README

   1 ==========================================================================
   2 fdkaac - command line frontend encoder for libfdk-aac
   3 ==========================================================================
   4
   5 Prerequisites
   6 -------------
   7 You need libfdk-aac.
   8 On Posix environment, you will also need GNU gettext (for iconv.m4) and
   9 GNU autoconf/automake.
  10
  11 How to build on Posix environment
  12 ---------------------------------
  13 First, you need to build libfdk-aac and install on your system.
  14 Once you have done it, the following will do the task.
  15 (MinGW build can be done the same way, and doesn't require gettext/iconv)
  16
  17 $ autoreconf -i
  18 $ ./configure && make && make install
  19
  20 How to build on MSVC
  21 --------------------
  22 First you have to extract libfdk-aac source here, so that directory tree will
  23 look like the following:
  24 +- fdk-aac ---+-documentation
  25 |             +-libAACdec
  26 |             +-libAACenc
  27 |             :
  28 +- m4
  29 +- missings
  30 +- MSVC
  31 +- src
  32
  33 MSVC solution for Visual Studio 2010 is under MSVC directory.
  34
  35 Available input format
  36 ----------------------
  37 WAV (or RF64), upto 32bit int / 64bit float format is supported.
  38 However, since FDK AAC encoder is implemented based on fixed point integer,
  39 encoder itself treats 16bit input only.
  40 Therefore, when feeding non-integer input, be careful so that input doesn't
  41 exceed 0dBFS to avoid hard clips.
  42 You might also want to apply dither/noise shape beforehand when your input
  43 has higher resolution.
  44
  45 Note that fdkaac doesn't automatically resample for you
  46 when input samplerate is not supported by AAC spec.
  47
  48 Tagging Options
  49 ---------------
  50 Generic tagging options like --tag, --tag-from-file, --long-tag allows you
  51 to set arbitrary tags.
  52 Available tags and their fcc (four char code) for --tag and --tag-from-file
  53 can be found at http://code.google.com/p/mp4v2/wiki/iTunesMetadata
  54
  55 For tags such as Artist where first char of fcc is copyright sign,
  56 you can skip first char and just say like --tag="ART:Foo Bar" or
  57 --tag-from-file=lyr:/path/to/your/lyrics.txt
  58
  59 Currently, --tag-from-file just stores file contents into m4a without any
  60 character encoding / line terminater conversion.
  61 Therefore, only use UTF-8 (without BOM) when setting text tags by this option.
  62
  63 On the other hand, --tag / --long-tag (and other command line arguments) are
  64 converted from locale character encoding to UTF-8 on Posix environment.
  65 On Windows, command line arguments are always treated as Unicode.
  66
  67 Tagging using JSON
  68 ------------------
  69 With --tag-from-json, fdkaac can read JSON file and set tags from it.
  70 By default, tags are assumed to be in the root object(dictionary) like this:
  71
  72 {
  73   "title": "No Expectations",
  74   "artist": "The Rolling Stones",
  75   "album": "Beggars Banquet",
  76   "track": 2
  77 }
  78
  79 In this case, you can simply specify the filename like:
  80 --tag-from-json=/path/to/json
  81
  82 If the object containing tags is placed somewhere else, you can optionally
  83 specify the path of the object with dotted notation.
  84
  85 {
  86   "format" : {
  87     "filename" : "Middle Curse.flac",
  88     "nb_streams" : 1,
  89     "format_name" : "flac",
  90     "format_long_name" : "raw FLAC",
  91     "start_time" : "N/A",
  92     "duration" : "216.146667",
  93     "size" : "11851007.000000",
  94     "bit_rate" : "438628.000000",
  95     "tags" : {
  96       "ALBUM" : "Scary World Theory",
  97       "ARTIST" : "Lali Puna",
  98       "DATE" : "2001",
  99       "DISCID" : "9208CC0A",
 100       "TITLE" : "Middle Curse",
 101       "TRACKTOTAL" : "10",
 102       "track" : "2"
 103     }
 104   }
 105 }
 106
 107 In this example, tags are placed under the object "format.tags".
 108 ("format" is a child of the root, and "tags" is a child of the "format").
 109 In this case, you can say:
 110 --tag-from-json=/path/to/json?format.tags
 111
 112 For your information, ffprobe of ffmpeg project (or avprobe of libav) can
 113 output media information/metadata in json format like this.
 114
 115 Note that not all tags can be read/written this way.