🚀 go-pugleaf

Vivian Collins wrote:

> I Hope that; everyone who is complaining about the MD being a lossy
>  compression technique are true to their beliefs and stick by the
> LD player when DVD arrives as DVD uses compression techniques to fit the
> entire movie onto a CD

I believe that the audio compression used on DVD is lossless compression. 
Its the same think as shorthand where a new symbol is used for a whole 
word (or multiple groups of the normal symbols). Since the new symbol is 
smaller than the whole word, the result is smaller than before. If you 
pick a bunch of new symbols, the compression ratio can be significant 
without losing a single bit of information. In other words, the input 
prior to encoding can be exactly the same as the output after encoding 
(at a digital level).

It's also similar to encryption in its replacement of symbols. But the 
replacement symbols have to be smaller than the original symbols for 
compression to result.

The ATRAC compression is a "perceptual encoding" in which, not only is 
the data compressed as described above, the some of the information is 
removed prior to encoding. The reason it is called "perceptual" is that 
someone decided what the limits of human hearing are and removed 
information that "cannot be heard." Many people contend that what was 
removed can actually be heard (or, really, can be missed. Since its not 
there you can't hear it, can you?)

The video compression on DVD is lossy compression, I think. Someone 
decided what cannot be seen (or doesn't bother you if you don't see it) 
and removed that part of the picture before encoding on the disc. The 
reader decodes and creates a complete picture from what is left. If you 
wish to see one example of the effect of a bad video compression 
algorithm, look at a basketball game coming from one of the 18" video 
sattelite systems. When they pan the crowd, there is too much information 
to fit in the transmitted signal (even after compression) and some 
information is removed. When you have all those people moving in the 
stands, they will twinkle on the screen because of the missing 
information.

I reiterate, the audio isn't lossily compressed on DVD.

-- Lee Meador