K-Lite Codec Pack 64-bit is a bundle of 64-bit DirectShow filters that can be used together with 64-bit players, such as Windows Media Center. [Important! K-Lite Codec Pack 64-bit's development was discontinued.]
AviSynth is a tool for video post-production which uses specialized scripts and no graphical interface. Once you master it, you can apply unrestricted and extensive editing options to your video files.