A Blu-ray recorder refers to a recorder based on the Blu-ray DVD technology standard.

[Edit this paragraph] Overview of the two major international DVD standards:

1. HD DVD standard Toshiba leads the way, HD-DVD uses 8/15 encoding signal processing, single-sided single-layer capacity Up to 17~27GB. The main selling point is that manufacturing costs are lower than Blu-ray.

2. Blu-ray DVD standard Sony is the leader, and the Blu-ray standard (Blu-ray DVD) represented by Panasonic, Hitachi, Samsung, Philips, etc. has a single-sided single-layer capacity of 23.3/25/27GB, and a single-sided double-layer 50GB .

[Edit this paragraph] Analysis of Blu-ray and HD DVD technology

In the 1980s, Sony and Philips*** jointly advocated the CD specification standard and used it for Record data information. With the needs of music and image recording, CDs with a standard storage capacity of 640MB can no longer meet people's requirements, and larger-capacity optical storage technology has emerged. This is DVD (DVD) with a capacity of 4.7GB (single-sided and single-layer). Digital Video Universal Disc).

Initially, DVD used the MPEG2 compression standard, which could store broadcast-quality movies. However, as HDTV heats up, DVD is no longer capable. According to the current DVD standard, a DVD disc can hold less than one hour of HDTV program time, which cannot fully record a movie. Moreover, the resolution of HDTV programs is much higher than the existing DVD specifications. The former has 720p (1280×720), 1080i/p (1920×1080) and other formats, while the latter only supports 480p (640×480).

There is another reason why the market needs new DVD specifications, and that is to protect intellectual property rights. Currently, pirated DVDs are flooding in, and major video companies are looking forward to the next generation of DVD specifications to bring more effective anti-piracy features to their DVDs. Based on the above situation, the International DVD Forum has successively adopted two new DVD standards - Blu-ray and HD DVD.

Blu-ray or HD DVD, which one is better?

1. Blu-ray technology characteristics

Blu-Ray is produced by 9 electronics companies including Sony, Panasonic, Hitachi, Pioneer, Sharp, LG Electronics, Samsung, Thomson and Philips. The giant launched a new generation of DVD disc standards on February 19, 2002. One of the biggest advantages of Blu-ray discs is their large capacity, currently up to 23.3GB/25GB/27GB for a single side and single layer. Calculated according to current standards, a 27GB Blu-ray disc can store 2 hours of high-definition TV programs, or more than 13 hours of standard-definition TV programs. The same as existing CDs or DVDs, the diameter of Blu-ray disc is 120mm and the thickness is also 1.2mm.

Blu-ray technology belongs to Phase Change Disk technology. Phase Change Disk uses laser to make the recording medium reversible phase change structure between crystalline and amorphous states to record and erase information. . When writing data, the purpose of heating the recording medium with a focused laser beam is to change the crystal state of the phase-change recording medium, using the crystalline state and the amorphous state to distinguish 0 and 1; when reading data, the crystallized state and the amorphous state have different reflectivities. This feature is used to detect 0 and 1 signals.

In terms of disc structure, Blu-ray discs completely break away from the "0.6mm 0.6mm" design of DVD discs and adopt a new "1.1mm disc base 0.1mm protective layer" structure, combined with high NA (numerical aperture) ) value ensures extremely low disc tilt error. The 0.1mm protective layer structure has a large tolerance for tilt angle and does not require a tilt servo, thus reducing read and write abnormalities caused by tilt during the rotation of the disc, making data reading easier. However, as the cover layer becomes thinner, the damage and stain resistance of the optical disc decreases. In order to protect the surface of the optical disc, a disc box must be installed outside the optical disc.

This not only increases the production cost of Blu-ray discs, but also makes the development of thin drives more difficult.

Comparison of DVD and Blu-ray laser light sources

Comparison of DVD and Blu-ray laser light sources

The difference in NA value and recording point between CD, DVD and Blu-ray

In order to increase storage capacity, Blu-ray technology uses a blue laser with a wavelength of 405nm and an aperture of NA of 0.85 to replace the 650nm red laser and aperture of NA of 0.6 used in DVD, which greatly reduces the reading time. The size of the focus point diameter of the laser light used to record data also reduces the size of the recording point used to record data on the data recording layer of the optical disc. On Blu-ray Discs, the distance between data recording tracks is reduced from DVD's 0.74μm to 0.32μm, which means that more data recording tracks can be accommodated on the same disc area.

In terms of storage method, Blu-ray still uses the in-groove recording method, but in terms of addressing, it uses an improved wobble addressing method based on STW MSK technology. The basic unit of address information in Blu-ray technology is called a pre-groove address (ADIP). One unit stores 1 bit of address information, and each ADIP consists of 56 swings in the slot. The 56 swings can be divided into areas modulated by MSK (minimum frequency shift keying) and areas modulated by STW (sawtooth swing). The former uses MSK modulation to determine the position in the swing groove, while the latter uses the STW method. The "sawtooth" direction is used to determine "0" and "1" information.

