So I tried to enable the rewind feature but I had so success so far.
I enabled it in the /opt/retropie/emulators/retroarch/retroarch.cfg
# Enable rewinding. This will take a performance hit when playing, so it is disabled by default.
# rewind_enable = true
# Rewinding buffer size in megabytes. Bigger rewinding buffer means you can rewind longer.
# The buffer should be approx. 20MB per minute of buffer time.
# rewind_buffer_size = 20
# Rewind granularity. When rewinding defined number of frames, you can rewind several frames at a time, increasing the rewinding speed.
# rewind_granularity = 1
And I bind my L2 Button of my Xbox 360 Controller to it in my /opt/retropie/emulators/retroarch/configs/XboxGamepad(userspacedriver).cfg
Ok so I figured out that input_rewind_btn = "+5" was wrong and I have to use input_rewind_axis = "+5" instead.
But anyways even if I set rewind_enable = true it isn’t activated, when I check it in the retroarch GUI. And even if I activate it there, the rewind doesn’t work. If I push the button I get a short message that says “rewinding” but actually nothing happens.
P.S.: I forgot to mention that I’m using the Retropie 3.0beta2 Image on an Raspberry Pi 2