| /* |
| * Copyright (c) 2015 The WebRTC project authors. All Rights Reserved. |
| * |
| * Use of this source code is governed by a BSD-style license |
| * that can be found in the LICENSE file in the root of the source |
| * tree. An additional intellectual property rights grant can be found |
| * in the file PATENTS. All contributing project authors may |
| * be found in the AUTHORS file in the root of the source tree. |
| */ |
| |
| #include "webrtc/modules/rtp_rtcp/source/rtcp_packet/nack.h" |
| |
| #include <algorithm> |
| |
| #include "webrtc/base/checks.h" |
| #include "webrtc/base/logging.h" |
| #include "webrtc/modules/rtp_rtcp/source/byte_io.h" |
| |
| using webrtc::RTCPUtility::RtcpCommonHeader; |
| |
| namespace webrtc { |
| namespace rtcp { |
| |
| // RFC 4585: Feedback format. |
| // |
| // Common packet format: |
| // |
| // 0 1 2 3 |
| // 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 |
| // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| // |V=2|P| FMT | PT | length | |
| // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| // 0 | SSRC of packet sender | |
| // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| // 4 | SSRC of media source | |
| // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| // : Feedback Control Information (FCI) : |
| // : : |
| // |
| // Generic NACK (RFC 4585). |
| // |
| // FCI: |
| // 0 1 2 3 |
| // 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 |
| // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| // | PID | BLP | |
| // +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |
| bool Nack::Parse(const RtcpCommonHeader& header, const uint8_t* payload) { |
| RTC_DCHECK(header.packet_type == kPacketType); |
| RTC_DCHECK(header.count_or_format == kFeedbackMessageType); |
| |
| if (header.payload_size_bytes < kCommonFeedbackLength + kNackItemLength) { |
| LOG(LS_WARNING) << "Payload length " << header.payload_size_bytes |
| << " is too small for a Nack."; |
| return false; |
| } |
| size_t nack_items = |
| (header.payload_size_bytes - kCommonFeedbackLength) / kNackItemLength; |
| |
| ParseCommonFeedback(payload); |
| const uint8_t* next_nack = payload + kCommonFeedbackLength; |
| |
| packet_ids_.clear(); |
| packed_.resize(nack_items); |
| for (size_t index = 0; index < nack_items; ++index) { |
| packed_[index].first_pid = ByteReader<uint16_t>::ReadBigEndian(next_nack); |
| packed_[index].bitmask = ByteReader<uint16_t>::ReadBigEndian(next_nack + 2); |
| next_nack += kNackItemLength; |
| } |
| Unpack(); |
| |
| return true; |
| } |
| |
| bool Nack::Create(uint8_t* packet, |
| size_t* index, |
| size_t max_length, |
| RtcpPacket::PacketReadyCallback* callback) const { |
| RTC_DCHECK(!packed_.empty()); |
| // If nack list can't fit in packet, try to fragment. |
| size_t nack_index = 0; |
| const size_t kCommonFbFmtLength = kHeaderLength + kCommonFeedbackLength; |
| do { |
| size_t bytes_left_in_buffer = max_length - *index; |
| if (bytes_left_in_buffer < kCommonFbFmtLength + kNackItemLength) { |
| if (!OnBufferFull(packet, index, callback)) |
| return false; |
| continue; |
| } |
| size_t num_nack_fields = |
| std::min((bytes_left_in_buffer - kCommonFbFmtLength) / kNackItemLength, |
| packed_.size() - nack_index); |
| |
| size_t size_bytes = |
| (num_nack_fields * kNackItemLength) + kCommonFbFmtLength; |
| size_t header_length = ((size_bytes + 3) / 4) - 1; // As 32bit words - 1 |
| CreateHeader(kFeedbackMessageType, kPacketType, header_length, packet, |
| index); |
| CreateCommonFeedback(packet + *index); |
| *index += kCommonFeedbackLength; |
| size_t end_index = nack_index + num_nack_fields; |
| for (; nack_index < end_index; ++nack_index) { |
| const auto& item = packed_[nack_index]; |
| ByteWriter<uint16_t>::WriteBigEndian(packet + *index + 0, item.first_pid); |
| ByteWriter<uint16_t>::WriteBigEndian(packet + *index + 2, item.bitmask); |
| *index += kNackItemLength; |
| } |
| RTC_DCHECK_LE(*index, max_length); |
| } while (nack_index < packed_.size()); |
| |
| return true; |
| } |
| |
| size_t Nack::BlockLength() const { |
| return (packed_.size() * kNackItemLength) + kCommonFeedbackLength + |
| kHeaderLength; |
| } |
| |
| void Nack::WithList(const uint16_t* nack_list, size_t length) { |
| RTC_DCHECK(nack_list); |
| RTC_DCHECK(packet_ids_.empty()); |
| RTC_DCHECK(packed_.empty()); |
| packet_ids_.assign(nack_list, nack_list + length); |
| Pack(); |
| } |
| |
| void Nack::Pack() { |
| RTC_DCHECK(!packet_ids_.empty()); |
| RTC_DCHECK(packed_.empty()); |
| auto it = packet_ids_.begin(); |
| const auto end = packet_ids_.end(); |
| while (it != end) { |
| PackedNack item; |
| item.first_pid = *it++; |
| // Bitmask specifies losses in any of the 16 packets following the pid. |
| item.bitmask = 0; |
| while (it != end) { |
| uint16_t shift = static_cast<uint16_t>(*it - item.first_pid - 1); |
| if (shift <= 15) { |
| item.bitmask |= (1 << shift); |
| ++it; |
| } else { |
| break; |
| } |
| } |
| packed_.push_back(item); |
| } |
| } |
| |
| void Nack::Unpack() { |
| RTC_DCHECK(packet_ids_.empty()); |
| RTC_DCHECK(!packed_.empty()); |
| for (const PackedNack& item : packed_) { |
| packet_ids_.push_back(item.first_pid); |
| uint16_t pid = item.first_pid + 1; |
| for (uint16_t bitmask = item.bitmask; bitmask != 0; bitmask >>= 1, ++pid) |
| if (bitmask & 1) |
| packet_ids_.push_back(pid); |
| } |
| } |
| |
| } // namespace rtcp |
| } // namespace webrtc |