Originally Posted by streetdragon
so do lossy files only lose data? or compress and lose data as well ?
That's a very good question !
I have never seen the entire source-code for AAC-encoding so I can't say for sure .
What I DO know is : There is NOTHING left to compress in lossy-encoded video-files .
It doesn't matter how you try to compress a mpeg-video, the only way to get it smaller is to transcode it to a
even worse format .
Likewise, it doesn't matter what compression-level you choose in 7zip, win-zip or win-rar when you try to compress a AAC,mp3 or any other
lossy media-file . In fact, you will sometimes end up with LARGER files !
In matters like these, WIKI isn't all that bad :
In computer science and information theory, data compression, source coding, or bit-rate reduction involves encoding information using fewer bits than the original representation.
Compression can be either lossy or lossless. Lossless compression reduces bits by identifying and eliminating statistical redundancy. No information is lost in lossless compression.
Lossy compression reduces bits by identifying marginally important information and removing it.
The process of reducing the size of a data file is popularly referred to as data compression, although its formal name is source coding (coding done at the source of the data, before it is stored or transmitted).
Without having seen the source-code, my guess is that lossy formats do both,or attempt to, since the main purpose is to reduce file-size .
It's important to note that the word 'compression' doesn't (always?) mean the same in computer-science as it does in audio !
Edited by AKG240mkII - 8/28/12 at 10:17am