Success! Ok i figured it out. This is going to be a long one so sit back, but anyone with a similar problem, i hope this will work for you. Again I am running RetroPie on a raspberry Pi 3 with a Pi2Jamma adaptor and i ran the retropiergb mod to output to a 15khz monitor. so i figured that this was an issue with the run command, so i found a file in the /opt.retropie/configs/all, named runcommand-onend.sh . In it there is a line for HDMI timings that was different then the one in the global config.txt in the boot folder. so i added the correct timings and # out the originals and it worked! but then for some reason mame was outputting a very stretched image at 1920x240, so i went into the configuration options in the run command menu and changed the settings in the edit custom retroarch config option. In it you will see that the custom viewport is set to 1920x240, so i just added a pond symbol before the commands. Since the layout seems to be UK it is a £ instead of # for us Americans but it works just the same. and now mame defaults to the listed game resolution. I have no Idea why these options did this but I wasn't going to let this beat me. I hope this helps.
I'm returning to advise you of my good fortune and to help any others who may have been in the same situation as me.
I had been using my Xarcade tank stick controller in "Mode 1" with the Xarcade2Jstick driver which meant that Retropie was recognising it as a keyboard (iPac-type encoder).
I have now switched the controller to "Mode 4" and omitted the driver which means that Retropie recognises the controller as two separate XBox 360 controllers.
I can now configure each side of the controller with identical mappings and any game/platform I wish to use the right side instead of the left side of the controller, I simply change the Port 1 binds for in Retroarch.
When I do this, Hotkey+Start (even on the righthand side) performs correctly and exits the game.
@pscotto1234 I don't know, I used 'rm' from the command line, and ended up just downloading the few bezels I wanted "by hand" from the bezel project github and other places mentioned in this forum.
However, this got very tedious, so if you don't need the GB of space, just leave it there? The problem for me was that my card got totally filled and things like updates started to fail in way that I didn't notice :(
I think to do this:
from terminal ls > system_name.txt in each system folder to obtain a file containing roms name;
rename the listed file extension in .png ;
from terminal ls > system_image.txt in each bezel folder to obtain image list;
compare files for the same system to mantain only image name for roms not present in my collection;
with command cat system_name.txt | xargs rm I can remove not useful image;
@iandaemon Not exactly. An arcade cocktail table and I installed dual monitors in them with a Raspberry Pi 4. My plan B is to use a VGA or HDMI splitter but I'd like to see if can be done with the dual HDMI outputs already available on the Raspberry Pi 4. Any ideas?
but if you can't get into the runcommand menu, it's a moot point i guess.
now, as for your issue - donkey kong's 2 player mode uses one stick - the real cabinet only had one (and why not, since, the 2 player mode isn't simultaneous). you take turns on one stick.
it's possible that there's a cocktail/2p mode you can select via the service menu or dipswitches, or you could map the player 2 controls as alternatives for player 2 via the MAME menu for this game only, or something like that.
note, these instructions are for mame2003 (which is recommended), not the mame2016 which you're using (which is not recommended).
That happened also in 4.6 and it's not specific to RetroPie.
Since the Pi4 supports 4k, by default it will use the video mode advertised as 'preferred' by the TV. If that's 4k, then this is what it will use. Previous models didn't have this issue, since they didn't support 4k. You can check with tvservice -m CEA what video modes your TV supports and what is the preferred mode.