rtcp_rr_t Struct Reference

#include <MNRTPNetTypes.h>

List of all members.

Public Attributes
u_int32	ssrc
unsigned int	fraction:8
int	lost:24
u_int32	last_seq
u_int32	jitter
u_int32	lsr
u_int32	dlsr

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Detailed Description

Reception report block.
A reception report block contained in RTCP sender reports as specified in RFC1889, 6.3.1.

See also:

sr_t

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Member Data Documentation

u_int32 rtcp_rr_t::dlsr

Delay since last SR packet. The delay, expressed in units of 1/65536 seconds, between receiving the last SR packet from source SSRC_n and sending this reception report block. If no SR packet has been received yet from SSRC_n, the DLSR field is set to zero.

unsigned int rtcp_rr_t::fraction

Fraction lost since last SR/RR. The fraction of RTP data packets from source SSRC_n lost since the previous SR or RR packet was sent, expressed as a fixed point number with the binary point at the left edge of the field. (That is equivalent to taking the integer part after multiplying the loss fraction by 256.) This fraction is defined to be the number of packets lost divided by the number of packets expected, as defined in the next paragraph. An implementation is shown in Appendix A.3. If the loss is negative due to duplicates, the fraction lost is set to zero. Note that a receiver cannot tell whether any packets were lost after the last one received, and that there will be no reception report block issued for a source if all packets from that source sent during the last reporting interval have been lost.

u_int32 rtcp_rr_t::jitter

Interarrival jitter. An estimate of the statistical variance of the RTP data packet interarrival time, measured in timestamp units and expressed as an unsigned integer. See RFC1889 for the formulae.

u_int32 rtcp_rr_t::last_seq

Extended highest sequence number received. The low 16 bits contain the highest sequence number received in an RTP data packet from source SSRC_n, and the most significant 16 bits extend that sequence number with the corresponding count of sequence number cycles, which may be maintained according to the algorithm in Appendix A.1. Note that different receivers within the same session will generate different extensions to the sequence number if their start times differ significantly.

int rtcp_rr_t::lost

Cumulative number of pkts lost (signed!). The total number of RTP data packets from source SSRC_n that have been lost since the beginning of reception. This number is defined to be the number of packets expected less the number of packets actually received, where the number of packets received includes any which are late or duplicates. Thus packets that arrive late are not counted as lost, and the loss may be negative if there are duplicates. The number of packets expected is defined to be the extended last sequence number received, as defined next, less the initial sequence number received. This may be calculated as shown in Appendix A.3.

u_int32 rtcp_rr_t::lsr

Last SR packet from this source. The middle 32 bits out of 64 in the NTP timestamp (as explained in Section 4) received as part of the most recent RTCP sender report (SR) packet from source SSRC_n. If no SR has been received yet, the field is set to zero.

u_int32 rtcp_rr_t::ssrc

Data source being reported. The SSRC identifier of the source to which the information in this reception report block pertains.

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The documentation for this struct was generated from the following file:

• MNRTPNetTypes.h

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