The DVD is a digital storage medium, which is similar in appearance to a CD, but has a much higher storage capacity. It is one of the optical data storage. The acronym "DVD" was originally developed from the abbreviation of Digital Video Disc, later, the acronym has been interpreted as Digital Versatile Disc (English for digital versatile disc ). In everyday language, the term " DVD " is often used in connection with films in the sense of logical format DVD-Video.
- 2.2.1 formats with two data layers
- 4.1 life
- 4.2 Storage and access technology
- 4.3 Error Correction 4.3.1 New Technologies
- 4.3.2 Data Coding
- 4.3.3 burner
History and distribution
The mid- 1990s, the Compact Disc was able to prevail as a mass storage medium in computers. This not only grew the fields of application, but also the needs of consumers and the entertainment industry. Was desired, a medium that could be handled similarly comfortable with videos such as music and voice recordings with the CD. Although there was this already as Video CD ( VCD) and laser disc (LD), but were on the VCD maximum of 74 minutes ( in a concise VHS quality ) and on the LD up to 128 minutes of video material are housed ( in full broadcast quality). This resulted in films means that the VCD / LD had to be changed in to the movie / flipped, like what happened with the Compact Cassette, or the record. The LD was with its massive 30 -centimeter discs also very expensive medium and player.
The entertainment industry has worked to increase the storage capacity of the CD on. Here, there were two different concepts: Sony and Philips operated the development of the Multimedia CD ( MMCD ), Toshiba and Time Warner favored the Super Density disc (SD).
Under pressure from the film industry, which did not want to support, as with the launch of the video recorder, multiple standards, the competitors in Tokyo on 15 September 1995 agreed on a common standard. Since the DVD was initially intended solely as a storage medium for video, DVD initially stood for "Digital Video Disc". However, this was changed, were foreseen as other uses. As an alternative, " Digital Versatile Disc" was ( versatile versatile = ) brought into play, but could not prevail. The current official position of the DVD Forum is that DVD just three letters without precisely defined meaning.
A year later, the first players and DVD media came onto the market. Previously, you had disagreements regarding the encryption method (CSS ) are eliminated. Also succeeded in the film industry to win a region code market control. With the code is to be prevented that, for example, a DVD of the United States is played on a European device. The film industry here feared loss of revenue, as films in the U.S. are often already available on the video market, while they have not yet been shown in Europe in the cinema. As a sales strategy of the provider is also known that the regional restriction on the applicability in different regions have different prices ( "Market Price " ) can be achieved.
Both the replay protection using Content Scramble System as well as the region code are now easy to get around. The industry responded with one hand, legal measures and the other to the pressure on the manufacturers of DVD drives to implement the query region code device technology.
End of 1996, the first DVD burners were commercially available, but prices were at about $ 10,000 and the price of a 3.6 GB blank was above 100 DM
Meanwhile, Blu- ray Disc is advertised as a successor to the DVD, which was able to prevail against the rival format HD DVD from March 2008. It will still be accommodated by sampling the more closely set pits and lands with a blue-violet laser beam higher volumes of data. They are especially high-resolution video content store, which require a much higher storage capacity than a DVD can provide.
Source: Association of Audiovisual Media eV
Source: Association of Audiovisual Media eV
Source: International Video Federation
DVD are available in many variants, are referred to as DVD formats:
- Special DVD formats that have optimized data structures for certain uses ( and originally only read access allowed ): DVD-Video, DVD-Audio, DVD-ROM and DVD hybrid
- For the consumer recordable DVD formats: DVD -RAM, DVD -R, DVD R, DVD- RW, DVD RW, DVD-R DL, DVD R DL
Especially the recordable formats and the DVD-RAM can be distinguished from the pressed based on their data page with the naked eye because they have such as blue, purple, or brown due to their alloys colors. The DVD-RAM also has characteristic visible sector brands.
DVD data structures
The DVD will be used for the following three uses have been created for their own DVD formats for specific data structures:
- DVD-Audio allows playback of still images and sound in very high quality with DVD-Audio compatible playback.
- DVD -ROM can read general data ( computer data).
- DVD-Video allows playback of moving pictures and sound with DVD-Video compatible playback.
