Line data Source code
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/rpsi.h"
12 :
13 : #include "webrtc/base/checks.h"
14 : #include "webrtc/base/logging.h"
15 : #include "webrtc/modules/rtp_rtcp/source/byte_io.h"
16 : #include "webrtc/modules/rtp_rtcp/source/rtcp_packet/common_header.h"
17 : #include "webrtc/modules/rtp_rtcp/source/rtp_utility.h"
18 :
19 : using webrtc::RtpUtility::Word32Align;
20 :
21 : namespace webrtc {
22 : namespace rtcp {
23 : constexpr uint8_t Rpsi::kFeedbackMessageType;
24 : // RFC 4585: Feedback format.
25 : // Reference picture selection indication (RPSI) (RFC 4585).
26 : //
27 : // 0 1 2 3
28 : // 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
29 : // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
30 : // |V=2|P| RPSI=3 | PT=PSFB=206 | length |
31 : // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
32 : // 0 | SSRC of packet sender |
33 : // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
34 : // 4 | SSRC of media source |
35 : // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
36 : // 8 | Padding Bits |
37 : // 9 |0| Payload Type|
38 : // 10 | Native RPSI bit string :
39 : // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
40 : // : defined per codec ... | Padding (0) |
41 : // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
42 : namespace {
43 : constexpr size_t kPaddingSizeOffset = 8;
44 : constexpr size_t kPayloadTypeOffset = 9;
45 : constexpr size_t kBitStringOffset = 10;
46 :
47 : constexpr size_t kPidBits = 7;
48 : // Calculates number of bytes required to store given picture id.
49 0 : uint8_t RequiredBytes(uint64_t picture_id) {
50 0 : uint8_t required_bytes = 0;
51 0 : uint64_t shifted_pid = picture_id;
52 0 : do {
53 0 : ++required_bytes;
54 0 : shifted_pid >>= kPidBits;
55 0 : } while (shifted_pid > 0);
56 :
57 0 : return required_bytes;
58 : }
59 : } // namespace
60 :
61 0 : Rpsi::Rpsi()
62 : : payload_type_(0),
63 : picture_id_(0),
64 0 : block_length_(CalculateBlockLength(1)) {}
65 :
66 0 : bool Rpsi::Parse(const CommonHeader& packet) {
67 0 : RTC_DCHECK_EQ(packet.type(), kPacketType);
68 0 : RTC_DCHECK_EQ(packet.fmt(), kFeedbackMessageType);
69 :
70 0 : if (packet.payload_size_bytes() < kCommonFeedbackLength + 4) {
71 0 : LOG(LS_WARNING) << "Packet is too small to be a valid RPSI packet.";
72 0 : return false;
73 : }
74 :
75 0 : ParseCommonFeedback(packet.payload());
76 :
77 0 : uint8_t padding_bits = packet.payload()[kPaddingSizeOffset];
78 0 : if (padding_bits % 8 != 0) {
79 0 : LOG(LS_WARNING) << "Unknown rpsi packet with fractional number of bytes.";
80 0 : return false;
81 : }
82 0 : size_t padding_bytes = padding_bits / 8;
83 0 : if (padding_bytes + kBitStringOffset >= packet.payload_size_bytes()) {
84 0 : LOG(LS_WARNING) << "Too many padding bytes in a RPSI packet.";
85 0 : return false;
86 : }
87 0 : size_t padding_offset = packet.payload_size_bytes() - padding_bytes;
88 0 : payload_type_ = packet.payload()[kPayloadTypeOffset] & 0x7f;
89 0 : picture_id_ = 0;
90 0 : for (size_t pos = kBitStringOffset; pos < padding_offset; ++pos) {
91 0 : picture_id_ <<= kPidBits;
92 0 : picture_id_ |= (packet.payload()[pos] & 0x7f);
93 : }
94 : // Required bytes might become less than came in the packet.
95 0 : block_length_ = CalculateBlockLength(RequiredBytes(picture_id_));
96 0 : return true;
97 : }
98 :
99 0 : bool Rpsi::Create(uint8_t* packet,
100 : size_t* index,
101 : size_t max_length,
102 : RtcpPacket::PacketReadyCallback* callback) const {
103 0 : while (*index + BlockLength() > max_length) {
104 0 : if (!OnBufferFull(packet, index, callback))
105 0 : return false;
106 : }
107 0 : size_t index_end = *index + BlockLength();
108 :
109 0 : CreateHeader(kFeedbackMessageType, kPacketType, HeaderLength(), packet,
110 0 : index);
111 0 : CreateCommonFeedback(packet + *index);
112 0 : *index += kCommonFeedbackLength;
113 :
114 0 : size_t bitstring_size_bytes = RequiredBytes(picture_id_);
115 : size_t padding_bytes =
116 0 : Word32Align(2 + bitstring_size_bytes) - (2 + bitstring_size_bytes);
117 0 : packet[(*index)++] = padding_bytes * 8;
118 0 : packet[(*index)++] = payload_type_;
119 :
120 : // Convert picture id to native bit string (defined by the video codec).
121 0 : for (size_t i = bitstring_size_bytes - 1; i > 0; --i) {
122 0 : packet[(*index)++] =
123 0 : 0x80 | static_cast<uint8_t>(picture_id_ >> (i * kPidBits));
124 : }
125 0 : packet[(*index)++] = static_cast<uint8_t>(picture_id_ & 0x7f);
126 0 : constexpr uint8_t kPadding = 0;
127 0 : for (size_t i = 0; i < padding_bytes; ++i)
128 0 : packet[(*index)++] = kPadding;
129 0 : RTC_CHECK_EQ(*index, index_end);
130 0 : return true;
131 : }
132 :
133 0 : void Rpsi::SetPayloadType(uint8_t payload) {
134 0 : RTC_DCHECK_LE(payload, 0x7f);
135 0 : payload_type_ = payload;
136 0 : }
137 :
138 0 : void Rpsi::SetPictureId(uint64_t picture_id) {
139 0 : picture_id_ = picture_id;
140 0 : block_length_ = CalculateBlockLength(RequiredBytes(picture_id_));
141 0 : }
142 :
143 0 : size_t Rpsi::CalculateBlockLength(uint8_t bitstring_size_bytes) {
144 : return RtcpPacket::kHeaderLength + Psfb::kCommonFeedbackLength +
145 0 : Word32Align(2 + bitstring_size_bytes);
146 : }
147 : } // namespace rtcp
148 : } // namespace webrtc
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