H.264 Codec String Parser (video, profile, level) - February 2022

h264_codec_string_parser.js

// FROM: https://gist.github.com/eladkarako/119e91525d34db9f61cca23b18fd62a0#file-h264_codec_string_parser-js
// 
// Changes:
// 1. Change to work on uppercase strings
// 2. Allow passing codec string as command line argument, e.g. `node h264_codec_string_parser.js avc1.42C03E`
// 3. Parse `constraint_set_flags` as well
//
ISOAVC_MAP = {
 "avc1": "H.264"
,"avc2": "H.264"
,"svc1": "Scalable Video Coding"
,"mvc1": "Multiview Video Coding"
,"mvc2": "Multiview Video Coding"
};


PROFILE = {                                       //https://en.wikipedia.org/wiki/H.264/MPEG-4_AVC#Profiles
   "0":  "No"                   //  0             - *** when profile=RCDO and level=0 - "RCDO"  - RCDO bitstream MUST obey to all the constraints of the Baseline profile
 ,"42":  "Baseline"             // 66 in-decimal
 ,"4d":  "Main"                 // 77 in-decimal
 ,"58":  "Extended"             // 88 in-decimal
 ,"64":  "High"                 //100 in-decimal
 ,"6e":  "High 10"              //110 in-decimal
 ,"7a":  "High 4:2:2"           //122 in-decimal
 ,"f4":  "High 4:4:4"           //244 in-decimal
 ,"2c":  "CAVLC 4:4:4"          // 44 in-decimal
 
 //profiles for SVC - Scalable Video Coding extension to H.264
 ,"53":  "Scalable Baseline"    // 83 in-decimal
 ,"56":  "Scalable High"        // 86 in-decimal

 //profiles for MVC - Multiview Video Coding extension to H.264
 ,"80":  "Stereo High"          // 128 in-decimal
 ,"76":  "Multiview High"       // 118 in-decimal
 ,"8a":  "Multiview Depth High" // 138 in-decimal
};


function avcoti_to_str(s){
  var REGEX = /([0-9a-f]{2})([0-9a-f]{2})([0-9a-f]{2})/i
     ,matches
     ,profile_idc
     ,constraint_set_flags
     ,level_idc
     ;

  if(false === REGEX.test(s)) throw new Error("error: please provide a 3-bytes hex-sequence for example: 42001e");
  matches = s.match(REGEX);
  matches.shift();            //kills first one (regex matchs entire string)
  
  profile_idc           = matches[0];
  var orig_profile_idc = profile_idc;
  profile_idc           = PROFILE[profile_idc];
  profile_idc           = "string" === typeof profile_idc ? profile_idc : "Unknown";  //explicit fix.

  // FROM: https://cgit.freedesktop.org/gstreamer/gst-plugins-good/tree/gst/qtdemux/qtdemux.c?id=ccef64be3996e6bb47a974cf64c0fa311c463700
  // avc_profile_idc_to_string()
  constraint_set_flags  = parseInt(matches[1], 16);
  console.log(matches[1]);
  console.log(constraint_set_flags);

  var csf1 = (constraint_set_flags & 0x40) >> 6;
  var csf3 = (constraint_set_flags & 0x10) >> 4;
  console.log(csf1);
  console.log(csf3);
  if (orig_profile_idc === '42' && csf1) {
    // 66 in decimal
    constraint_set_flags = ' Constrained';
  } else if (orig_profile_idc === '6e' && csf3) {
    // 110 in decimal
    constraint_set_flags = ' Intra';
  } else if (orig_profile_idc === '7a' && csf3) {
    // 122 in decimal
    constraint_set_flags = ' Intra';
  } else if (orig_profile_idc === 'f4' && csf3) {
    // 244 in decimal
    constraint_set_flags = ' Intra';
  } else if (orig_profile_idc === '2c') {
    // 44 in decimal
    constraint_set_flags = ' Intra';
  } else {
    constraint_set_flags = '';
  }

  level_idc             = matches[2];
  level_idc             = Number.parseInt(level_idc, 16);        //will give something like 30  (integer thirty)
  level_idc             = String(level_idc).split("").join(".")  //will give something like "3.0"

  return "\"" + profile_idc + constraint_set_flags + "\" Profile, Level " + level_idc;
}


function h264avc_to_string(s){
  s = s.toLowerCase();
  var REGEX = /(avc1|avc2|svc1|mvc1|mvc2)\.([0-9a-f]{6})/i
     ,matches
     ,avc_codec
     ;
  if(false === REGEX.test("avc1.42001e")) throw new Error("Codec string is not formatted according to H.264/AVC standards for example avc1.42001e (maybe an iOS friendly version...)");
  matches = s.match(REGEX);
  matches.shift();    //first one is the entire-string.
  
  avc_codec = ISOAVC_MAP[ matches[0] ];
  avc_codec = "string" === typeof avc_codec ? avc_codec : "Unknown";  //explicit fix
  
  return avc_codec + " Video ("  + avcoti_to_str( matches[1] )  + ")";
}


//Try It...
//more examples in  https://tools.ietf.org/id/draft-gellens-mime-bucket-bis-02.html#sec-5

// console.log(
//   h264avc_to_string("avc1.42001e")
//  ,h264avc_to_string("avc1.640029")
// )
console.log(process.argv[2]);
console.log(h264avc_to_string(process.argv[2]));


/************************************
 * H.264-Codec Profile/Level Parser *
 *        /Elad Karako. August 2017 *
 * /Malthe Jørgensen. February 2022 *
 ************************************/


/*
References:
https://developer.apple.com/library/content/documentation/NetworkingInternet/Conceptual/StreamingMediaGuide/FrequentlyAskedQuestions/FrequentlyAskedQuestions.html
https://tools.ietf.org/html/draft-pantos-http-live-streaming-23
https://tools.ietf.org/html/rfc6381
https://tools.ietf.org/html/rfc6381#section-3.6
https://en.wikipedia.org/wiki/H.264/MPEG-4_AVC
https://en.wikipedia.org/wiki/H.264#Levels
https://tools.ietf.org/html/draft-ietf-avt-rtp-h264-rcdo-08
http://h264bitstream.sourceforge.net/doxygen/0.1.5/structsps__t.html
https://www.iana.org/assignments/media-types/video/H264-SVC
https://tools.ietf.org/html/rfc6381#ref-AVC-Formats
*/