1 /*
2 * Copyright (c) 2014 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/rtp_rtcp/source/rtp_format_h264.h"
12
13 #include <string.h>
14
15 #include <cstddef>
16 #include <cstdint>
17 #include <iterator>
18 #include <memory>
19 #include <utility>
20 #include <vector>
21
22 #include "absl/types/optional.h"
23 #include "absl/types/variant.h"
24 #include "common_video/h264/h264_common.h"
25 #include "common_video/h264/pps_parser.h"
26 #include "common_video/h264/sps_parser.h"
27 #include "common_video/h264/sps_vui_rewriter.h"
28 #include "modules/rtp_rtcp/source/byte_io.h"
29 #include "modules/rtp_rtcp/source/rtp_packet_to_send.h"
30 #include "rtc_base/checks.h"
31 #include "rtc_base/logging.h"
32
33 namespace webrtc {
34 namespace {
35
36 static const size_t kNalHeaderSize = 1;
37 static const size_t kFuAHeaderSize = 2;
38 static const size_t kLengthFieldSize = 2;
39
40 // Bit masks for FU (A and B) indicators.
41 enum NalDefs : uint8_t { kFBit = 0x80, kNriMask = 0x60, kTypeMask = 0x1F };
42
43 // Bit masks for FU (A and B) headers.
44 enum FuDefs : uint8_t { kSBit = 0x80, kEBit = 0x40, kRBit = 0x20 };
45
46 } // namespace
47
RtpPacketizerH264(rtc::ArrayView<const uint8_t> payload,PayloadSizeLimits limits,H264PacketizationMode packetization_mode)48 RtpPacketizerH264::RtpPacketizerH264(rtc::ArrayView<const uint8_t> payload,
49 PayloadSizeLimits limits,
50 H264PacketizationMode packetization_mode)
51 : limits_(limits), num_packets_left_(0) {
52 // Guard against uninitialized memory in packetization_mode.
53 RTC_CHECK(packetization_mode == H264PacketizationMode::NonInterleaved ||
54 packetization_mode == H264PacketizationMode::SingleNalUnit);
55
56 for (const auto& nalu :
57 H264::FindNaluIndices(payload.data(), payload.size())) {
58 input_fragments_.push_back(
59 payload.subview(nalu.payload_start_offset, nalu.payload_size));
60 }
61
62 if (!GeneratePackets(packetization_mode)) {
63 // If failed to generate all the packets, discard already generated
64 // packets in case the caller would ignore return value and still try to
65 // call NextPacket().
66 num_packets_left_ = 0;
67 while (!packets_.empty()) {
68 packets_.pop();
69 }
70 }
71 }
72
73 RtpPacketizerH264::~RtpPacketizerH264() = default;
74
NumPackets() const75 size_t RtpPacketizerH264::NumPackets() const {
76 return num_packets_left_;
77 }
78
GeneratePackets(H264PacketizationMode packetization_mode)79 bool RtpPacketizerH264::GeneratePackets(
80 H264PacketizationMode packetization_mode) {
81 for (size_t i = 0; i < input_fragments_.size();) {
82 switch (packetization_mode) {
83 case H264PacketizationMode::SingleNalUnit:
84 if (!PacketizeSingleNalu(i))
85 return false;
86 ++i;
87 break;
88 case H264PacketizationMode::NonInterleaved:
89 int fragment_len = input_fragments_[i].size();
90 int single_packet_capacity = limits_.max_payload_len;
91 if (input_fragments_.size() == 1)
92 single_packet_capacity -= limits_.single_packet_reduction_len;
93 else if (i == 0)
94 single_packet_capacity -= limits_.first_packet_reduction_len;
95 else if (i + 1 == input_fragments_.size())
96 single_packet_capacity -= limits_.last_packet_reduction_len;
97
98 if (fragment_len > single_packet_capacity) {
99 if (!PacketizeFuA(i))
100 return false;
101 ++i;
102 } else {
103 i = PacketizeStapA(i);
104 }
105 break;
106 }
107 }
108 return true;
109 }
110
PacketizeFuA(size_t fragment_index)111 bool RtpPacketizerH264::PacketizeFuA(size_t fragment_index) {
112 // Fragment payload into packets (FU-A).
113 rtc::ArrayView<const uint8_t> fragment = input_fragments_[fragment_index];
114
115 PayloadSizeLimits limits = limits_;
116 // Leave room for the FU-A header.
117 limits.max_payload_len -= kFuAHeaderSize;
118 // Update single/first/last packet reductions unless it is single/first/last
119 // fragment.
