Explain to me the differences in dvd quality

hello932

Why are some dvd's better than others? i mean why are there different size's-700mb, 1.4 GB and 4.2 GB?

Run_to_da_hills

Its down to quantity of information it can hold.

The more info the better the quality it can store, hence high definition on Blue ray uses up up to 25 GB per single-layered and 50 GB per dual-layered disc.

hello932

Would it be safe to assume the following?-

700mb- standard definition dvd
1.4GB-High definition dvd
4.2GB-blueray dvd

Teutorix

hello932 wrote: »

Would it be safe to assume the following?-

700mb- standard definition dvd
1.4GB-High definition dvd
4.2GB-blueray dvd

700mb = CD
1.4 = dual layer CD
4.7 = Dvd6
9.4 = DVD9
15 = HD-DVD *obsolete
25 = BD
30 = Dual layer HD-DVD *obsolete
50 = Dual layer BD

It also has nothing to do with quality, you could put a 300*450 res movie on a 50GB disc and it wont look any better

biko

Not sure but we'll try A/V forum for this one.
From After Hours.

hello932

Teutorix wrote: »

700mb = CD
1.4 = dual layer CD
4.7 = Dvd6
9.4 = DVD9
15 = HD-DVD *obsolete
25 = BD
30 = Dual layer HD-DVD *obsolete
50 = Dual layer BD

It also has fúck all to do with quality, you could put a 300*450 res movie on a 50GB disc and it wont look any better

So what does determine quality then?

Teutorix

hello932 wrote: »

So what does determine quality then?

The resolution it was captured at, the resolution the actual file is at, the resolution it is displayed at, the cables carrying the signal, the quality of the display device.
For example a DVD quality video is an .MKV container would fit on a data-cd but in the format a dvd player uses it would need to be on a dvd6. The higher the resolution of a video the better the quality (roughly) as well as higher size. If you get your movies form a legitimate shop a Blu-Ray movie will be at a res of 1920×1080 and a dvd will be at 720×576

NealB

When a film is edited and mastered for either cinema or broadcast it is top quality, or uncompressed. But the file is too big to fit on a domestic disk so it gets compressed. The less space on the disk the more compressed the film needs to be to fit. So the bit rate or amount of data per frame gets reduced, loosing picture quality. It's not the disk it's how much they tired to fit on it. In fairness official DVDs/Blu Ray disks look really good. Bootlegs look lousy.

Any weak point in your AV set-up can mess up the picture quality. The higher the hertz on the screen the smoother the picture, low hertz TVs give bad stagger on panning shots. Some screens have bad viewing angles. And get this, the CRT TV is still the better screen, it has a higher contrast ratio than Plasma or LCD.

HD ready does not automatically mean HD. I can't believe how many people were conned into buying HD Ready TVs, which were not Full HD TVs. HD Ready TVs down sample HD pictures to standard def. A guy in Cleary’s once tried to tell me that there was no difference in picture quality between the Full HD screen and the HD Ready one beside it. They were playing a standard def DVD on both.

Teutorix

NealB wrote: »

A guy in Cleary’s once tried to tell me that there was no difference in picture quality between the Full HD screen and the HD Ready one beside it. They were playing a standard def DVD on both.

Why would they try to sell you the cheaper tv? surely that just terrible salesmanship?

zt-OctaviaN

Teutorix wrote: »

Why would they try to sell you the cheaper tv? surely that just terrible salesmanship?

Some poor unsuspecting sod has to buy the old stock!

Technically telling him there was no difference he may have been correct considering they were looking at a DVD!

n



@Hello932 - I will try to explain this simply withou going into the details of industry standards of resolution, bitrate and containers.

Do you ever see those black and white pictures in the news paper?
Well they are made up of dots.
On a paper its measure dots per inch.
Think of the tiny square pixel on your TV as being one of those dots well there are so many, this is if you like the resolution or number of dots/pixels on your TV screen.

Now on a single frame of a movie - just one picture on the screen frozen you have all the pixels.
Now for all these pixels to be stored at normal DVD quality it takes average 4.7Gb on a DVD thus the DVD-6 referred in a post below each and every pixel is recorded in that position for each frame!

However lets say you want to keep the resolution (number of pixels) the same, BUT use less data, this is called compression, and what happens is,
the number of pixels stay the same however the sheer number of different coloured pixels is lessend and blurred if you like so that there are more common pixels and whats more, a calculable pattern so that the movie can be compressed to a smaller amount of data - This my friend is what affects the quality - its the number of dots/pixels re-used in a pattern or BLOCK to shrink it.
e.g. a small square area of the picture frame on screen is taken, its looked at and if you like normalised so that what did have 1,000 pixels all arranged as it was filmed, is now rearranged to only use 100 different coloured pixels thats why quality gets affected, but dont confuse this necessarily with reducing the colour, its simply taking an average of pixel position and smoothing it out so there is less differeing data.

If you lessen the number of dots used on a black and white newspaper photogragh it will get blurry but you save on dots of ink!!

The measure of level of data used in we will say 1 second (24 frames of film (24p))
is called the Bitrate a lower bitrate = lower image quality (less bits of data)



Different DVD sizes are just for flexability e.g. Lord of the rings may have been released on DVD-9 discs but a shorter film would have been put sufficiently on a DVD-6 disc DVDs arent just for video so the advantage of bitrate adjustment means more flexibility of getting the data onto the disc with minimal loss or looking at it image blockiness.
Bluray takes up an average of 25Gb plus!



does this help?
Nick

NealB

Teutorix wrote: »

Why would they try to sell you the cheaper tv? surely that just terrible salesmanship?

zt-OctaviaN: 'Technically telling him there was no difference he may have been correct considering they were looking at a DVD. '

You're right, I guess that an SD image on both screens and they will look the same. This was before Full HD screens came down in price. He was just flogging off stock under false pretenses.

To the thread question, there is no difference in the quality of different DVD disks; the difference is in how much you can fit on it. Take a photo with your digital camera and copy it to a CD/DVD/Memory stick etc as long as it fits it is exactly the same quality.