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
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
|
/*
* Copyright (c) 2016 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/include/flexfec_sender.h"
#include <string.h>
#include <cstdint>
#include <list>
#include <memory>
#include <optional>
#include <utility>
#include <vector>
#include "absl/strings/string_view.h"
#include "api/array_view.h"
#include "api/environment/environment.h"
#include "api/rtp_parameters.h"
#include "api/units/data_rate.h"
#include "api/units/time_delta.h"
#include "api/units/timestamp.h"
#include "modules/include/module_fec_types.h"
#include "modules/rtp_rtcp/include/rtp_header_extension_map.h"
#include "modules/rtp_rtcp/include/rtp_rtcp_defines.h"
#include "modules/rtp_rtcp/source/forward_error_correction.h"
#include "modules/rtp_rtcp/source/rtp_header_extension_size.h"
#include "modules/rtp_rtcp/source/rtp_header_extensions.h"
#include "modules/rtp_rtcp/source/rtp_packet_to_send.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
#include "rtc_base/race_checker.h"
#include "rtc_base/synchronization/mutex.h"
namespace webrtc {
namespace {
// Let first sequence number be in the first half of the interval.
constexpr uint16_t kMaxInitRtpSeqNumber = 0x7fff;
// See breakdown in flexfec_header_reader_writer.cc.
constexpr size_t kFlexfecMaxHeaderSize = 32;
// Since we will mainly use FlexFEC to protect video streams, we use a 90 kHz
// clock for the RTP timestamps. (This is according to the RFC, which states
// that it is RECOMMENDED to use the same clock frequency for FlexFEC as for
// the protected media stream.)
// The constant converts from clock millisecond timestamps to the 90 kHz
// RTP timestamp.
const int kMsToRtpTimestamp = kVideoPayloadTypeFrequency / 1000;
// How often to log the generated FEC packets to the text log.
constexpr TimeDelta kPacketLogInterval = TimeDelta::Seconds(10);
RtpHeaderExtensionMap RegisterSupportedExtensions(
const std::vector<RtpExtension>& rtp_header_extensions) {
RtpHeaderExtensionMap map;
for (const auto& extension : rtp_header_extensions) {
if (extension.uri == TransportSequenceNumber::Uri()) {
map.Register<TransportSequenceNumber>(extension.id);
} else if (extension.uri == AbsoluteSendTime::Uri()) {
map.Register<AbsoluteSendTime>(extension.id);
} else if (extension.uri == TransmissionOffset::Uri()) {
map.Register<TransmissionOffset>(extension.id);
} else if (extension.uri == RtpMid::Uri()) {
map.Register<RtpMid>(extension.id);
} else {
RTC_LOG(LS_INFO)
<< "FlexfecSender only supports RTP header extensions for "
"BWE and MID, so the extension "
<< extension.ToString() << " will not be used.";
}
}
return map;
}
} // namespace
FlexfecSender::FlexfecSender(
const Environment& env,
int payload_type,
uint32_t ssrc,
uint32_t protected_media_ssrc,
absl::string_view mid,
const std::vector<RtpExtension>& rtp_header_extensions,
ArrayView<const RtpExtensionSize> extension_sizes,
const RtpState* rtp_state)
: env_(env),
random_(env_.clock().TimeInMicroseconds()),
payload_type_(payload_type),
// Reset RTP state if this is not the first time we are operating.
// Otherwise, randomize the initial timestamp offset and RTP sequence
// numbers. (This is not intended to be cryptographically strong.)
timestamp_offset_(rtp_state ? rtp_state->start_timestamp
: random_.Rand<uint32_t>()),
ssrc_(ssrc),
protected_media_ssrc_(protected_media_ssrc),
mid_(mid),
seq_num_(rtp_state ? rtp_state->sequence_number
: random_.Rand(1, kMaxInitRtpSeqNumber)),
ulpfec_generator_(
env_,
ForwardErrorCorrection::CreateFlexfec(ssrc, protected_media_ssrc)),
rtp_header_extension_map_(
RegisterSupportedExtensions(rtp_header_extensions)),
header_extensions_size_(
RtpHeaderExtensionSize(extension_sizes, rtp_header_extension_map_)),
fec_bitrate_(/*max_window_size=*/TimeDelta::Seconds(1)) {
// This object should not have been instantiated if FlexFEC is disabled.
