Q?What? How? All about DVDs & Blu Rays.

Public Specs
On this page, you can download public specifications issued by the Blu-ray Disc Association.


BD-J Baseline Application and Logical Model Definition for BD-ROM (March 2005 – PDF)


A note for operating system developers about implementing “hooks” for Blu-ray Disc in your operating system. This note explains very simple requirements for any operating system to properly recognize and handle Blu-ray Disc. The operating system can recognize Blu-ray Discs by recognizing
(1) That the media is of UDF 2.5 or 2.6 format, and
(2) That the directory name (placed immediately under root directory) is “BDAV” (for BD-RE or BD-R) or “BDMV” (for BD-ROM)

Information on UDF 2.6 and its implementation on Blu-ray Disc can be found at the UDF 2.6 specification http://osta.org/specs/pdf/udf260.pdf [see Section 6.16] .

Information on directory structure of Blu-ray Disc can be found at the White paper: BD-RE logical and AV application format, section 3.1.5 (page 18) and the White paper: BD-ROM logical and AV application format, section 2.3 (page 14) , both available in the Technical section from the menu on this site.


Q?What? How? All about DVDs.

In a nutshell, a DVD stands for Digital Versatile Disc.

It is a new standard format which at first glance has exactly the same appearance as a conventional Compact Disc. Unlike a CD, which has a maximum capacity of 74 minutes worth of digital audio, a DVD (dual-layer, dual-side) can hold a staggering 8 hours of near-broadcast quality video. So it’s just like a laserdisc then? Wrong. Unlike laserdisc, a DVD disc is only 12cm in diameter, and has the massive advantage of being able to hold an entire movie on one side, meaning that you won’t have to get up out of your comfortable chair half way through to turn it over. DVD discs can also have two layers on one side, and two sides. This gives loads of room available for extra features.

The most talked about application for the new standard disc is digital video. The goal of the entertainment and compact disc industries is to put a full length (over 2 hours) MPEG-2 compressed motion picture onto one side of a single CD-ROM. The current density or capacity of today’s CD-ROMs does not allow for this. Currently, only approximately 75 minutes of MPEG-1 compressed full-motion video fit onto one “regular” CD.

The following is a summary of the most common DVD capacities:

– 4.7 GB (Single Layer Single Side)

– 8.5 GB (Dual Layer Single Side)

– 9.4 GB (Single Layer Double Side)

– 17.0 GB (Dual Layer Double Side)

Therefore, the new DVD discs can store from 4.7 GB (single sided, single layer) up to 17.0 GB (double sided, dual layer per side for a total of 4 layers of information). Each layer of data on a DVD disc will allow up to 133 minutes of full motion MPEG-2 video. This amount of playing time will allow 95% of all movies to be contained on one side of a disc. This new disc will also support a variable bit data rate which will increase the quality of digital video playback thanks to a substantial buffer memory. The new DVD movie players are also capable of seamless switching between the two layers of information on each side of the disc.

Cutting a full 4.7GB single layer of a DVD disc today at the fastest encoding speeds available takes over 90 minutes. As the mastering software and hardware are improved, this time will decrease. Remember, a full DVD disc could contain up to four mastered layers of information. A mastering cut must be done for each layer of information put onto a DVD disc. Therefore, as the number of layers of information increases, so will the mastering cost and time.

Q?What types of video and audio compressions do we offer?

.avi – Windows Media by Microsoft Windows:
Windows Media is a multimedia framework for media creation and distribution for Microsoft Windows. The files played (WAM) need windows media player 6 or 7. High resolution video with CD quality sound, can play MPEG1 MPEG 2 MPEG 3 and MPEG4.  More Info.

.mov – QuickTime by Apple:
QuickTime is a multimedia technology with a built-in media player, QuickTime lets you view internet video, HD movie trailers, and personal media in a wide range of file. More Info.

