Rtcp.c File Reference

#include "../Include_i.h"

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Macros
#define	LOG_CLASS   "RtcRtcp"

Functions
STATUS	parseRtcpTwccPacket (PRtcpPacket pRtcpPacket, PTwccManager pTwccManager)
STATUS	computeTwccTrendline (PTwccManager pTwccManager, PDOUBLE pDelayTrend, PDOUBLE pQueueDelay)
	Estimates network congestion trend using least-squares linear regression on accumulated one-way delay variations, smoothed with an exponential moving average (EMA).
STATUS	updateTwccHashTable (PTwccManager pTwccManager, PINT64 duration, PUINT64 receivedBytes, PUINT64 receivedPackets, PUINT64 sentBytes, PUINT64 sentPackets)
STATUS	onRtcpTwccPacket (PRtcpPacket pRtcpPacket, PKvsPeerConnection pKvsPeerConnection)
STATUS	onRtcpPacket (PKvsPeerConnection pKvsPeerConnection, PBYTE pBuff, UINT32 buffLen)
STATUS	onRtcpRembPacket (PRtcpPacket pRtcpPacket, PKvsPeerConnection pKvsPeerConnection)
STATUS	onRtcpPLIPacket (PRtcpPacket pRtcpPacket, PKvsPeerConnection pKvsPeerConnection)
STATUS	createRtcpPLIPacket (UINT32 senderSsrc, UINT32 mediaSsrc, PBYTE pRawPacket, PUINT32 pPacketLen)
STATUS	transceiverSendPictureLoss (PRtcRtpTransceiver pRtcRtpTransceiver)
	Send a Picture Loss Indication (PLI) to ask the remote sender for a new keyframe.

Macro Definition Documentation

LOG_CLASS

#define LOG_CLASS   "RtcRtcp"

Function Documentation

computeTwccTrendline()

STATUS computeTwccTrendline	(	PTwccManager	pTwccManager,
		PDOUBLE	pDelayTrend,
		PDOUBLE	pQueueDelay )

Estimates network congestion trend using least-squares linear regression on accumulated one-way delay variations, smoothed with an exponential moving average (EMA).

Algorithm overview:

1. For each consecutive packet pair (i-1, i), compute the inter-arrival delay variation: d_i = (recvTime_i - recvTime_{i-1}) - (sendTime_i - sendTime_{i-1}) A positive d_i means the network took longer to deliver packet i than packet i-1.
2. Accumulate these variations into a running sum (the "accumulated delay"): D_i = D_{i-1} + d_i (where D_0 = 0) This represents the total queuing delay buildup over the observation window.
3. Fit a line to the points (x_i, y_i) = (i, D_i) using ordinary least-squares regression. The slope formula is: rawSlope = (n * sum(x_i * y_i) - sum(x_i) * sum(y_i)) / (n * sum(x_i^2) - (sum(x_i))^2) A positive slope indicates delay is growing (congestion building up). A near-zero slope indicates stable network conditions. A negative slope indicates delay is decreasing (congestion clearing).
4. Smooth the slope with an EMA to reduce noise: smoothedSlope = alpha * rawSlope + (1 - alpha) * prevSmoothedSlope where alpha = TWCC_TRENDLINE_SMOOTHING_FACTOR (0.2 by default).

Parameters

[in]	pTwccManager	TWCC manager containing packet timing history
[out]	pDelayTrend	Smoothed slope in ms per sample (positive = congestion building)
[out]	pQueueDelay	Total accumulated delay variation in ms over the window

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createRtcpPLIPacket()

STATUS createRtcpPLIPacket	(	UINT32	senderSsrc,
		UINT32	mediaSsrc,
		PBYTE	pRawPacket,
		PUINT32	pPacketLen )

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onRtcpPacket()

STATUS onRtcpPacket	(	PKvsPeerConnection	pKvsPeerConnection,
		PBYTE	pBuff,
		UINT32	buffLen )

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onRtcpPLIPacket()

STATUS onRtcpPLIPacket	(	PRtcpPacket	pRtcpPacket,
		PKvsPeerConnection	pKvsPeerConnection )

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onRtcpRembPacket()

STATUS onRtcpRembPacket	(	PRtcpPacket	pRtcpPacket,
		PKvsPeerConnection	pKvsPeerConnection )

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onRtcpTwccPacket()

STATUS onRtcpTwccPacket	(	PRtcpPacket	pRtcpPacket,
		PKvsPeerConnection	pKvsPeerConnection )

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parseRtcpTwccPacket()

STATUS parseRtcpTwccPacket	(	PRtcpPacket	pRtcpPacket,
		PTwccManager	pTwccManager )

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updateTwccHashTable()

STATUS updateTwccHashTable	(	PTwccManager	pTwccManager,
		PINT64	duration,
		PUINT64	receivedBytes,
		PUINT64	receivedPackets,
		PUINT64	sentBytes,
		PUINT64	sentPackets )

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