How does a public standard stay “patented” for longer than 20 years?

Dolby engages in legally dubious strategies known as “evergreening” to abuse the patent system and extend their licensing monopoly for AC-3. Some of these tactics include:

  • refusing to provide lists of their standard-essential patents in most cases (see ATSC patent statements)
  • filing new patents, claiming that they cover portions of existing standards
  • acquiring irrelevant patents from competitors, alleging that they are now important to the standard


I’m a user. Why should I care?

You have probably paid many AC-3 license fees over the years. AC-3 license fees are part of the cost of TVs, game consoles, and other AV equipment sold in the last 25 years.

You may have had problems playing certain video files on your computers and mobile devices. In 2012, Dolby started threatening the authors of various video player apps, forcing developers to remove their apps, remove support for AC-3, or increase prices.


When would I need to decode AC-3?

  • Playing most live TV content
  • Playing most recorded TV content
  • Playing many videos from DVD
  • Playing many videos from Blu-Ray
  • Playing videos recorded by some digital camcorders
  • Playing some online streaming content offered in 5.1 surround sound

When would I need to encode AC-3?

Hopefully never! In practice, there are a few cases:

  • Encoding surround sound audio for some legacy TVs and devices that only support AC-3 for surround. Modern devices can decode other multichannel formats such as AAC, DTS, and Opus.
  • Encoding surround sound audio to be sent to a legacy AV receiver using an optical cable (S/PDIF). Modern AV receivers can accept other formats over HDMI, including multichannel PCM.

Is AC-3 any good? Should I use it for new stuff?

No, of course not. AC-3 is over 25 years old and horribly inefficient.