RTPReceptionStats::RTPReceptionStats(unsigned int SSRC,unsigned short initialSeq):m_SSRC(0),m_numPacketsReceivedSinceLastReset(0),
m_totalNumPacketsReceived(0),m_totalBytesReceived_hi(0),m_totalBytesReceived_lo(0),
m_haveSeenInitialSequenceNumber(0),m_baseExtSeqNumReceived(0),m_lastResetExtSeqNumReceived(0),
m_highestExtSeqNumReceived(0),m_lastTransit(0),m_previousPacketRTPTimestamp(0),
m_jitter(0),m_lastReceivedSR_NTPmsw(0),m_lastReceivedSR_NTPlsw(0),
m_minInterPacketGapUS(0),m_maxInterPacketGapUS(0),m_hasBeenSynchronized(0)
{
gethostname(m_CNAME,100);
m_CNAME_length=strlen(m_CNAME);
initSeqNum(initialSeq);
initStats(SSRC);
}
void RTPReceptionStats
::noteIncomingPacket(u_int16_t seqNum, u_int32_t rtpTimestamp,
unsigned timestampFrequency,
Boolean useForJitterCalculation,
struct timeval& resultPresentationTime,
Boolean& resultHasBeenSyncedUsingRTCP,
unsigned packetSize) {
if (!fHaveSeenInitialSequenceNumber) initSeqNum(seqNum);
++fNumPacketsReceivedSinceLastReset;
++fTotNumPacketsReceived;
u_int32_t prevTotBytesReceived_lo = fTotBytesReceived_lo;
fTotBytesReceived_lo += packetSize;
if (fTotBytesReceived_lo < prevTotBytesReceived_lo) { // wrap-around
++fTotBytesReceived_hi;
}
// Check whether the new sequence number is the highest yet seen:
unsigned oldSeqNum = (fHighestExtSeqNumReceived&0xFFFF);
unsigned seqNumCycle = (fHighestExtSeqNumReceived&0xFFFF0000);
unsigned seqNumDifference = (unsigned)((int)seqNum-(int)oldSeqNum);
unsigned newSeqNum = 0;
if (seqNumLT((u_int16_t)oldSeqNum, seqNum)) {
// This packet was not an old packet received out of order, so check it:
if (seqNumDifference >= 0x8000) {
// The sequence number wrapped around, so start a new cycle:
seqNumCycle += 0x10000;
}
newSeqNum = seqNumCycle|seqNum;
if (newSeqNum > fHighestExtSeqNumReceived) {
fHighestExtSeqNumReceived = newSeqNum;
}
} else if (fTotNumPacketsReceived > 1) {
// This packet was an old packet received out of order
if ((int)seqNumDifference >= 0x8000) {
// The sequence number wrapped around, so switch to an old cycle:
seqNumCycle -= 0x10000;
}
newSeqNum = seqNumCycle|seqNum;
if (newSeqNum < fBaseExtSeqNumReceived) {
fBaseExtSeqNumReceived = newSeqNum;
}
}
// Record the inter-packet delay
struct timeval timeNow;
gettimeofday(&timeNow, NULL);
if (fLastPacketReceptionTime.tv_sec != 0
|| fLastPacketReceptionTime.tv_usec != 0) {
unsigned gap
= (timeNow.tv_sec - fLastPacketReceptionTime.tv_sec)*MILLION
+ timeNow.tv_usec - fLastPacketReceptionTime.tv_usec;
if (gap > fMaxInterPacketGapUS) {
fMaxInterPacketGapUS = gap;
}
if (gap < fMinInterPacketGapUS) {
fMinInterPacketGapUS = gap;
}
fTotalInterPacketGaps.tv_usec += gap;
if (fTotalInterPacketGaps.tv_usec >= MILLION) {
++fTotalInterPacketGaps.tv_sec;
fTotalInterPacketGaps.tv_usec -= MILLION;
}
}
fLastPacketReceptionTime = timeNow;
// Compute the current 'jitter' using the received packet's RTP timestamp,
// and the RTP timestamp that would correspond to the current time.
// (Use the code from appendix A.8 in the RTP spec.)
