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/*
* Copyright (c) 2019 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/loss_notification.h"
#include <cstddef>
#include <cstdint>
#include "modules/rtp_rtcp/source/byte_io.h"
#include "modules/rtp_rtcp/source/rtcp_packet/common_header.h"
#include "modules/rtp_rtcp/source/rtcp_packet/psfb.h"
#include "rtc_base/checks.h"
namespace webrtc {
namespace rtcp {
// Loss Notification
// -----------------
// 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=15 | PT=206 | length |
// +=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+=+
// 0 | SSRC of packet sender |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 4 | SSRC of media source |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 8 | Unique identifier 'L' 'N' 'T' 'F' |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 12 | Last Decoded Sequence Number | Last Received SeqNum Delta |D|
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
LossNotification::LossNotification()
: last_decoded_(0), last_received_(0), decodability_flag_(false) {}
LossNotification::LossNotification(uint16_t last_decoded,
uint16_t last_received,
bool decodability_flag)
: last_decoded_(last_decoded),
last_received_(last_received),
decodability_flag_(decodability_flag) {}
LossNotification::LossNotification(const LossNotification& rhs) = default;
LossNotification::~LossNotification() = default;
size_t LossNotification::BlockLength() const {
return kHeaderLength + kCommonFeedbackLength + kLossNotificationPayloadLength;
}
bool LossNotification::Create(uint8_t* packet,
size_t* index,
size_t max_length,
PacketReadyCallback callback) const {
while (*index + BlockLength() > max_length) {
if (!OnBufferFull(packet, index, callback))
return false;
}
const size_t index_end = *index + BlockLength();
// Note: `index` updated by the function below.
CreateHeader(Psfb::kAfbMessageType, kPacketType, HeaderLength(), packet,
index);
CreateCommonFeedback(packet + *index);
*index += kCommonFeedbackLength;
ByteWriter<uint32_t>::WriteBigEndian(packet + *index, kUniqueIdentifier);
*index += sizeof(uint32_t);
ByteWriter<uint16_t>::WriteBigEndian(packet + *index, last_decoded_);
*index += sizeof(uint16_t);
const uint16_t last_received_delta = last_received_ - last_decoded_;
RTC_DCHECK_LE(last_received_delta, 0x7fff);
const uint16_t last_received_delta_and_decodability =
(last_received_delta << 1) | (decodability_flag_ ? 0x0001 : 0x0000);
ByteWriter<uint16_t>::WriteBigEndian(packet + *index,
last_received_delta_and_decodability);
*index += sizeof(uint16_t);
RTC_DCHECK_EQ(index_end, *index);
return true;
}
bool LossNotification::Parse(const CommonHeader& packet) {
RTC_DCHECK_EQ(packet.type(), kPacketType);
RTC_DCHECK_EQ(packet.fmt(), Psfb::kAfbMessageType);
if (packet.payload_size_bytes() <
kCommonFeedbackLength + kLossNotificationPayloadLength) {
return false;
}
const uint8_t* const payload = packet.payload();
if (ByteReader<uint32_t>::ReadBigEndian(&payload[8]) != kUniqueIdentifier) {
return false;
}
ParseCommonFeedback(payload);
last_decoded_ = ByteReader<uint16_t>::ReadBigEndian(&payload[12]);
const uint16_t last_received_delta_and_decodability =
ByteReader<uint16_t>::ReadBigEndian(&payload[14]);
last_received_ = last_decoded_ + (last_received_delta_and_decodability >> 1);
decodability_flag_ = (last_received_delta_and_decodability & 0x0001);
return true;
}
bool LossNotification::Set(uint16_t last_decoded,
uint16_t last_received,
bool decodability_flag) {
const uint16_t delta = last_received - last_decoded;
if (delta > 0x7fff) {
return false;
}
last_received_ = last_received;
last_decoded_ = last_decoded;
decodability_flag_ = decodability_flag;
return true;
}
} // namespace rtcp
} // namespace webrtc
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