Audio and video codecs for dummies: Deciphering home theaters


Have you ever bought a new TV, home theater system or AV receiver and you're like a kid with new shoes? Then you pick up the technical specifications book and your soul falls at your feet. You have in front of you an alphabet soup full of audio and video codec acronyms that you just can't get your head around. You look to heaven and entrust yourself to divine providence. And no wonder: video definitions (4K, 1080p, HDR) or surround sound formats (Dolby, DTS, Atmos, Auro 3D…) are a pain for most mortals. And it is important to know their differences and the use we can make of our new devices to get the most out of them. That's why we've prepared this help manual for dummies with all the specifications you need to know when operating or purchasing a home theater system.

What is Home Theater Surround Sound?

In 1982 Dolby Laboratories introduced Dolby Surroundto the market. It allowed a surround sound to be emitted through a process known as Matrix decoding. Matrix? Easy tiger. This term has nothing to do with the red or blue pill.

So what's with the matrix? Refers to the decoding of different audio signals within a stereo source. This technology was the basis for many surround sound formats to see the light of day and today we have many surround sound options for use with a home theater system. The following are the main ones in chronological order:

Dolby Pro Logic

Dolby Pro Logic logo

Dolby used the Matrix system with Pro Logic to achieve surround sound by decoding separate signals from the left and right channels of home stereos. This made it possible to reproduce sound with two extra channels with the old VHS video tapes. The surround sound of the Pro Logic format had limited bandwidth and each surround speaker reproduced the same sound.

What is Dolby Digital 5.1? What about DTS format?

surround sound

With the appearance of laser discs (LD), both the amount of sound information in the recordings and their quality increased. Taking advantage of this new technology, Dolby created the AC-3 format, now known as Dolby Digital. I'm sure you've heard of it. This format improved the performance of Pro Logic by allowing the use of stereo surround speakers that provided better bandwidth. It also added a dedicated channel for bass frequencies (the “.1” of 5.1 home cinema systems) driven by a subwoofer.

This format was the one used by most home theater systems for a long time, even when DVDs started to appear in 1997. Today, the Dolby Digital 5.1 format remains one of the most popular surround sound codecs. This is the first format to provide independent audio information for each speaker, a pattern followed by the most popular surround sound codecs later on.

Dolby dominated the surround sound market until DTS (Digital Theater Systems) appeared in 1993. Did you know that the first time this format appeared in theaters was with the movie Jurassic Park? Later this technology started to be integrated into DVDs as well. The DTS format uses a higher bandwidth than Dolby Digital, thus providing more audio information. The difference in quality between DTS and Dolby Digital, however, is hardly noticeable.

Dolby Digital Plus, Dolby TrueHD, DTS-HD and DTS-Master HD

7.1 home theater systems

Home Cinema 7.1 systems were introduced with the advent of DVD-HD and Blu-ray discs. With these came new Dolby and DTS formats that can take advantage of the larger memory capacity of these discs.
Dolby offers two formats designed to work with Home Cinema 7.1: Dolby Digital Plus, which works with compressed audio files that take up less space; and Dolby TruHD, an uncompressed version. DTS also has two options: DTS-HD, which works with compressed files; and Dolby TrueHD, for uncompressed files.

Not all Blu-ray discs offer 7.1 surround sound mixes, as they are very heavy. On the other hand, a 5.1 mix can be used by a 7.1 home theater system through the AV receiver, although the two extra surround speakers will not output a different sound.

Pro Logic II, Pro Logic IIx and Pro Logic IIz

If you have or have been looking to purchase a new AV receiver, you will find that they have several Pro Logic format options: Pro Logic II, Pro Logic IIx and Pro Logic IIz.

Pro Logic II can create surround sound for 5.1 Home Cinema systems from a stereo source. It is perfect for use with movies or TV shows that feature a stereo mix.
Pro Logic IIx is a format that can take 5.1 surround sound mixes and expand them to 6.1 or 7.1 systems. On the other hand, the Pro Logic IIz allows the addition of two speakers that are placed above the center speaker and between the front side speakers, providing a greater depth of surround sound compared to the other versions.

