RTP Packet Recovery via Probe and RTCP Feedback
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Solution Overview
Problem
Current media delivery systems using RTP Protocol lack built-in support for packet retransmission, relying on FEC to recover lost packets, which is inefficient and does not address the need for automatic detection and re-sending of lost packets.
Innovation Solution
A system comprising a probe device and a detection block that automatically detects lost packets, reports them using RTCP messages, and re-sends the missing packets from a cyclic buffer, allowing for re-ordering and re-insertion into the original stream without relying on FEC.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If FEC (Forward Error Correction) is used to recover lost packets, then packet loss is reduced, but the system complexity increases and does not provide automatic detection and retransmission capability
Solution Approach 1:
The system implements feedback through RTCP (Real-Time Control Protocol) messages that carry information about lost packets from the receiver back to the transmitter. This feedback mechanism enables the transmitter to automatically detect packet loss and retransmit only the lost packets, replacing the need for complex FEC codes while maintaining reliability.
Solution Approach 2:
The system enables self-service by allowing the receiver to automatically detect lost packets and request their retransmission without external intervention. The probe device monitors the stream, detects losses, and triggers retransmission requests automatically, making the system self-healing without requiring manual configuration or complex FEC processing.
2Reliability
If FEC packets are transmitted with data packets, then packet recovery is enabled, but the transmission efficiency decreases due to additional packets
Solution Approach 1:
The system performs preliminary action by buffering packets at the probe device before transmission. When packet loss is detected, the system retrieves the lost packet from the buffer and retransmits it only when needed, rather than continuously transmitting redundant FEC packets. This improves transmission efficiency by sending packets only when necessary.
Solution Approach 2:
The system discards the need for continuous FEC packet transmission and instead recovers only the specific lost packets that occur. By using RTCP feedback to identify exactly which packets are lost, the system recovers only those specific packets rather than relying on inefficient FEC codes that protect against all possible loss patterns.
3Reliability
If automatic packet detection and retransmission is implemented, then data integrity is improved, but the system requires additional components like probe devices and RTCP processing
Solution Approach 1:
The probe device performs multiple functions: it buffers packets, monitors for packet loss, extracts lost packets, and prepares retransmission requests. This multi-functionality reduces the need for separate dedicated components for each function, thereby limiting the increase in system complexity while achieving improved data integrity.
Solution Approach 2:
The RTCP message acts as an intermediary carrier that transmits packet loss information from the receiver to the transmitter. This standard protocol-based intermediary enables reliable communication about packet losses without requiring custom complex signaling mechanisms, thus improving data integrity with minimal added complexity.
Data Source
AI summary
In a network for reliable transfer of packets from a transmitter to a receiver using a Real-time Transport Protocol (RTP), a system for packet recovery, the system comprising a detection block (detector) for packet loss detection and a probe device (probe) for lost packet retransmission, wherein the detector is configured to send a packet retransmit request to the probe upon detecting a packet loss (a lost packet), and wherein the probe is configured to store received packets and retransmit the lost packet responsive to the retransmit request.