SCI: QFG2 - Heavy reverb from city street sounds continues to incorrectly affect other game sounds and music when using MT32 emulator

[Lambonius83]

ScummVM 2.3.0git257-g0e4e3354bd (Sep 4 2020 22:42:10)

(I also experienced this bug using ScummVM 2.1.2)

This bug seems to happen when using Scummvm's MT32 emulator for audio in this game. When the game starts, audio plays normally, with the appropriate amount of reverb. When you enter one of the city street maze screens, the ambient sounds are blanketed in heavy reverb, which is also correct (I believe.) The bug begins when you exit any of these city street maze screens into any other area with sounds (like the fountain plaza, for example.) The heavy reverb from the ambient city street noises continues to impact all other sounds in the game from that point on.

To reproduce this, start a new game and exit the inn. Note the sound of the snake charmer's tune. Now walk north from the the plaza into the first city street maze screen, then turn around and walk back to the gate plaza. It will be immediately clear that the snake charmer's music sounds like it's playing from the far end of a tunnel. This happens any time you exit any of the street screens, as far as I can tell.

Game version & Language: 1.102 DOS/English (GoG release)
OS: Windows 7 Home Premium 64-bit

[ZvikaZ]

Have you verified that it's ok with adlib?
Can you check it with Dosbox as well (if you can install Munt for MT32 emulation under Dosbox)

[Lambonius83]

I checked it with Adlib, and the sound is fine. The ambient street sounds actually don't exist with Adlib, so the reverb problem is a non-issue there.

I checked it out with the same game version and Roland roms in Dosbox using Munt, and the lingering reverb does exist, but only for a few seconds, and then the reverb cuts out (as it's supposed to) and the non-reverbed sounds play as normal.

For some reason, Scummvm prevents the MT32 emulator from turning off the reverb effect after it's turned on. I tested this using both the ScummVM built-in MT32 emulator as the MT32 device, and selecting MUNT as the MT32 device (in ScummVM,) and the problem occurs either way.

[ZvikaZ]

Well, I have started debugging it.
Unfortunately, I'm not a musical person ;-)

If you could help me with this, we might solve it together.

First thing, I run ScummVM with '--dump-midi' flag, which dumped all Midi commands issued by ScummVM to a .mid file (attached).
In that file, the first few seconds are in the plaza, before entering the tunnel, then it's in the tunnel until about 20 seconds, and then back again in the plaza.

When opening the .mid file an editor (I like Sekaiju), it seems that there are a bunch of 'Pitch Bend' commands after roughly 20 seconds from the beginning. I guess they are the source of the reverb.

Do you know how to work with midi files?
If yes - you can try and "play" with that file, and try to fix it in an editor.
If you can pinpoint me to the point where there's a missing/wrong/extra midi command, I can try to trace it's source in ScummVM, and fix it.
If not, we'll have harder work, but it's still possible, if you want to cooperate ;-)

[darksoul42]

I would like to add a further piece of information :

• It will also remain in saved games
• It will remain even if you do a Restart (with F9), so you can hear the reverb on the first game screen

[sluicebox]

Fixed by athrxx in: ​https://github.com/scummvm/scummvm/commit/92639d8ba408cc47cebda2345c9df393acc9694f