Dolby technology has been synonymous with movies and home cinema for decades
Dolby was founded by American Ray Dolby in London in 1965. In its early years, Dolby was best known for its Noise Reduction system, which reduced background hiss in audio tape recordings.
However, in 1975 it launched Dolby Stereo, which cleverly encoded four-channel audio into a stereo soundtrack. The success of Star Wars made Dolby Stereo synonymous with film sound, and the company hasn’t looked back since.
From the advent of Dolby Digital in 1992 to the arrival of Dolby Atmos in 2012, the company has pioneered movie audio in the cinema and at home.
When it comes to Dolby in the home, there are a number of multi-channel formats that span both the history of the company, and the evolution of film surround sound.
This is the latest iteration of the original Dolby Stereo surround sound format first introduced on consumer VCRs back in 1982. Dolby Pro Logic still uses the same basic approach to decode four channels of film sound from a stereo track.
The extra front centre and rear surround channels in the 4.0 soundtrack are encoded within the stereo carrier using an active matrix that essentially hides the additional channels by placing them out of phase with the front left and right channels.
While an efficient method of delivering surround sound, this audio format has two limitations: the rear channel is mono; and there’s no dedicated channel for low frequency effects (LFE). Dolby Pro Logic is rarely used these days, unless you’re watching legacy content encoded in the format.
This all-digital format was first introduced in cinemas with the release of Batman Returns in 1992, while the consumer version was launched in 1995 with the LaserDisc release of Clear and Present Danger. Dolby Digital was chosen as the default audio format for DVD when it arrived in 1997, and remains the dominant method of delivering surround sound to this day.
The major benefit of Dolby Digital is that it offers a full 5.1-channel experience, with stereo surrounds, and a dedicated LFE channel (that’s the ‘.1’). Every channel is discreet, rather than using an active matrix like Dolby Pro Logic, although to achieve this a compression algorithm is applied, which is why Dolby Digital is often referred to as a ‘lossy’ audio format.
The release of The Phantom Menace in 1999 saw the arrival of Dolby Digital EX, which added an extra back surround channel to create a 6.1 soundtrack. In a tip of the hat to Dolby’s past, this used an active matrix to encode the additional channel. The ubiquitous nature of Dolby Digital means that almost every consumer electronics device supports it in one form or another.
This enhanced version of Dolby Digital was launched in 2006, and uses a higher bit-rate to allow for less compression and the delivery of more discrete channels. The flexibility and increased efficiency of Dolby Digital Plus has resulted in the format being the default choice for all the major video streaming services, and even allows for the delivery of Dolby Atmos. As with Dolby Digital, there is widespread support for the format on almost every consumer electronics device.
This lossless audio format was also first introduced in 2006, and is capable of delivering a maximum of 16 discrete channels without resorting to compression. This possible thanks to the adoption of Meridian Lossless Packing (MLP), and Dolby TrueHD is able to deliver 5.1 channels at a resolution of 24-bit/192kHz, or 7.1 channels at 24-bit/96kHz.
The lossless nature of Dolby TrueHD results in a superior sonic experience, but also requires the increased storage capacity of Blu-rays and 4K discs. The format was never widely adopted on Blu-ray, with the studios favouring DTS-HD Master Audio instead, but since Dolby TrueHD is now used to deliver Dolby Atmos on 4K Ultra HD Blu-ray, it’s the most common choice on that format.
This object-based audio format was first introduced into cinemas in 2012 with the release of Pixar’s Brave. It was launched as a consumer format with the Blu-ray release of Transformers: Age of Extinction in 2014, and offers increased immersion using an expanded array of speakers that include overhead channels to produce a three-dimensional soundstage.
In the home, Dolby uses a spatially-coded sub-stream to embed Atmos into a Dolby TrueHD or Dolby Digital Plus soundtrack. This makes the format backwards compatible, but also ensures the sub-stream is an efficient representation of the full, original object-based mix. The channels are all discrete rather than matrix-encoded, with spatially-encoded digital panning metadata.
The consumer version of Dolby Atmos can support up to 35 channels, and uses the spatially-encoded object audio sub-stream to actively mix the audio presentation to match the installed speaker configuration. Dolby Atmos supports a maximum of 128 audio objects composed of 118 dynamic sound effects and a 9.1-channel base layer.
The result is an incredible sonic delivery that moves audio objects seamlessly within an acoustic bubble, creating a more lifelike aural experience. This hemisphere of sound results is a heightened realism that makes any film a more enjoyable and immersive experience. Dolby Atmos is the main audio format on 4K Ultra HD Blu-ray, and is also used by all the major video streamers.
Thousands of songs are available in Dolby Atmos spatial audio mixes, available from streaming services such as Apple Music and TIDAL - and that number's only going one way. And from smartphones and wireless speakers to soundbars and a huge, dedicated Dolby Atmos concert venue in Las Vegas, the number of ways to consume Dolby Atmos music is growing inexorably too.
As with movies, music mastered in Dolby Atmos has a far more precise sensation of space and sound placement than stereo or surround-sound, and the experience is more immersive as a result. And the fact that the Atmos spatial audio effect can be introduced either at the recording stage or in post-production means any recording is fair game for change.
This is the name given to Dolby’s upmixing algorithm, which applies cutting-edge processing to ‘upscale’ any non-immersive soundtrack for greater envelopment, allowing you to take advantage of all the speakers in your system.
It’s amazing how good a simple 5.1 mix can sound when Dolby Surround is applied, and you’ll almost believe you’re listening to a native immersive audio track. Whether its a TV broadcast, streaming service, DVD, or Blu-ray, Dolby Surround can give the audio a super-sonic upgrade.
Dolby has been included on physical media for decades, going all the way back to VHS in the 1980s. So there’s a healthy catalogue of film titles that use the format for their soundtracks.
While it’s unlikely you’re still using a VCR these days, you’ll almost certainly have DVDs with Dolby Digital soundtracks in your collection, and a number of Blu-rays that use Dolby TrueHD – although DTS-HD Master Audio is the track of choice for most releases on this disc format.
However, when it comes to 4K Ultra HD Blu-ray and video streaming, Dolby Atmos completely dominates, with most discs and all the streaming services using the format to deliver object-based audio.
Dolby has been incredibly successful at incorporating its technologies into products from every major consumer electronics brand. Whether it’s a TV, soundbar, AV receiver or high-end AV processor it will almost certainly sport some version of Dolby decoding. So if you want to enjoy the sonic benefits of Dolby’s many audio formats, just look for the iconic double-D logo.
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