In order to watch a video packaged as DCP, the video generally must be converted to a format that can be read by consumer media players, such as H.265 (HEVC). This post will use Creative Commons-licensed Tears of Steel 4K DCP package as an example.

ffmpeg -i tos_version_05/tos_picture.mxf -i tos_version_05/tos_sound.mxf -map 0:0 -c:v libx265 -pix_fmt yuv420p -crf 22 -map 1:0 -c:a opus -b:a 160k Tears.of.Steel.2012.4K.x265.opus.mkv

Note that the video pixel format must be specified.