Prototypology/Transcodology-2

How to compress audio?

Why compressing audio?

• Which formats can be used on a web page?
  • mp3
  • ogg
  • opus

The fancy and hard way

Uses FFmpeg. FFmpeg is a powerful, open-source tool for decoding, encoding, and manipulating multimedia files.

ffmpeg -i input.wav -b:a 128k output.mp3

• the option "-i" is the input file
• the option "-b:a" specifies the bit rate. its in kilobit per seconds. more bit less information is lost. possible option could be:
  • 96k
  • 112k
  • 128k
  • 160k
  • 192k
  • 256k
  • 320k
• the last argument is the output file. with the format(.mp3) you define the compression format. options for audio would be:
  • mp3
  • ogg (or oga) https://www.xiph.org/ogg/
  • opus https://opus-codec.org/

The easy way

Use audacity :D

1. Open the file with audacity
2. Click on [File] -> [Export]
   1. Select [Export as MP3]
   2. Select [Export as OGG]
   3. Select [Export Audio ...] for opus
3. In the new window that open you can select different format optins.
4. select a name for the new file
5. Click on [Save]

Further readings

• Audio compression artifacts
• Interview with Jonathan Sterne