Demos not recorded with v1.9

[Grimm]

Forgive me for asking a question I should probably already know the answer to, but what exactly does one do to view a demo that wasn't recorded with Doom 1.9? I have a demo for a PWAD here that ALMOST ran right, until he got nuked by a caco fireball and everything got borked. I also have some interest in viewing the old 1.2 shareware demos . . .

[Grazza]

In general, a demo will play back only with the exe that was used to record it.

However, several ports can also play back demos recorded with other exes, thanks to compatibility modes that are built into them. Most notable is prboom-plus. Just try to play back the demo as normal - if the format is recognized, then it will attempt to play it back with the appropriate compatibility settings. v1.2 demos, however, are poorly supported, and will not always play back OK (improvements have been made, but problems remain due to the 1.2 source code not being available). For these, I recommend using doom.exe 1.2, if necessary running under Dosbox.

[myk]

Since the demo ran in the first place, it was recorded with one of the v1.9 variants or with compatibility with them. Sometimes the text file says the exact version used, it could be:

• Doom v1.9: Comes with the shareware, DOOM v1.9 and DOOM II v1.9
  
• The Ultimate Doom (v1.9): Comes with The Ultimate DOOM
  
• Final Doom (v1.9): Comes with Final DOOM
  
• Doom95 (v1.9): The port by microsoft
  
• An engine emulating one of the above*

* I think an exception is DOSDoom and some of its variants; these are very similar to The Ultimate Doom (except when overflows occur, see below).

Doom95 and The Ultimate Doom should be identical for demo playback, and their difference with Doom v1.9 is that Lost souls behave in a slightly different way (bouncing on the floor).

Final Doom is like The Ultimate Doom, but has a slight glitch in the teleporter code, which may affect playback on the other versions.

Older versions of PrBoom, PrBoom-plus, and Chocolate Doom sometimes has small bugs that made demos play differently. In the latest versions differences are unlikely, besides, PrBoom-plus can emulate its earlier buggy versions to play demos recorded with them.

Finally, rarely Doom's bugs and limits may cause overflows that may make demos play differently under different operating systems (e.g., Windows 98 vs. Windows XP). In that case it's best to use PrBoom-plus to check the demo (because it has options for detecting these) and apply "overflow emulation" to play it back.

Additionally, wads are sometimes modified after they are released, which may cause demos recorded in the earlier version to fail to play back properly in the newer, or vise versa.

[Eugene]

Has someone next demos for pre 1.5 Doom.exe versions?

CYBRLMPS.ZIP
3manlmp.zip (Seems for 1.4)
3pdm-02.zip
4p-death.zip

[myk]

A quick way to tell the version of a demo of v1.4 or higher is by opening the lump with a hex editor, the hexadecimal value of the first byte should be 100 plus the decimal version number. Version 1.9 is 6D which means 109 (m in ascii mode), so version 1.4 should be 68 (equalling 104), and v1.5 should be 69 (or 105).

Earlier versions did not have the version identifier.

[Grimm]

This level was released April 10, 1994. Do we know what the latest .EXE around was at that time?

Based on the official Doom FAQ, it must have been recorded with either 1.2, 1.4, or 1.5. 1.666 was released in September of '94.

The level is an updated version however, which makes it possible that he didn't re-record the demo.

[Never_Again]

There was only one version in common use in the first half of '94, and that is v1.2.