Consults the master?

Wants to ask that CD and DVD have any difference.What moreover their compact disc has in the computer to distinguish?
CD may put the CD compact disc not to have the image

DVD may put DVD \ CD to have the image Superficially, the DVD plate and the CD/VCD plate are very similar.But materially, between both has the essential difference.If everybody believed that between DVD and the CD/VCD difference lies in merely the broadcast effect, as if appeared some in is extremely simple.

1st, looked from the technology

DVD/CD is the same, because they are the data storage which needs in the compact disc track in the minimum scoop channel, then the transmitted light drives again the laser beam carries on the read work.But in compact disc’s density aspect, DVD must be much bigger than CD/VCD, therefore in reads the DVD data time needs compared to reads CD/VCD when the data the shorter wave length laser beam.Because only then like this, only then can let the laser beam accurately above the compact disc the focusing and the localization.The CD smallest pit length for 0.834?m, the group interval for 1.6?m, uses the wave length is the 780~790nm infrared laser read data, but the DVD smallest pit length is only 0.4?m, the group interval for 0.74?m, uses the wave length is the 635~650nm infrared laser read data.

2nd, when broadcasts the phantom

VCD can only achieve 240 standards, but DVD may reach as high as 720 standards, therefore in the clarity aspect, DVD occupied the absolute superiority.

3rd, in data capacity

CD/VCD can only hold about 650MB-700MB the data, but DVD most little may hold 4.7GB the data.According to the list/two-sided with list/two-course construction’s each kind of combination, DVD may divide into the one-sided monolayer, one-sided double-decked, the two-sided monolayers and the two-sided double-decked four physical structures.The one-sided single-layer DVD plate’s capacity is 4.7GB (approximately is CD-ROM capacity 7 times), the two-sided double-decked DVD plate’s capacity reaches as high as 17GB (approximately is CD-ROM capacity 26 times).

The one-sided DVD plate possibly has or a two record level.Is the same with CD, the laser reads on the single facial cast’s data from plate’s, on the two-sided DVD plate’s data deposits separately in plate’s about both sides.

Two methods read on the double facial cast’s data:

(1) after broadcasting on the plate the first program, the plate from the broadcast machine takes out, after turning hostile, again puts in the broadcast machine to continue to broadcast second on the program;

(2) reads the laser in broadcast machine Chinese dress two, separately from plate’s about both sides read data, or only installs one in the broadcast machine to read the laser, but after reading off plate’s first may jump automatically to plate’s other aspect continues to broadcast.

If uses the latter kind of plan, then after reading off plate’s first, does not need to take out the plate turns hostile.

The double-decked plate in fact is puts together two plate repeats, the lower level is half reflection layer, may read the upper formation by it the data.Reads when the lower level plate always starts from the inner loop, and toward the outside reads from, after reading off the lower level, reads the upper formation again.The read upper formation plate has two methods:

(one) reversed light path diameter OTP (Opposite Track Path) the law, namely reads when the upper formation plate starts from the addendum circle, and moves from the extroversion;

(two) along ecliptic way PTP (Parallel Track Path) the law, namely reads when the upper formation plate starts from the inner loop, and moves outward from.Reads the laser when reads on the lower level plate’s data, its optics focal point will change.

Regardless of being the single-layer plate or the double-decked plate is composed of two film base bottoms, each film base bottom’s thickness is 0.6mm, therefore DVD plate’s thickness is 1.2mm.Speaking of the single facial cast, only then the lower level basis contains the data, the upper formation basis does not have the data; But in the double facial cast’s about two bases has the data.

4th, in function aspect

DVD may provide such as many axles (multi-languages), many kinds of writing supports as well as multiple perspectives watching and so on richly colorful function, but these are CD and VCD do not have.

Regarding between DVD and CD/VCD difference approximately so, although looks like is quite simple, but was only merely such several spots different then sufficiently lets DVD thorough defeat CD/VCD, but because, both are relying on at present in the price aspect superiority, therefore still held the high superiority in the market, but believed that in not the far future, DVD official will substitute for CD and VCD comprehensively becomes the absolute mainstream.

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