computer science

Blu-ray

Blu-ray is a computer science topic covered in the lgStudy science library. This page brings together a partial reference excerpt, illustrations, worked examples, real-world applications and a short study plan, so you can understand Blu-ray rather than just read about it. In short: Blu-ray (Blu-ray Disc or BD) is a digital optical disc data storage format designed to supersede the DVD format. It was invented and developed in the early-mid 2000s and released worldwide on June 20, 2006, capable of storing several hours of high-definition video (HDTV 720p and 1080p).

Key takeaways

Blu-ray belongs to computer science; place it in that map before memorising details.
Learn the definition first, then one example that makes the definition concrete.
Connect Blu-ray to a quantity you can measure, compute or draw — that is where exam questions come from.
Reproduce the core statement of Blu-ray from memory before moving on to harder problems.

Reference excerpt

Blu-ray (Blu-ray Disc or BD) is a digital optical disc data storage format designed to supersede the DVD format. It was invented and developed in the early-mid 2000s and released worldwide on June 20, 2006, capable of storing several hours of high-definition video (HDTV 720p and 1080p). The main application of Blu-ray is as a medium for video material such as feature films and for the physical distribution of video games for the PlayStation 3, PlayStation 4, PlayStation 5, Xbox One, and Xbox Series X. The name refers to the blue laser used to read the disc, which allows information to be stored at a greater density than is possible with the longer-wavelength red laser used for DVDs, resulting in an increased capacity. The polycarbonate disc is 12 centimetres (4+3⁄4 inches) in diameter and 1.2 millimetres (1⁄16 inch) thick, the same size as DVDs and CDs. Conventional (or "pre-BDXL") Blu-ray discs contain 25 GB per layer, with dual-layer discs (50 GB) being the industry standard for feature-length video discs. Triple-layer discs (100 GB) and quadruple-layer discs (128 GB) are available for BDXL re-writer drives. While the DVD-Video specification has a maximum resolution of 480p (NTSC, 720 × 480 pixels) or 576p (PAL, 720 × 576 pixels), the initial specification for storing movies on Blu-ray discs defined a maximum resolution of 1080p (1920 × 1080 pixels) at up to 24 progressive or 29.97 interlaced frames per second. Revisions to the specification allowed newer Blu-ray players to support videos with a resolution of 1440 × 1080 pixels, with Ultra HD Blu-ray players extending the maximum resolution to 4K (3840 × 2160 pixels) and progressive frame rates up to 60 frames per second. Aside from an 8K resolution (7680 × 4320 pixels) Blu-ray format exclusive to Japan, videos with non-standard resolutions must use letterboxing to conform to a resolution supported by the Blu-ray specification. Besides these hardware specifications, Blu-ray is associated with a set of multimedia formats. Given that Blu-ray discs can contain ordinary computer files, there is no fixed limit as to which resolution of video can be stored when not conforming to the official specifications. The BD format was developed by the Blu-ray Disc Association, a group representing makers of consumer electronics, computer hardware, and motion pictures. Sony unveiled the first Blu-ray Disc prototypes in October 2000, and the first prototype player was released in Japan in April 2003. Afterward, it continued to be developed until its official worldwide release on June 20, 2006, beginning the high-definition optical disc format war, where Blu-ray Disc competed with the HD DVD format. Toshiba, the main company supporting HD DVD, discontinued the format in February 2008, and later released its own Blu-ray Disc player in late 2009. According to Media Research, high-definition software sales in the United States were slower in the first two years than DVD software sales. Blu-ray's competition includes video on demand (VOD) and DVD.