The AUDIO_TS folder plays a central role in audio DVDs. For DVD video, however, the audio data in the VIDEO_TS folder can be found, as well as the various language versions, subtitles, chapter information and special features (all within so-called " VOB container files "). The compression format commonly used on DVDs is MPEG-2, according to the DVD standard, however, the quality far inferior MPEG -1 format is also provided, which otherwise applies especially for video CDs. The MPEG -2 video stream ( the video) is when creating a video DVD interwoven ( "muxed ", see Multiplexing) together with the audio stream and, where appropriate, with other data blocks and in a. VOB file (" Video Object " ) created, which may never be greater than 1 gigabyte, according to the DVD standard. If this amount of data is exceeded, the programs will automatically create a new. VOB file for DVD authoring (DVD authoring software). So the. VOB file serves as a " container file " of all program streams.
When changing the files of the transition is not detected because of the built- in DVD players buffer. When playing back video, audio, and possibly control information are alternately read, temporarily stored and played back. The VIDEO_TS folder also contains the. IFO file with the menu and usually several. BUP files, but only serve as a backup. IFO file.
When multiple audio tracks formats are allowed; next to the data-intensive - because uncompressed - linear PCM data stream, there are several compression methods: mp2 (usually 192-256 Kbit / s) in any bit rate for stereo, Dolby Digital or DTS multi-channel audio to 5.1 surround (usually 448 Kbit / s ). Also SDDS is specified for the DVD, but there are for home use neither appropriate nor decoder DVDs with SDDS soundtrack. Nor is the sound format MPEG- 2 has been able to enforce multi-channel.
The total budget for the entire data stream to 10.08 Mbit / s is available, for the audio stream up to 6144 Kbit / s The picture quality of DVD depends not so much on the bandwidth of the video stream as on the efficiency of compression. It is often encoded using MPEG encoder in multiple passes to achieve a maximum of efficiency. In MPEG -2 data streams in VBR method can be compressed, which means that the bandwidth can vary greatly in different parts of the film (variable bit rate).
The bit rate depends on the right amount of data, so that for example in scenes sedentary bandwidth and disc space can be saved. In MPEG - 2, only the differences to the previous image stored (P or B frames) to save space on the disc in successive images as a rule. More information in the article DVD-Video.
Data DVDs (DVD -ROM) are different from DVD-Video discs subject to any restrictions and can contain any folders and files. As file systems either are predominant in the computer field formats to ISO 9660 and ISO / Joliet or UDF be used; both systems can be combined within the UDF Bridge format (ISO 9660 Level 3 Layer). Just as CDs and DVDs can be described ( multi border, analogous to multisession CDs in ) in several sessions ( sessions). However, some older operating systems or DVD players can only access the first session, which is why it is recommended in this case to describe the DVD in a train. To read the rest of the sessions are additional programs as IsoBuster that also run on older operating systems.
Physical Hybrid DVD
There are also hybrid DVD that combines the features of DVD- Video, DVD-Audio or DVD-ROM in a DVD. Such a hybrid DVD contains videos, music and computer data and presented in the DVD player, DVD recorder or DVD drive of the computer each playable content.
Technically, a hybrid DVD can be created easily, because the DVD-Video and DVD-Audio are based on the DVD -ROM. The DVD - ROM stores all the contents from the files after the UDF file system. For the DVD-Video and DVD-Audio only two other determinations must be made: The allowed file format and the location on the DVD. For the hybrid DVD of the location is particularly interesting. When a DVD -Video or hybrid DVD is inserted, for example, a DVD recorder, so look for this movie files in the VIDEO_TS subdirectory. By the same token, a DVD player explores the audio data in the directory AUDIO_TS. In the DVD drive of a computer, however, all files in a DVD are shown because these treats each DVD as a DVD- ROM.
Recordable DVD formats
The end user can not only purchasable play DVDs (which were made in the press shop ), but it can also create your own DVD-Video, DVD-Audio and DVD-ROM with a DVD burner. DVD burners are installed, for example in computers and hi-fi DVD recorders and need writable DVD formats. Historically, for reasons of cost the five different DVD formats DVD -R, DVD R, DVD- RW, DVD RW and DVD-RAM have single and double storage capacity (DL - Double Layer) developed. They are referred to the following system:
The three DVD formats that are from the DVD Forum are also referred to as a negative standard. Only these formats may also carry the official DVD logo. Accordingly, the two DVD formats of the DVD RW alliance with a " " as a plus standard called. The DVD formats after the Plus standard are technically simpler construction, which, for example, the DVD RW supports other methods of writing as the DVD -RW. The license fees for the use of patents are significantly lower. These initial price advantages of the Plus standards, there are now no longer the fierce competition with the minus - standard.
