• The Data Structure of DVD Discs
  • DVD and CD has the same data organization, each layer is divided into lead-in area, program area, and lead out area three parts.There is a middle area for OTP discs.

    The data on the DVD disc is organized by sectors. Each sector is made up by 1024 bytes of data.there would be no intervals between sectors, and they are stored on the disc as below:
    1. For the single layer disc, the starting point of lead in area is the end of lead out area.
    2. For the 0 layer of the double layer disc, the lead in area starts from the start of middle area and ends at the ends of lead out area.
    3. For the dual-layer disc layer 1, the lead in area from the beginning of the middle zone to the export zone at the end.

    For the use of OTP (backlighting Road path) mode dual-layer disc, a layer of the middle zone at the beginning of sector number from 0-layer data area according to the last place to take a sector number in fact receive, after a continuous increase in the number of sectors up to a layer of lead-out at the end.

    Sectors
    The user data is 2048 bytes, the data sector is 2064 bytes.The user dat is set with a four bytes of Sector Identification Data (ID for short) which is to show the information on sector format, rail mode, reflective ratio,areas where sector lies, data type, number of layers, numbers of sectors and so on.The second byte is used for ID Error Detection Code, called as IED for short.Then, six bytes is used for the Copy Protection information (called CPR for short), in all 12 bytes is added to the beginning of the sector. At the same time,the end of the sector is set with 4 bytes of Error Detection Code( called EDC for short).
    Sector with 2064 bytes of data is arranged into 12 rows × 172 column array structure, and then a row of 16 data sectors are combined with Reed-Solomon error correction coding, then work out the OCP and the ICP, constitutes a 208 × 182 array error correction block (ECC BLOCK). After encoding, each sector has got an increase of 302 bytes. The newly formed sector is called recording sector. A recordinbg sector is 2366 bytes.Physical sector is to separate the recording sector into two and a half from the middle, each half-frame is added a 26 byte sync code. After the process of 8-16 modulation then a physical sector with sync frame is formed.The concocted physical sector has 4836 bytes which equals to the 2418 bytes before concocting.The data on the physical sector shall form channel data line after line, then recorded onto the DVD discs, it is the real sector on the disc.

    The lead in area, data area, lead out are, middle area has a changeable number of sectors that mainly determined by the length of programming.Generally speaking, the first sector of data area is set with the number of 196608 (030000H).

    The lead in area is made up by reference code and control data.Of which, the reference code is made up by two error correction blocks with a length of 32 sectors. The control data contains 192 error correction blocks with the information on physic format, production of DVD, program provider and so on.The data is user data on the data area.The main value is set 0 in the middle area.The primary data is also set with 0 in the lead out area.

    8-16 modulation
    DVD has the same principle in reading and writing in data with CD.The pit and land on the disc is to store information. The pit and land are all read as 0. the length of pit and land shall determine the number of 0.The joint of pit and land is read as 1.If the binary numbers works as channel code without concocting, the laser heas will have difficult in reading and writing in data.When coming up with "10101010" the read-write frequency is high, and the bandwidth of the laser ciruit shall be wider, while coming up with "00000000", the read-write frequency is very low and the laser beam shall lose the track rail information.Therefor, CD uses EFM, which is 8-14 moldulation technology and  3 bits of segregation code to from a 17 bit channel code. DVD is the 8-16 the use of advanced modulation techniques, without separation code, you can not meet up to have more than 10 continuous 0, at least two consecutive 0 requirements. The formation of the channel code is 16 bit, save one digit compared with CD.

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