[CD-i] Sound mixing not faithful to the real machine

[Slamy]

MAME version

0.270 (mame0270-59-g9c54072486b)

System information

Debian 12

INI configuration details

No response

Emulated system/software

CD-i (cdimono1)

Incorrect behaviour

Multiple mono audio sources are played back with total stereo separation. For example, Zelda - Wand of Gamelon has the BGM on the left and SFX on the right.

Expected behaviour

Zelda - Wand of Gamelon has the BGM and SFX mixed on both channels.

Steps to reproduce

Play some Zelda - Wand of Gamelon and experience it during while playing a 2D level

Additional details

No response

[rb6502]

Do you have reference video from a real CD-i player connected with stereo cables?

[rb6502]

CC @MooglyGuy

[Vincent-Halver]

Another example is for Kether.
In Kether, you will hear French narration in the left channel, and English narration in the right.

This technique was often employed in bilingual audio tracks, however one of the tracks is likely supposed to be muted depending on your chosen language.

[Slamy]

@rb6502 I've totally forgotten to provide some example files here. I don't have a good capture card for video so I'll provide some audio instead if this is ok.
wand_of_gamelon.zip
This is the whole boot process of Zelda Wand of Gamelon on a CD-i 210/05. During this, the game switches various modes.

The first accuracy issue starts at 0:47 as the hardware mixer will fade out the audio when selecting "Start game". This is missing right now in mame as the volume stays the same.

The same happens again at about 1:14 when selecting "Aru Ainu" on the map.

At 1:20 the audio you hear from a real CD-i is both stereo channels mixed to mono as the BGM is hard on the left and the SFX is on the right. On mame you will notice this with headphones.

Edit: At 1:30 things are again interesting. If you crouch by pressing down and press B2, the menu opens. The external mixer is used to lower the volume. This effect is also missing on mame.