dvd`s/how is this possible?

21st Nov 2002 06:05 #1

Member

i`ve been ripping dvd`s for a while now, but i ran into a problem i just don`t understand. after ripping with dvd decryptor and stripping with ifoedit, the movies "life" 87m clocks in at 4.63gb. "shaft" 97m clocks in at 5.30gb and as you probably know; i can`t do a 1:1 copy. now what puzzles me is that i`ve done "ghost of mars" 99m at under 4.3gb and other movies that were up to 115m with a 1:1 copy. it makes no since to me on how a longer movie can have a smaller file and some shorter movies (even after being stripped) can have a larger file, making it impossible to do a 1:1 copy...........thanx

Quote

21st Nov 2002 06:47 #2

garryheather

Member

It's all down to bitrate and the bit management employed by the author.

If you've got a fast paced action movie with lots of action, this will typically have a higher bitrate than say a cartoon where there is a lot of redundancy in large areas of solid colour with a lot less detail.

Then, if the author wants to put a load of extras on the same disc, this eats into the capacity of the disc that is available to him. For example, the Superbit range by Columbia consists of a series of films that have no extras, but have been encoded at a higher bitrate so the film content is of a higher quality (ie less compressed) than the extra laden version.

Add to this numerous soundtracks, commentaries and the like, and suddenly the amount of data a DVD can hold doesn't look like a lot. So if you've got a DVD-9 disc but stripped out the non-essentials that you won't use (like a 5.1 soundtrack in classic Mandarin or a commentary recorded by the cleaners), you might find that the actual movie is a lot smaller than you think. Unfortunately a long epic at a low bitrate could easily use as much of that available space as a fast paced action-fest that goes for an hour or so. There's no hard and fast rule as far as this is concerned, some bit management is done automatically in 2 or more passes by a machine, some have an operator look at the video and allocate more data for some scenes than another, hell you might even find a constant bitrate movie one day - the whole point is no two films will have their data allocated in the same way. For example, even the retail version might be encoded differently to the one you hire from a rental shop.

It's all down to bits and what you do with them and at what speed.