Object-based surround sound codecs

The latest and most complex surround sound codecs(Dolby Atmos, DTS:X and Auro-3D) generate a new sense of three-dimensional sound not present in older formats. They are known as “object-based” systems because the mixture of these formats allows the representation of sound objects in a 3D space, where each object, or packet of information, contains independent audio information.

What is Dolby Atmos?

Dolby Atmos

Dolby Atmos is the most popular of these new formats today. Atmos can process up to 128 different audio objects in a scene. Atmos surround sound, for example, can have the sound of an explosion emitted from different points, achieving a unique 3D effect by using additional ceiling speakers. This codec began to be used in theaters with Pixar's Brave and has been available for quality AV receivers since 2015.

What is the DTS:X codec?

surround sound

DTS also has its own version of an object-based codec: DTS:X. While Dolby Atmos supports 128 objects per scene, DTS:X has no limits. It is more flexible than Atmos, as it does not require overhead speakers, and can support up to 32 surround speakers in a home theater system. It is newer and less popular than Atmos, but the best AV receiver companies are integrating this format into their new equipment.


home theater system

Auro-3D is not as well known as Dolby Atmos or DTS:X but has been on the market longer. This technology has been in theaters since 2006, but only recently companies like Marantz and Denon are offering this format for their full-featured AV receivers. Auro-3D does not technically work with object-based systems, but performs very similarly. Provides good surround sound, although additional speakers are required. It is used with large Home Cinema systems, such as 9.1 or 11.1.

Video in home theater systems

If we acquire a quality TV or AV receiver, there are several aspects, as far as video is concerned, that we have to take into account so that our purchase can be adequate for several years. Capabilities for 4K resolution, HDCP 2.2, HDMI 2.0 and HDR are the main ones to look for. The following is a brief explanation of what these acronyms refer to:

What is 4K (Ultra HD)?

4K home theater systems

Full HD resolution (1920p x 1080p) has been the most widely used high-definition format for several years, but new TV sets and AV receivers are now capable of playing higher quality movies: 4K or Ultra HD.

The terms 4K and Ultra HD are interchangeable. Both report a resolution of 3,840 x 2,160 pixels.. This is slightly less than that of 4K digital cinemas (4,096 x 2,160 pixels) but is a fourfold increase in HD definition.

Today there are few programs or movies available to enjoy this definition, but we believe that 4K will undoubtedly be the high definition standard within a few years. If you are thinking of purchasing a new TV or AV receiver, we recommend that you have it included.

What is HDMI 2.0?

HDMI 2.0 ports are a specification linked to 4K resolution that we must take into account for our home theater systems. 4K resolution requires more bandwidth to transmit than HD resolution (it contains much more information). To optimally support the new resolution, the HDMI 2.0 port has been created. It allows transferring 2160p videos at up to 60 frames per second. The above HDMI ports can transmit 4K video but not 60 frames per second. The higher transfer rate of the HDMI 2.0 port is also necessary for playing 4K movies or series from services such as Netflix.

What is HDCP 2.2?

HDCP 2.2(High-Bandwidth Digital Content) refers to a new content protection standard available on the new Blu-ray Discs. HDCP 2.2 can prevent new 4K movies from being captured by an illegal recorder by generating encrypted keys between the TV and the Blu-ray player. In order to enjoy a movie with this type of encryption, it is necessary that our TV sets and AV receivers support HDCP 2.2.


Dolby Vision

Finally, we would like to mention HDR(High Dynamic Range). HDR is a video format that is already available in the latest high-end TVs. It has the same resolution as 4K video, but adds additional color and brightness data. An HDR video, in formats such as HDR10 or Dolby Vision, is more eye-catching and sharper than normal high-definition videos. To enjoy HDR video you need your TV and AV receiver to be compatible with this technology.

In this article we briefly explain the most important specifications you should consider if you want to buy a new AV receiver or TV. If you want to get information about the best Home Cinema systems, or any quality sound equipment, we recommend you to visit our culturasonora page.

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