Specifications
1
Introduction
Broadcasters and content producers use Dolby
®
Professional Loudness solutions to help ensure consistent audio loudness levels. Because
dierences in levels provoke a large number of consumer complaints, all steps in the broadcast production chain require tools to help
maintain uniformity. Dolby Laboratories initially implemented loudness measurement with the Dolby LM100 Broadcast Loudness Meter
and now provides a range of tools aimed at helping to deliver content with more consistent loudness levels.
As le-based workows started to become more prevalent, Dolby developed the DP600 Program Optimizer. This award-winning tool
enabled broadcasters and content producers to ensure that the loudness levels of audio content were set correctly. Users could now
analyze content in a wide range of formats, and if they found that the loudness levels were incorrect, the DP600 would automatically
adjust the levels to meet the users’ required specications.
Use of these tools should ultimately lead to a reduction in customer complaints. Television viewers set their preferred listening levels
subjectively, based on the loudness of dialogue. They do not adjust their volume controls for naturally occurring variations in programs,
such as quiet sections with no dialogue or brief high-level impulses such as gunshots. They do adjust the volume—and complain—when
the dialogue level varies signicantly from one channel or program to another, or when commercials sound much louder than programs.
The rst stage of xing these problems is to objectively and accurately measure what viewers subjectively experience. Dolby technologies
accomplish this by measuring appropriate portions of the signal—those portions that contain dialogue. The Dolby Professional Loudness
Metering solution combines the use of standards-based loudness estimation algorithms with Dialogue Intelligence™ technology. Dialogue
Intelligence accurately detects when content contains speech, and it measures loudness only during those periods.
The second stage of xing these problems is to correct the content based on knowledge of the measured loudness levels. Content in
a Dolby metadata-aware format, such as Dolby E or Dolby Digital Plus, will have the loudness metadata adjusted so that it correctly
matches the associated audio content. Updating of the metadata maintains higher audio quality and reduces the computational
complexity of the loudness correction process. For formats that are not metadata-aware, such as linear PCM, the content is adjusted to a
user-dened target level. The Dolby Professional Loudness Correction library enables manufacturers to add this functionality, which has
proven itself within the Dolby DP600 Program Optimizer, to their Intel
®
processor-based le-processing products.
Dolby Laboratories licenses professional equipment manufacturers to incorporate Dolby Professional Loudness Metering and Correction
solutions in a variety of products, including video encoders and decoders, monitoring products, and test and measurement products. The
license covers real-time and le-based applications for measurement, and le-based applications for correction. This license also covers
real-time updating of loudness metadata based on premeasured values for Intel processor-based products. This document describes
the licensing options and procedures for the developers of products and implementations that incorporate Dolby Professional Loudness
Metering and Correction solutions.
Dolby also manufactures a range of products that use the same loudness measuring and correction technologies. Manufacturers that are
developing products based on this license may use these Dolby products for reference or comparison. For more details on these products,
see the Dolby broadcast loudness solutions overview.
For more information about the Dolby DP600 Program Optimizer, please refer to the Dolby DP600 Program Optimizer page.