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/*
* Copyright (c) 2016 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/remb.h"
#include <cstddef>
#include <cstdint>
#include <utility>
#include <vector>
#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"
#include "rtc_base/logging.h"
namespace webrtc {
namespace rtcp {
// Receiver Estimated Max Bitrate (REMB) (draft-alvestrand-rmcat-remb).
//
// 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 | Unused = 0 |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 8 | Unique identifier 'R' 'E' 'M' 'B' |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 12 | Num SSRC | BR Exp | BR Mantissa |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// 16 | SSRC feedback |
// +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// : ... :
Remb::Remb() : bitrate_bps_(0) {}
Remb::Remb(const Remb& rhs) = default;
Remb::~Remb() = default;
bool Remb::Parse(const CommonHeader& packet) {
RTC_DCHECK(packet.type() == kPacketType);
RTC_DCHECK_EQ(packet.fmt(), Psfb::kAfbMessageType);
if (packet.payload_size_bytes() < 16) {
RTC_LOG(LS_WARNING) << "Payload length " << packet.payload_size_bytes()
<< " is too small for Remb packet.";
return false;
}
const uint8_t* const payload = packet.payload();
if (kUniqueIdentifier != ByteReader<uint32_t>::ReadBigEndian(&payload[8])) {
return false;
}
uint8_t number_of_ssrcs = payload[12];
if (packet.payload_size_bytes() !=
kCommonFeedbackLength + (2 + number_of_ssrcs) * 4) {
RTC_LOG(LS_WARNING) << "Payload size " << packet.payload_size_bytes()
<< " does not match " << number_of_ssrcs << " ssrcs.";
return false;
}
ParseCommonFeedback(payload);
uint8_t exponent = payload[13] >> 2;
uint64_t mantissa = (static_cast<uint32_t>(payload[13] & 0x03) << 16) |
ByteReader<uint16_t>::ReadBigEndian(&payload[14]);
bitrate_bps_ = (mantissa << exponent);
bool shift_overflow =
(static_cast<uint64_t>(bitrate_bps_) >> exponent) != mantissa;
if (bitrate_bps_ < 0 || shift_overflow) {
RTC_LOG(LS_ERROR) << "Invalid remb bitrate value : " << mantissa << "*2^"
<< static_cast<int>(exponent);
return false;
}
const uint8_t* next_ssrc = payload + 16;
ssrcs_.clear();
ssrcs_.reserve(number_of_ssrcs);
for (uint8_t i = 0; i < number_of_ssrcs; ++i) {
ssrcs_.push_back(ByteReader<uint32_t>::ReadBigEndian(next_ssrc));
next_ssrc += sizeof(uint32_t);
}
return true;
}
bool Remb::SetSsrcs(std::vector<uint32_t> ssrcs) {
if (ssrcs.size() > kMaxNumberOfSsrcs) {
RTC_LOG(LS_WARNING) << "Not enough space for all given SSRCs.";
return false;
}
ssrcs_ = std::move(ssrcs);
return true;
}
size_t Remb::BlockLength() const {
return kHeaderLength + kCommonFeedbackLength + (2 + ssrcs_.size()) * 4;
}
bool Remb::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;
}
size_t index_end = *index + BlockLength();
CreateHeader(Psfb::kAfbMessageType, kPacketType, HeaderLength(), packet,
index);
RTC_DCHECK_EQ(0, Psfb::media_ssrc());
CreateCommonFeedback(packet + *index);
*index += kCommonFeedbackLength;
ByteWriter<uint32_t>::WriteBigEndian(packet + *index, kUniqueIdentifier);
*index += sizeof(uint32_t);
const uint32_t kMaxMantissa = 0x3ffff; // 18 bits.
uint64_t mantissa = bitrate_bps_;
uint8_t exponenta = 0;
while (mantissa > kMaxMantissa) {
mantissa >>= 1;
++exponenta;
}
packet[(*index)++] = static_cast<uint8_t>(ssrcs_.size());
packet[(*index)++] = (exponenta << 2) | (mantissa >> 16);
ByteWriter<uint16_t>::WriteBigEndian(packet + *index, mantissa & 0xffff);
*index += sizeof(uint16_t);
for (uint32_t ssrc : ssrcs_) {
ByteWriter<uint32_t>::WriteBigEndian(packet + *index, ssrc);
*index += sizeof(uint32_t);
}
RTC_DCHECK_EQ(index_end, *index);
return true;
}
} // namespace rtcp
} // namespace webrtc
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