modules/rtp_rtcp/source/rtcp_packet/tmmbr.cc

/*
 *  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/tmmbr.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 Tmmbr::kFeedbackMessageType;
// 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               |
//  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//  |                  SSRC of packet sender                        |
//  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//  |             SSRC of media source (unused) = 0                 |
//  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//  :            Feedback Control Information (FCI)                 :
//  :                                                               :
// Temporary Maximum Media Stream Bit Rate Request (TMMBR) (RFC 5104).
// The Feedback Control Information (FCI) for the TMMBR
// consists of one or more FCI entries.
// 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
//  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//  |                              SSRC                             |
//  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
//  | MxTBR Exp |  MxTBR Mantissa                 |Measured Overhead|
//  +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

Tmmbr::Tmmbr() = default;

Tmmbr::~Tmmbr() = default;

bool Tmmbr::Parse(const CommonHeader& packet) {
  RTC_DCHECK_EQ(packet.type(), kPacketType);
  RTC_DCHECK_EQ(packet.fmt(), kFeedbackMessageType);

  if (packet.payload_size_bytes() < kCommonFeedbackLength + TmmbItem::kLength) {
    RTC_LOG(LS_WARNING) << "Payload length " << packet.payload_size_bytes()
                        << " is too small for a TMMBR.";
    return false;
  }
  size_t items_size_bytes = packet.payload_size_bytes() - kCommonFeedbackLength;
  if (items_size_bytes % TmmbItem::kLength != 0) {
    RTC_LOG(LS_WARNING) << "Payload length " << packet.payload_size_bytes()
                        << " is not valid for a TMMBR.";
    return false;
  }
  ParseCommonFeedback(packet.payload());

  const uint8_t* next_item = packet.payload() + kCommonFeedbackLength;
  size_t number_of_items = items_size_bytes / TmmbItem::kLength;
  items_.resize(number_of_items);
  for (TmmbItem& item : items_) {
    if (!item.Parse(next_item))
      return false;
    next_item += TmmbItem::kLength;
  }
  return true;
}

void Tmmbr::AddTmmbr(const TmmbItem& item) {
  items_.push_back(item);
}

size_t Tmmbr::BlockLength() const {
  return kHeaderLength + kCommonFeedbackLength +
         TmmbItem::kLength * items_.size();
}

bool Tmmbr::Create(uint8_t* packet,
                   size_t* index,
                   size_t max_length,
                   PacketReadyCallback callback) const {
  RTC_DCHECK(!items_.empty());
  while (*index + BlockLength() > max_length) {
    if (!OnBufferFull(packet, index, callback))
      return false;
  }
  const size_t index_end = *index + BlockLength();

  CreateHeader(kFeedbackMessageType, kPacketType, HeaderLength(), packet,
               index);
  RTC_DCHECK_EQ(0, Rtpfb::media_ssrc());
  CreateCommonFeedback(packet + *index);
  *index += kCommonFeedbackLength;
  for (const TmmbItem& item : items_) {
    item.Create(packet + *index);
    *index += TmmbItem::kLength;
  }
  RTC_CHECK_EQ(index_end, *index);
  return true;
}
}  // namespace rtcp
}  // namespace webrtc