The UMC simple_player sample utilizes the UMC decoders, where I dont see any existing decoder for MPEG1 video.
Did you try an MPEG-2 stream or other video format supported by the UMC, in order to validate the built simpl_player.exe you have?
Please refer to the readme.htm, included within the simple_player project directory, and locate the current supported formats by the application; also, check the codec folder to see the full list of the sample implementations, UMC currently have.
Its good to know that your problem got solved.
Also, Im curious to know about the MPEG-1 decoding results with UMC, if you dont mind to share this result as well.