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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.
*/
#ifndef MODULES_RTP_RTCP_SOURCE_RTCP_PACKET_LOSS_NOTIFICATION_H_
#define MODULES_RTP_RTCP_SOURCE_RTCP_PACKET_LOSS_NOTIFICATION_H_
#include <cstddef>
#include <cstdint>
#include "absl/base/attributes.h"
#include "modules/rtp_rtcp/source/rtcp_packet/common_header.h"
#include "modules/rtp_rtcp/source/rtcp_packet/psfb.h"
namespace webrtc {
namespace rtcp {
class LossNotification : public Psfb {
public:
LossNotification();
LossNotification(uint16_t last_decoded,
uint16_t last_received,
bool decodability_flag);
LossNotification(const LossNotification& other);
~LossNotification() override;
size_t BlockLength() const override;
ABSL_MUST_USE_RESULT
bool Create(uint8_t* packet,
size_t* index,
size_t max_length,
PacketReadyCallback callback) const override;
// Parse assumes header is already parsed and validated.
ABSL_MUST_USE_RESULT
bool Parse(const CommonHeader& packet);
// Set all of the values transmitted by the loss notification message.
// If the values may not be represented by a loss notification message,
// false is returned, and no change is made to the object; this happens
// when `last_received` is ahead of `last_decoded` by more than 0x7fff.
// This is because `last_received` is represented on the wire as a delta,
// and only 15 bits are available for that delta.
ABSL_MUST_USE_RESULT
bool Set(uint16_t last_decoded,
uint16_t last_received,
bool decodability_flag);
// RTP sequence number of the first packet belong to the last decoded
// non-discardable frame.
uint16_t last_decoded() const { return last_decoded_; }
// RTP sequence number of the last received packet.
uint16_t last_received() const { return last_received_; }
// A decodability flag, whose specific meaning depends on the last-received
// RTP sequence number. The decodability flag is true if and only if all of
// the frame's dependencies are known to be decodable, and the frame itself
// is not yet known to be unassemblable.
// * Clarification #1: In a multi-packet frame, the first packet's
// dependencies are known, but it is not yet known whether all parts
// of the current frame will be received.
// * Clarification #2: In a multi-packet frame, the dependencies would be
// unknown if the first packet was not received. Then, the packet will
// be known-unassemblable.
bool decodability_flag() const { return decodability_flag_; }
private:
static constexpr uint32_t kUniqueIdentifier = 0x4C4E5446; // 'L' 'N' 'T' 'F'.
static constexpr size_t kLossNotificationPayloadLength = 8;
uint16_t last_decoded_;
uint16_t last_received_;
bool decodability_flag_;
};
} // namespace rtcp
} // namespace webrtc
#endif // MODULES_RTP_RTCP_SOURCE_RTCP_PACKET_LOSS_NOTIFICATION_H_
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