The variety of formats initially led to a reluctance among consumers, because it was unclear which DVD recordable format has the greater investment security. The industry responded with it since 2003 ( cheapest ) Multi- burners which supported both the minus and the plus format.
Formats with two data layers
Since 2004, recordable DVDs with two offered instead of just one data layer on the mass market. They are labeled " DL" what is in the minus format for " Dual Layer" ( DVD -R DL) in the plus format, however, for "Double Layer" ( DVD R DL). Both formats are common to the two superimposed layers bonded on the same side of the plate, which required certain changes in the structure of the DVD. Only in this way, the additional layer can be written and read. The DVD ± R DL provides 8.5GB capacity per disc, or about 1.8 times a single-layer DVD. Your additional capacity is often sufficient to large individual files to burn (about high definition video ) to a single medium, rather than distributed among two conventional DVDs and without the data having to recompress. For RW media, however, these changes are not possible towards the DL discs. At low reflection properties prevent the reliable use of the second data layer.
In addition, there also exist double-sided media in the DVD -R, DVD R and DVD-RAM formats. This actually take 2 x 4.7 GB, so 9.4GB per disc, since they basically consist of two individual DVDs. The disadvantage will be affected, especially with large files, because they can not be stored contiguously as ± DL- DVDs. Each page represents a separate disk, and to access each other's data stock can that DVD has to be removed and turned over. Drives that can use both sides at the same time ( read-write ), do not exist. Since the Double-Layer-/Dual-Layer-DVDs despite lower total capacity offer several advantages (higher maximum file size, space for detailed labeling, etc.), double-sided DVD ± R discs were almost completely disappeared from the market. More recently (July 2008), however, double-sided discs are available again. Double-sided DVD-RAM are also available. For them, no DL media are currently available.
The recordable DVD formats can be distinguished according to their mutability and data security.
- DVD media that can be written only once DVD -R and DVD R. In these media, the information is written into a dye. This is an organic dye, often a violet color.
- DVD media that are subsequently changed: DVD-RW, DVD RW, DVD- RAM. RW media use as functional layer in place of the dyes used in DVD media, a metallic layer. For DVD media, the DVD-RAM is 100 times more often rewritable (about 100,000 times ) than the DVD -RW or DVD RW, which are about 500 to 1,000 write operations.
- The DVD ± R reacts due to their organic dyes much more sensitive to sunlight and heat than the DVD ± RW. If it is exposed to the direct sunlight or strong ultraviolet light exposure can lead to a rapid loss of data.
- The DVD ± RW, however, is more sensitive to extreme temperature fluctuations; by lightweight material deformations, the data may be damaged.
- DVD-RAM includes all recordable DVD formats is the highest data security, because it additionally includes the following two characteristics: Sectoring: DVD -RAM media have an embossed sectoring, which visually appear as a pattern of scattered small rectangles on the underside of a DVD-RAM ( see figure). They serve a higher reading and writing accuracy.
- Defect management: The DVD-RAM has the same proven defect management such as hard disk drives. Any written information is read as control of the hardware ( verified ) and possibly improved. There is therefore no hidden typo as the DVD ± R or DVD ± RW.
The default data rate is 1 × corresponds with DVDs at a speed of 11.08 Mbit / s ( 1.385 MB / s or about 1.32 MiB / s ) and thus in about a CD drive with the speed factor of 9 ×. The write speed 1 × corresponds thus, by definition, the maximum data rate that can occur when playing a standard-compliant DVD-Video.
Current DVD drives create internal and write speeds of up to 24 ×. Full speed is reached, however, this only at the outer edge of the disc, while on the inside can be read and written much slower.
Technology of DVD
DVDs need to play its own DVD player. To distinguish normal CD -ROM drives, this is marked on the front with the DVD emblem. In comparison with the CD is carried out with lasers of shorter wavelength for DVDs, and at the same time because of the shorter optical paths of the focusing optics, resulting from the laser spot size, which in the data carrier layers correspondingly smaller structures can be read and written.
