Dolby Digital and DTS – what is it and what is the difference?

Surround sound has long been an integral part of the soundtrack of movies and TV shows. For several decades now, two different technologies have been fighting on the battlefield of surround audio standards – Dolby Digital and DTS. What are the differences between them? And which is better in the end? We will tell in this article.

What is surround sound?
As you know, the human brain with the help of two eyes can form a three-dimensional picture – after all, we see the world not flat, but in volume. Similarly, with the help of two ears, a person can distinguish the position of sound in space.

Cinema became the first mass means of audiovisual transmission of information with the help of technology. The black-and-white picture was replaced by color, then the resolution began to grow. Movies eventually came to 3D, but the technology never caught on in mainstream home movie viewing equipment, and became more of an adjunct to traditional “flat” movies in theaters and home TVs. But with sound – on the contrary, because it is simply impossible to imagine modern films without surround sound.

At the dawn of cinematography, sound was monophonic, that is, it had only one single channel. Later, during the heyday of stereo, most of the films began to be shot using it – two channels of audio could already convey part of the three-dimensional picture. However, it is impossible to reproduce the full surround sound using stereo.

Before the advent of a single surround sound standard, there were many different attempts to create a similar technology in different films. Standardization only came with formats from Dolby Laboratories. Prior to the ubiquity of full-fledged surround sound, stereo simulations were often used with Dolby Surround, Dolby Stereo, and Dolby Pro Logic. But true surround sound with independent channels only became possible with the complete transition from analog to digital audio and the advent of the Dolby Digital family of formats.

Dolby Digital
The first version of the old-timer digital surround technology was released back in 1991. The goal of Dolby Digital at the time of its release was to offer surround sound with minimal quality loss for cinemas. Six channels of 5.1 audio were used. The debut film with a soundtrack encoded in this format was released exactly 30 years ago, in 1992.

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The development of digital video and audio technologies has brought Dolby Digital support to home electronics users as well. In this form, the format was first distributed on DVDs, and later on Blu-Ray discs and in online cinemas.

After the release of Dolby Digital, several more improved versions of it saw the light. Dolby Digital Plus has expanded the number of channels and increased the audio bitrate. Following Dolby Digital TrueHD, the MLP algorithm was introduced, which made it possible to switch to lossless audio compression.

For the latest version of Dolby Atmos technology, object-based surround sound has been a major innovation. Its task is to position each sound source as accurately as possible depending on its location.

The differences between different versions of Dolby Digital are in the following table.

Dolby Digital Version Audio channels Max Audio Bitrate Compression
Dolby Digital Up to 6 (diagram 5.1) Up to 640 kbps With losses
Dolby Digital Plus Up to 8 (diagram 7.1) Up to 3 Mbps With losses
Dolby Digital True HD Up to 8 (diagram 7.1)* Up to 18 Mbps Lossless
Dolby Atmos 10 (diagram 9.1)* Limit not mentioned Lossless
* the Dolby Digital True HD standard supports up to 14 channels, but in practice more than 8 channels are not used at the moment. The Dolby Atmos standard supports up to 64 channels, but in practice no more than 10 are used in the same way – standard 7.1, plus 2 ceiling dynamics.

DTS
Work on an alternative to Dolby Digital began after its release on the market, and already in 1993 the first tape with support for DTS Digital Surround technology was presented to the public in cinemas. The number of channels and their scheme were similar to those of the competitor. On DTS discs, Dolby Digital appeared as an audio track a little later, presenting a worthy alternative to it. The spread of high-speed Internet has systematically led to the appearance of DTS tracks in films broadcast by online cinemas.

 

Technology has not stood still, and the first generation of surround audio has been replaced by the second – DTS-HD High Resolution Audio. Similar to the development of Dolby Digital, the second generation of DTS saw an increase in the number of channels and increased audio bitrate. In the subsequent DTS-HD Master Audio, like the competitor, lossless audio compression was implemented, which improved the sound.

The latest and most up-to-date version of DTS:X, like Dolby Atmos, is an object-oriented audio technology. However, the approach to implementing technologies is different. While additional in-ceiling speakers are required for full-fledged Dolby Atmos, DTS:X can also be implemented on more standard and widespread 7.1 surround sound systems.

The differences between the various DTS versions are in the following table.

DTS Version Audio channels Max Audio Bitrate Compression
DTS Digital Surround Up to 6 (diagram 5.1) Up to 1.5 Mbps With losses
DTS-HD High Resolution Audio Up to 8 (diagram 7.1) Up to 6 Mbps With losses
DTS-HD Master Audio Up to 8 (diagram 7.1) Up to 24.5 Mbps Lossless
DTS: X 8 (diagram 7.1)* Limit not mentioned Lossless
* most commonly used. The DTS: X standard itself supports up to 13 channels according to the 11.2 scheme, but in practice this format is implemented only in cinemas, and even then infrequently.

What are the differences and which is better
In fact, there are not so many differences between competing technologies. The advantages of all variations of DTS are a higher bitrate, which in theory should contribute to higher sound quality. But Dolby Laboratories claims that its compression method is more efficient than the competitor’s for the same quality.

However, both technologies are closed, and it is not possible to confirm or disprove this statement without having access to the internal coding scheme. Blind listening to tracks encoded in each format usually does not reveal a clear winner, even on expensive audio equipment. Therefore, it is quite possible to put an end to the question “what is better in quality” – despite the different formats and bitrate, in terms of sound quality, both technologies are comparable.

 

The first implementation of Dolby Digital is a competitor to DTS Digital Surround, Dolby Digital Plus is an opponent of DTS-HD High Resolution Audio. Although the technology is obsolete, for compatibility it is still used as a backup track on Blu-Ray discs for older hardware that does not support uncompressed audio. And also, due to the relatively low bitrate, for use as an audio track in streaming video.

The lossless audio version of Dolby Digital True HD competes with DTS-HD Master Audio. In fact, apart from the newfangled Dolby Atmos and DTS:X, these are the latest technologies in traditional surround sound. But there are more differences between both technologies of object-oriented sound than between their predecessors. Dolby Atmos is focused on the use of two speakers in the ceiling in addition to the traditional 7.1 system. That is, in their absence, you will not hear the sound as it was originally intended. However, many Dolby Atmos-enabled home systems feature upward-firing speakers to bounce sound off the ceiling. This allows you to simulate the operation of the technology in full mode.

In contrast, the object-oriented DTS:X is designed from the ground up for mainstream 7.1 sound systems, so it doesn’t experience these problems. This can be written as a plus for him. Well, all previous traditional surround sound technologies without object orientation simply do not need more than a 7.1 speaker system.

Conclusion
Summing up, one thing can be said: if you want high-quality sound in films, then choose, first of all, good acoustics. And the receiver to it with support for modern surround sound technologies, respectively. This will affect the quality of the surround sound much more than whether the movie soundtrack is in Dolby Digital or DTS.