Windows:ffplay -vf "drawtext=text='%{pts\:gmtime\:0\:%H\\\:%M\\\:%S}':x=1:y=1:fontsize=20:fontcolor=white:box=1:boxcolor=black:boxborderw=2" myfile.mp4
Unix:ffplay -vf "drawtext=text='%{pts\:gmtime\:0\:%H\\\\\:%M\\\\\:%S}':x=1:y=1:fontsize=20:fontcolor=white:box=1:boxcolor=black:boxborderw=2" myfile.mp4