The media Imation granted on CD- R, CD- RW, DVD- R, DVD- RW, DVD R, DVD RW, DVD- RAM currently a guarantee of ten years. However, this does not apply to the data, but is limited to the haptic components. For long-term archiving are above DVD formats unanimous expert opinion not suitable, the only exception could possibly represent the DVD-RAM, here too the long term durability has not been proven safe. Verbatim offers in Austria and Switzerland with a lifetime warranty, but not in Germany. This applies to all manufactured by Verbatim optical media, however, covers only manufacturing defects, not normal wear and improper handling. In the worst case, DVD ± R and DVD ± RW may also have a few months data defects. A durability of data from up to 1000 years since 2012, the manufacturer promises Millenniata for its M- Disc. Millenniata it refers to tests of the U.S. military. To describe M- Disc -enabled burners are required. Otherwise, an M- Disc is handled as an ordinary DVD.
Storage and access technology
The specifications see the following types of DVD discs available in version 2. The representation of the rare version 1 is omitted.
In comparison to the CD with the same geometry of the disk about six times as high data capacity of the DVD is half as long pit lead-in area achieved by less than a less than half as large trace spacing and more space for the data by a narrower. Double Layer DVDs require about 10 % longer pits, so two layers do not offer twice the capacity of a single layer DVD in this configuration. The finer structures of the DVD are more susceptible to scratches and dirt, which is compensated by the more used two-dimensional error correction method.
On the DVD two Reed-Solomon code C1 ( 182,172,11 ) and C2 ( 208,192,17 ), which are formed by reduction of a ( 255,245,11 ) and ( 255,239,17 ) RS code. C1 and C2 is the line coding of the column encoding. The resulting matrix is used for error correction, each with 8 errors can be corrected in each of the rows 5 and error in the columns. The bits and parity bits are generated during encoding.
When interleaving the DVD a 182 × 208- byte frame at 16 frames is composed of 182 × 13 bytes divided. Here, a parity line () at the end of a 182 × 12-byte frames will be shifted on. This means that the following are arranged in a new matrix:
The matrix produced in this way is decoded similarly to the CD. A maximum of 4832 bits or a surface errors can be corrected with 2932 bits.
The use of both enhanced techniques it takes higher frequency (that is, the color of the laser is moved in the direction of blue ), and more accurate laser than for reading a CD. To read the second data layer, the laser must be easy to do anwinkelbar. Along with the change in laser focusing so it is possible that lower one ( "hidden " ) to read layer.
The binary data on a DVD can be written to the " Eight -to- Fourteen Modulation -plus " ( EFM ). This ensures that every two to ten bars changes the polarity of the read-out signal. This happens when the laser in the track a transition from a depression ( " pit" ) to a section without depression ( " land" ) happened or vice versa.
The background in this case is as follows: the sections of recesses or without recesses have to be long enough to allow the laser to detect the change. If you were to write a bit pattern directly to disk, incorrect values would in an alternating signal (1010101010101010 ... ) read since the laser could not read reliably the transition from 1 to 0 or from 0 to 1. The EFM modulation puffs up the signal from eight to 16 bits and selects the padding bits so that the above- mentioned requirement that every two to ten bars changes the polarity and a transition from 1 to 0 or vice versa, is considered to be met. The CD uses a simpler 8-to -14 -bit method with more additional intermediate bits called EFM, where the now actually wrong name was retained for the DVD; correct would be " Eight -to- Sixteen".
After the first DVD burner ( DVD recorder) could only store a data volume of 3.56 GB on a write-once blank DVD, the capacity was later raised to the full size of a DVD -5 (4.7GB ) and additionally rewritable media presented with this capacity. Since mid-2004, master DVD burner and the double-layer technique ( dual layer ), which allows the storage of data on a dual layer disc. The second data layer has further set the pits and lands to allow the reading by the lower layer pass, and is thus smaller. So summarizes such a blank instead of 9.4 GB (the capacity of two DVD -5), only about 8.5 GB.
- DVD Squeeze: The production of a DVD or CD (ROM and video) consists of four steps after delivery of the master DVD -R or a streamer tapes ( " DLT " format) to the pressing plant.
- Pre-mastering: First, it is checked whether the standard ( the book) is satisfied, ie if the media meets specifications. Thereafter starting the calculation of EDC ( Error Detection Code ), and ECC ( Error Correction Code). This was initially for between five and 16 hours. Subsequently, Time - code, content information of the tracks and TOC ( Table of contents ), etc. generated and created an image of the DVD / CD. The data can then be fed to the mastering.
