Because unwanted loudness variations have no single cause, Dolby® offers a range of solutions. These fall into three categories:
Measurement, analysis, and correction
Consumer-end volume leveling
See the Tools tab for specific Dolby hardware and software tools.
All of Dolby's broadcast audio formats—Dolby Digital Plus, Dolby Digital, and Dolby’s implementation of HE AAC—include full Dolby metadata.
Dolby metadata includes tools that control loudness levels and tailor the audio to the consumer’s replay environment. This metadata:
Gives broadcasters and operators control over final replay
Provides end users with consistent loudness
Can be set in transmission
Employs presets to suit the content genre and station style
Includes listener-adjustable dynamic range modes
Measurement, Analysis, and Correction
Effective loudness control requires accurate measurement. Dolby and our partners offer a variety of effective tools that support a range of international standards, including:
The Importance of Dialogue in Measurement
Viewers judge loudness by the level of the anchor element, typically dialogue, in the mix. ATSC A/85 and some other international specifications now explicitly call for loudness measurement using dialogue.
Dolby meets this need with Dialogue Intelligence™, an automatic, consistent technology for accurate dialogue measurement. Available in tools from Dolby as well as from partner manufacturers, Dialogue Intelligence:
Measures signal loudness only during presence of speech
Couples with ITU-R BS.1770 and other standards
Objectively quantifies what listeners subjectively hear
Uses a unique algorithm developed by Dolby's audio experts
Manufacturers who wish to include Dolby technologies in their loudness measurement products can download Dolby's speech-gating reference code free of cost.
Consumer-End Volume Leveling
Even with proper use of metadata and control procedures, some programs will still reach the consumer without any loudness control or correction. Other inputs to the TV or set-top box (STB) may come from non-broadcast sources such as Internet-connected devices or user-generated content.
To help resolve this need for volume leveling in programs that lack proper metadata, Dolby created Dolby Volume. Designed for inclusion in TVs, A/V receivers, and STBs, Dolby Volume:
Draws on four decades of research in human sound perception
Offers a new and uniquely effective approach
Delivers natural, artifact-free sound
Preserves audio detail even at very low volume levels
Learn more about Dolby Volume.