processes each TS packet independently to extract PCR timestamps, allowing parallel processing across multiple video channels without requiring sequential decoding of entire PES streams. This segmentation enables scalable deployment across hundreds of channels with linearly increasing resources.
4Measurement precision
If TS packets are decoded to reconstruct PES before extracting media rate, then the embedded rate can be obtained, but the processing time and computational load increase
Solution Approach 1:
The PCR timestamps are extracted directly from the TS packet headers as preliminary timing information, eliminating the need for complete PES reconstruction. This preliminary extraction of critical timing data provides sufficient information for DF calculation without the time-consuming full decoding process.
Data Source
AI summary
A method and apparatus for measuring network performance. A stream of packets of encoded data, sent by a transmitter across a network, are received. The stream of packets includes (n+1) packets having transmittal timestamps from a clock local to the transmitter, where n is an integer greater than or equal to one. An (n+1)th transmittal timestamp and an nth transmittal timestamp are determined. A value is calculated based on the (n+1)th and the nth transmittal timestamps. The value corresponds to the size of a virtual buffer needed to store the packets during a measurement interval. The value is used to determine a performance measure for the network.