Key Dolby Metadata Parameters
Consumers' listening systems vary widely, from full multichannel home theaters to conventional stereo to mono TVs. Dolby metadata provides a number of key parameters designed to give consumers the optimal sound for any program, no matter the listening system.
These key parameters are the three Ds:
Dynamic range control
Proper setting of the three Ds offers a simple and easily used method that provides the best quality sound reproduction without regard to the number of speaker channels, ambient noise levels, or playback equipment quality.
The dialogue level parameter, known as dialogue normalization or dialnorm, provides a loudness level normalization value to the home decoder. Dialnorm helps in level-matching between programs or between media.
Dialnorm measures average program loudness based on speech, rather than signal peaks. The loudness value is measured (referenced to dBFS using an algorithm such as ITU-R BS-1770) and carried by Dolby Digital Plus directly to a home’s STB or TV.
Setting dialnorm is simply a matter of monitoring program loudness with a dedicated loudness meter and entering that loudness level within the metadata stream. Alternatively, you can mix the program to achieve the target loudness level on the meter.
Dynamic Range Control
Dynamic range control (or dynamic range compression, DRC, or “midnight mode”) allows the consumer to listen with a reduced dynamic range. This lets viewers watch TV without disturbing neighbors or others in the household. (The control is optional on consumer equipment.)
The dynamic range control essentially raises the level of softer program portions while lowering the level of loud segments. The listener can hear everything without having to continually reach for the volume control.
The dynamic range control in Dolby metadata involves two parameters, RF mode and Line mode.
Matches the delivery of conventional analog broadcasts
Closely approximates dynamic range levels of DTV with MPEG stereo audio
Includes a level shift that boosts the audio by 11 dB
Provides lighter compression
Allows user adjustment of low-level boost and high-level cut
Before setting dynamic range values, you need to select the appropriate dialnorm value. You then preview the source mix before choosing a dynamic range preset.
Downmixing is a feature of Dolby Digital Plus (and Dolby Digital) that allows a multichannel program to be reproduced by fewer speakers. Viewers do not need a 5.1-channel system to enjoy a digital TV broadcast.
The downmixing parameter lets you adjust the levels of the surround and center channels that are mixed into the stereo outputs. You have considerable flexibility in making surround sound work effectively in stereo.
Stereo output can be of two types:
A stereo-compatible Lt/Rt downmix suitable for Dolby Pro Logic® decoding
A simple stereo Lo/Ro downmix for stereo hi-fi or headphones
Specific parameters also allow you to select which stereo analog signal is preferred as the default. Other, separate parameters adjust the Lo/Ro and Lt/Rt downmix conditions.
Metadata can be set for each specific program. Dolby also provides genre-specific presets optimized for various program types. It’s important that you consider which presets to use.
Another consideration in choosing metadata is the delivery specifications set by downstream operators, who may require specific presets.
See our Settings tab for charts with typical presets.
Dolby offers a number of solutions to help in setting metadata.
Dolby’s solutions for automated, non-real-time control:
Dolby DP600 Program Optimizer
Dolby Media Emulator software
Dolby’s solutions for real-time metadata generation and emulation:
Dolby DP570 Multichannel Audio Tool
Dolby Media Emulator software
Our partners also offer a wide array of hardware and software.
We offer extensive training resources. Please contact a Dolby representative for details. We also have a network of full-service consultants who can provide everything from training to turnkey operations. Additionally, you can contact our partners for advice and products for metadata carriage.