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, RF64, CAF, RAW, upto 32bit int / 64bit float format is supported.
  38 Metadata in CAF info chunk can be read and copied to the resulting m4a.
  39 This is especially useful and works well when you pipe from ffmpeg via CAF.
  40 For example, you can copy tag from original "foo.flac" to "foo.m4a"
  41 through the following pipeline:
  42
  43 $ ffmpeg -i foo.flac -f caf - | fdkaac -m3 - -o foo.m4a
  44
  45 Since FDK AAC encoder is implemented based on fixed point integer,
  46 encoder itself handles 16bit input only.
  47 Therefore, when feeding non-integer input, be careful so that input doesn't
  48 exceed 0dBFS to avoid hard clips.
  49 You might also want to apply dither/noise shape beforehand when your input
  50 has higher resolution.
  51
  52 Note that fdkaac doesn't automatically resample for you
  53 when input samplerate is not supported by AAC spec.
  54
  55 Tagging Options
  56 ---------------
  57 Generic tagging options like --tag, --tag-from-file, --long-tag allows you
  58 to set arbitrary tags.
  59 Available tags and their fcc (four char code) for --tag and --tag-from-file
  60 can be found at http://code.google.com/p/mp4v2/wiki/iTunesMetadata
  61
  62 For tags such as Artist where first char of fcc is copyright sign,
  63 you can skip first char and just say like --tag="ART:Foo Bar" or
  64 --tag-from-file=lyr:/path/to/your/lyrics.txt
  65
  66 Currently, --tag-from-file just stores file contents into m4a without any
  67 character encoding / line terminater conversion.
  68 Therefore, only use UTF-8 (without BOM) when setting text tags by this option.
  69
  70 On the other hand, --tag / --long-tag (and other command line arguments) are
  71 converted from locale character encoding to UTF-8 on Posix environment.
  72 On Windows, command line arguments are always treated as Unicode.
  73
  74 Tagging using JSON
  75 ------------------
  76 With --tag-from-json, fdkaac can read JSON file and set tags from it.
  77 By default, tags are assumed to be in the root object(dictionary) like this:
  78
  79 {
  80   "title": "No Expectations",
  81   "artist": "The Rolling Stones",
  82   "album": "Beggars Banquet",
  83   "track": 2
  84 }
  85
  86 In this case, you can simply specify the filename like:
  87 --tag-from-json=/path/to/json
  88
  89 If the object containing tags is placed somewhere else, you can optionally
  90 specify the path of the object with dotted notation.
  91
  92 {
  93   "format" : {
  94     "filename" : "Middle Curse.flac",
  95     "nb_streams" : 1,
  96     "format_name" : "flac",
  97     "format_long_name" : "raw FLAC",
  98     "start_time" : "N/A",
  99     "duration" : "216.146667",
 100     "size" : "11851007.000000",
 101     "bit_rate" : "438628.000000",
 102     "tags" : {
 103       "ALBUM" : "Scary World Theory",
 104       "ARTIST" : "Lali Puna",
 105       "DATE" : "2001",
 106       "DISCID" : "9208CC0A",
 107       "TITLE" : "Middle Curse",
 108       "TRACKTOTAL" : "10",
 109       "track" : "2"
 110     }
 111   }
 112 }
 113
 114 In this example, tags are placed under the object "format.tags".
 115 ("format" is a child of the root, and "tags" is a child of the "format").
 116 In this case, you can say:
 117 --tag-from-json=/path/to/json?format.tags
 118
 119 For your information, ffprobe of ffmpeg project (or avprobe of libav) can
 120 output media information/metadata in json format like this.
 121
 122 Note that not all tags can be read/written this way.