Dolby Digital is a technology that has enabled surround sound from theaters to be transported into the home via home theaters. Developed in the 1980s, it was first applied commercially in the 1992 film “Batman Returns”.
Since then, Dolby Digital has passed through the Laserdisc, DVD, HD-DVD, and Blu-ray eras, and is now present on all major streaming platforms – in addition to theaters, of course. Below are some details about surround technology, the difference from rival DTS, and how to enjoy Dolby Digital in the comfort of your own home.
What is surround sound?
A surround system consists of multiple channels distributed throughout the room to create a sense of three-dimensional sound. The system usually has at least five main boxes (three in the front, two in the back) plus a subwoofer box for reproducing the bass sounds. This is why this system is known as 5.1 – but there are also systems with more channels, reaching numbers such as 11.2.
The advantage of surround sound is that it creates a very real sense of immersion. In action scenes, for example, you can follow the sound of a helicopter or a car approaching the screen in a very realistic way.
Once restricted to movie theaters, surround technology became more popular in the 1990s, especially with the launch of receivers and speaker kits for home theaters. With this, surround technologies such as Dolby Digital have been integrated into DVD and Blu-ray players. More recently, even video game consoles and smartphones have started to play surround sound.
Technology has advanced to such an extent that it is not mandatory to have a home theater with multiple boxes to take advantage of surround technology. Some headphones and soundbars emulate the sensation of three-dimensional sound using Dolby Atmos or DTS:X technology. It doesn’t feel the same as a real 5.1 system, but it is an option for those who don’t have that much space.
What is Dolby Digital?
Dolby Digital was the first digital audio compression system capable of delivering surround sound. Created by audio engineering company Dolby Labs, Dolby Digital has become an industry-standard since its commercial debut with Tim Burton’s “Batman Returns.
In 1995, the technology (which was originally called Dolby AC-3) was released for home use with the Laserdisc of the film “Real and Immediate Danger.” Soon after, it was also adopted by television stations and cable companies in the USA and integrated into the first DVD players.
What makes Dolby Digital interesting is its ability to adapt to the user’s sound system. Thanks to downmix technology, a movie with 5.1 surround sound can be played normally on a stereo (2.0) TV. This is because Dolby’s algorithm remixes the original audio file to the format of the device. So a DVD only needs a single audio track to play on any type of device.
The Dolby Digital versions
As technology has advanced, Dolby Digital has also evolved. Because of the 1999 movie “Star Wars: Episode 1: The Phantom Menace” Dolby Digital EX was developed, which added two extra channels to Dolby Digital, creating the 6.1 and 7.1 systems.
Then came Dolby Digital Plus, aimed at HD-DVD and Blu-Ray discs. Because these formats have greater storage capacity compared to DVDs, Dolby increased the maximum playback rates to up to 1.7 Mb/s (Megabits per second) bitrate.
Shortly thereafter Dolby TrueHD was launched. Unlike previous versions, this technology is capable of playing back uncompressed (lossless) files with a bitrate of up to 18 Mb/s, as well as a sampling rate of 192 kHz and 24 bits deep. It is a direct rival to the also popular DTS-HD Master Audio – both are present on many Blu-ray discs and are the least compressed options.
The latest version of the system is Dolby Atmos, which adds speakers to the ceiling to give the sound verticality and create a kind of sound bubble that envelops the viewer. The distinguishing feature of this technology is that the sound of an object can be manipulated three-dimensionally to create an even greater sense of immersion.
Dolby vs. DTS
Digital Theater Systems, also known by the acronym DTS, is a digital audio compression system that competes with Dolby. It was created in 1993 and gained worldwide fame for being chosen by Steven Spielberg to reproduce the sounds of the movie “Jurassic Park”.
The main difference between the two systems is in the level of compression. DTS can reproduce at higher rates and a higher bitrate than Dolby. On Blu-ray discs, DTS supports files with up to 1.5 Mb/s, while Dolby can handle only 640 kbits/s. On DVDs, the difference is somewhat smaller: 768 kbits/s versus 448 kbits/s.
In the high-resolution formats, the difference is more significant: DTS-HD plays 6 Mb/s, while Dolby Digital Plus reaches 1.7 Mb/s. DTS-HD Master Audio reaches 24.5 Mb/s versus Dolby TrueHD’s 18 Mb/s.
In theory, the more bitrate a file has, the better the sound quality. However, Dolby claims that their codecs are more efficient and can more accurately eliminate noise that is not heard by the human ear. Thus, their technology would be able to compress files into smaller sizes while maintaining sound quality.
Apart from this technical part, there is the question of support. So far, the Dolby system is more dominant on streaming platforms, being present on services such as Netflix, Amazon Prime Video, and Disney+. DTS, on the other hand, is available on a few streaming services, mostly in Asia, such as Rakuten TV and iQiyi.
How to use Dolby Digital?
To get cinema sound at home, all you need is a compatible source (a smart TV or Blu-ray player, for example) and a surround sound system. The connection between the parties can be made via HDMI cable (both the source and the system must have HDMI ARC technology), optical cable, or digital coaxial cable (S/PDIF).
Finally, the reproduced content must also be compatible with the Dolby Digital system. Not all movies and series available on streaming platforms have 5.1 audio. The same goes for some DVD and Blu-ray discs, especially older movies or series.