120 if (input_fragments_.size() != 1) {
121 // if this fragment is put into a single packet, it might still be the
122 // first or the last packet in the whole sequence of packets.
123 if (fragment_index == input_fragments_.size() - 1) {
124 limits.single_packet_reduction_len = limits_.last_packet_reduction_len;
125 } else if (fragment_index == 0) {
126 limits.single_packet_reduction_len = limits_.first_packet_reduction_len;
127 } else {
128 limits.single_packet_reduction_len = 0;
129 }
130 }
131 if (fragment_index != 0)
132 limits.first_packet_reduction_len = 0;
133 if (fragment_index != input_fragments_.size() - 1)
134 limits.last_packet_reduction_len = 0;
135
136 // Strip out the original header.
137 size_t payload_left = fragment.size() - kNalHeaderSize;
138 int offset = kNalHeaderSize;
139
140 std::vector<int> payload_sizes = SplitAboutEqually(payload_left, limits);
141 if (payload_sizes.empty())
142 return false;
143
144 for (size_t i = 0; i < payload_sizes.size(); ++i) {
145 int packet_length = payload_sizes[i];
146 RTC_CHECK_GT(packet_length, 0);
147 packets_.push(PacketUnit(fragment.subview(offset, packet_length),
148 /*first_fragment=*/i == 0,
149 /*last_fragment=*/i == payload_sizes.size() - 1,
150 false, fragment[0]));
151 offset += packet_length;
152 payload_left -= packet_length;
153 }
154 num_packets_left_ += payload_sizes.size();
155 RTC_CHECK_EQ(0, payload_left);
156 return true;
157 }
158
PacketizeStapA(size_t fragment_index)159 size_t RtpPacketizerH264::PacketizeStapA(size_t fragment_index) {
160 // Aggregate fragments into one packet (STAP-A).
161 size_t payload_size_left = limits_.max_payload_len;
162 if (input_fragments_.size() == 1)
163 payload_size_left -= limits_.single_packet_reduction_len;
164 else if (fragment_index == 0)
165 payload_size_left -= limits_.first_packet_reduction_len;
166 int aggregated_fragments = 0;
167 size_t fragment_headers_length = 0;
168 rtc::ArrayView<const uint8_t> fragment = input_fragments_[fragment_index];
169 RTC_CHECK_GE(payload_size_left, fragment.size());
170 ++num_packets_left_;
171
172 auto payload_size_needed = [&] {
173 size_t fragment_size = fragment.size() + fragment_headers_length;
174 if (input_fragments_.size() == 1) {
175 // Single fragment, single packet, payload_size_left already adjusted
176 // with limits_.single_packet_reduction_len.
177 return fragment_size;
178 }
179 if (fragment_index == input_fragments_.size() - 1) {
180 // Last fragment, so StrapA might be the last packet.
181 return fragment_size + limits_.last_packet_reduction_len;
182 }
183 return fragment_size;
184 };
185
186 while (payload_size_left >= payload_size_needed()) {
187 RTC_CHECK_GT(fragment.size(), 0);
188 packets_.push(PacketUnit(fragment, aggregated_fragments == 0, false, true,
189 fragment[0]));
190 payload_size_left -= fragment.size();
191 payload_size_left -= fragment_headers_length;
192
193 fragment_headers_length = kLengthFieldSize;
194 // If we are going to try to aggregate more fragments into this packet
195 // we need to add the STAP-A NALU header and a length field for the first
196 // NALU of this packet.
197 if (aggregated_fragments == 0)
198 fragment_headers_length += kNalHeaderSize + kLengthFieldSize;
199 ++aggregated_fragments;
200
201 // Next fragment.
202 ++fragment_index;
203 if (fragment_index == input_fragments_.size())
204 break;
205 fragment = input_fragments_[fragment_index];
206 }
207 RTC_CHECK_GT(aggregated_fragments, 0);
208 packets_.back().last_fragment = true;
209 return fragment_index;
210 }
211
PacketizeSingleNalu(size_t fragment_index)212 bool RtpPacketizerH264::PacketizeSingleNalu(size_t fragment_index) {
213 // Add a single NALU to the queue, no aggregation.