History

Early history The information density of the DVD format was limited by the wavelength of the laser diodes used. Following protracted development, blue laser diodes operating at 405 nanometers became available on a production basis, allowing for the development of a denser storage format that could hold higher-definition media, with prototype discs made with diodes at a slightly longer wavelength of 407 nanometers in October 1998. Sony commenced two projects in collaboration with Panasonic, Philips, and TDK, applying the new diodes: UDO (Ultra Density Optical), and DVR Blue (together with Pioneer), a format of rewritable discs that would eventually become Blu-ray Disc (more specifically, BD-RE). The core technologies of the formats are similar. The first DVR Blue prototypes were unveiled by Sony at the CEATEC exhibition in October 2000. A trademark for the "Blue Disc" logo was filed on February 9, 2001. On February 19, 2002, the project was officially announced as Blu-ray Disc, and Blu-ray Disc Founders was founded by the nine initial members. The first consumer device arrived in stores on April 10, 2003: the Sony BDZ-S77, a US$3,800 BD-RE recorder that was made available only in Japan. However, there was no standard for pre-recorded video, and no movies were released for this player. Hollywood studios insisted that players be equipped with digital rights management before they would release movies for the new format, and they wanted a new DRM system that would protect more against unauthorized copying than the failed Content Scramble System (CSS) used on DVDs. On October 4, 2004, the name Blu-ray Disc Founders was officially changed to the Blu-ray Disc Association (BDA), and 20th Century Fox joined the BDA's Board of Directors. The Blu-ray Disc physical specifications were completed in 2004. The recording layer on which the data is stored lies under a 0.1 mm protective layer and on top of a 1.1 mm substrate made of polycarbonate plastic, compared to 0.6 mm on either side on DVDs. Sony also announced in April 2004 a version using paper as the substrate developed with Toppan Printing, with up to 25 GB storage. In January 2005, TDK announced that it had developed an ultra-hard yet very thin polymer coating called Durabis for Blu-ray Discs; this was a significant technical advance because a far tougher protection was desired in the consumer market to protect bare discs against scratching and damage compared to DVD, given that Blu-ray Discs technically required a much thinner layer for the denser and higher-frequency blue laser. Cartridges, originally used for scratch protection, were no longer necessary and were scrapped. The BD-ROM specifications were finalized in early 2006. Advanced Access Content System Licensing Administrator (AACS LA), a consortium founded in 2004, had been developing the DRM platform that could be used to distribute movies to consumers while preventing copying. However, the final AACS standard was delayed, and then delayed again when an important member of the Blu-ray Disc group voiced concerns. At the request of the initial hardware manufacturers, including Toshiba, Pioneer, and Samsung, an interim standard was published that did not include some features, such as managed copy, which would have let end users create copies limited to personal use.

… excerpt ends here. Continue reading the full article.

Illustrations

Blu-ray: Front (label side) of an experimental 200 GB rewritable Blu-ray Disc — Front (label side) of an experimental 200 GB rewritable Blu-ray Disc

Worked examples

Example 1 — a first encounter with Blu-ray

Start with the simplest possible case. Write down what Blu-ray claims or describes in one sentence, then invent the smallest concrete situation in which that sentence is true. In computer science, the smallest case is usually a single object, a single equation or a single measurement. Check that every symbol or term in your sentence has a meaning in that case.

Example 2 — changing one variable

Take the situation from Example 1 and change exactly one quantity: double it, halve it, or set it to zero. Predict what should happen to Blu-ray before you calculate. Comparing your prediction with the result is the fastest way to find out whether you understand the idea or only the words.

Example 3 — an exam-style question

Typical questions about Blu-ray ask you to (a) state it precisely, (b) apply it to given data, and (c) explain a limitation. Practise writing all three answers in under five minutes; the third part is what separates a full-mark answer from an average one.

Applications of Blu-ray

In research: Blu-ray appears in computer science research whenever the underlying quantities have to be modelled precisely. Papers usually cite it as a starting assumption and then explore where it breaks down.
In technology and industry: Engineering practice reuses Blu-ray in design rules, simulations and safety margins. Knowing the idea lets you read a specification sheet and understand why the numbers look the way they do.
In the classroom: Blu-ray is common in secondary-school and first-year university syllabi. It links to neighbouring topics 2006 in technology, 21st-century inventions, Audio storage, so understanding it makes those chapters shorter.
In everyday life: Look for Blu-ray outside the textbook — in sport, cooking, traffic, electronics or the sky above you. An example you found yourself is remembered far longer than one you were given.

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How to study Blu-ray in 20 minutes

Read the reference excerpt below once, without taking notes.
Close the page and write down what Blu-ray means in your own words.
Compare your version with the excerpt and mark what you missed.
Work through the three examples above with pen and paper.
Explain Blu-ray out loud to somebody else — or to Teacher Smith in the lgStudy chat.

Frequently asked questions

What is Blu-ray in simple terms?

Why does Blu-ray matter?

Because it connects several computer science ideas at once: it gives you a definition you can apply, a quantity you can calculate, and a way to check whether a result is plausible.

How should I study Blu-ray?

Read the excerpt, restate it from memory, then work through the examples and applications listed on this page. The five-step study plan above takes about twenty minutes.

What does this page cover?

It gives you a compact reference excerpt plus original lgStudy explanations, examples, applications and study material on Blu-ray.