Netplay: Multiplayer feature overrides spectator mode

[gaafiz]

Hello,

First of all, thank you for adding support for Multiplayer via Netplay, as it makes the GBA emulation experience much more complete!
However, this new feature appears to completely override the possibility of using Netplay in spectator mode, which is important for my use case.

Use case:

• Play Pokémon Roms (such as Leaf Green and Emerald) on a PSVita
• Allow friends with Retroarch for PC or Phone to spectate my game
• We started playing Nuzlocke challenges together, while spectating and occasionally switching the first player.
• Retroarch is the only way to have a spectate + switch-player experience on the PSVita
• GPSP is the only GBA core with decent performance on the PSVita.

To date, we have accomplished all this with an older version of gpsp (0.9.1). However, we recently updated the core to 1.0.0 and couldn't manage to make the spectator mode work anymore. By reading here and there, I discovered that this is due to the new Multiplayer feature introduced, which now uses Netplay to enable Link Cable connections.

Is there a workaround to still allow what was possible in the older versions of gpsp core (Spectate + Switching player)?
I tried forcing spectator mode from Netplay/Network options, and marking as OFF the "Link Cable Connectivity" core option. Anything else I can try?

As an alternative, is there a way to download a pre-built older version of the gpsp core (0.9.1) for Android?
I tried visiting https://buildbot.libretro.com, but the Android apk of older RetroArch does not contain the cores. I tried to use those from the Linux build, but didn't work

Any help is appreciated : )

[davidgfnet]

There are essentially 2 netplay modes in Retroarch. They are unfortunately hidden to the user in the sense that it's unclear which one is being used.

The old fashion netplay, usually used to play a console that features multiple gamepads (aka I play Zelda on the SNES with a friend). This one is snapshot based and allows for spectators to join.
Then we have the "true multiplayer" mode, that was introduced in 1.17 (see https://www.libretro.com/index.php/retroarch-1-17-new-netplay-features/). This mode is for multiplay using mutiple consoles (ie. two DOS PCs or two GBAs).

This last mode is more or less real in the sense that each person has an emulator and a ROM and they play independently, only exchaning data (like in the past via Wifi or internet). For this there's no possibility of spectator mode, since there's no snapshots being sent around. SOrry!

[gaafiz]

No need to be sorry, what you implemented is already awesome :D

I'm aware of these 2 netplay modes: Same console multiple players (old fashion netplay) versus Multiple consoles connected (true multiplayer). With the latter depending much on actual netplay implementation done by the libretro plugin developer.

With gpsp I would like to use both:

• True multiplayer -> for when I want to do some pokemon battles with a friend
• Old-fashioned way -> for when we want to spectate the same single player game, while switching player 1 control from time to time (i.e. after each death)

Using the same Retroarch version, my workaround is the following:

• When I want to play True multiplayer -> I install latest gpsp and do netplay
• When I want to play in spectator mode with player1 switching -> I re-install manually gpsp 0.9.1

Is there a way to avoid this headache and add a "netplay mode" configuration at the core level, which can switch between old-fashion to true multiplayer and viceversa?
This way I can always keep using the latest gpsp version.

[davidgfnet]

Yeah unfortunately there's no way to use both netplay modes for a core (I think?)
We could conditionally skip RETRO_ENVIRONMENT_SET_NETPACKET_INTERFACE but given it happens at init() I am not sure this can be a switchable core option. I think the libretro iface assumes that this remains stable from load to unload.
If you want to use the latest version without netpacket (the "real" netplay) simply comment the line "environ_cb(RETRO_ENVIRONMENT_SET_NETPACKET_INTERFACE, (void*)&netpacket_iface);" and build the core. But yeah you would have to build it yourself :P