I know it is very old question to discuss, but i want to make it more clear today ... Just want to say that CD and DVD has same physical shape but still having different size ..WHY????? And even DVD's are of different sizes in the market...
Do you know a DVD holds about 7 times larger data than CD..
In simple tone it is said that DVD has higher capacity than CD due to one main reasons that are...
1)A DVD uses a different laser with a smaller wavelength to record data..Hence it can store larger data than CD.
But i want to discuss it briefly. DVD can store more data than CD because of three main reasons that are mentioned below:
1)Higher-Density data storage
2)Less overhead, more area
3)Multi-layer storage
Lets discuss the above reason...
1)Higher-Density data storage :- A standard DVD can store 7 times more data than CD..This is because pits and tracks are smaller in DVD's in comparison to CD's.
By reading above we can guess about how much data will be available on DVD more than CD due to tighter pits and tracks. The track pitch on a DVD is 2.16 times smaller, and the minimum pit length for a single-layer DVD is 2.08 times smaller than on a CD. By multiplying these two numbers, we find that there is room for about 4.5 times as many pits on a DVD. So where does the rest of the increase come from?
Do you know a DVD holds about 7 times larger data than CD..
In simple tone it is said that DVD has higher capacity than CD due to one main reasons that are...
1)A DVD uses a different laser with a smaller wavelength to record data..Hence it can store larger data than CD.
But i want to discuss it briefly. DVD can store more data than CD because of three main reasons that are mentioned below:
1)Higher-Density data storage
2)Less overhead, more area
3)Multi-layer storage
Lets discuss the above reason...
1)Higher-Density data storage :- A standard DVD can store 7 times more data than CD..This is because pits and tracks are smaller in DVD's in comparison to CD's.
By reading above we can guess about how much data will be available on DVD more than CD due to tighter pits and tracks. The track pitch on a DVD is 2.16 times smaller, and the minimum pit length for a single-layer DVD is 2.08 times smaller than on a CD. By multiplying these two numbers, we find that there is room for about 4.5 times as many pits on a DVD. So where does the rest of the increase come from?
2)Less overhead, more area :-
On a CD, there is a lot of extra information encoded on the disc to allow for error correction -- this information is really just a repetition of information that is already on the disc. The error correction scheme that a CD uses is quite old and inefficient compared to the method used on DVDs. The DVD format doesn't waste as much space on error correction, enabling it to store much more real information. Another way that DVDs achieve higher capacity is by encoding data onto a slightly larger area of the disc than is done on a CD.
On a CD, there is a lot of extra information encoded on the disc to allow for error correction -- this information is really just a repetition of information that is already on the disc. The error correction scheme that a CD uses is quite old and inefficient compared to the method used on DVDs. The DVD format doesn't waste as much space on error correction, enabling it to store much more real information. Another way that DVDs achieve higher capacity is by encoding data onto a slightly larger area of the disc than is done on a CD.
3)Multi-layer storage :-
This facility has increased the storage capacity between varieties of DVD's...A DVD has multi layer storege capacity means it can store information in form of layers..A DVD has maximum 4 layers i.e 2 layer at each side..
Hope you got the answer ...
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