Demos?

[Chronoteeth]

What the hell are demos? And do they run on zdoom or EDGE? I never knew what they meaned!

[Relica Religia]

Oh dear.

You have no idea what a demo is? It's a recording of someone else playing the game, usually for showing off speed records or awesome tricks.

There is a Demos section in the forums, here.

And yeah, they work with ZDOOM and EDGE.

[Grazza]

A demo is a recording of the player's actions. Most ports support the recording and playing back of demos. However, in general they only play back with the same engine that they were recorded with.

To watch a demo, you put "-playdemo" in the command-line, followed by the name of the demo file. Thus:
doom2 -playdemo 30nm3112
plays back the demo named 30nm3112.lmp using doom2.exe and the doom2 iwad.

To play back a pwad demo, you need to include the pwad in the command line, as normal, using "-file". Example:
prboom -file hr.wad hrmus.wad -playdemo 30hr2843
plays back the demo named 30hr2843.lmp using prboom, and Hell Revealed.

Dragging and dropping also works with prboom - drag and drop the demo file (and any pwads and dehs needed) onto an icon for prboom. Note that the default iwad it uses is Doom2.wad. If you need to use a different iwad, then you need to specify it with "iwad" in the command line, or else to make an icon to abother copy of prboom that has a different iwad (simplest way: to put a copy in a folder, where there is a copy of doom.wad {or one of the Final Doom iwads, whatever} but no doom2.wad).

To record a demo, you need to put "-record" in the command line, followed by the name you want the demo to have. You will also need to specify a skill level and warp to the level on which you want to begin.

In some ports, compatibility modes have been implemented that enable them to play back demos from some other ports. Most notable are Eternity and Prboom, which will play back demos from the original games, Boom, MBF (and some others) with a high degree of success. (A failure is known as a "desync", and generally means the player starts acting crazily, shooting walls, and most often dying.)

Prboom (versions 2.2.x) can also be used to record demos in several formats. See the documentation for details.

The majority of demos you'll find online will playback with Prboom or Eternity. Both programs will normally autodetect the demo format. There should generally be a textfile accompanying a demo. Read this to see if you need to use a different port to watch the demo. The most common other ports for recording are Legacy and Zdoom. In each case, you will need to make sure you have the same version of the port that was used to record it. (A Zdoom demo from version 2.0.47, for instance, is quite unlikely to play back with 2.0.63a, etc.)

Useful links:
PrBoom
Eternity
Compet-n
Doomed Speed Demos Archive
Doomworld Demos Forum
Doom2.net

[Opulent]

great post, Grazza.
unfortunately, there is some confusion sometimes between 'playable game demos' and 'playback demos' in the gaming communities.
(I think that is why they are called 'replays' sometimes instead of 'demos')

[Grazza]

Yes, I was thinking that we needed a sticky/announcement in the Demos forum about the basics of watching and recording demos. This seemed like a perfect opportunity to start drafting it. :)

You're right that "demo" has more than one meaning (as does "replay" too). Thankfully, I don't recall anyone ever confusing "Demos" with the moon of Mars though.

[Kristian Ronge]

Grazza said:
Thankfully, I don't recall anyone ever confusing "Demos" with the moon of Mars though.

Hahahahaha.... :-D

[Enjay]

Grazza said:

Thankfully, I don't recall anyone ever confusing "Demos" with the moon of Mars though.

Well, it seems your thanks fell on deaf ears. When looking through the forum and coming upon this topic I actually thought "heh, someone spelled Deimos incorrectly" and assumed it was a thread where someone was asking something about the Martian moon. Doh! It's too early for me.