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Blu-ray Disc

Blu-ray disc format is a next-generation optical diameter of 12 cm (same as CD and DVD) for high-definition video and high data storage density. Its storage capacity reaches about 25 GB per layer.

Blu-ray disc also known as Blu-ray or BD, is a form of optical disc format (digital data storage, consisting of a circular disc in which the information is encrypted, is saved and stored, making microscopic grooves with a laser on one of the flats that comprise it), next-generation 12 cm in diameter (same as CD and DVD) for high-definition video and high data storage density. Its storage capacity reaches 25 GB per layer, while Sony and Panasonic have developed a new evaluation index (i-MLSE) that would expand by 33% the amount of stored data, from 25 to 33.4 GB per layer.


The Blu-ray was developed jointly by a group of technology companies called Blu-Ray Disc Association (BDA), led by Sony and Philips. This uses a blue laser with a wavelength of 405 nanometers (one millionth of a meter), unlike the red laser used in DVD players, which has a wavelength of 650 nanometers. This, together with other technological advances, can store substantially more information than the DVD disc the same size and appearance.

Storage capacity and speed

A layer Blu-ray disk can hold around 25 GB or about 6 hours of HD video plus audio, is also on the market dual-layer disc that can hold about 50 GB. The data transfer rate is 36 Mbit / s (54 Mbps for BD-ROM), but they are already developing prototypes 2x transfer rate (double, 72 Mbit per second).

Region Codes

Each Blu-ray disc contains one or more region codes, which denote the place or areas of the world to which each distribution is addressed. At times, the region codes are called zones. The specifications of each team indicate which player can play zone.

In theory, this allows the movie studios to control various aspects of the launch, which includes the content, date and price, based on the acquisition by region. In practice, several players let you play any disc, or can be modified for that purpose. Unlike the data encryption, region codes allow regional blockade, which originated in the gaming industry.

Region codeArea
A Includes most North, Central and South American and Southeast Asian countries plus the Republic of China (Taiwan), Japan, Hong Kong, Macau and Korea.
B Includes most European countries, African and Southwest Asian countries plus Australia and New Zealand.
Today, many players fail multiregion unlock the regional block and the ETS through the identification and selection of the region supported by the Blu-Ray, or allowing the user to select a particular region. Others simply bypass the check of the region altogether. Some manufacturers of players now freely supply information on how to disable regional lockout, and in some recent models, appears to have been disabled by default.

Codecs and BD-J

The Blu-ray supports the same file systems as its predecessors, such as the UDF and ISO 9660. With its storage capacity, the video is high definition and up to 8 audio channels. Supported compression formats MPEG-2, MPEG-4 and VC-1. MPEG-4 AVC and SMPTE VC-1 compression algorithms implemented more advanced that can offer high quality (at a similar level).

The MPEG-2 is maintained for backward compatibility, it is almost obsolete (compared to the others), but still has been used to encode most of the first films that have come out on Blu-Ray. This is because the MPEG-4 AVC has high requirements, resource consumption and high encoding time.

The SMPTE VC-1 belongs to a consortium of companies dominated by Microsoft. This makes the degree of implementation of the codec is uneven, favoring the HD DVD. Despite this, Microsoft has made a remarkable effort conducting seminars for companies in the sector, which has increased the acceptance of the VC-1.

New is the inclusion of the Java platform in the standard of films recorded to Blu-ray. This platform, which has been called BD-J (Blu-ray Disc Java), allows more freedom to developers to include content in the film. Not only the ability to display a menu at any time during playback, or the ability to embed applications on the disk. It also projects the ability to download additional content from the Internet to disk. For example, certain language subtitles, special content, cut scenes, among others. On the other hand, there are detractors who say it is unnecessarily complex and royalties for its use are excessive.

The audio compression codecs supported by Blu-ray are LPCM (uncompressed), DTS, Dolby Digital, Dolby True HD and DTS-HD Master Audio (there are more, but these are the main ones). The first three are kept backward with respect to the DVD as the video. The latter two represent a great improvement, allowing lossless compression (in the following table you can see how they maintain the same sample rate with high transfer rate).

Anti-copy protections

Blu-ray systems incorporate five anticopy: AACS, BD + Rom-Mark, SPDG and ICT.


The AACS is an improvement over the DVD CSS, due to the initiative of Disney, Sony, Microsoft, IBM, Intel, Panasonic, Toshiba and Warner Brothers. Its main function is to control content distribution. One consequence is that this method creates a copy of blacklisted writers. This system provides a key for each model of recorder. This makes tracking which keys are decrypted and what recorders allow copies, the consequence would be to revoke the key and not included in these players, ensuring the incompatibility with the recorder. This possibility has generated great controversy, as if carried out, users who never gave illegal use would see your recorder is useless. For now announced that only focus on industrial players are used to bulk copy. The system, in theory, could allow even provide each individual player a set of keys so you could revoke the keys to the system by preventing the duplication only within it.

BD + and ROM-Mark

Blu-ray standard have in their exclusive system called BD + copy. This system allows you to dynamically change the keys for cryptographic protection of the original BD. If one of these keys is discovered, manufacturers have only to change the password, so that new units of the product can not be pirated key to that discovery. At the request of HP, was added the possibility that a user can buy these keys to perform a limited number of copies of the disc you bought, removing copyright users to use this format. The BD + can also check if the hardware has been modified and prevent reproduction.

It was also agreed that the BD with a digital watermark. Under the name of Rom-Mark, this technology will be present at all the original disks and requires a special hardware component degree in specific writers to insert the watermark in the copy. All DVD Blu-ray to look for that brand. Thus, the ADB aims to slow bulk copy of this record.


SPDG stands for Self-Protecting Digital Content is a program that includes the reader of the Blu-Ray an operating system whose function is to prevent the recorder to duplicate the films that are being played. According to its creators, the SPDG provides added security in case the AACS protection system is overcome by the recorders.

ICT stands for Image Constraint Token is a signal that prevents high-definition content on media traveling unencrypted and therefore susceptible to being copied. In practice, what it does is limit the output video to 960x540 resolution if the cable from the player to the TV is analog, but support high definition television. The ICT is not mandatory, each company decides freely whether or not to add their titles.
For example, Warner is in favor of its use, while Fox is against.

HD Ready, Full HD and HDMI

If we want high-definition resolution of 1920x1080 in progressive mode devices must be those marked under the logo of Full-HD, or 1080p.

The Blu-ray technology enables higher transfer for the video. This difference has not been used in many cases due to several factors. First, the rate is variable and depends on the company you choose which to use, not necessarily the maximum. Second, the rate may have other uses besides video transmission. Finally, influences the codec used, the companies used in their first releases the MPEG-2 that made not only the quality is lower than expected in a high-definition playback, but was below its competitor HD DVD from the beginning mainly encoded VC-1. The audio transfer rate is also higher in Blu-ray than HD DVD.

To understand the differences between Blu-ray and HD DVD have to realize that while the first is a new technology that seek to increase performance, the second DVD you want better support without substantially increasing costs. The HD DVD therefore has enough going for it that a few changes to the DVD production equipment while in Blu-ray has been necessary to install expensive new production equipment.

As for the hybrid securities (DVD and HD) seems best Blu-ray system that allows each format to assign a layer without changing face. HD DVD is mapped by side with what is necessary to change it. In addition the hybrid support is limited to two formats (both sides) while the disc can have as many as layers (although so far no sense to add other formats is possible to do so in the future).


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