1 /*
2 * Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
3 *
4 * Use of this source code is governed by a BSD-style license
5 * that can be found in the LICENSE file in the root of the source
6 * tree. An additional intellectual property rights grant can be found
7 * in the file PATENTS. All contributing project authors may
8 * be found in the AUTHORS file in the root of the source tree.
9 */
10
11 #include "modules/audio_coding/neteq/red_payload_splitter.h"
12
13 #include <assert.h>
14 #include <stddef.h>
15
16 #include <cstdint>
17 #include <list>
18 #include <utility>
19 #include <vector>
20
21 #include "modules/audio_coding/neteq/decoder_database.h"
22 #include "modules/audio_coding/neteq/packet.h"
23 #include "rtc_base/buffer.h"
24 #include "rtc_base/logging.h"
25 #include "rtc_base/numerics/safe_conversions.h"
26
27 namespace webrtc {
28
29 // The method loops through a list of packets {A, B, C, ...}. Each packet is
30 // split into its corresponding RED payloads, {A1, A2, ...}, which is
31 // temporarily held in the list |new_packets|.
32 // When the first packet in |packet_list| has been processed, the orignal packet
33 // is replaced by the new ones in |new_packets|, so that |packet_list| becomes:
34 // {A1, A2, ..., B, C, ...}. The method then continues with B, and C, until all
35 // the original packets have been replaced by their split payloads.
SplitRed(PacketList * packet_list)36 bool RedPayloadSplitter::SplitRed(PacketList* packet_list) {
37 // Too many RED blocks indicates that something is wrong. Clamp it at some
38 // reasonable value.
39 const size_t kMaxRedBlocks = 32;
40 bool ret = true;
41 PacketList::iterator it = packet_list->begin();
42 while (it != packet_list->end()) {
43 const Packet& red_packet = *it;
44 assert(!red_packet.payload.empty());
45 const uint8_t* payload_ptr = red_packet.payload.data();
46
47 // Read RED headers (according to RFC 2198):
48 //
49 // 0 1 2 3
50 // 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
51 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
52 // |F| block PT | timestamp offset | block length |
53 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
54 // Last RED header:
55 // 0 1 2 3 4 5 6 7
56 // +-+-+-+-+-+-+-+-+
57 // |0| Block PT |
58 // +-+-+-+-+-+-+-+-+
59
60 struct RedHeader {
61 uint8_t payload_type;
62 uint32_t timestamp;
63 size_t payload_length;
64 };
65
66 std::vector<RedHeader> new_headers;
67 bool last_block = false;
68 size_t sum_length = 0;
69 while (!last_block) {
70 RedHeader new_header;
71 // Check the F bit. If F == 0, this was the last block.
72 last_block = ((*payload_ptr & 0x80) == 0);
73 // Bits 1 through 7 are payload type.
74 new_header.payload_type = payload_ptr[0] & 0x7F;
75 if (last_block) {
76 // No more header data to read.
77 ++sum_length; // Account for RED header size of 1 byte.
78 new_header.timestamp = red_packet.timestamp;
79 new_header.payload_length = red_packet.payload.size() - sum_length;
80 payload_ptr += 1; // Advance to first payload byte.
81 } else {
82 // Bits 8 through 21 are timestamp offset.
83 int timestamp_offset =
84 (payload_ptr[1] << 6) + ((payload_ptr[2] & 0xFC) >> 2);
85 new_header.timestamp = red_packet.timestamp - timestamp_offset;
86 // Bits 22 through 31 are payload length.
87 new_header.payload_length =
88 ((payload_ptr[2] & 0x03) << 8) + payload_ptr[3];
89 payload_ptr += 4; // Advance to next RED header.
90 }
91 sum_length += new_header.payload_length;
92 sum_length += 4; // Account for RED header size of 4 bytes.
93 // Store in new list of packets.
94 new_headers.push_back(new_header);
95 }
96
97 if (new_headers.size() <= kMaxRedBlocks) {
98 // Populate the new packets with payload data.
99 // |payload_ptr| now points at the first payload byte.
100 PacketList new_packets; // An empty list to store the split packets in.
101 for (size_t i = 0; i != new_headers.size(); ++i) {
102 const auto& new_header = new_headers[i];
103 size_t payload_length = new_header.payload_length;
104 if (payload_ptr + payload_length >
105 red_packet.payload.data() + red_packet.payload.size()) {
106 // The block lengths in the RED headers do not match the overall
107 // packet length. Something is corrupt. Discard this and the remaining
108 // payloads from this packet.
109 RTC_LOG(LS_WARNING) << "SplitRed length mismatch";
110 ret = false;
111 break;
112 }
113
114 Packet new_packet;
115 new_packet.timestamp = new_header.timestamp;
116 new_packet.payload_type = new_header.payload_type;
117 new_packet.sequence_number = red_packet.sequence_number;
118 new_packet.priority.red_level =
119 rtc::dchecked_cast<int>((new_headers.size() - 1) - i);
120 new_packet.payload.SetData(payload_ptr, payload_length);
121 new_packet.packet_info = RtpPacketInfo(
122 /*ssrc=*/red_packet.packet_info.ssrc(),
123 /*csrcs=*/std::vector<uint32_t>(),
124 /*rtp_timestamp=*/new_packet.timestamp,
125 /*audio_level=*/absl::nullopt,
126 /*absolute_capture_time=*/absl::nullopt,
127 /*receive_time_ms=*/red_packet.packet_info.receive_time_ms());
128 new_packets.push_front(std::move(new_packet));
129 payload_ptr += payload_length;
130 }
131 // Insert new packets into original list, before the element pointed to by
132 // iterator |it|.
133 packet_list->splice(it, std::move(new_packets));
134 } else {
135 RTC_LOG(LS_WARNING) << "SplitRed too many blocks: " << new_headers.size();
136 ret = false;
137 }
138 // Remove |it| from the packet list. This operation effectively moves the
139 // iterator |it| to the next packet in the list. Thus, we do not have to
140 // increment it manually.
141 it = packet_list->erase(it);
142 }
143 return ret;
144 }
145
CheckRedPayloads(PacketList * packet_list,const DecoderDatabase & decoder_database)146 void RedPayloadSplitter::CheckRedPayloads(
147 PacketList* packet_list,
148 const DecoderDatabase& decoder_database) {
149 int main_payload_type = -1;
150 for (auto it = packet_list->begin(); it != packet_list->end(); /* */) {
151 uint8_t this_payload_type = it->payload_type;
152 if (decoder_database.IsRed(this_payload_type)) {
153 it = packet_list->erase(it);
154 continue;
155 }
156 if (!decoder_database.IsDtmf(this_payload_type) &&
157 !decoder_database.IsComfortNoise(this_payload_type)) {
158 if (main_payload_type == -1) {
159 // This is the first packet in the list which is non-DTMF non-CNG.
160 main_payload_type = this_payload_type;
161 } else {
162 if (this_payload_type != main_payload_type) {
163 // We do not allow redundant payloads of a different type.
164 // Remove |it| from the packet list. This operation effectively
165 // moves the iterator |it| to the next packet in the list. Thus, we
166 // do not have to increment it manually.
167 it = packet_list->erase(it);
168 continue;
169 }
170 }
171 }
172 ++it;
173 }
174 }
175
176 } // namespace webrtc
177