@mitu Thanks for the pointer on the docs. I've gone through a lot of research and reorganizing since my last post, but it now appears to be working! There were two issues at play: bad rom directory structure and bad install of vldp2.
For reference to the curious, here's the problem I was having with vldp2. Every time the emulator started, it would give this daphne error saying ERROR: could not open the VLDP2 dynamic library (file not found maybe?):
daphne-error.png
For the sake of testing, I ran the following from the command line to see the console output:
/opt/retropie/emulators/daphne/daphne.sh $HOME/RetroPie/roms/daphne/lair.daphne
And at the end of the output, I saw this:
libvldp2.so: cannot open shared object file: No such file or directory
Could not load VLDP dynamic library!!!
Shutting down sound system...
Shutting down video display...
Well the install script for daphne is supposed to install vldp2 for you, but in my case, it wasn't doing that.
You can manually install the Linux x64 version of it by running the following in a temporary directory:
git clone https://github.com/DavidGriffith/daphne.git
cd daphne/src/vldp2
./configure --disable-accel-detect
make -f Makefile.linux_x64
sudo cp libvldp2.so /lib
My theory is that the script was compiling vldp2, but then failing to copy it to the /lib directory that it's supposed to get installed to (that last line in the command above).
I tried fiddling with the script a little to get it to work automatically, but gave up because it was hard to debug. If I can gather the motivation, I'll try to fix it properly and then send a PR to include the changes in RetroPie-Setup.