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Type 1 Hanging Note bug

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First post, by maxtherabbit

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From the Vogons wiki:

Type 1: Illegitimate hanging notes […]
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Type 1: Illegitimate hanging notes

This variant of the bug manifests itself as "rogue" MIDI notes being generated during MIDI playback. Since these notes are not part of the soundtrack, they are not stopped and hang for a long time. Also, these 'illegitimate' notes tend to be high-pitched, which makes this variant of the bug a rather annoying experience.

It occurs in the following games:
Games using the DMX sound system by Paul Radek:

Doom
Doom2
Heretic
Hexen
Raptor
Hocus Pocus

Build engine games

Duke Nukem 3D
Blood
Shadow Warrior (Shareware)

does this mean that the bug ONLY affects the aforementioned games? Or that it can affect all games but it's most obvious in those listed?

Reply 1 of 2, by Cloudschatze

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maxtherabbit wrote on 2022-04-22, 14:21:

does this mean that the bug ONLY affects the aforementioned games? Or that it can affect all games but it's most obvious in those listed?

On affected cards, and where the MPU has been initialized, the last (latched) MIDI byte is re-sent with each and every DMA interrupt that occurs during digital audio playback. The frequency of the DMA interrupts, and whether the resulting extraneous MIDI bytes are sequential, determines whether those bytes get interpreted as valid MIDI data, or just get ignored by a target MIDI device. With the affected cards, all games leveraging concurrent MIDI and digital audio playback exhibit this behavior. The problematic games-in-question tend to use a 4K DMA buffer though, resulting in a greater number of DMA interrupts, and a corresponding and larger incidence of problematic MIDI behavior.

The latter, in short.

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