You have lossless formats
WMA - Lossless
These are the “big” four. They all are lossless which means you can freely convert between them as much as you want and you will never lose quality.
Lossy formats mean that part of the quality is sacrificed for the sake of file size.
While lossless is about 40% to 60% of the uncompressed file, lossy formats can be as little at 10% to 15%.
Lossy formats include
wma - lossy
mp4 (a4a) [they are the different file names for the same thing]
Once you convert a format from lossless to lossy you lose quality. You can never regain the quality by upconverting it. Once it’s gone it’s gone forever.
Now as I said, lossless is lossless. You can go freely between WavPack, WMA Lossless or FLAC, a hundred times and never lose quality
But there are different types of lossy formats
We’ll use mp3 as an example.
mp3 has three ways to compress. Average, Variable or Constant. It also allows you to choose the bit rate. The lowest typical bitrate you can have and have reasonable sound quality in mp3 is 128. The highest is 320. (You can go above 320 but theirs no added benefit and the file size increases so much you may as well use a lossless format)
If you compress a music track to 320cbr (constant bit rate) this means all bits of that song will take up 320bitrate whether they need it or not.
This isn’t the most efficient eay of doing things. Suppose you have a song and it contains a 5 second silence. Well in 320cbr the 5 seconds of silence is going to take up as much space as music. There’s no need to allot that space, it’s a waste.
Now if you use 320vbr (variable bitrate) that means the compression will use UP TO 320 IF needed. If it’s not needed it won’t use it. So if you set compression to 320vbr you may wind up with 250vbr when the track is finished, because the track didn’t need to use high bit rates for whatever reason.
The debates is whether you can go from higher bit rate to lower bit rate. In otherwords can you go from a 320cbr to 192cbr?
The answer is you probably could do it an not notice anything but in reality you would lose quality because the algorithm to compress music is based on lossless not lossy. So the algorithm would be messed up. In otherwords the alogrithm would be using data it is assuming is lossless and using that to calculate the lossy result. As you can see that would be wrong.
So in reality you would lose quality but whether you’d notice it or not depends, not only on the person, but the type of music. For instance, classical music is much more susceptible to compression issues.
[note: notice windows media has two formats
wma-lossless which is true lossless
wma-lossy which is a compressed format like mp3
BOTH use the file extension wma and you cannot tell if it’s lossless or lossy by the file extension. You’d have to look at the file size and guess.]