The process of handling an .ecm file is strictly a "decompress" operation. You are not converting it to a different format per se; you are restoring it to the format it was before it was compressed (usually .bin or .img ).
You have downloaded a file named something like Final_Fantasy_VII_Disc_1.bin.ecm . You load up your favorite emulator—perhaps ePSXe, DuckStation, or RetroArch—and try to open the file. It doesn't work. .ecm file psx
A command window will appear, process the file, and output a usable .bin file in the same folder. Using Command Line (Linux/macOS) The process of handling an