DVD Monthly

Blu-ray To Z

Tuesday, August 5th, 2008

THE COMPLETE GUIDE TO BLU-RAY AND HD.

Following the success of the article in the magazine, we’ve decided to reprint the text of our complete guide to everything you need to know about Blu-ray and HD right here. So if you’ve ever wondered what the difference was between HD and Full HD, or puzzled over exactly what interlacing and progressive scan are (and whether you should care), then wonder no more. We’re going A-Z to cover everything you might need to know about the world of Blu-ray, HD and all the technologies surrounding it. This is the only reference guide you need to decode high-def.

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1080i, 1080p, 720p, 576i
See ‘Screen Resolution’.

16:9
See ‘Aspect Ratio’.

24fps/24p
A normal UK TV picture runs at 25 frames per second (fps), while film is shot at 24fps, resulting in UK DVDs running 4% faster than the same film at the cinema. A 24fps HD player coupled to a 24fps compatible TV will run a Blu-ray at the same speed it was filmed at, resulting in a smoother picture that’s truer to the original.

36Mbits/s
36 megabits per second – the standard rate the laser reads information from a Blu-ray disc, although some players and drives can read information faster.

405nm Laser
405 nanometre laser – the wavelength of the blue-violet laser used to read information on Blu-ray discs. This compares with a 650nm laser for DVD and 780nm for CDs. Generally, the smaller the wavelength of the laser, the more information can be packed on a disc. One nanometre equals a billionth of a metre.

4:3
See ‘Aspect Ratio’.

50Hz/100Hz
How often a TV updates the picture. A normal interlaced picture running at 25fps updates the picture 50 times a second (i.e. 50Hz). Better quality TVs run at 100Hz, and it is normally these that offer 24fps Blu-ray playback.

AACS
Advanced Access Content System – A system of copyright protection which is used on Blu-ray discs, designed to make them far more difficult for pirates to hack.

Anamorphic Widescreen
The type of encoding used on most DVDs, where the picture is encoded as a 4:3 image, then stretched vertically to 16:9 for playback. Although not perfect, it’s the best type of encoding for 16:9 widescreen TVs. Blu-ray is non-anamorphic widescreen, as the picture is encoded at 16:9 resolution.

Artefacts
Unwanted objects that appear in a TV picture, often during fast moving action. These can appear as a result of problems with signal reception, the picture processing unit in the TV, the quality of the player being used or the encoding of the content on the disc.

Aspect Ratio
This is the ratio between the height of the picture and its width. Old style TV was four times as wide as it was tall, which was expressed as 4:3 (or 1.33:1). Newer widescreen TVs are 16:9 (aka 1.78:1). Modern films are generally shot to be shown at either 1.85:1 or 2.35:1. It’s important to note that even on a widescreen TV, movies encoded for 2.35:1 presentation will still have black bars at the top and bottom of the screen.

AVC
Advanced Video Coding – aka MPEG-4 AVC or H.264/AVC. An encoding standard designed to offer high-quality HD picture at lower bandwidths than previously possible. It is used to encode many Blu-ray movies as well as online HD content.

AVCREC
A lower capacity variant of Blu-ray, designed to store BD compatible content on a normal DVD disc (HD DVD has a similar variant called HD REC). It’s mainly being promoted for camcorders and bespoke cost-sensitive projects.

BBC HD
Auntie Beeb’s hi-def channel, which broadcasts HD content in the evenings. Currently only available on Sky, Virgin Media and Freesat.

BD+
Like AACS, this is part of Blu-ray copy protection system, and was cited by some studios as the reason they preferred Blu-ray to HD DVD. It’s designed so that a disc can create a ‘virtual machine’ on a player, to check it hasn’t been tampered with or is otherwise vulnerable.

BD9/BD5
Like AVCREC, this is a format that allows Blu-ray content to be stored on normal DVDs.

BD/DVD Combo
A format proposed by JVC that would encrypt both Blu-ray and DVD information on a disc.

BD-Java/BD-J
A Blu-ray specific version of the Java platform. This allows advanced interactive bonus content to appear on discs, such as network access, picture in picture features and more sophisticated games. Few early Blu-ray players were capable of accessing this content, but all players released since last November should be able to.

BD-Live
The name given to Blu-ray content that can only be accessed by going online. Early players generally don’t have network connectivity, but many newer players do.

BD Recordable
As with CD and DVD, these are recordable Blu-ray formats split into two types. BD-R discs can be recorded onto once, while BD-RE disc can be erased and re-recorded onto.

BD-ROM
Another name for the Blu-ray disc format, normally used in connection with the technical specifications of the format.

BD-ROM Mark
A small piece of data stored differently from normal Blu-ray data. The BD-ROM Mark is designed to make it more difficult to pirate discs, and supposedly renders it impossible to reproduce them on a large scale, unless you have the licensed software to create the mark.

Bitrate
The number of bits of data that can be read and decrypted in a given amount of time, normally expressed as megabits per sec (Mbits/s). The standard for basic DVD is 10.55Mbits/s, while 36Mbits/s is the standard for Blu-ray.

Blu-ray Disc
The official name of Sony’s HD disc format.

Blu-ray Disc Association
A group of manufacturers and content providers who banded together to standardise and promote the uptake of the Blu-ray format.

Blue-Violet Laser
This is the type of laser used in Blu-ray players to read information off discs. Older formats such as CD and DVD use red laser, while the blue-violet laser is preferred for higher density formats, because it has a smaller wavelength, so more information can be packed on a disc.

Bonus View
Sometimes used to describe picture-in-picture content encoded on Blu-ray discs.

