With the continued popularity of HDTV (High Definition Television) broadcasting in North America and Japan, and the promotion of High Definition (High Definition) brought by the 2006 Football World Cup in Europe and other parts of the world, we (DVD Forum) We believe that now is the time to introduce HD DVD corresponding to high definition. Because as screen sizes increase, the shortcomings of standard definition (Standard Definition) video have been exposed, and things that were acceptable before seem to suddenly become intolerable. A consumer study shows that people's perception of image quality is directly related to viewing distance and screen size. The evaluation of standard definition video quality has tended to be "poor" when the screen size exceeds 36 inches; while the image quality of HDTV is still considered "good" even when the screen size reaches or exceeds 60 inches. of. As the price of large-screen TVs gradually falls into an acceptable range, more and more large-screen TVs have entered the homes of ordinary consumers. HD DVD, as a packaged form of media, can exactly meet the public's demand for high-quality HDTV content. In addition, the popularity of broadband and interactive television has also placed higher expectations on packaged media in terms of enhanced interactivity. (Annotation: Compared with traditional DVD, HD DVD has indeed greatly improved in terms of interactivity!)

DVD Forum - a group that has been committed to formulating DVD industry standards since the birth of the DVD format. Organization - has worked extensively with equipment manufacturers and major film producers to adopt a new optical disc (media and format) that perfectly meets the needs of the consumer home entertainment market and PC computer applications. This article provides a summary of the main technical features of HD DVD; for further information, please visit the DVD Forum website: www.dvdforum.org.

HD DVD still uses optical disc media with a diameter of 12 cm and a thickness of 1.2 mm, which is the same as current DVD discs. However, a single-sided, double-layer HD DVD can hold up to 8 hours of high-definition video! Enhanced interactivity, multimedia capabilities (annotation: the integration of video, audio, images, animations, fonts, text and other media forms), secure AACS content protection and the capacity of a single disc to load an average of 10,000 MP3 songs, all of this It means that HD DVD can truly meet the needs of today's consumer market. For the IT industry, a double-sided HD DVD-R disc can hold up to 30 GB of data. How exciting! For the optical disc copying industry, you can also take reassurance here: DVDs with traditional specifications can be produced on future HD DVD production lines!

Although current DVD discs are read with red lasers, this type of DVD can still be played normally in the new generation of HD DVD systems. The secret behind HD DVD's higher capacity is that it uses a blue-violet laser with a shorter wavelength. (Annotation: The shorter the wavelength, the smaller the granularity and the higher the accuracy of data storage/reading. In this case, it is not surprising that a disc can store more data.) This blue-violet light is almost close to reaches the limit of the visible spectrum. Some wavelengths of visible light are given in the figure below. In order to give everyone a perceptual understanding of the magnitude of these wavelengths, we give a reference: the average thickness of a human hair is about 100,000 nanometers.

Looking back when the DVD format was first born in Japan in 1996, the MPEG-2 video compression bit rate was specified to be approximately 8 Mbps. Codec efficiency has improved dramatically since then, but some projectors still insist that high-definition MPEG-2 images require a maximum bit rate of 19.3 Mbps. Some video enthusiasts even believe that in order to maximize high-definition quality, the bit rate needs to reach 25 Mbps. Fortunately, MPEG-2 is no longer our only choice. In addition to MPEG-2, we can also choose more advanced compression algorithms, such as AVC (also known as MPEG-4), or VC-1 ( That is, Microsoft's Windows Media), these encoders can reduce the data bit rate of high-definition content to 8 Mbps or even lower.

HD DVD can distribute high-definition content at any of the above bitrates without sacrificing any functionality. Take the movie "Gone with the Wind" (English title: Gone with the Wind) as an example. It is 233 minutes long and can be loaded on an HD DVD disc with a bit rate of 25 Mbps and MPEG-2 HL compression configuration. The new compression strategy allows an hour or more of value-added content to be released alongside the longest movies if larger than recommended HDTV satellite transmission bandwidths are used. It can be seen that HD DVD has been designed from the beginning to meet the actual needs of content owners and their users.

