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      1 /*
      2  *  Copyright (c) 2012 The WebRTC project authors. All Rights Reserved.
      3  *
      4  *  Use of this source code is governed by a BSD-style license
      5  *  that can be found in the LICENSE file in the root of the source
      6  *  tree. An additional intellectual property rights grant can be found
      7  *  in the file PATENTS.  All contributing project authors may
      8  *  be found in the AUTHORS file in the root of the source tree.
      9  */
     10 
     11 #ifndef WEBRTC_MODULES_RTP_RTCP_SOURCE_FORWARD_ERROR_CORRECTION_INTERNAL_H_
     12 #define WEBRTC_MODULES_RTP_RTCP_SOURCE_FORWARD_ERROR_CORRECTION_INTERNAL_H_
     13 
     14 #include "webrtc/modules/rtp_rtcp/source/forward_error_correction.h"
     15 #include "webrtc/typedefs.h"
     16 
     17 namespace webrtc {
     18 
     19 // Packet mask size in bytes (L bit is set).
     20 static const int kMaskSizeLBitSet = 6;
     21 // Packet mask size in bytes (L bit is cleared).
     22 static const int kMaskSizeLBitClear = 2;
     23 
     24 namespace internal {
     25 
     26 class PacketMaskTable {
     27  public:
     28   PacketMaskTable(FecMaskType fec_mask_type, int num_media_packets);
     29   ~PacketMaskTable() {}
     30   FecMaskType fec_mask_type() const { return fec_mask_type_; }
     31   const uint8_t*** fec_packet_mask_table() const {
     32     return fec_packet_mask_table_;
     33   }
     34 
     35  private:
     36   FecMaskType InitMaskType(FecMaskType fec_mask_type, int num_media_packets);
     37   const uint8_t*** InitMaskTable(FecMaskType fec_mask_type_);
     38   const FecMaskType fec_mask_type_;
     39   const uint8_t*** fec_packet_mask_table_;
     40 };
     41 
     42 // Returns an array of packet masks. The mask of a single FEC packet
     43 // corresponds to a number of mask bytes. The mask indicates which
     44 // media packets should be protected by the FEC packet.
     45 
     46 // \param[in]  num_media_packets       The number of media packets to protect.
     47 //                                     [1, max_media_packets].
     48 // \param[in]  num_fec_packets         The number of FEC packets which will
     49 //                                     be generated. [1, num_media_packets].
     50 // \param[in]  num_imp_packets         The number of important packets.
     51 //                                     [0, num_media_packets].
     52 //                                     num_imp_packets = 0 is the equal
     53 //                                     protection scenario.
     54 // \param[in]  use_unequal_protection  Enables unequal protection: allocates
     55 //                                     more protection to the num_imp_packets.
     56 // \param[in]  mask_table              An instance of the |PacketMaskTable|
     57 //                                     class, which contains the type of FEC
     58 //                                     packet mask used, and a pointer to the
     59 //                                     corresponding packet masks.
     60 // \param[out] packet_mask             A pointer to hold the packet mask array,
     61 //                                     of size: num_fec_packets *
     62 //                                     "number of mask bytes".
     63 void GeneratePacketMasks(int num_media_packets, int num_fec_packets,
     64                          int num_imp_packets, bool use_unequal_protection,
     65                          const PacketMaskTable& mask_table,
     66                          uint8_t* packet_mask);
     67 
     68 }  // namespace internal
     69 }  // namespace webrtc
     70 #endif  // WEBRTC_MODULES_RTP_RTCP_SOURCE_FORWARD_ERROR_CORRECTION_INTERNAL_H_
     71