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Blu-ray

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Article Genealogy
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Blu-ray
Blu-ray
source
NameBlu-ray
CaptionA Blu-ray Disc and its case
TypeOptical disc
Capacity25 GB (single-layer), 50 GB (dual-layer), Up to 128 GB (BDXL)
Read405 nm laser diode
OwnerBlu-ray Disc Association
UseData storage, high-definition video (1080p), 3D video (1080p), 4K resolution (Ultra HD Blu-ray)
Extended fromDVD

Blu-ray. It is an optical disc format designed to supersede the DVD and capable of storing several hours of high-definition video. The format was developed by the Blu-ray Disc Association, a consortium of leading consumer electronics, personal computer, and media manufacturers, and emerged victorious in a format war with HD DVD. Its primary application is for the distribution of feature films, television series, and video games, offering significantly greater storage capacity and video quality than its predecessors.

History

The development of the format was initiated by Sony and Philips in the early 2000s, building upon research from their earlier Universal Media Disc project. A major milestone was the public demonstration of a prototype at the CEATEC exhibition in 2003. The ensuing format war with Toshiba's HD DVD was a defining commercial and technological battle, heavily influenced by the support of major Hollywood studios like Warner Bros., Disney, and 20th Century Fox. The war effectively ended in 2008 when Warner Bros. announced it would exclusively support the format, followed by Toshiba's concession. Subsequent developments included the introduction of 3D support and the Ultra HD Blu-ray standard for 4K resolution content.

Technical specifications

The format utilizes a blue-violet laser diode with a wavelength of 405 nanometers, a shorter wavelength than the red laser used for DVD and CD. This allows for a smaller laser spot size, enabling data to be packed more densely. A single-layer disc holds 25 gigabytes (GB), while a dual-layer disc holds 50 GB. For data archiving, the BDXL specification supports 100 GB and 128 GB discs. Video is typically encoded using the H.264/MPEG-4 AVC or HEVC codecs, supporting resolutions up to 1080p and, in the case of Ultra HD Blu-ray, 4K resolution with HDR. The maximum data transfer rate is 54 Mbit/s.

Disc structure

A standard disc is 120 millimeters in diameter and 1.2 millimeters thick, identical to a DVD or CD. It consists of a substrate, a recording layer, a reflective layer, and a protective coating. The data layer is situated closer to the surface of the disc compared to a DVD, which necessitated the development of a hard coating to resist scratches. This structure is read from the bottom (label side) by the laser passing through the transparent substrate. The BD-R and BD-RE variants denote recordable and rewritable versions, respectively, used for data storage and personal video recording.

Variants and compatibility

Several physical and application-specific variants exist. The Mini Blu-ray Disc is an 8 cm diameter version. Ultra HD Blu-ray is a separate specification supporting 4K resolution, HDR, and Dolby Atmos audio. While standard players cannot play Ultra HD Blu-ray discs, most Ultra HD Blu-ray players are backward compatible with standard discs and DVDs. The Blu-ray 3D specification allows for stereoscopic 3D content. There are also three regional codes (A, B, C), but many discs are released as region-free. Compatibility with PlayStation 3, PlayStation 4, and PlayStation 5 consoles has been a significant driver of adoption.

Applications and market impact

The primary application is the distribution of high-definition video for home video and broadcasting. It is the dominant medium for feature film sales and rentals, having completely replaced DVD for high-definition releases. The PlayStation 3 was a crucial early adopter, integrating a player and helping to win the format war. The format is also used for data storage and archiving, particularly in professional and corporate environments via BD-R discs. Its market impact includes revitalizing the home video market with premium quality, enabling the widespread consumer adoption of 1080p and later 4K resolution content, and serving as a physical counterpart to streaming media services like Netflix.