/
reception_report.go
133 lines (115 loc) · 5.43 KB
/
reception_report.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
// SPDX-FileCopyrightText: 2023 The Pion community <https://pion.ly>
// SPDX-License-Identifier: MIT
package rtcp
import "encoding/binary"
// A ReceptionReport block conveys statistics on the reception of RTP packets
// from a single synchronization source.
type ReceptionReport struct {
// The SSRC identifier of the source to which the information in this
// reception report block pertains.
SSRC uint32
// The fraction of RTP data packets from source SSRC 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.
FractionLost uint8
// The total number of RTP data packets from source SSRC that have
// been lost since the beginning of reception.
TotalLost uint32
// The low 16 bits contain the highest sequence number received in an
// RTP data packet from source SSRC, and the most significant 16
// bits extend that sequence number with the corresponding count of
// sequence number cycles.
LastSequenceNumber uint32
// An estimate of the statistical variance of the RTP data packet
// interarrival time, measured in timestamp units and expressed as an
// unsigned integer.
Jitter uint32
// The middle 32 bits out of 64 in the NTP timestamp received as part of
// the most recent RTCP sender report (SR) packet from source SSRC. If no
// SR has been received yet, the field is set to zero.
LastSenderReport uint32
// The delay, expressed in units of 1/65536 seconds, between receiving the
// last SR packet from source SSRC and sending this reception report block.
// If no SR packet has been received yet from SSRC, the field is set to zero.
Delay uint32
}
const (
receptionReportLength = 24
fractionLostOffset = 4
totalLostOffset = 5
lastSeqOffset = 8
jitterOffset = 12
lastSROffset = 16
delayOffset = 20
)
// Marshal encodes the ReceptionReport in binary
func (r ReceptionReport) Marshal() ([]byte, error) {
/*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* | SSRC |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | fraction lost | cumulative number of packets lost |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | extended highest sequence number received |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | interarrival jitter |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | last SR (LSR) |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | delay since last SR (DLSR) |
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
*/
rawPacket := make([]byte, receptionReportLength)
binary.BigEndian.PutUint32(rawPacket, r.SSRC)
rawPacket[fractionLostOffset] = r.FractionLost
// pack TotalLost into 24 bits
if r.TotalLost >= (1 << 25) {
return nil, errInvalidTotalLost
}
tlBytes := rawPacket[totalLostOffset:]
tlBytes[0] = byte(r.TotalLost >> 16)
tlBytes[1] = byte(r.TotalLost >> 8)
tlBytes[2] = byte(r.TotalLost)
binary.BigEndian.PutUint32(rawPacket[lastSeqOffset:], r.LastSequenceNumber)
binary.BigEndian.PutUint32(rawPacket[jitterOffset:], r.Jitter)
binary.BigEndian.PutUint32(rawPacket[lastSROffset:], r.LastSenderReport)
binary.BigEndian.PutUint32(rawPacket[delayOffset:], r.Delay)
return rawPacket, nil
}
// Unmarshal decodes the ReceptionReport from binary
func (r *ReceptionReport) Unmarshal(rawPacket []byte) error {
if len(rawPacket) < receptionReportLength {
return errPacketTooShort
}
/*
* 0 1 2 3
* 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
* | SSRC |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | fraction lost | cumulative number of packets lost |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | extended highest sequence number received |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | interarrival jitter |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | last SR (LSR) |
* +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
* | delay since last SR (DLSR) |
* +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
*/
r.SSRC = binary.BigEndian.Uint32(rawPacket)
r.FractionLost = rawPacket[fractionLostOffset]
tlBytes := rawPacket[totalLostOffset:]
r.TotalLost = uint32(tlBytes[2]) | uint32(tlBytes[1])<<8 | uint32(tlBytes[0])<<16
r.LastSequenceNumber = binary.BigEndian.Uint32(rawPacket[lastSeqOffset:])
r.Jitter = binary.BigEndian.Uint32(rawPacket[jitterOffset:])
r.LastSenderReport = binary.BigEndian.Uint32(rawPacket[lastSROffset:])
r.Delay = binary.BigEndian.Uint32(rawPacket[delayOffset:])
return nil
}
func (r *ReceptionReport) len() int {
return receptionReportLength
}