// Note, however, that we don't use this packet if its timestamp is
// the same as that of the previous packet (this indicates a multi-packet
// fragment), or if we've been explicitly told not to use this packet.
if (useForJitterCalculation
&& rtpTimestamp != fPreviousPacketRTPTimestamp) {
unsigned arrival = (timestampFrequency*timeNow.tv_sec);
arrival += (unsigned)
((2.0*timestampFrequency*timeNow.tv_usec + 1000000.0)/2000000);
// note: rounding
int transit = arrival - rtpTimestamp;
if (fLastTransit == (~0)) fLastTransit = transit; // hack for first time
int d = transit - fLastTransit;
fLastTransit = transit;
if (d < 0) d = -d;
fJitter += (1.0/16.0) * ((double)d - fJitter);
}
// Return the 'presentation time' that corresponds to "rtpTimestamp":
if (fSyncTime.tv_sec == 0 && fSyncTime.tv_usec == 0) {
// This is the first timestamp that we've seen, so use the current
// 'wall clock' time as the synchronization time. (This will be
// corrected later when we receive RTCP SRs.)
fSyncTimestamp = rtpTimestamp;
fSyncTime = timeNow;
}
int timestampDiff = rtpTimestamp - fSyncTimestamp;
// Note: This works even if the timestamp wraps around
// (as long as "int" is 32 bits)
// Divide this by the timestamp frequency to get real time:
double timeDiff = timestampDiff/(double)timestampFrequency;
// Add this to the 'sync time' to get our result:
unsigned const million = 1000000;
unsigned seconds, uSeconds;
if (timeDiff >= 0.0) {
seconds = fSyncTime.tv_sec + (unsigned)(timeDiff);
uSeconds = fSyncTime.tv_usec
+ (unsigned)((timeDiff - (unsigned)timeDiff)*million);
if (uSeconds >= million) {
uSeconds -= million;
++seconds;
}
} else {
timeDiff = -timeDiff;
seconds = fSyncTime.tv_sec - (unsigned)(timeDiff);
uSeconds = fSyncTime.tv_usec
- (unsigned)((timeDiff - (unsigned)timeDiff)*million);
if ((int)uSeconds < 0) {
uSeconds += million;
--seconds;
}
}
resultPresentationTime.tv_sec = seconds;
resultPresentationTime.tv_usec = uSeconds;
resultHasBeenSyncedUsingRTCP = fHasBeenSynchronized;
// Save these as the new synchronization timestamp & time:
fSyncTimestamp = rtpTimestamp;
fSyncTime = resultPresentationTime;
fPreviousPacketRTPTimestamp = rtpTimestamp;
}
RTPReceptionStats::RTPReceptionStats(u_int32_t SSRC, u_int16_t initialSeqNum) {
initSeqNum(initialSeqNum);
init(SSRC);
}
void RTPReceptionStats::noteIncomingPacket(
unsigned short seqNum,
unsigned int rtpTimestamp,unsigned int timestampFrequency,
bool useForJitterCalculation,
timeval& resultPresentationTime,
bool& resultHasBeenSyncedUsingRTCP,
unsigned int packetSize)
{
if (!m_haveSeenInitialSequenceNumber)
{
initSeqNum(seqNum);
}
m_numPacketsReceivedSinceLastReset++;
m_totalNumPacketsReceived++;
unsigned int lastTotalBytesReceived_Io=m_totalBytesReceived_lo;
m_totalBytesReceived_lo+=packetSize;
if (m_totalBytesReceived_lo<lastTotalBytesReceived_Io)
{
m_totalBytesReceived_hi++;
}