2 Overview of HD DVD technology

From a technical perspective, HD DVD evolved based on the traditional DVD format. For video compression strategies, we now have three options, including: MPEG-2 HL (current DVDs use MPEG-2 ML, MPEG-2 HL uses a higher resolution than MPEG-2 ML), AVC (that is, MPEG-2 ML) 4. Under the premise that the image quality is equivalent, the bit rate can be much lower than other compression strategies) and VC-1 (that is, Microsoft's Windows Media 9). By the way, the file structure of HD DVD discs adopts the UDF 2.5 standard.

The new HD DVD format also offers an olive branch to those music enthusiasts. Dolby Digital Plus (lossy) and DTS (lossy) merge the current Dolby Digital (AC-3) and MPEG, and are required to be supported in HD DVD. The two-channel LPCM currently supported by DVD must also be supported by HD DVD. At the same time, HD DVD must also support the two-channel MLP format (the MLP format has been adopted by DVD-Audio). DTS HD is an alternative audio format for lossless compression.

The following table lists some major differences in technical parameters between traditional DVD-Video specifications and HD DVD-Video specifications.

HD DVD-Video DVD-Video

Disc type HD DVD ROM 3x speed DVD ROM DVD ROM

Laser wavelength 405 nm 650 nm 650 nm

Digital aperture 0.65 0.6 0.6

Storage capacity (ROM) Dual layer 30 GB 8.5 GB 8.5 GB

Single layer 15 GB 4.7 GB 4.7 GB

Disc playback time (example) 8 hours of HD video with double layer, 2.6 hours of HD video with 3.5 hours of SD video

4 hours with single layer

(compressed by AVC, bit rate 8 Mbps) 1.3 hours

(Compressed with AVC, bit rate 8 Mbps) 2 hours

(Compressed with MPEG-2 VBR, average bit rate 5 Mbps)

Video Codec AVC MPEG-4 / VC-1 / MPEG-2 MPEG-2

Audio Codec Lossless (required) LPCM / MLP (True HD) [Binaural] LPCM [Binaural]

Lossless (optional) DTS HD (lossless)

Lossy (required) Dolby Digital Plus / DTS

Dolby Digital / MPEG Audio Dolby Digital

MPEG Audio (Europe)

Maximum data transfer rate 36.55 Mbps 11.08 Mbps

Content protection Advanced Access Content System

Video system 1920×1080 50/60 HDTV 720×480 or 720×576 50/60 SDTV

The current DVD disc is a A widely accepted and reliable data storage and circulation medium. A 1.2 mm thick optical disc is divided into three layers, with the data layer in the middle and the upper and lower layers being transparent plastic protective layers. This format has proven to be very reliable and has therefore been adopted by HD DVD. In other words, HD DVD uses the same physical specifications as traditional DVD discs.

The result of this is that the replacement of old and new has become a relatively simple matter for both equipment manufacturers and optical disc copyers. Tests have shown that converting an HD DVD production line to traditional DVD duplication production can be completed in less than 5 minutes. No other platter architecture offers such revolutionary compatibility, or a smarter solution!

Using a blue-violet laser and a lens with a 0.65 digital aperture, the available spot diameter on an HD DVD disc will be reduced compared to the current ordinary DVD using red light. This directly results in a corresponding increase in theoretical data storage density. Coupled with the higher rotation speed, the maximum data transfer rate is more than three times that of ordinary DVDs, reaching 36.55 Mbps.

HD DVD supports formats ranging from the lowest CIF (320×240), to various subsets recognized by SDTV, to the highest HDTV (1920×1080). In addition, video streams on the Internet can also be synchronized to previously pre-recorded content on the disc.

Note: For convenience, in the following illustrations we use multiple laser beams and show two different ways of the beams coming from above and below the disc. But in fact, there is only one laser beam in the HD DVD drive, and it only enters from below the disc.

Although the data density has been greatly improved in HD DVD, its structure is still very similar to that of currently used DVDs. There are two types of discs: single-sided and double-sided. In theory, a single disc can provide 60 GB of storage space.

The following introduces two optional disc structure solutions.

