Turning resolution is lowered when recording demos

If a player is recording a demo under Vanilla Doom, the resolution with which they can turn the player is decreased. This is due to a limit in the Doom demo format.

Internally Doom uses a 16-bit integer (two bytes) to store the turning movement. When playing network games, two bytes are transmitted, for example. However, the Doom demo format uses a single byte to record the turning movement of the player. Because of this, the range of values that a player can turn each tic is substantially reduced.

To cope with this limitation, the resolution when turning must be reduced when recording a demo; otherwise, the demo might become desyncronised when played back. Doom does this, but the effect is noticable to experienced players (while aiming over a long distance, for example). Playing while recording a demo is arguably more difficult than playing normally, and this makes speedruns more difficult.

Solution to the problem
Colin "cph" Phipps developed a solution to the problem in the form of a modified Doom binary. His "DOOM v1.9 to v1.91 patcher" modifies the version 1.9 Doom executable to record demos using a 16-bit format for turning values. This removes the problem of reduced resolution.

A slight problem with this solution is that demos recorded using the modified binary will not play in v1.9 Vanilla Doom, and vice-versa. However, prBoom also supports the format.