A year and a half later, there is still no solution to fix the sound in the beebem.
Here's what we have so far:
The sound does not work at all or sometimes only works for a few seconds, if we turn it off and on again in the menu.
I looked in the src folder and saw that a large portion of the sdl.cpp file contained sdl sound entries, but I'm not skilled enough to determine where the problem is.
In the same emulator running through teminal windows inside desktop raspbian, the sound works ok.
I also read that support for alsa audio driver needs to be added but I don't know if anyone has done this successfully and how.
Another problem is that the emulator crash (with some GTK error) when using the floppy requester in the internal menu but this can be overcome using the command line options.
For now, the lack of sound is the biggest problem and I hope someone will know how to customize this emulator for retropie.
I have contacted the author by email regarding these issues but for now I have not received an answer.
@mediamogul That sorted the Channel F (with a bit of tweaking), cheers.
The Astrocade I'd already fixed, and it works fine for every game I've tried EXCEPT Space Fortress (unfortunately the best game on the system), which used to run fine but now goes at about 1fps. I tried using your .RC file instead, but the exact same thing happened.
The really freaky one is the Arcadia, though. I can get it to run no problem, right up to the point where I start any game, at which point it plays them by itself. No matter how I set the controls, the player ship will just lurch around, moving and shooting (or whatever) all on its own, regardless of whether I touch the controls or not.
But here's the REALLY wacky part.
If I boot up Pleiades on the Arcadia, it plays through the first three stages by itself. It's pretty good - it clears them all. So I wondered if I'd (somehow) recorded and then played back a previous game. But THEN, and only then, it gives me back control for the last stage (the one where you steer onto an airstrip dodging the parked ships). Keyboard and joystick both control the ship perfectly.
Once I've steered to the target and completed the stage, the Pi takes over and plays by itself again.
I'm still using AdvanceMame, but have lr-mess compiled so will probably give that a go with the BBC Micro B and with the Electron, which I haven't had a go at emulating yet.
I had another look at the stardot forum again. Still no one working on a Linux or Raspberry Pi variant of Beebem or of any other BBC emulator unfortunately. All the current emulation is in relation to MacOS or Windows.
With emulating the Acorn Archimedes, I've seen somewhere on the web that it can be done using a Raspberry Pi, but as it is based on RiscOS, Retropie is a no go.
input_map[key_lshift] keyboard[0,lshift] or joystick_button[0079_0006_3,2]
bbcbp128[home_pi_retropie_roms_bbcmicro_thrust]/input_map[key_lshift] joystick_button[0079_0006_3,2] or keyboard[0,lshift]
bbcbp128[home_pi_retropie_roms_bbcmicro_thrust]/input_map[key_rshift] joystick_button[0079_0006_3,2] or keyboard[0,lshift]
Obviously, the joystick buttons will be different for you. There's unfortunately not a lot of consistency overall between everyone's setups, so experimentation is probably the only way to get there.