View source for Converting audios

'''Converting audio files''' is a frequently needed task when serving audio files to target services and users.

= How to convert large batch of audios ? =
== Dependencies ==
:''<span style="color:#B10000">Warning : <code>avconv</code> have been removed from Ubuntu packages since 18.04. Use ffmpeg instead.</span>''
<syntaxhighlight lang="bash">
sudo apt-get install lame ffmpeg
man lame                           # then search for parameters via "/{param}". ex: /-m
</syntaxhighlight>

== Technolect ==
* <code>cbr</code>: constant bit rate.
* <code>abr</code>: average bit rate.
* <code>vbr</code>: variable bit rate.
For more, see <code>man lame</code>.

== Helpers ==
<syntaxhighlight lang="bash">
$ mkdir -p ./new/                    # create folder, if not existing (-p)
$ file="./data/cmn-0a0a8a8b.flac"    # path to .flac file into varible &quot;$file&quot;
$ ffprobe -hide_banner "$file"       # print out metadata of $file, for some formats only

$ ffprobe -hide_banner ./data/cmn-0a0a8a8b.ogg
Input #0, ogg, from './data/cmn-0a0a8a8b.ogg':
  Duration: 00:00:01.25, start: 0.000000, bitrate: 99 kb/s
  Stream #0:0: Audio: vorbis, 44100 Hz, mono, fltp, 80 kb/s
    Metadata:
      TITLE           : 高低
      LICENSE         : Creative Commons BY-SA 3.0 U.S
      COPYRIGHT       : (c) 2009 Yue Tan
      ARTIST          : Tan
      DATE            : 2009-07-08
      GENRE           : Speech
      SWAC_LANG       : cmn
      SWAC_TEXT       : 高低
      SWAC_ALPHAIDX   : gāodī
      SWAC_SPEAK_NAME : Tan
      SWAC_SPEAK_GENDER: F
      SWAC_SPEAK_BIRTH_YEAR: 1978
      SWAC_SPEAK_LANG : zho
      SWAC_SPEAK_LANG_REGION: Liaoning
      SWAC_SPEAK_LIV_COUNTRY: FR
      SWAC_SPEAK_LIV_TOWN: Caen
      SWAC_PRON_PHON  : gāodī
      SWAC_COLL_SECTION: HSK niveau IV
      SWAC_COLL_LICENSE: Creative Commons BY-SA 3.0 U.S
      SWAC_COLL_COPYRIGHT: (c) 2009 Yue Tan
      SWAC_TECH_DATE  : 2009-07-08
      SWAC_TECH_SOFT  : Shtooka Recorder/1.3
</syntaxhighlight>

== Simple batch format conversion ==
<syntaxhighlight lang="bash">
for file in ./flac/*.flac
do
  key=$(basename "$file" .flac).mp3                                 # name of the file minus .flac, plus .mp3 
  lame --abr 24    -m m -h --resample 22.05 "$file" "./new/$key";
done
</syntaxhighlight>

== Metadata-based format conversion ==
This example works on SWAC recorder audio files available at https://packs.shtooka.net. Those files contain rich metadata, with a <code>SWAC_TEXT</code> metadata field. In this example, we assume a folder with file <code>audio-0a6f36g.flac</code> and metadata <code>SWAC_TEXT    : 很</code>.

<syntaxhighlight lang="bash">
for file in ./flac/*.flac
do
  key=$(ffmpeg -i "$file" 2>&1 | sed -ne 's/.*SWAC_TEXT *: //p')                 # print metadata, assign SWAC_TEXT's value to variable.
  lame --abr 24    -m m -h --resample 22.05 "$file" "./new-24k/cmn-$key.mp3";    # ex: cmn-很.mp3 (24k abr)
  lame --cbr -b 96 -m m -h --resample 22.05 "$file" "./new-96k/cmn-$key.mp3";    # ex: cmn-很.mp3 (96k cbr)
done</syntaxhighlight>

== See also ==
* [[:c:Commons:Audio]]
{{Technicals}}

[[Category:Lingua Libre:Help{{#translation:}}]]