unsigned int oldSeqNum=(m_highestExtSeqNumReceived&0xffff);
unsigned int seqNumCycle=(m_highestExtSeqNumReceived&0xffff0000);
unsigned int seqNumDifference=(unsigned int)((int)seqNum-(int)oldSeqNum);
//32bit contains cycle seqNum;
unsigned int newSeqNum=0;
if (seqNumLT((unsigned short)oldSeqNum,seqNum))
{
//newSeq<oldSeq,uint<0,seqNumDifference>>0,进入新的循环;
if (seqNumDifference>0x8000)
{
seqNumCycle+=0x10000;
}
newSeqNum=seqNumCycle|seqNum;
if (newSeqNum>m_highestExtSeqNumReceived)
{
m_highestExtSeqNumReceived=newSeqNum;
}
}else if(m_totalNumPacketsReceived>1)
{
//newSeq>>oldSeq回到上一个循环;
if ((int)seqNumDifference>0x8000)
{
seqNumCycle-=0x10000;
}
newSeqNum=seqNumCycle|seqNum;
if (m_baseExtSeqNumReceived>newSeqNum)
{
m_baseExtSeqNumReceived=newSeqNum;
}
}
//记录包延时;
timeval timeNow;
gettimeofday(&timeNow,0);
if (m_lastPacketReceptionTime.tv_sec!=0&&
m_lastPacketReceptionTime.tv_usec!=0)
{
unsigned int gapUsec=(timeNow.tv_sec-m_lastPacketReceptionTime.tv_sec)*1000000+
(timeNow.tv_usec-m_lastPacketReceptionTime.tv_usec);
if (gapUsec>m_maxInterPacketGapUS)
{
m_maxInterPacketGapUS=gapUsec;
}
if (gapUsec<m_minInterPacketGapUS)
{
m_minInterPacketGapUS=gapUsec;
}
m_totalInterPacketGaps.tv_usec+=gapUsec;
while (m_totalInterPacketGaps.tv_usec>1000000)
{
m_totalInterPacketGaps.tv_sec++;
m_totalInterPacketGaps.tv_usec-=1000000;
}
}
m_lastPacketReceptionTime=timeNow;
//rtp jitter：时间抖动;
//Si:RTP 时间戳;
//Ri:RTP 接收到时的时间戳;
//D(i,j)=(Rj-Ri)-(Sj-Si)=(Rj-Sj)-(Ri-Si);
//J=J+(|D(i-1,i)|-J)/16;
//RFC 1889 A.8
if (useForJitterCalculation&&
rtpTimestamp!=m_previousPacketRTPTimestamp)
{
unsigned int arrival=(timestampFrequency*timeNow.tv_sec);
arrival+=(unsigned int)((2.0*timestampFrequency*timeNow.tv_usec+1000000.0)/2000000.0);
int transit=arrival-rtpTimestamp;
if (m_lastTransit==~0)
{
m_lastTransit=transit;
}
int d=transit-m_lastTransit;
m_lastTransit=transit;
if (d<0)
{
d=-d;
}
m_jitter+=(1.0/16.0)*((double)d-m_jitter);
}
if (m_syncTime.tv_usec==0&&m_syncTime.tv_sec==0)
{
m_syncTime=timeNow;
m_syncTimestamp=rtpTimestamp;
}
//时间戳间距;
int timestampDiff=rtpTimestamp-m_syncTimestamp;
//乘以采样率，获得真实时间差;
double timeDiff=timestampDiff/(double)timestampFrequency;
unsigned int seconds=0,useconds=0;
if (timeDiff>=0.0)
{
seconds=m_syncTime.tv_sec+(unsigned int)timeDiff;
useconds=m_syncTime.tv_usec+
(unsigned int)((timeDiff-(unsigned int)timeDiff)*UMILLION);
if (useconds>=UMILLION)
{
seconds++;
useconds-=UMILLION;
}
}else
{
timeDiff=-timeDiff;
seconds=m_syncTime.tv_sec-(unsigned int)timeDiff;
useconds=m_syncTime.tv_usec-
(unsigned int)((timeDiff-(unsigned int)timeDiff)*UMILLION);
if ((int)useconds<0)
{
useconds+=UMILLION;
--seconds;
}
}
resultPresentationTime.tv_sec=seconds;
resultPresentationTime.tv_usec=useconds;
resultHasBeenSyncedUsingRTCP=m_hasBeenSynchronized;
//保存这一包的信息;
m_syncTimestamp=rtpTimestamp;
m_syncTime=resultPresentationTime;
m_previousPacketRTPTimestamp=rtpTimestamp;
}
