1 /*
2 * Copyright (c) 2016 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 "webrtc/modules/rtp_rtcp/source/rtcp_packet/tmmbn.h"
12
13 #include "webrtc/base/logging.h"
14 #include "webrtc/modules/rtp_rtcp/source/byte_io.h"
15
16 using webrtc::RTCPUtility::PT_RTPFB;
17 using webrtc::RTCPUtility::RTCPPacketRTPFBTMMBN;
18 using webrtc::RTCPUtility::RTCPPacketRTPFBTMMBRItem;
19
20 namespace webrtc {
21 namespace rtcp {
22 namespace {
23 const uint32_t kUnusedMediaSourceSsrc0 = 0;
AssignUWord8(uint8_t * buffer,size_t * offset,uint8_t value)24 void AssignUWord8(uint8_t* buffer, size_t* offset, uint8_t value) {
25 buffer[(*offset)++] = value;
26 }
AssignUWord32(uint8_t * buffer,size_t * offset,uint32_t value)27 void AssignUWord32(uint8_t* buffer, size_t* offset, uint32_t value) {
28 ByteWriter<uint32_t>::WriteBigEndian(buffer + *offset, value);
29 *offset += 4;
30 }
31
ComputeMantissaAnd6bitBase2Exponent(uint32_t input_base10,uint8_t bits_mantissa,uint32_t * mantissa,uint8_t * exp)32 void ComputeMantissaAnd6bitBase2Exponent(uint32_t input_base10,
33 uint8_t bits_mantissa,
34 uint32_t* mantissa,
35 uint8_t* exp) {
36 // input_base10 = mantissa * 2^exp
37 assert(bits_mantissa <= 32);
38 uint32_t mantissa_max = (1 << bits_mantissa) - 1;
39 uint8_t exponent = 0;
40 for (uint32_t i = 0; i < 64; ++i) {
41 if (input_base10 <= (mantissa_max << i)) {
42 exponent = i;
43 break;
44 }
45 }
46 *exp = exponent;
47 *mantissa = (input_base10 >> exponent);
48 }
49
CreateTmmbrItem(const RTCPPacketRTPFBTMMBRItem & tmmbr_item,uint8_t * buffer,size_t * pos)50 void CreateTmmbrItem(const RTCPPacketRTPFBTMMBRItem& tmmbr_item,
51 uint8_t* buffer,
52 size_t* pos) {
53 uint32_t bitrate_bps = tmmbr_item.MaxTotalMediaBitRate * 1000;
54 uint32_t mantissa = 0;
55 uint8_t exp = 0;
56 ComputeMantissaAnd6bitBase2Exponent(bitrate_bps, 17, &mantissa, &exp);
57
58 AssignUWord32(buffer, pos, tmmbr_item.SSRC);
59 AssignUWord8(buffer, pos, (exp << 2) + ((mantissa >> 15) & 0x03));
60 AssignUWord8(buffer, pos, mantissa >> 7);
61 AssignUWord8(buffer, pos, (mantissa << 1) +
62 ((tmmbr_item.MeasuredOverhead >> 8) & 0x01));
63 AssignUWord8(buffer, pos, tmmbr_item.MeasuredOverhead);
64 }
65
66 // Temporary Maximum Media Stream Bit Rate Notification (TMMBN) (RFC 5104).
67 //
68 // FCI:
69 //
70 // 0 1 2 3
71 // 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
72 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
73 // | SSRC |
74 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
75 // | MxTBR Exp | MxTBR Mantissa |Measured Overhead|
76 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
77
CreateTmmbn(const RTCPPacketRTPFBTMMBN & tmmbn,const std::vector<RTCPPacketRTPFBTMMBRItem> & tmmbn_items,uint8_t * buffer,size_t * pos)78 void CreateTmmbn(const RTCPPacketRTPFBTMMBN& tmmbn,
79 const std::vector<RTCPPacketRTPFBTMMBRItem>& tmmbn_items,
80 uint8_t* buffer,
81 size_t* pos) {
82 AssignUWord32(buffer, pos, tmmbn.SenderSSRC);
83 AssignUWord32(buffer, pos, kUnusedMediaSourceSsrc0);
84 for (uint8_t i = 0; i < tmmbn_items.size(); ++i) {
85 CreateTmmbrItem(tmmbn_items[i], buffer, pos);
86 }
87 }
88 } // namespace
89
WithTmmbr(uint32_t ssrc,uint32_t bitrate_kbps,uint16_t overhead)90 bool Tmmbn::WithTmmbr(uint32_t ssrc, uint32_t bitrate_kbps, uint16_t overhead) {
91 assert(overhead <= 0x1ff);
92 if (tmmbn_items_.size() >= kMaxNumberOfTmmbrs) {
93 LOG(LS_WARNING) << "Max TMMBN size reached.";
94 return false;
95 }
96 RTCPPacketRTPFBTMMBRItem tmmbn_item;
97 tmmbn_item.SSRC = ssrc;
98 tmmbn_item.MaxTotalMediaBitRate = bitrate_kbps;
99 tmmbn_item.MeasuredOverhead = overhead;
100 tmmbn_items_.push_back(tmmbn_item);
101 return true;
102 }
103
Create(uint8_t * packet,size_t * index,size_t max_length,RtcpPacket::PacketReadyCallback * callback) const104 bool Tmmbn::Create(uint8_t* packet,
105 size_t* index,
106 size_t max_length,
107 RtcpPacket::PacketReadyCallback* callback) const {
108 while (*index + BlockLength() > max_length) {
109 if (!OnBufferFull(packet, index, callback))
110 return false;
111 }
112 const uint8_t kFmt = 4;
113 CreateHeader(kFmt, PT_RTPFB, HeaderLength(), packet, index);
114 CreateTmmbn(tmmbn_, tmmbn_items_, packet, index);
115 return true;
116 }
117
118 } // namespace rtcp
119 } // namespace webrtc
120