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/sli.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
17 using webrtc::RTCPUtility::RtcpCommonHeader;
18
19 namespace webrtc {
20 namespace rtcp {
21 // RFC 4585: Feedback format.
22 //
23 // Common packet format:
24 //
25 // 0 1 2 3
26 // 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
27 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
28 // |V=2|P| FMT | PT | length |
29 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
30 // | SSRC of packet sender |
31 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
32 // | SSRC of media source |
33 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
34 // : Feedback Control Information (FCI) :
35 // : :
36 //
37 // Slice loss indication (SLI) (RFC 4585).
38 // FCI:
39 // 0 1 2 3
40 // 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
41 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
42 // | First | Number | PictureID |
43 // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Macroblocks(uint8_t picture_id,uint16_t first,uint16_t number)44 Sli::Macroblocks::Macroblocks(uint8_t picture_id,
45 uint16_t first,
46 uint16_t number) {
47 RTC_DCHECK_LE(first, 0x1fff);
48 RTC_DCHECK_LE(number, 0x1fff);
49 RTC_DCHECK_LE(picture_id, 0x3f);
50 item_ = (first << 19) | (number << 6) | picture_id;
51 }
52
Parse(const uint8_t * buffer)53 void Sli::Macroblocks::Parse(const uint8_t* buffer) {
54 item_ = ByteReader<uint32_t>::ReadBigEndian(buffer);
55 }
56
Create(uint8_t * buffer) const57 void Sli::Macroblocks::Create(uint8_t* buffer) const {
58 ByteWriter<uint32_t>::WriteBigEndian(buffer, item_);
59 }
60
Parse(const RtcpCommonHeader & header,const uint8_t * payload)61 bool Sli::Parse(const RtcpCommonHeader& header, const uint8_t* payload) {
62 RTC_DCHECK(header.packet_type == kPacketType);
63 RTC_DCHECK(header.count_or_format == kFeedbackMessageType);
64
65 if (header.payload_size_bytes <
66 kCommonFeedbackLength + Macroblocks::kLength) {
67 LOG(LS_WARNING) << "Packet is too small to be a valid SLI packet";
68 return false;
69 }
70
71 size_t number_of_items =
72 (header.payload_size_bytes - kCommonFeedbackLength) /
73 Macroblocks::kLength;
74
75 ParseCommonFeedback(payload);
76 items_.resize(number_of_items);
77
78 const uint8_t* next_item = payload + kCommonFeedbackLength;
79 for (Macroblocks& item : items_) {
80 item.Parse(next_item);
81 next_item += Macroblocks::kLength;
82 }
83
84 return true;
85 }
86
Create(uint8_t * packet,size_t * index,size_t max_length,RtcpPacket::PacketReadyCallback * callback) const87 bool Sli::Create(uint8_t* packet,
88 size_t* index,
89 size_t max_length,
90 RtcpPacket::PacketReadyCallback* callback) const {
91 RTC_DCHECK(!items_.empty());
92 while (*index + BlockLength() > max_length) {
93 if (!OnBufferFull(packet, index, callback))
94 return false;
95 }
96 CreateHeader(kFeedbackMessageType, kPacketType, HeaderLength(), packet,
97 index);
98 CreateCommonFeedback(packet + *index);
99 *index += kCommonFeedbackLength;
100 for (const Macroblocks& item : items_) {
101 item.Create(packet + *index);
102 *index += Macroblocks::kLength;
103 }
104 return true;
105 }
106
107 } // namespace rtcp
108 } // namespace webrtc
109