PureVideo HD Glossary

As you read about HD DVD and Blu-ray movie playback on PCs, you'll come across many acronyms describing new technologies and standards. We've provided a glossary of some of the most common terms.

The Advanced Access Content System (AACS) is a copy protection standard used with HD DVD and Blu-ray discs.

Advanced Encryption Standard (AES) is an encryption standard used worldwide that has a fixed block size of 128 bits and a key size of 128, 192 or 256 bits.

Bitstream Processing
Variable-length decoding of entropy coding schemes such as CABAC, and CAVLC.

Blu-ray Disc
Blu-ray is a new high-definition video disc standard that offers up to six times the visual detail of traditional DVDs. Blu-ray discs can hold up to 25GB on a single-layer disc and 50GB on a dual-layer disc. This extra capacity combined with the use of advanced video and audio codecs offers consumers an amazing HD experience.

Context Adaptive Binary Arithmetic Coding (CABAC) is a lossless entropy coding system used in H.264 video compression. Decoding it is extremely costly and inefficient to implement as a pure software implementation both in terms of processing cycles and system power.

CAVLC is a five-letter abbreviation standing for context-adaptive variable-length coding. CAVLC is a form of entropy coding used in H.264/AVC/MPEG-4 video/audio encoding and is an inherently lossless compression technique. Thus a file can be encoded this way without causing any quality loss.

Technique used to minimize the block boundary artifacts: in-loop algorithm is used in H.264, and both in-loop and out-of-loop algorithms are used in VC-1.

Digital Visual Interface (DVI) is a video interface standard designed to maximize the visual quality of digital display devices such as flat panel LCD computer displays and digital projectors.

H.264, also known as MPEG-4 AVC (Advanced Video Coding), is a video compression standard that offers significantly greater compression than its predecessors. It is one of the 3 CODECs that can be used by the Hollywood studios when authoring Blu-ray and HD DVD movies.

High-Bandwidth Digital Content Protection (HDCP) is a form of copy protection technology designed to prevent transmission of non-encrypted high-definition content as it travels across DVI or HDMI digital connections.

HD DVD is a new high definition video disc standard that delivers up to six times the image quality of standard DVD movies. HD DVD promises a major advancement over video discs in the same way that HDTVs deliver superior image detail over standard TV.

High Definition Multimedia Interface (HDMI) is a new interface standard for consumer electronics devices that combines HDCP-protected digital video and audio into a single, consumer-friendly connector.

Image constraint token (ICT) is a software-based flag within Advanced Access Copy System (AACS) that would automatically reduce the quality of the image produced by a high-definition video disc player to 540 lines of vertical resolution, when the player is connected to an analog display.

Inverse Discrete Cosine Transform
Inversing the Discrete Cosine Transformations used in video compression to encode the differences between two frames.

Motion Compensation
Reconstruction of sections of predicted frames by using reference frames and motion vectors that describe where and how much the section has moved from its position in the reference frame.

VC-1 is a video codec based on Windows Media Video Version 9. Both HD DVD and Blu-ray Disc have adopted
VC-1 as a codec, meaning all video playback devices will be capable of decoding and playing video-content compressed using VC-1. VC-1 minimizes the complexity of decoding high-definition content through improved intermediate stage processing and more robust transforms. As a result, VC-1 decodes HD video twice as fast as H.264, while offering two to three times better compression than MPEG-2.