- Mastering: The processed data from the pre-mastering (one glass sheet ) is transferred by a modulated laser beam applied thereto, the substrate layer ( a dye ) is exposed from the inside out on a glass master. In the developing bath then the exposed areas are washed, the pits formed. Then, the glass master is vapor-deposited with a 100 nm thick silver layer. This is followed by a first reading as a quality check. The cost of the glass master production ( between 300 and 3,000 € ) will be provided with short print runs of most pressing plants into account.
- Electroplating: It negatives the glass master will now be created that can be used for the pressure as a stamp.
In general, the discs all DVD formats from two different injection-molded polycarbonate plastic discs are made of about 0.6 mm thickness ( exception: Ecodisc ). The lower " half slice" (Layer 0) has a stacking ring as a spacer. The upper " half-disk " (Layer 1 ) contributes to the format DVD-5 no useful information and is therefore called a "dummy". The actual DVD is formed when the two halves are glued to curing under UV varnish ( " bonding", thickness of about 50 microns ). To ensure consistent quality of the discs produced in manufacturing plants are usually high resolution camera systems, so called inline scanner, integrated. Random samples are also off-line measurement drives are used to analyze the electrical signals from the DVD. Should creep in the bonding of the two layers of air (called Bondingfehler ), the DVD can quickly be damaged. For example, when you insert the DVD part of a spall layer. This may cause an imbalance that can lead to further damage to the DVD or even on the player. However, these errors are only a visual problem in general and do not affect the playability of the DVD.
In the fabrication process, there are large differences between recorded media (purchase videos) and unrecorded / rewritable discs (blanks). The formats of DVD-5, -9 and -10 are usually made on the same machine. The information matrices ( Stamper ) are pressed into the hot polycarbonate ( injection-compression molding ). In order to make the data for the drives readable, the half-discs are coated with metal ( sputtering ). For DVD- 5, DVD - 10 and the Layer 1 DVD- 9 aluminum is fully reflective sputtered ( about 50 nm). As DVD- 9, both information layers to be read from one side, the bottom (Layer 0) is semi-transparent with gold, silicon coated or silver alloys (for example, 10-15 nm). DVD -14 and DVD -18 is obtained by an already provided with other DVD structures foil is inserted between the half-discs.
When burning no glass master is required, but only a computer, a DVD burner and a CD burning program.
For burning you need blank DVDs, which are available in different qualities as DVD-R, DVD R, DVD- RW, DVD RW and DVD-RAM. Through the various DVD formats and the fact that these were partially specified only after the definition of the original DVD set of rules and variants thereof are, there is a certain probability that the burned DVD is on some DVD players not be playable. Therefore, one should be according to the compatibility of the burner and the desired players before buying the blanks exactly inquire. Some DVD writers offer the opportunity to characterize DVD R and DVD RW discs with the Book Type DVD -ROM and thereby increase their acceptance by significantly older DVD players.
Often the DVDs must be finalized after burning. With DVD RW and DVD-Ram a Finalize is not necessary but it is recommended to create a DVD menu.
Label printing / labeling
As well as in the CD are different printing techniques available for the label imprint in the DVD:
In screen printing up to six label colors are available, it can be selected spot color (HKS or Pantone). Screen printing is currently the most common variant to print CDs or DVDs, but is increasingly replacing the offset printing. Screen printing is suitable for pressed CDs and DVDs; the Rohlingsbedruckung screen printing is possible. In screen printing, the colors are brilliant.
In dry offset are four possible label colors ( CMYK ), combined with the screen printing up to six label colors (CMYK offset and additionally white full face and a spot color or gloss varnish screen printing ). Due to the higher resolution than screen printing, offset printing is ideal for photorealistic renderings. Since early 2004, the offset printing is possible not only for pressed CDs and DVDs, but also for Blank CD and DVD media.
In this printing process, ink is transferred from an ink ribbon by heating the print head in the CD or DVD with a special printer. For technical reasons, the printing method is more suitable for headlines and logos. In practice, this method is used for small print runs ( burned CDs and DVDs).
The Thermoretransferdruck is the evolution of thermal transfer printing. The label design is first printed using thermal transfer printing process on a transfer belt and it then applied a film on the CD or DVD. By this technique, a better resolution is possible. For example, a photo-realistic printing can already be achieved with short runs.