One is called "Combination Format". This disc has a traditional DVD-9 on one side and a dual-layer HD DVD on the other side. This provides retailers with an easier way to sell products (Annotation: one disc can satisfy the needs of both ordinary DVD and HD DVD customers), and provides consumers with future-proof film and television products (Annotation: even if you only have ordinary DVDs now) A DVD player can also play this kind of disc if you buy it; when you have an HD DVD player in the future, you only need to turn the disc over and you can easily enjoy the content of HD DVD). There is another technical solution called "Twin Format". This format has been adopted by the DVD Forum and is included as an optional format in the HD DVD-ROM v1.2 specification. During the reading process of this kind of optical disc, the layer close to the laser probe can reflect red light, but is transparent to blue-violet light (Annotation: The blue-violet laser beam can completely penetrate this layer). If this disc structure is used, traditional DVD players can only "see" ordinary DVD-5 content, while HD DVD players using Blu-ray can penetrate the first layer and read the content hidden in the first layer. HD DVD content behind.

Author: Lu Qiming 2006-11-3 08:09 Reply to this statement

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3 Overview of HD DVD technology

Let’s briefly summarize the HD DVD disc family: HD DVD-ROM: 12 cm in diameter, 1.2mm thick, single or dual-layer construction, holding up to 15 GB in single layer and 30 GB in dual layer. The double-sided one can expand the single- and double-layer capacity to 30 GB and 60 GB respectively. 3x speed DVD-ROM: The traditional DVD format can also release high data rate HD DVD content, which requires the use of AVC or VC-1 encoding to reduce the bit rate, so that it can be stored on an ordinary DVD-ROM Nearly 135 minutes of HD DVD content. 8cm Mini HD DVD: Single layer capacity is 4.7 GB, double layer capacity is up to 9.4 GB. Standards for double-sided platters are under development. HD DVD-R: A write-once disc type with a single-sided capacity of 15 GB and a maximum of 30 GB. HD DVD-RW: A disc type that can be erased multiple times, with a single-sided capacity of 20 GB and a maximum of 40 GB.

AACS (Advanced Content Access Control System) is the product of collaboration between major film producers, consumer electronics manufacturers and the IT industry. Its founders include Toshiba, Microsoft, IBM and Warner Brothers. Implementing the AACS solution on the HD DVD format to protect digital media distribution and consumer access control for next-generation digital devices.

AACS is a replacement for the CSS encryption system (Content Scrambling System) currently used on DVDs, and its encryption algorithm strength has been upgraded to 128 bits. AACS solves the legacy issues of CSS in content protection, providing more secure protection of HD content and SD content on HD DVD discs.

AACS not only prohibits illegal copying, but also provides management of content transmission to licensed devices (such as home media servers). It is suitable for stand-alone, networked, and portable terminal devices, and integrates Content protection policies to prevent non-digital copies.

The content owner (Content Owner) provides the completed HD DVD data to the authorized copyer (Licensored Replicator), including the rules for the use of these contents.

The AACS Licensing Authority provides the copyist with a set of keys and a cryptographically signed content certificate, along with data used to block devices and content that have had their authorization revoked.

Copiers can then create HD DVD discs containing encrypted content and AACS data and eventually market them to consumers.

The AACS certification agency also provides device keys and public keys to authorized player (Licensored Player) manufacturers, which allows the players they produce to play legal discs normally. Content owners can also arrange to open additional business channels by themselves, such as providing additional content (such as movie highlights) through service providers, optional synchronized languages ????and subtitles, or supporting other interactive business connections through the Internet ,etc.

The structure of HD DVD-Video includes an extended version of the traditional DVD video object (VOB) and video navigation (Navigation). Unique to HD DVD-Video is Advanced Object, which includes images and text with enhanced functions. For example, users can choose the font and position of subtitles, which will greatly benefit viewers with hearing or visual impairments. Benefit.

Advanced Navigation makes it possible to obtain and play image, video or audio content in real time and synchronize with the content being viewed locally without interrupting the main video and audio. If an HD DVD player supports IPv4, it can also play streaming media.

Leading companies in the industry have begun to provide a variety of tools for creating HD DVDs. Professionals and enthusiasts who want to create advanced HD DVD projects have the opportunity to flex their muscles!