"A demo (also called LMP, from the lump file extension) is any recording of a game session that can be played back using the game engine. Internally, it is a sequence of tic commands, keeping track of just the input control states during each frame. Thus, a demo is much more compact than a video capture, or even than a recording of the states of all objects in the level." (http://doom.wikia.com/wiki/Demo
So, you do not need my demos as I post them. I just provide them in case anyone wants to view my runs in higher quality. If you do want to watch them, install GZDoom, download the doom wad, and download the demo.
You can then use this command to play the demo :
gzdoom -iwad /path/to/doom/wad -playdemo /path/to/demo/lmp
If you just want to play the game, use this command :
gzdoom -iwad /path/to/doom/wad -warp 1 1 -skill 5 -record E1M1.lmp
Refer to >>1507
to see what this command does.