There are special DVD or CD blanks, which is opposite to the data page have a white printing page. This consists of a particular absorbent material to prevent running of the ink. To print on special printers are needed, the technology is not much different from the one that is used for printing on paper. Consequently, there are printers that can print on both CDs, DVDs and paper. In practice, this method is of only home users and very small runs of burned media application.
This method is not recommended for home users. As with a bimetal the DVD bulges at temperature differences, since the sticker and the polycarbonate lens expand to different degrees. Unlike normal CDs have been enough for a DVD of low distortion, that the player can not read the data. This effect is exacerbated by the heat inside of the DVD player so that pasted DVDs often fail after a certain amount of play time. To prevent this, special DVD labels from plastic film available that will expand evenly with the disk. Another disadvantage is that usually by the sticker, an imbalance is created. In DVD drives can lead to detachment of the label or even a disruption of the DVD this imbalance at high speeds.
Overhead markers, CD markers, and other reviewers for smooth surfaces DVDs can of course also be labeled and painted by hand. This is the cheapest and fastest method. DVDs are - unlike CDs - quite insensitive pins that may scratch the surface or chemically attack since their data layer is centered and is therefore protected by a relatively thick layer of plastic.
Label of the disk by the laser directly in the drive. This requires a special burner and appropriate blanks that govern such a process. The advantages of laser labels are in the printing in mobile operation, avoidance of new investments in new printers and the ability to print in multiple sessions ( Lightscribe ). Disadvantages are the only monochrome printing, the low quality, low pressure rate (optimum contrast at about 30 min. Printing time ) as well as the expensive and increasingly difficult blanks available.
Disposable DVD and DVD-D
For years, you always hear of a new-found disposable DVD, which is set to revolutionize particularly the theatrical distribution of video rental stores. When the DVD is removed from the air-tight envelope and is in contact with oxygen, there is a chemical reaction that makes the DVD unusable within eight to 48 hours. After this time the DVD can be simply discarded by the customer, which is why these DVDs are also called disposable DVDs. The advantage is that you no longer have to return these DVDs the video store and therefore late fees are no longer an issue, are facing ecological disadvantages, even if the product material is completely recyclable.
The company Flex Play has released such a disposable DVD under the name EZ -D. This was tested in September 2003 by Buena Vista Home Entertainment in the U.S. market. It appeared the same disk with a film for about five to seven U.S. dollars shortly before the actual premiere. The product was, however, not enough buyers, so this already disappeared in early 2004 again from the shelves. A similar method had also the company Spectra Disc presented above, but after the principle of which the disposable DVDs were unusable due to light sensitivity.
Another variant distributes the company DVD-D Germany Ltd.. The data on the DVD -D ( D for engl. ' Disposable ', dt ' disposable ') are after the first time 48 hours to read, then appears in the player "no disc". Data destruction is started by the rotation in the player, will be deleted according to the company, the control menu of the DVD. However, there is no detailed information on the mechanism. In part, this is explained by liquid tanks in the DVD, which break through the rotation ( centrifugal force). On the company's DVD-D Germany Website several movies have been offered in this format for price of around € 4. The largest spread is currently available in France, Italy and Scandinavia.
Aspirations to a better environmental compatibility of the DVD led to the development of Ecodisc. This DVD is made up only of a polycarbonate plate, and has only eight grams. The storage capacity is the same as the DVD-5 4.7 GB.
DivX and DivX
While nowadays the DivX format is known as video compression algorithm, DIVX refers to a special pay- per-view variant in the U.S., which no longer exists today. In 1998, the idea came up to offer to the still considerably more expensive DVDs a cheap version that could be played for 48 hours, each additional use was free of charge. For decoding, and accounting of special films, equipped with a modem players were needed to regularly linked with a special server to transmit billing data.
DIVX used is an MPEG -4 derivative, which was provided with special DIVX flags for identification and decoding of the film. In the end, could not prevail against the DVD system and ended after only a year as a flop.
In 2010, the DVD victims of the April Fool's renowned computer magazine c't was. According to the article pressed DVDs should be susceptible to bacterial attack. As a feature spots were called on the DVDs. The bacterium can whole stack - but only recently - destroy DVDs and would also spread through infected drives. The readers were asked to rearrange their DVD collection, so that between two old DVDs are still new to handle their DVD drives, and for days not to use. A fictitious letter from the Association of the video store owner, dated April 1, and the use of a number occurring in the television series Lost as vaccine Order unmask the article as April Fool's joke.