.ra (RealAudio) or .rm (RealMedia) – Real Player by Real:
RealMedia is any media that is specifically created to be streamed from RealServer. RealAudio is an audio only streaming format. RealVideo is a video streaming format that includes both audio and video. RealServer is the software that streams media (RealAudio and RealVideo) over a network. The client receives the media in real-time, and does not have to wait for the clip to download. More Info.

.MPEG 1 .MPEG 2 .MPEG 3 and .MPEG 4 by MPEG:
MPEG (pronounced M-peg), which stands for Moving Picture Experts Group, is the name of a family of standards used for coding audio-visual information (e.g., movies, video, music) in a digital compressed format. The major advantage of MPEG compared to other video and audio coding formats is that MPEG files are much smaller for the same quality. This is because MPEG uses very sophisticated compression techniques. More Info.

 .AIFF Audio Interchange File Format by Apple Computer based on Electronic Arts’ Interchange File Format.
AIFF files generally end with a .AIF or .IEF extension. It is an audio file format standard used for storing sound data for personal computers and other electronic audio devices. The AIFF format does not support data compression, so AIFF files tend to be large. However, there is another format called AIFF-Compressed (AIFF-C or AIFC) that supports compression ratios as high as 6:1. More Info.


Q?What Is Video Compression?

Video takes up a lot of space. Uncompressed footage from a camcorder takes up about 17MB per second of video. Because it takes up so much space, video must be compressed before it is put on the web. “Compressed” just means that the information is packed into a smaller space. There are two kinds of compression: lossy and lossless.

Lossy compression means that the compressed file has less data in it than the original file. In some cases this translates to lower quality files, because information has been “lost,” hence the name. However, you can lose a relatively large amount of data before you start to notice a difference.

Lossless compression is exactly what it sounds like, compression where none of the information is lost. This is not nearly as useful because files often end up being the same size as they were before compression.

Q?What High Definition video format does N-Media provide?

We provide the following formats:

Resolution Aspect ratio Interlaced frames per second (fps) Progressive fps
1280 x 720 16:9 23.976, 24, 29.97, 30, 59.94, 60
1920 x 1080 16:9 25 (50i), 29.97 (59.94i), 30 (60i) 23.976, 24, 29.97, 30

Frame Sizes
HD source formats are almost always either 1920 x 1080 resolution or 1280 x 720 resolution. Note that a substantial difference exists between the 1080 and 720 standards. The 1920 x 1080 resolution contains 2.25 times more pixels than 1280 x 720 resolution at the same frame rate. This difference substantially increases requirements for processing 1080 content in terms of encoding time, decoding speed, and storage.

Q?What terrestrial HDTV transmission systems are available?
Main characteristics of three DTTV systems
Source coding
Video Main Profile syntax of ISO/IEC 13818-2 (MPEG-2 – Video)
Audio ATSC Standard A/52 (Dolby AC-3) ISO/IEC 13818-2 (MPEG-2 – Layer II Audio) and Dolby AC-3 ISO/IEC 13818-7 (MPEG-2 – AAC Audio)
Transmission system
Channel coding
Outer coding R-S (207, 187, t = 10) R-S (204, 188, t = 8)
Outer interleaver 52 R-S block convolutional (I=12, M=17, J=1) 12 R-S block
Inner coding rate 2/3 Trellis code PCC: rate 1/2, 2/3, 3/4, 5/6, 7/8; constraint length = 7, Polynomials (octal) = 171, 133
Inner interleaver 12 to 1 Trellis code bit-wise, frequency, selectable time
Data randomization 16-bit PRBS
Modulation 8-VSB and 16-VSB COFDM
Hierarchical modulation: multi-resolution constellation (16QAM and 64QAM)
Guard interval: 1/32, 1/16, 1/8 & 1/4 of OFDM symbol
Two modes: 2k and 8k FFT
BST-COFDM with 13 frequency segments
Hierarchical modulation: choice of three different modulations on each segment
Guard interval: 1/32, 1/16, 1/8 & 1/4 of OFDM symbol
Three modes: 2k, 4k and 8k FFT