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RTCP: Calculate correctly the fraction lost in RTCP report blocks 

Defined in RFC3550 Appendix A.3, related to issue #30
This commit is contained in:
Heikki Tampio 2022-12-14 12:07:22 +02:00
parent be34a7ce4d
commit e037e02105
2 changed files with 28 additions and 6 deletions
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4
include/uvgrtp/rtcp.hh
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@ -41,6 +41,10 @@ namespace uvgrtp {
uint32_t received_bytes = 0; /* Number of bytes received excluding RTP Header */
bool received_rtp_packet = false; // since last report
uint32_t expected_pkts = 0; /* Number of expected packets */
uint32_t received_prior = 0; /* Number of received packets in last report */
uint32_t expected_prior = 0; /* Number of expected packets in last report */
double jitter = 0; /* The estimation of jitter (see RFC 3550 A.8) */
uint32_t transit = 0; /* TODO: */

30
src/rtcp.cc
View File

@ -23,6 +23,7 @@
#include <cstring>
#include <iostream>
#include <set>
#include <algorithm>
/* TODO: explain these constants */
@ -768,9 +769,12 @@ void uvgrtp::rtcp::zero_stats(uvgrtp::receiver_statistics *stats)
stats->received_pkts = 0;
stats->lost_pkts = 0;
stats->received_bytes = 0;
stats->received_rtp_packet = false;
stats->expected_pkts = 0;
stats->received_prior = 0;
stats->expected_prior = 0;
stats->jitter = 0;
stats->transit = 0;
@ -1694,12 +1698,26 @@ rtp_error_t uvgrtp::rtcp::generate_report()
if (p.second->stats.received_rtp_packet)
{
uint32_t dropped_packets = p.second->stats.lost_pkts;
// TODO: Fraction should be the number of packets lost compared to number of packets expected (see fraction lost in RFC 3550)
// see https://datatracker.ietf.org/doc/html/rfc3550#appendix-A.3
//uint8_t fraction = dropped_packets ? p.second->stats.received_bytes / dropped_packets : 0;
uint8_t fraction = 0; // disabled, because it was incorrect
/* RFC3550 page 83, Appendix A.3 */
/* Determine number of packets lost and expected */
uint32_t extended_max = p.second->stats.cycles + p.second->stats.max_seq;
uint32_t expected = extended_max - p.second->stats.base_seq + 1;
/* Calculate number of packets lost */
uint32_t lost = expected - p.second->stats.received_pkts;
lost = std::clamp(lost, uint32_t(8388607), uint32_t(8388608));
uint32_t expected_interval = expected - p.second->stats.expected_prior;
p.second->stats.expected_prior = expected;
uint32_t received_interval = p.second->stats.received_pkts - p.second->stats.received_prior;
p.second->stats.received_prior = p.second->stats.received_pkts;
int32_t lost_interval = expected_interval - received_interval;
/* Calculate fractions of packets lost during last reporting interval */
uint32_t fraction = 0;
if (expected_interval == 0 || lost_interval <= 0) { fraction = 0; }
else { fraction = (lost_interval << 8) / expected_interval; }
uint64_t diff = (u_long)uvgrtp::clock::hrc::diff_now(p.second->stats.sr_ts);
uint32_t dlrs = (uint32_t)uvgrtp::clock::ms_to_jiffies(diff);