Medium to High. Developers often downsampled heavy audio or video files to fit the 1.2 GB GD-ROM data onto a standard 700 MB or 800 MB CD-R.
Finding "highly compressed" usually means looking for or specialized CDI rip sets. dreamcast games highly compressed
While it featured a massive map for its time, its arcade roots kept the core data relatively lean compared to cinematic RPGs. The Dreamcast Junkyard Modern Compression: The CHD Format Medium to High
Modern emulators decompress .CHD files on the fly in system memory. This means you will not experience lag, stuttering, or increased loading times during gameplay. or increased loading times during gameplay.