The established standard for home theater, broadcast, and cinema surround sound, Dolby Digital 5.1 redefined the entertainment experience for audiences around the world.
Dolby Digital benefits
A global standard
Every DVD worldwide and all HD broadcasts in the United States use Dolby Digital® (also known as AC-3). Dolby Digital 5.1 has evolved into Dolby Digital Plus™, delivering up to 7.1 channels of surround sound in devices ranging from TVs to mobile phones.
5.1 Multichannel sound
With 5.1 channels of high-quality audio, Dolby Digital places you in the center of the action. It expands the left and right traditional stereo channels to deliver an enveloping 360 degrees of sound.
Cinema, TV, DVDs, and games
The same audio technology that revolutionized the cinema enables the sound in all DVDs and US HDTV broadcasts. Even many video games feature Dolby Digital surround sound.
Automatic stereo version
Dolby Digital automatically provides a stereo version of the audio tracks so your favorite movies, TV shows, and other entertainment will sound great on any device.
Compatible with the future
As new audio formats like Dolby Digital Plus appear, you can be sure that your Dolby Digital content will remain compatible for years to come.
Efficient 5.1 sound
At its core, Dolby Digital technology represents a very efficient way for movie studios, television networks, and other content providers to compress the size of multichannel audio files without impairing the sound quality. The smaller the file, the easier it is to distribute. With Dolby Digital, it's possible to include a full 5.1-channel audio mix on a film print or a DVD, or as part of a TV broadcast. This expands the creative palette for artists, and allows those of us in the audience to experience greater realism and excitement.
Encoding and decoding
Dolby Digital operates in a world of ones and zeroes — digital information. Since the audio we hear consists of analog waveforms, not ones and zeroes, the first step in the process of creating a Dolby Digital audio track is to convert the original analog signal into digital information. This process is called encoding.
But rather than simply converting waveforms to numbers blindly, Dolby Digital analyzes the original audio and intelligently determines what parts of the audio track are important to keep and what parts you're less likely to hear.
By retaining the important parts of the audio track and eliminating redundant data, Dolby Digital delivers excellent multichannel sound at low data rates.
The distribution of Dolby Digital audio can take many forms: a film print, a DVD, a television broadcast, a download. Once distributed, the compressed audio needs decoding.
At the cinema, this decoding occurs in an audio processor, while in your home it can take place in a DVD player, a set-top box, a game console, or another familiar piece of equipment.
To ensure consistent playback regardless of your specific setup, Dolby Digital uses something called metadata.
Metadata is a set of instructions created during programming production and carried in the Dolby Digital bitstream. It ensures you enjoy a high-quality audio experience, whether you're listening on a mono, stereo, or 5.1-channel system, and also lets content creators offer additional features so you have more control over playback.
The role of each channel in 5.1 sound
The channels in a 5.1 audio mix serve distinct purposes. The three front channels (Left, Center, and Right) provide crisp, clean dialogue and accurate placement of onscreen sounds. The twin surround channels (Left Surround and Right Surround) create the sense of being in the middle of the action.
The Low-Frequency Effects (LFE) channel delivers deep, powerful bass effects that can be felt as well as heard. As it needs only about one-tenth the bandwidth of each of the other channels, the LFE channel is referred to as a ".1" channel.
Dolby Digital Plus: surround sound anywhere, everywhere
Dolby Digital Plus delivers a definitive surround sound experience for all your devices from home theaters to smartphones.
Dolby Digital for professionals
Dolby Digital delivers up to 5.1 discrete channels of high-quality surround sound for broadcasting, home theater, cinema, PC, online streaming, and video game programming.
Dolby Digital for content creators
Surround sound can add realism and depth to your work, and open up new possibilities for engaging audiences. Whether you're making films, television programming, or video games, Dolby Digital provides the means for you to create compelling audio tracks for playback in the cinema and the home.
Expand your audio horizons
- A worldwide standard in surround sound, Dolby Digital offers compatibility with millions of existing playback systems. These include cinema processors, A/V receivers, set-top boxes, DVD players, PCs, and game systems.
- Metadata parameters ensure that a single audio bitstream faithfully delivers your vision for the audio whether your audience is listening on a mono, stereo, or 5.1-channel system.