Camcorder
Many modern camcorders now offer HD recording, some up to 1080p quality.

Cartridges
When Blu-ray was first announced, the discs had to be enclosed in special cartridges, due to the fact the information layer had to be so close to the surface that they could very be easily damaged. This problem was overcome by the development of tough scratchproof resins, which protect the surface of the disc. (See also Durabis).

Casino Royale
Currently the biggest selling Blu-ray title ever, and the first to sell more than 100,000 copies.

Channel 4 HD
The first UK TV channel to offer an HD simulcast of its standard definition sibling. Available on Sky and Freesat.

Chroma/Chrominance
The information carried in a video signal about colour.

Coax Digital
The preferred cable for sending DVD surround sound information to a receiver. While not compatible with new HD audio formats, most Blu-ray players still offer a coax out, which will transmit standard 5.1 channel audio to a receiver by downmixing any compatible tracks on the disc.

Codec
Short for coder-decoder. These are the file formats that content is encoded into for storage and later decoded from for playback. There are numerous different codecs used for HD content. (See also ‘AVC’, ‘MPEG-2’, ‘MPEG-4’, ‘Divx’ and ‘VC-1’).

Component Video
This is the act of breaking a video into its component parts to make it easier to transmit through a cable without losing signal clarity. SCART and S-video are analogue component video formats, however what most stores sell as component video is YPbPr cables, which splits the signal into three parts, and as a digital signal can offer up to 1080p video (although most TVs only accept up to 1080i from YPbPr inputs).

Compression
In order to fit a large amount of information into a set amount of space, the data sometimes needs to be compressed (this is what the various codecs and audio formats do). Generally the more compressed the data, the worse the picture or audio quality, however advanced codecs can offer very high quality despite the amount of compression.

Contrast Ratio
On a TV, this is the difference between the brightest whites it’s capable of displaying and the darkest blacks. Therefore a TV claiming a 10,000:1 contrast ratio should have whites 10,000 times brighter than its darkest blacks. Generally the higher the number the better.

CRT
Cathode Ray Tube – this is the old type of TV, which is now being replaced by LCD and plasma.

Deinterlacing
The process of converting interlaced video into a progressive scan signal. (See all ‘Interlaced’ and ‘Progressive Scan’).

DivX
A codec which allows high quality video to be compressed into a comparatively small file size. It is most commonly associated with video on the Internet.

Dolby and DTS
Companies that creates audio format used in both cinemas and for home entertainment.

Audio Format	No. Of Channels	Type of format
	Up to 5.1	Lossy – Compresses the audio signal to allow surround sound at low bandwidths (up to 640kbits/s)
	Up to 6.1	Lossy – Similar to Dolby Digital but adds a matrix-encoded centre rear channel.
	Up to 7.1	Lossy – A new HD format used on Blu-rays, designed to be backwards compatible with Dolby Digital, but allowing data rates up to 6Mbits/s.
	Up to 7.1	Lossless – This HD format used on Blu-rays has no compression for a purer sound. It needs an HDMI interface and compatible receiver. It could have more channels but is limited to 7.1 for Blu-ray.
	Up to 5.1	Lossy – similar to Dolby Digital, but generally considered a superior format due to less compression.
	Up to 6.1	Lossy – DTS’ take on the concept behind Dolby Digital EX
	Up to 7.1	Lossy – Allows audio bitrates up to 6Mbits/s, and is designed for use where there isn’t space for a full lossless DTS track.
	Up to 7.1	Lossless – An adaptable format which can offer lossless sound at up to 24.5 Mbits/s on Blu-ray, but can downmix for lower bandwidths and smaller channel configurations.
LPCM	Up to 7.1	Lossless – Linear Pulse Code Modulation. While the bandwidth needed for this pure sound lossless format is generally too high for DVD, it’s sometimes included on Blu-rays.

Downscaling
This is when a high grade video or audio signal is converted for use with equipment only capable of receiving a lower grade signal. E.g. An HD picture being downscaled for viewing on a standard definition TV.

DRM
Digital Rights Management – A generic name for technologies designed to make it more difficult for unauthorised people to use copyrighted materials in non-approved way (e.g. film piracy). 

Dual-Layer Blu-ray
A Blu-ray disc that offers 50Gb of storage, arranged in two layers.

Durabis
The name of the first hard polymer coating that TDK developed, which enabled Blu-rays to be durable enough not to need to be enclosed in cartridges.

DVB-T/DVB-S
Digital Video Broadcasting-Terrestrial/Satellite. The standard Europe has adopted for digital TV, which includes the possibility for HD channels.

DVD
The most popular home entertainment format today, but which does not offer an HD picture.

DVD Forum
The organisation of manufacturers and content providers behind DVD and HD DVD.

D-VHS
Digital-VHS (initially Data VHS). A digital version of the VHS format, originally launched in the late 90s as a competitor to DVD. Although not popular, it’s pretty much a tape version of a hard drive, and so can actually record and playback HD pictures, with a storage capacity comparable to Blu-ray.

DVI
Digital Video Interface. Initially the cable of choice for HD, this has since been superseded by HDMI (partly because HDMI can carry audio as well, while DVI is just video). However many TVs still have a DVI input, and it’s very common in PCs.

DVR-Blue
An early name for Blu-ray, when it was at the prototype stage.

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And for all the latest news, reviews, features and info about Blu-ray and everything HD, make sure you get the latest copy of DVD Monthly, which includes the 32 page HD Monthly mini-magazine. It’s available at all good new agents or by clicking here.