Comment by stavros
3 months ago
But JPEG has a lossless mode as well. How do you distinguish between the two now?
This is an arbitrary distinction, for example then why do mp3 and ogg (vorbis) have different extensions? They're both lossy audio formats, so by that requirement, the extension should be the same.
Otherwise, we should distinguish between bitrates with different extensions, eg mp3128, mp3192, etc.
In theory JPEG has a lossless mode (in the standard), but it's not supported by most applications (not even libjpeg) so it might as well not exist. I've certainly never come across a lossless JPEG file in the wild.
Filenames also of course try to indicate technical compatibility as to what applications can open them, which is why .mp3 and .ogg are different -- although these days, extensions like .mkv and .mp4 tell you nothing about what's in them, or whether your video player can play a specific file.
At the end of the day it's just trying to achieve a good balance. Obviously including the specific bitrate in a file extension goes too far.