WireItRight
home theatre installation and pre-wire services
What is HDTV?
High-definition television (HDTV)
Advantages of HDTV
Recording and compression
Blue-Ray
HD DVD
Dolby
What is
Blu Ray ?
The name Blu-ray Disc is derived from the blue-violet laser used to read and write this type of disc. Because of its shorter wavelength (405 nm), substantially more data can be stored on a Blu-ray Disc than on the DVD format, which uses a red, 650 nm laser. A single layer Blu-ray Disc can store 25 GB, over 5 times the size of a single layer DVD at 4.7GB. A dual layer Blu-ray Disc can store 50 GB, almost 6 times the size of a dual layer DVD at 8.5GB.
Blu-ray Disc is similar to PDD, another optical disc format developed by Sony (which has been available since 2004) but offering higher data transfer speeds. PDD was not intended for home video use and was aimed at business data archiving and backup.
Blu-ray Disc is currently in a "format war" with rival format HD DVD please click here">HD DVD
Technical specifications
About 9 hours of high-definition (HD) video can be stored on a 50 GB disc.
About 23 hours of standard-definition (SD) video can be stored on a 50 GB disc.
On average, a single-layer disc can hold a High Definition feature of 135 minutes using MPEG-2, with additional room for 2 hours of bonus material in standard definition quality. A dual layer disc will extend this number up to 3 hours in HD quality and 9 hours of SD bonus material.
Blu-ray Disc / HD DVD comparison
The primary rival to Blu-ray Disc is HD DVD, championed by Toshiba, NEC Corporation, Microsoft, and Intel. HD DVD has a lower disc capacity per layer (15 GB vs 25 GB). However the majority of Blu-ray titles released before 2007 are in the 25 GB single layer format while almost all HD DVD movies are in the 30 GB dual layer format. [27] The first 50GB release for Blu-Ray was not made until October 2006. The Blu-ray Disc version of the Adam Sandler movie Click was released on October 10, 2006 as the first ever dual-layer release. So far in 2007 approx half of the new releases for Blu-ray movies were released in 25GB Discs with the other half being released in 50GB dual layer format. Sony's goal is to use 50 GB dual-layer discs to store up to nine hours of HD video content. Alternatively, studios releasing movies on Blu-ray Disc can choose to use VC-1 or H.264/AVC instead of MPEG-2 as an alternative way to put four hours of high-definition content on a (single layer) BD.
In terms of audio/video compression, Blu-ray Disc and HD DVD are similar on the surface: both support MPEG-2, VC-1, and H.264 for video compression, and Dolby Digital (AC-3), PCM, and DTS for audio compression. The first generation of Blu-ray Disc movies released used MPEG-2 (the standard currently used in DVDs, although encoded at a much higher video resolution and a much higher bit rate than those used on conventional DVDs), while initial HD DVDs releases used the VC-1 codec. Due to greater total disc capacity, the Blu-ray Disc producers may choose in the future to utilize a higher maximum video bit rate, as well as potentially higher average bit rates. In terms of audio, there are some differences. Blu-ray Disc allows conventional AC-3 audiotracks at 640 kbit/s, which is higher than HD DVD's maximum of 504 kbit/s. Nevertheless, Dolby Digital Plus support is mandatory for standalone HD DVD players at a maximum of 3 Mbit/s, while optional for BD players with support at a bitrate of 1.736 Mbit/s.[28]
Both HD DVD and Blu-ray Disc support the 24p (traditional movie) frame rate, but technical implementations of this mode are different between the formats. Blu-ray Disc supports 24p with its native timing, while HD DVD uses 60i timing for 24p (encoded progressively, replacing missing fields with "repeat field flags"). Decoders can ignore the “flags” to output 24p.[29] There is no impact on picture resolution or storage space as a result of this, as the HD DVD format uses the same video information—it simply adds notational overhead.
Currently, five Hollywood studios exclusively support Blu-ray Disc: Columbia Pictures, MGM, Disney, Lionsgate and 20th Century Fox (Columbia Pictures and MGM are owned by Sony Pictures). Four Hollywood studios support both Blu-ray and HD DVD: Paramount Pictures, DreamWorks, Warner Bros. and New Line Cinema (the former two are owned by Viacom, and the latter two by Time Warner). Two Hollywood studios exclusively support HD DVD: Universal Studios and the Weinstein Company.
