Download and install foobar2000
After the download link
is downloaded and installed, the dff file cannot be played and converted directly, and a plug-in needs to be downloaded and installed
Download and install the plugin
After downloading the plug-in address
, decompress and install the file in the red box below . After the installation is complete, you must click Apply to take effect.
Play and Convert
Click File – Open of Foobar2000 to open the DFF lossless music file and play it. 
Right-click on it and select convert->quick convert to start the conversion