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
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
|
/*
* Copyright (c) 2015 The WebRTC project authors. All Rights Reserved.
*
* Use of this source code is governed by a BSD-style license
* that can be found in the LICENSE file in the root of the source
* tree. An additional intellectual property rights grant can be found
* in the file PATENTS. All contributing project authors may
* be found in the AUTHORS file in the root of the source tree.
*/
#include "modules/rtp_rtcp/source/rtcp_packet/nack.h"
#include <algorithm>
#include <cstddef>
#include <cstdint>
#include <utility>
#include <vector>
#include "modules/rtp_rtcp/source/byte_io.h"
#include "modules/rtp_rtcp/source/rtcp_packet/common_header.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
namespace webrtc {
namespace rtcp {
// RFC 4585: Feedback format.
//
// Common packet format:
//
// 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
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// |V=2|P| FMT | PT | length |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 0 | SSRC of packet sender |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 4 | SSRC of media source |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// : Feedback Control Information (FCI) :
// : :
//
// Generic NACK (RFC 4585).
//
// FCI:
// 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
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// | PID | BLP |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Nack::Nack() = default;
Nack::Nack(const Nack& rhs) = default;
Nack::~Nack() = default;
bool Nack::Parse(const CommonHeader& packet) {
RTC_DCHECK_EQ(packet.type(), kPacketType);
RTC_DCHECK_EQ(packet.fmt(), kFeedbackMessageType);
if (packet.payload_size_bytes() < kCommonFeedbackLength + kNackItemLength) {
RTC_LOG(LS_WARNING) << "Payload length " << packet.payload_size_bytes()
<< " is too small for a Nack.";
return false;
}
size_t nack_items =
(packet.payload_size_bytes() - kCommonFeedbackLength) / kNackItemLength;
ParseCommonFeedback(packet.payload());
const uint8_t* next_nack = packet.payload() + kCommonFeedbackLength;
packet_ids_.clear();
packed_.resize(nack_items);
for (size_t index = 0; index < nack_items; ++index) {
packed_[index].first_pid = ByteReader<uint16_t>::ReadBigEndian(next_nack);
packed_[index].bitmask = ByteReader<uint16_t>::ReadBigEndian(next_nack + 2);
next_nack += kNackItemLength;
}
Unpack();
return true;
}
size_t Nack::BlockLength() const {
return kHeaderLength + kCommonFeedbackLength +
packed_.size() * kNackItemLength;
}
bool Nack::Create(uint8_t* packet,
size_t* index,
size_t max_length,
PacketReadyCallback callback) const {
RTC_DCHECK(!packed_.empty());
// If nack list can't fit in packet, try to fragment.
constexpr size_t kNackHeaderLength = kHeaderLength + kCommonFeedbackLength;
for (size_t nack_index = 0; nack_index < packed_.size();) {
size_t bytes_left_in_buffer = max_length - *index;
if (bytes_left_in_buffer < kNackHeaderLength + kNackItemLength) {
if (!OnBufferFull(packet, index, callback))
return false;
continue;
}
size_t num_nack_fields =
std::min((bytes_left_in_buffer - kNackHeaderLength) / kNackItemLength,
packed_.size() - nack_index);
size_t payload_size_bytes =
kCommonFeedbackLength + (num_nack_fields * kNackItemLength);
size_t payload_size_32bits = CheckedDivExact<size_t>(payload_size_bytes, 4);
CreateHeader(kFeedbackMessageType, kPacketType, payload_size_32bits, packet,
index);
CreateCommonFeedback(packet + *index);
*index += kCommonFeedbackLength;
size_t nack_end_index = nack_index + num_nack_fields;
for (; nack_index < nack_end_index; ++nack_index) {
const PackedNack& item = packed_[nack_index];
ByteWriter<uint16_t>::WriteBigEndian(packet + *index + 0, item.first_pid);
ByteWriter<uint16_t>::WriteBigEndian(packet + *index + 2, item.bitmask);
*index += kNackItemLength;
}
RTC_DCHECK_LE(*index, max_length);
}
return true;
}
void Nack::SetPacketIds(const uint16_t* nack_list, size_t length) {
RTC_DCHECK(nack_list);
SetPacketIds(std::vector<uint16_t>(nack_list, nack_list + length));
}
void Nack::SetPacketIds(std::vector<uint16_t> nack_list) {
RTC_DCHECK(packet_ids_.empty());
RTC_DCHECK(packed_.empty());
packet_ids_ = std::move(nack_list);
Pack();
}
void Nack::Pack() {
RTC_DCHECK(!packet_ids_.empty());
RTC_DCHECK(packed_.empty());
auto it = packet_ids_.begin();
const auto end = packet_ids_.end();
while (it != end) {
PackedNack item;
item.first_pid = *it++;
// Bitmask specifies losses in any of the 16 packets following the pid.
item.bitmask = 0;
while (it != end) {
uint16_t shift = static_cast<uint16_t>(*it - item.first_pid - 1);
if (shift <= 15) {
item.bitmask |= (1 << shift);
++it;
} else {
break;
}
}
packed_.push_back(item);
}
}
void Nack::Unpack() {
RTC_DCHECK(packet_ids_.empty());
RTC_DCHECK(!packed_.empty());
for (const PackedNack& item : packed_) {
packet_ids_.push_back(item.first_pid);
uint16_t pid = item.first_pid + 1;
for (uint16_t bitmask = item.bitmask; bitmask != 0; bitmask >>= 1, ++pid) {
if (bitmask & 1)
packet_ids_.push_back(pid);
}
}
}
} // namespace rtcp
} // namespace webrtc
|
