DOOM v1.9 to v1.91 patcher (

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Sept 23, 2004: doomp191 version 1 is released! This is a historic day. For the past 10 years, Doom players have had to deal with an inherent problem in Doom: when you record, your mouse is less precise, and when you move your mouse really slowly, your guy doesn't even turn at all! Those days are officially over. We now have a program that will patch Doom2.exe (and fdoom.exe and doom.exe {ultimate doom}) such that full mouse precision during recording is restored. This is an actual hack to the executables, not a port. Because of the significance of this change, we are calling this patched version of Doom by version number 1.91.

Please note that version 1.91 is not an official 'id software' patch for the Doom executables (like the 1.666 to 1.9 patch). It was created and released by the people listed in the program documentation textfile, and they are not associated with id software.

The patched 1.91 doom.exe, doom2.exe, and fdoom.exe executables record demos in an expanded format as compared with the old version, and the .lmp files are about 25% larger. These differences are a direct result of the additional data that is stored in the .lmp file for player turning. This means that the demos made with 1.91 absolutely cannot be played back on the old 1.9 version executables. The version 1.91 executable, or prboom version 2.2.5 or newer, is required to play the demos back.

Conversely, because the changes to create version 1.91 are a hex edited hack to the executables and are not compiled from source, 1.91 cannot play older 1.9 demos either. The demos  from versions 1.9 and 1.91 are truly exclusive to their own version (with the exception of prboom version 2.2.5 and later, and possibly other ports that may be able to play back demos from 1.91 in the future). You will need to keep a copy of the original 1.9 doom executables around if you want to participate in Compet-N or have a 16-bit executable for watching version 1.9 demos, all historical demos as well as Compet-N are version 1.9).

Instructions on how to use the patcher, and other details, are listed below in the doomp191 documentation. Details about exactly how the patch works can be read on cph's Doom2 Longtics Hack page. The prboom homepage is .

doomp191 documentation:

Program to patch the last official id software release versions of Ultimate Doom, Doom2, and Final Doom to version 1.91.

Doom/Doom2/fdoom version 1.91 is an unofficial exe release version that was created to repair a problem with the original executables' characteristics during the recording of games. In the original id software release versions, recording causes mouse and trackball players' turning precision to be decreased as compared with gameplay during nonrecorded games. This makes for in-game symptoms of generally decreased aiming precision for players who use low sensitivity mouse/trackball settings or acceleration, and for all players, very slow turns are impossible. Version 1.19 restores the full mouse resolution into the game during recording.

The nature of this change causes .lmp files created by version 1.91 to be roughly 25% larger than those created by the original game, and they cannot be played back using the original game. The demos require version 1.91 to play back correctly, they will not play back using version 1.9. (Note: the next version of prboom will support playback and recording of 1.91 formatted demos). Conversely, version 1.91 cannot play back demos from 1.9.


Unzip into your Doom directory.

From a dos prompt, change into your Doom directory. To patch the three original executables, the usage would be:

doomp191 doom.exe
doomp191 doom2.exe
doomp191 fdoom.exe

Using the patcher this way causes your original executable to be backed up as "doom.v19", "doom2.v19", or "fdoom.v19", respectively.

To patch the original game executables without having the patcher make a backup copy of the original, the usage is:

doomp191 -o doom.exe

To remove the notice about the game requiring you to hit enter before each game start (this includes the stop screen when external wads are loaded), run the patcher a second time with this usage:

doomp191 -rn doom.exe


Misc. Info:

Players who use 1.91 for recording of games intended for release should be certain to specify version 1.91 in their documentation textfiles, to avoid confusion (a link to the patcher program could also be included in the demo textfile.)

The internal version tag for 1.91 demos is 1.11.

Prboom versions 2.2.5 and newer can record and play back version 1.91 demos.

Version 1.91 recordings are not being accepted for Compet-N at the time of this writing.

Wad authors take note: version 1.91, on game startup after the title screen, will search for internal demos within the wads named "DEMO1LT", "DEMO2LT", etc,  unlike 1.9 which searches for "DEMO1", "DEMO2", etc. This enables you to replace demos in your wad and include demos recorded in both 1.9 and 1.91, and both executables will handle the single player demo playback without crashing. (The "LT" stands for "longtics").

Check the doomp191 website for any updates! .

Where to get this file: or email the authors.

DOOM v1.9 to v1.91 patcher, version 1.0 [Sep 23 2004 18:57:16]
Assembly hacks by Colin Phipps (
with help from vv ( and Dashiva (,
with input from BahdKo ( and ocelot

Patcher utility written by vv <>

Documentation written by BahdKo
September 23, 2004