RTC_DCHECK_GE(payload_type, 0);
RTC_DCHECK_LE(payload_type, 127);
}
FlexfecSender::~FlexfecSender() = default;
// We are reusing the implementation from UlpfecGenerator for SetFecParameters,
// AddRtpPacketAndGenerateFec, and FecAvailable.
void FlexfecSender::SetProtectionParameters(
const FecProtectionParams& delta_params,
const FecProtectionParams& key_params) {
ulpfec_generator_.SetProtectionParameters(delta_params, key_params);
}
void FlexfecSender::AddPacketAndGenerateFec(const RtpPacketToSend& packet) {
// TODO(brandtr): Generalize this SSRC check when we support multistream
// protection.
RTC_DCHECK_EQ(packet.Ssrc(), protected_media_ssrc_);
ulpfec_generator_.AddPacketAndGenerateFec(packet);
}
std::vector<std::unique_ptr<RtpPacketToSend>> FlexfecSender::GetFecPackets() {
RTC_CHECK_RUNS_SERIALIZED(&ulpfec_generator_.race_checker_);
std::vector<std::unique_ptr<RtpPacketToSend>> fec_packets_to_send;
fec_packets_to_send.reserve(ulpfec_generator_.generated_fec_packets_.size());
size_t total_fec_data_bytes = 0;
for (const auto* fec_packet : ulpfec_generator_.generated_fec_packets_) {
std::unique_ptr<RtpPacketToSend> fec_packet_to_send(
new RtpPacketToSend(&rtp_header_extension_map_));
fec_packet_to_send->set_packet_type(
RtpPacketMediaType::kForwardErrorCorrection);
fec_packet_to_send->set_allow_retransmission(false);
// RTP header.
fec_packet_to_send->SetMarker(false);
fec_packet_to_send->SetPayloadType(payload_type_);
fec_packet_to_send->SetSequenceNumber(seq_num_++);
fec_packet_to_send->SetTimestamp(
timestamp_offset_ +
static_cast<uint32_t>(kMsToRtpTimestamp *
env_.clock().TimeInMilliseconds()));
// Set "capture time" so that the TransmissionOffset header extension
// can be set by the RTPSender.
fec_packet_to_send->set_capture_time(env_.clock().CurrentTime());
fec_packet_to_send->SetSsrc(ssrc_);
// Reserve extensions, if registered. These will be set by the RTPSender.
fec_packet_to_send->ReserveExtension<AbsoluteSendTime>();
fec_packet_to_send->ReserveExtension<TransmissionOffset>();
fec_packet_to_send->ReserveExtension<TransportSequenceNumber>();
// Possibly include the MID header extension.
if (!mid_.empty()) {
// This is a no-op if the MID header extension is not registered.
fec_packet_to_send->SetExtension<RtpMid>(mid_);
}
// RTP payload.
uint8_t* payload =
fec_packet_to_send->AllocatePayload(fec_packet->data.size());
memcpy(payload, fec_packet->data.cdata(), fec_packet->data.size());
total_fec_data_bytes += fec_packet_to_send->size();
fec_packets_to_send.push_back(std::move(fec_packet_to_send));
}
if (!fec_packets_to_send.empty()) {
ulpfec_generator_.ResetState();
}
Timestamp now = env_.clock().CurrentTime();
if (!fec_packets_to_send.empty() &&
now - last_generated_packet_ > kPacketLogInterval) {
RTC_LOG(LS_VERBOSE) << "Generated " << fec_packets_to_send.size()
<< " FlexFEC packets with payload type: "
<< payload_type_ << " and SSRC: " << ssrc_ << ".";
last_generated_packet_ = now;
}
MutexLock lock(&mutex_);
fec_bitrate_.Update(total_fec_data_bytes, now);
return fec_packets_to_send;
}
// The overhead is BWE RTP header extensions and FlexFEC header.
size_t FlexfecSender::MaxPacketOverhead() const {
return header_extensions_size_ + kFlexfecMaxHeaderSize;
}
DataRate FlexfecSender::CurrentFecRate() const {
MutexLock lock(&mutex_);
return fec_bitrate_.Rate(env_.clock().CurrentTime())
.value_or(DataRate::Zero());
}
std::optional<RtpState> FlexfecSender::GetRtpState() {
RtpState rtp_state;
rtp_state.sequence_number = seq_num_;
rtp_state.start_timestamp = timestamp_offset_;
return rtp_state;
}
} // namespace webrtc
|
