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* Copyright (c) 2012 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 <stddef.h>
#include <stdint.h>
#include "api/array_view.h"
#include "modules/include/module_fec_types.h"
namespace webrtc {
// Maximum number of media packets that can be protected
// by these packet masks.
constexpr size_t kUlpfecMaxMediaPackets = 48;
// Packet mask size in bytes (given L bit).
constexpr size_t kUlpfecPacketMaskSizeLBitClear = 2;
constexpr size_t kUlpfecPacketMaskSizeLBitSet = 6;
// Packet code mask maximum length. kFECPacketMaskMaxSize = MaxNumFECPackets *
// (kUlpfecMaxMediaPackets / 8), and MaxNumFECPackets is equal to maximum number
// of media packets (kUlpfecMaxMediaPackets)
constexpr size_t kFECPacketMaskMaxSize = 288;
// Convenience constants.
constexpr size_t kUlpfecMinPacketMaskSize = kUlpfecPacketMaskSizeLBitClear;
constexpr size_t kUlpfecMaxPacketMaskSize = kUlpfecPacketMaskSizeLBitSet;
namespace internal {
class PacketMaskTable {
PacketMaskTable(FecMaskType fec_mask_type, int num_media_packets);
rtc::ArrayView<const uint8_t> LookUp(int num_media_packets,
int num_fec_packets);
static const uint8_t* PickTable(FecMaskType fec_mask_type,
int num_media_packets);
const uint8_t* table_;
uint8_t fec_packet_mask_[kFECPacketMaskMaxSize];
rtc::ArrayView<const uint8_t> LookUpInFecTable(const uint8_t* table,
int media_packet_index,
int fec_index);
// Returns an array of packet masks. The mask of a single FEC packet
// corresponds to a number of mask bytes. The mask indicates which
// media packets should be protected by the FEC packet.
// \param[in] num_media_packets The number of media packets to protect.
// [1, max_media_packets].
// \param[in] num_fec_packets The number of FEC packets which will
// be generated. [1, num_media_packets].
// \param[in] num_imp_packets The number of important packets.
// [0, num_media_packets].
// num_imp_packets = 0 is the equal
// protection scenario.
// \param[in] use_unequal_protection Enables unequal protection: allocates
// more protection to the num_imp_packets.
// \param[in] mask_table An instance of the |PacketMaskTable|
// class, which contains the type of FEC
// packet mask used, and a pointer to the
// corresponding packet masks.
// \param[out] packet_mask A pointer to hold the packet mask array,
// of size: num_fec_packets *
// "number of mask bytes".
void GeneratePacketMasks(int num_media_packets,
int num_fec_packets,
int num_imp_packets,
bool use_unequal_protection,
PacketMaskTable* mask_table,
uint8_t* packet_mask);
// Returns the required packet mask size, given the number of sequence numbers
// that will be covered.
size_t PacketMaskSize(size_t num_sequence_numbers);
// Inserts |num_zeros| zero columns into |new_mask| at position
// |new_bit_index|. If the current byte of |new_mask| can't fit all zeros, the
// byte will be filled with zeros from |new_bit_index|, but the next byte will
// be untouched.
void InsertZeroColumns(int num_zeros,
uint8_t* new_mask,
int new_mask_bytes,
int num_fec_packets,
int new_bit_index);
// Copies the left most bit column from the byte pointed to by
// |old_bit_index| in |old_mask| to the right most column of the byte pointed
// to by |new_bit_index| in |new_mask|. |old_mask_bytes| and |new_mask_bytes|
// represent the number of bytes used per row for each mask. |num_fec_packets|
// represent the number of rows of the masks.
// The copied bit is shifted out from |old_mask| and is shifted one step to
// the left in |new_mask|. |new_mask| will contain "xxxx xxn0" after this
// operation, where x are previously inserted bits and n is the new bit.
void CopyColumn(uint8_t* new_mask,
int new_mask_bytes,
uint8_t* old_mask,
int old_mask_bytes,
int num_fec_packets,
int new_bit_index,
int old_bit_index);
} // namespace internal
} // namespace webrtc