The unique security system is another distinguishing feature of Blu-ray. Blu-ray uses 128bit AES encryption key. AES can update the anti-theft encryption key every 6KB of data. The new anti-theft encryption key technology is important because anti-theft encryption systems (DeCSS) and other DVD copy machines can easily break the unique anti-theft encryption key that protects standard DVD discs. If Anti-Theft Lock invades a Blu-ray disc, it can only steal 6KB of data.

2. HD DVD technical characteristics

On August 29, 2002, Toshiba and NEC submitted another new DVD disc specification to the DVD Forum - AOD (Advanced Optical Disc, Advanced Optical Disc) ), AOD was later renamed HD DVD.

From a technical point of view, although HD DVD also uses 405nm blue-violet laser, it pays more attention to compatibility with the DVD standard. For example, HD DVD uses an objective lens with a numerical aperture of 0.65 to read/write data, and the thickness of the protective substrate is also 0.6mm.

The capacity of Blu-ray DVD can reach five times that of DVD

In addition, HD DVD also increases the number of tracks by shortening the spacing of data recording tracks, thereby increasing the recording density. In terms of storage method, HD DVD uses the same Land-Groove recording method as DVD-RAM, which is different from Blu-ray's in-slot recording method. The advantage of the latter is that it can more easily realize read-only discs and removable disks. The compatibility between recording discs simplifies the optical head and eliminates switching between banks, but it faces a capacity limit of 27GB; the bank recording method can reach a single-sided capacity of 30GB.

Because it still uses a 0.65 aperture value and a 0.6mm protective substrate, the capacity of HD DVD is smaller than that of Blu-ray: 15GB for single-sided single layer and 30GB for single-sided double layer. However, the HD camp believes that with the help of high-efficiency new encoding technologies (such as H.264/MPEG-4 AVC and WMV9), 15GB capacity is sufficient, because if the encoding speed is 15Mbps, a 15GB disc can store 132 minutes of video , and single-sided double-layer HD DVD discs can record more data.

The biggest advantage of HD DVD technology compared to Blu-ray is that it is compatible with existing DVD standards. Manufacturers can put traditional red-ray DVD production equipment into the production of HDDVD. The manufacturer only modifies the laser head and control chip, which greatly reduces the cost. Reduce the modification cost of transitioning from existing DVD to HD DVD.

In terms of encryption technology, HD DVD will use Advanced Access Content System (AACS), which is an upgraded version of CSS. Compared with CSS encryption technology, when DVD players are produced, AACS will give each machine a set of 128bit device keys (Device Keys), which can be used in a single device or shared with other multi-tasking devices. MKB (Media Key Block) is an anti-theft code legally authorized by AACS. This set of anti-theft codes can decode and restore the content. If the anti-theft code is destroyed, MKB will regenerate immediately and destroy the original anti-theft code to protect itself. Therefore, the anti-theft code Cannot be restored. However, this design has a flaw, that is, if the DVD player's anti-theft code is damaged and detected, unless the ROM (read-only firmware) is upgraded, the DVD player will be locked to protect itself and cannot be started to avoid being copied.

Development prospects of the new generation of DVD standards

Technically, Blu-ray and HD DVD standards have their own advantages and disadvantages. Blu-ray is a more "radical" technology that can enable the storage capacity of optical discs to reach 50GB. The above is to meet the needs of high-definition video in the future, but this technical specification is incompatible with existing DVDs, and production equipment needs to be updated, causing the overall cost to be too high. Of course, the price will also be relatively expensive. Although HD DVD is not as capable as Blu-ray in terms of capacity, it allows manufacturers to maximize the use of existing DVD production equipment and has relatively low manufacturing costs.

The competition between these two standards for supporting manufacturers and content providers is also fierce. Microsoft has announced that its next-generation operating system, Longhorn, will support HDDVD. At the same time, in order to meet the competition from the PS3 game console with a built-in Blu-ray drive (expected to be released in November this year), the XBOX360 console launched by Microsoft this year will add an external HD DVD drive. As the main manufacturer of HD DVD, Toshiba's HD DVD player will also be launched soon. In addition, HD DVD has received support from the four major Hollywood studios including Warner and Universal Pictures, adding weight to the competition. However, the strong lineup of Blu-ray manufacturers has also been trying to maintain its strong position. For example, Sony acquired MGM Film Production Company and acquired more than 9,000 classic films; Disney recently announced its support for the Blu-ray standard, and major companies such as Pioneer and Samsung The manufacturer's products plan to all be commercialized this year.

While competing fiercely, the two camps are also discussing how to combine the two standards into one. The two parties have come up with two merger plans. One is a hybrid plan, which uses Blu-ray for recording and HD DVD for ROM discs; the other plan is that if the entire physical format cannot be used, If we can reach a consensus on the above, we should seek common ground on the high-level protocol and optical disc interaction layer. However, there are many unresolved problems in the hybrid solution, such as how to design a laser readout to be compatible with lenses of different NAs? Can a device that supports two lenses meet the requirements for mobile applications? At present, most manufacturers and content providers are still waiting to see whether Blu-ray or HD DVD will be the final winner, which depends on the mass production capabilities, cost control capabilities, and marketing capabilities of both parties.