blob: c196e29dc18febf092da3e09f3bad9292710dbff [file] [log] [blame]
/*
* 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 "modules/rtp_rtcp/source/rtcp_packet/nack.h"
#include <algorithm>
#include "modules/rtp_rtcp/source/byte_io.h"
#include "modules/rtp_rtcp/source/rtcp_packet/common_header.h"
#include "rtc_base/checks.h"
#include "rtc_base/logging.h"
namespace webrtc {
namespace rtcp {
constexpr uint8_t Nack::kFeedbackMessageType;
constexpr size_t Nack::kNackItemLength;
// 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 |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Nack::Nack() {}
Nack::~Nack() {}
bool Nack::Parse(const CommonHeader& packet) {
RTC_DCHECK_EQ(packet.type(), kPacketType);
RTC_DCHECK_EQ(packet.fmt(), kFeedbackMessageType);
if (packet.payload_size_bytes() < kCommonFeedbackLength + kNackItemLength) {
RTC_LOG(LS_WARNING) << "Payload length " << packet.payload_size_bytes()
<< " is too small for a Nack.";
return false;
}
size_t nack_items =
(packet.payload_size_bytes() - kCommonFeedbackLength) / kNackItemLength;
ParseCommonFeedback(packet.payload());
const uint8_t* next_nack = packet.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;
}
size_t Nack::BlockLength() const {
return kHeaderLength + kCommonFeedbackLength +
packed_.size() * kNackItemLength;
}
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.
constexpr size_t kNackHeaderLength = kHeaderLength + kCommonFeedbackLength;
for (size_t nack_index = 0; nack_index < packed_.size();) {
size_t bytes_left_in_buffer = max_length - *index;
if (bytes_left_in_buffer < kNackHeaderLength + kNackItemLength) {
if (!OnBufferFull(packet, index, callback))
return false;
continue;
}
size_t num_nack_fields =
std::min((bytes_left_in_buffer - kNackHeaderLength) / kNackItemLength,
packed_.size() - nack_index);
size_t payload_size_bytes =
kCommonFeedbackLength + (num_nack_fields * kNackItemLength);
size_t payload_size_32bits =
rtc::CheckedDivExact<size_t>(payload_size_bytes, 4);
CreateHeader(kFeedbackMessageType, kPacketType, payload_size_32bits, packet,
index);
CreateCommonFeedback(packet + *index);
*index += kCommonFeedbackLength;
size_t nack_end_index = nack_index + num_nack_fields;
for (; nack_index < nack_end_index; ++nack_index) {
const PackedNack& 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);
}
return true;
}
void Nack::SetPacketIds(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