- For game developers, the Dolby Game Developer Support Program can supply you with everything you need to create great audio with Dolby Digital. Visit the Dolby Developer portal to learn more.
- By enabling the efficient storage and transmission of high-quality 5.1-channel sound, Dolby Digital allows you to make multichannel audio an integral part of your storytelling every time.
- With Dolby Media Producer, the definitive suite of professional software designed to support Dolby audio codecs, you can master DVD-Video, DVD-Audio, and Blu-ray Discs™.
Dolby Digital for broadcasters
When you use Dolby Digital, you ensure that the audio portion of your signal will be compatible with playback systems and broadcasting standards throughout North America. At the same time, you provide viewers with high-quality multichannel sound.
Up to 5.1 channels into millions of homes
- Dolby Digital delivers up to 5.1 discrete channels of surround sound to add realism and depth to sporting events, dramatic features, and other types of programming.
- Whether HD or standard-definition, all digital TV broadcasts use Dolby Digital audio in the US, Canada, and other countries that have adopted the ATSC television standard.
- Metadata parameters ensure that a single audio bitstream faithfully delivers the producer's vision for the audio whether the audience is listening on a mono, stereo, or 5.1-channel system.
- Applied to the final broadcast transmission signal just prior to multiplexing with the digital video, Dolby Digital is used extensively in digital satellite (DBS and DVB), cable, and terrestrial high-definition TV (ATSC).
- Dolby Digital offers compatibility with millions of existing playback systems. These include nearly 60 million digital cable and satellite set-top boxes worldwide, and more than 30 million A/V receivers.
Dolby Digital for distributors and exhibitors
For most people, the cinema remains the best place to watch movies, and one reason is the sound. Dolby Digital redefined the cinema experience with multichannel sound, and it continues to be the most popular digital audio format for movie theaters worldwide.
The digital and analog solution
- Dolby Digital delivers up to 5.1 discrete channels of surround sound to add realism and depth to feature films, documentaries, and shorts.
- Dolby Digital provides extraordinary dynamic capability, wide frequency range, low distortion, and relative immunity to wear. Its combination of high quality, reliability, and practicality has been proven in cinemas around the world.
- Dolby has established standardized sound replay conditions for cinemas and mixing studios to ensure the consistent playback of all Dolby Digital films.
- The Dolby Digital soundtrack resides in the spaces between sprocket holes on 35 mm prints, next to the analog soundtrack. The combination of both digital and analog soundtracks on the same print means that films will play back satisfactorily in nearly every cinema.
- Every movie carrying the Dolby logo benefits from Dolby's unique mastering support services, which ensure that sound will be reproduced in the cinema just as the director intended.
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Dolby Digital specifications
See Dolby Digital® specifications below. You can also compare Dolby Digital to other similar technologies like Dolby Digital Plus™.
| Channels | 1.0 to 5.1, discrete |
|
DVD data rate, 5.1-channel audio |
384 or 448 kbps |
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Blu-ray Disc data rate, 5.1-channel audio |
640 kbps |
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Supports Dolby metadata |
Yes |
|
Connections |
S/PDIF, HDMI®, IEEE 1394 |
|
Mixing/streaming capabilities |
Yes |
DOLBY METADATA PARAMETERS
|
METADATA PARAMETER |
INFORMATIONAL |
CONTROL |
|---|---|---|
|
Dialogue level |
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Channel mode |
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LFE channel |
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Bitstream mode |
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Line mode compression |
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RF mode compression |
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RF overmodulation protection |
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Center downmix level |
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Surround downmix level |
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Dolby Surround mode |
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Audio production information |
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Mix level |
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Room type |
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Copyright bit |
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Original bitstream |
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Preferred stereo downmix |
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Lt/Rt Center downmix level |
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Lt/Rt Surround downmix level |
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Lo/Ro Center downmix level |
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Lo/Ro Surround downmix level |
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Dolby Digital Surround EX™ mode |
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A/D converter type |
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DC filter |
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Lowpass filter |
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LFE lowpass filter |
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Surround 3 dB attenuation |
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|
Surround phase shift |
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Hardware
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