I just recently set this up and here are a couple items I found as well as will summarize previous comments:
cdimono1 is the only MAME machine that works currently and is listed as "imperfect" on sound and graphics. Basically this means some games will not work. The cdi490a, cdi910, cdimono2 machines are non-working. They will get stuck at the "aqua" boot up screen. Also found sound on some games was "crackly" and mouse sensitivity was very high/controls erratic.
Per MAME/MESS setup for the machine these are the only extensions that will work with the cdimono1 machine (via -listmedia) : .chd .cue .toc .nrg .gdi .iso .cdr
I have converted all my ISO/CUE and BIN/CUE files to CHD format for easier use but ISO/CUE will work as well. You can use the chdman.exe file to convert bin/cue and iso/cue files to CHD. There are a couple Batch file CHDMAN examples here on LB site that I used and example BAT file is at end of this post.
I have found that some of the CUE files from web locations are INCORRECT and reference the wrong bin file. That may result in a black screen depending on which BIN file is wrong (or just stops immediately). If you are getting this open up the CUE and verify the name of the BIN/ISO is exactly the same as your files. If not, change and save and try again. If you use CHDMAN to convert files, then an incorrect CUE file will cause CHDMAD to gag and stop conversion. Unfortunately, sometimes a black screen means it just doesn't work even though you have it all setup correctly.
Test your MAME setup using command line in DOS CMD window. This will help if something is amiss with your setup or command is incorrect since you can see the error. Once you get working then setup in LB. An example command I used to test by going to the MAME directory and running is at end of post. Adjust your path accordingly. The command below is identical for CUE files . Again, handy to test and see what is going on if getting black screens. Note you will see in the CMD window that CDIC.BIN and SLAVE.BIN have "NO GOOD DUMP KNOWN" errors. You will get those even with games that work. These files are associated with the cdimono1 machine.
When booting a game it will stay at an "aqua" colored screen for about 20 to 30 seconds. Clicking will not speed it up. Remember it is emulating the 1.0x DVD player speeds so everything takes awhile. It then should go to the "Philips" screen. You will see a "Play" button in the middle right of the screen next to the "Play CD-i" text. Use your mouse to move the cursor over to the triangle/play button and click on it to run. Don't move your mouse too fast at first or it can zoom across off screen and appear to be "hidden". Move slow and should see black cursor on screen. I have looked and haven't found anything that skips this step. If the aqua boot screen stays up for longer than 45 seconds to 60 seconds, then the game is broken and will not work in MAME.
Some games you will get an error splash screen that says something along lines of "you need a Digital Video Cartridge to play this game". MAME does not emulate this currently. 7th Guest, Space Ace and Mad Dog Mcree are good examples of games that will boot but cannot run without the DVC since they need the MPEG1 decoder in the DVC to run. Edit: see link on MAME Developer site on this issue.
Unless you do substantial remapping in MAME, this emulator is setup for keyboard and mouse input with mouse doing most of work. Clicking button mouse on many games is like "Start" on controller.
Once booted into a game, you will notice a digital/LCD looking "CD-I" at top screen. You can remove that by going into the setup menu in MAME. So TAB, Video Options and then select MAIN SCREEN only and not Main + LCD. Basically, MAME is also emulating the LCD screen on the front of the CD-i player which is basically useless for our purposes. It should save the setting in your CFG file so you won't have to do on subsequent games.
Once you know things are working then you can go back into LB and under the MAME emulator and enter into Philips CD-i associated platform command-line parameters: cdimono1 - cdrom
On side note, I was just out of college when CD-i released at an obscenely high price and also at same time as SNES came out. After playing some of the games, I am glad I bought a SNES!
Example MAME Command (launch in MAME directory):
mame64.exe cdimono1 -cdrom "G:\Emulators\Philips CD-i\roms\Alien Gate (CD-i).chd"
Example CHDMAN batch file contents. Make sure to copy your CHDMAN.exe and batch file to same folder. Set your paths to your locations as well as change "ISO" to "CUE" if you are doing BIN/ISOs.
@echo off
@cls
set rompath=G:\Emulators\Panasonic 3DO\roms\
set destpath=G:\Emulators\Panasonic 3DO\chd\
for /R "%rompath%" %%G in (*.iso) do (
echo.
echo === Converting %%~nG to CHD ===
chdman createcd -i "%%G" -o "%destpath%\%%~nG.chd" -f
echo.
echo.
)