When I attempt to open a MPG file I get a notice in bottom of app window : AC3-Decoding is disabled for your version of SOUND FORGE. 5.1 to stereo down mix may have occurred.
I am using Sound Forge Pro 14.0 Build 111 64-bit. OS is windows 10.00.18363, Processor Intel(R) Core(TM) i7-4790K CPU @ 4.00GHz.