214 size_t payload_size_left = limits_.max_payload_len;
215 if (input_fragments_.size() == 1)
216 payload_size_left -= limits_.single_packet_reduction_len;
217 else if (fragment_index == 0)
218 payload_size_left -= limits_.first_packet_reduction_len;
219 else if (fragment_index + 1 == input_fragments_.size())
220 payload_size_left -= limits_.last_packet_reduction_len;
221 rtc::ArrayView<const uint8_t> fragment = input_fragments_[fragment_index];
222 if (payload_size_left < fragment.size()) {
223 RTC_LOG(LS_ERROR) << "Failed to fit a fragment to packet in SingleNalu "
224 "packetization mode. Payload size left "
225 << payload_size_left << ", fragment length "
226 << fragment.size() << ", packet capacity "
227 << limits_.max_payload_len;
228 return false;
229 }
230 RTC_CHECK_GT(fragment.size(), 0u);
231 packets_.push(PacketUnit(fragment, true /* first */, true /* last */,
232 false /* aggregated */, fragment[0]));
233 ++num_packets_left_;
234 return true;
235 }
236
NextPacket(RtpPacketToSend * rtp_packet)237 bool RtpPacketizerH264::NextPacket(RtpPacketToSend* rtp_packet) {
238 RTC_DCHECK(rtp_packet);
239 if (packets_.empty()) {
240 return false;
241 }
242
243 PacketUnit packet = packets_.front();
244 if (packet.first_fragment && packet.last_fragment) {
245 // Single NAL unit packet.
246 size_t bytes_to_send = packet.source_fragment.size();
247 uint8_t* buffer = rtp_packet->AllocatePayload(bytes_to_send);
248 memcpy(buffer, packet.source_fragment.data(), bytes_to_send);
249 packets_.pop();
250 input_fragments_.pop_front();
251 } else if (packet.aggregated) {
252 NextAggregatePacket(rtp_packet);
253 } else {
254 NextFragmentPacket(rtp_packet);
255 }
256 rtp_packet->SetMarker(packets_.empty());
257 --num_packets_left_;
258 return true;
259 }
260
NextAggregatePacket(RtpPacketToSend * rtp_packet)261 void RtpPacketizerH264::NextAggregatePacket(RtpPacketToSend* rtp_packet) {
262 // Reserve maximum available payload, set actual payload size later.
263 size_t payload_capacity = rtp_packet->FreeCapacity();
264 RTC_CHECK_GE(payload_capacity, kNalHeaderSize);
265 uint8_t* buffer = rtp_packet->AllocatePayload(payload_capacity);
266 RTC_DCHECK(buffer);
267 PacketUnit* packet = &packets_.front();
268 RTC_CHECK(packet->first_fragment);
269 // STAP-A NALU header.
270 buffer[0] = (packet->header & (kFBit | kNriMask)) | H264::NaluType::kStapA;
271 size_t index = kNalHeaderSize;
272 bool is_last_fragment = packet->last_fragment;
273 while (packet->aggregated) {
274 rtc::ArrayView<const uint8_t> fragment = packet->source_fragment;
275 RTC_CHECK_LE(index + kLengthFieldSize + fragment.size(), payload_capacity);
276 // Add NAL unit length field.
277 ByteWriter<uint16_t>::WriteBigEndian(&buffer[index], fragment.size());
278 index += kLengthFieldSize;
279 // Add NAL unit.
280 memcpy(&buffer[index], fragment.data(), fragment.size());
281 index += fragment.size();
282 packets_.pop();
283 input_fragments_.pop_front();
284 if (is_last_fragment)
285 break;
286 packet = &packets_.front();
287 is_last_fragment = packet->last_fragment;
288 }
289 RTC_CHECK(is_last_fragment);
290 rtp_packet->SetPayloadSize(index);
291 }
292
NextFragmentPacket(RtpPacketToSend * rtp_packet)293 void RtpPacketizerH264::NextFragmentPacket(RtpPacketToSend* rtp_packet) {
294 PacketUnit* packet = &packets_.front();
295 // NAL unit fragmented over multiple packets (FU-A).
296 // We do not send original NALU header, so it will be replaced by the
297 // FU indicator header of the first packet.
298 uint8_t fu_indicator =
299 (packet->header & (kFBit | kNriMask)) | H264::NaluType::kFuA;
300 uint8_t fu_header = 0;
301
302 // S | E | R | 5 bit type.
303 fu_header |= (packet->first_fragment ? kSBit : 0);
304 fu_header |= (packet->last_fragment ? kEBit : 0);
305 uint8_t type = packet->header & kTypeMask;
306 fu_header |= type;
307 rtc::ArrayView<const uint8_t> fragment = packet->source_fragment;
308 uint8_t* buffer =
309 rtp_packet->AllocatePayload(kFuAHeaderSize + fragment.size());
310 buffer[0] = fu_indicator;
311 buffer[1] = fu_header;
312 memcpy(buffer + kFuAHeaderSize, fragment.data(), fragment.size());
313 if (packet->last_fragment)
314 input_fragments_.pop_front();
315 packets_.pop();
316 }
317
318 } // namespace webrtc
319