RTP Packet Latency Measurement via Unique Tagging
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Solution Overview
Problem
Current VoIP systems lack a standard approach to measure latency introduced by transcoding operations, as available RTP packet analyzers cannot correlate incoming and outgoing packets due to differences in payload, sequence number, timestamp, SSRC, and CSRC, leading to unaccounted delays in voice codec conversions.
Innovation Solution
A method involving a Session Border Controller (SBC) and packet analyzer that extends the RTP packet header with a unique tag to identify incoming packets, allowing correlation with transcoded outgoing packets, and calculates latency by comparing transmission and arrival times, enabling accurate measurement of transcoding latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If transcoding operations are performed to support calls between different codec environments, then codec compatibility and call support are improved, but latency is introduced and cannot be accurately measured
Solution Approach 1:
The patent applies preliminary action by inserting a unique identifier tag into the RTP packet header before transcoding occurs. This tag remains embedded through the transcoding process, enabling future correlation between input and output packets. The preliminary tagging action sets up the measurement capability in advance, allowing latency calculation without interfering with the transcoding operation itself.
Solution Approach 2:
The unique identifier tag acts as an intermediary element that bridges the gap between incoming and outgoing RTP packets. Since transcoding fundamentally changes packet characteristics (payload, sequence numbers, timestamps), the tag serves as a stable mediator that allows packet correlation despite these transformations. This intermediary enables the measurement system to track packets through the transcoding process.
2Measurement precision
If standard RTP packet analysis is used to monitor voice traffic, then packet transmission can be tracked, but latency measurement during transcoding is impossible due to packet characteristic changes
Solution Approach 1:
The system performs preliminary action by embedding a unique identifier tag into the RTP packet header before the packet enters the transcoding process. This tag remains intact through transcoding, enabling the packet analyzer to correlate input and output packets despite changes in other packet characteristics. The preliminary tagging enables measurement capability that would otherwise be impossible.
Solution Approach 2:
The unique identifier tag serves as an intermediary that allows the packet analyzer to track packets through transcoding. Standard RTP analysis cannot measure transcoding latency because transcoding changes packet characteristics (payload, sequence numbers, timestamps). The tag acts as a stable mediator that bridges this gap, enabling the analyzer to correlate packets and calculate latency despite the transformations.
3Adaptability or versatility
If transcoding is performed to convert between different codecs, then call support across different environments is enabled, but the transcoding process introduces delays that degrade call quality
Solution Approach 1:
The system applies preliminary action by inserting a unique identifier tag into the RTP packet header before transcoding. This tag enables subsequent measurement and monitoring of transcoding latency, allowing network operators to identify and optimize transcoding operations that degrade call quality. The preliminary tagging doesn't interfere with transcoding but enables quality assessment.
Solution Approach 2:
The patent implements feedback by enabling the measurement and monitoring of transcoding latency through the unique identifier tag correlation. This measured latency information provides feedback about the impact of transcoding on call quality, allowing network operators to identify problematic transcoding operations and optimize them. The feedback loop enables continuous improvement of call quality while maintaining codec compatibility.
Data Source
AI summary
Systems and methods for computing latency introduced by media transcoding operations are described. In some embodiments, a method may include receiving incoming Real-Time Protocol (RTP) packets, each having time of arrival and a payload encoded with a first codec and receiving outgoing RTP packets, each having a time of transmission and a payload encoded with a second codec. The method may also include calculating a latency associated with a transcoding of at least one of the incoming RTP packets into at least one corresponding one of the outgoing RTP packets based upon a difference between the time of transmission of the at least one corresponding one of the outgoing RTP packets and the time of arrival of the at least one of the incoming RTP packets. In some cases, the incoming and outgoing RTP packets may be Voice-over-Internet Protocol (VoIP) packets.