Webcodecs parameter settings -avc1.42e01e meaning

codecs      := cod-simple / cod-fancy

1、cod-simple

AVC Words , Based on H.264 To encode and decode .vp9 Based on VP9 To encode and decode .hevc Indicates that the video is based on H.265 Coded .

2、cod-fancy

and cod-fancy Is written by a 16 Hexadecimal string . and AVC The coding group consists of three parts .

avc1.PPCCLL

PP = profile_idc  
CC = constraint_set flags  
LL = level_idc

2.1 profile_idc

 profile_idc Express   Different H.264 Characteristics of encoder . Different values , The coding performance required is different , The following are common in official definitions ：

enum eAVEncH264VProfile {  
  eAVEncH264VProfile_unknown                    = 0,
  eAVEncH264VProfile_Simple                     = 66,
  eAVEncH264VProfile_Base                       = 66,
  eAVEncH264VProfile_Main                       = 77,
  eAVEncH264VProfile_High                       = 100,
  eAVEncH264VProfile_422                        = 122,
  eAVEncH264VProfile_High10                     = 110,
  eAVEncH264VProfile_444                        = 144,
  eAVEncH264VProfile_Extended                   = 88,
  eAVEncH264VProfile_ScalableBase               = 83,
  eAVEncH264VProfile_ScalableHigh               = 86,
  eAVEncH264VProfile_MultiviewHigh              = 118,
  eAVEncH264VProfile_StereoHigh                 = 128,
  eAVEncH264VProfile_ConstrainedBase            = 256,
  eAVEncH264VProfile_UCConstrainedHigh          = 257,
  eAVEncH264VProfile_UCScalableConstrainedBase  = 258,
  eAVEncH264VProfile_UCScalableConstrainedHigh  = 259
};

2.2 constraint_set flags

  Represents the constraints of the coding level , The following are common ：

constraint_set0_flag  
constraint_set1_flag  
constraint_set2_flag  
constraint_set3_flag  
constraint_set4_flag  
constraint_set5_flag

  They aim at different profie And make it . And one of  0xE0  Convert to binary 11100000 That is to say constraint_set2_flag.？？？

2.3 level_idc

level_idc  Represents the video parameters of the video coding itself , Like resolution , Bit rate , Frame rate, etc .Level The higher the video quality, the better .

enum eAVEncH264VLevel {  
  eAVEncH264VLevel1    = 10,
  eAVEncH264VLevel1_b  = 11,
  eAVEncH264VLevel1_1  = 11,
  eAVEncH264VLevel1_2  = 12,
  eAVEncH264VLevel1_3  = 13,
  eAVEncH264VLevel2    = 20,
  eAVEncH264VLevel2_1  = 21,
  eAVEncH264VLevel2_2  = 22,
  eAVEncH264VLevel3    = 30,
  eAVEncH264VLevel3_1  = 31,
  eAVEncH264VLevel3_2  = 32,
  eAVEncH264VLevel4    = 40,
  eAVEncH264VLevel4_1  = 41,
  eAVEncH264VLevel4_2  = 42,
  eAVEncH264VLevel5    = 50,
  eAVEncH264VLevel5_1  = 51,
  eAVEncH264VLevel5_2  = 51
}

  that  0x1E  said  eAVEncH264VLevel3 ???