SACD discs are mainly sold in Japan. They have a much larger bit- & sample rate, file size and better sound quality (obviously) than traditional audio CD's or even .flac files.
These files come with the suffixes .dsf and .dff .
'foobar2000' is an audio player that can play these files, using a plugin. It can also directly play audio files stored within a .iso file.
So as an audiophile, I humbly request VLC player to support .dsf, .dff and .iso files.
Come to think of it: please also support .iso files with DVD and BluRay content, without having to mount it as a virtual drive.