Flipped Display on Pi2Scart (to use with a half-silvered mirror)

OneSwitch

I'm wondering if anyone has had any luck flipping the display using a CRT display, so that it appears the right-way around when reflected on glass (i.e. as is done with the original Space Invaders).

I've managed to do this with an HDMI monitor, but when I use...

display_hdmi_rotate
result
0 - no rotation
1 - rotate 90 degrees clockwise
2 - rotate 180 degrees clockwise
3 - rotate 270 degrees clockwise
0x10000 horizontal flip
0x20000 vertical flip
0x30000 both flipped

...the image rotates, but never flips.

Any ideas appreciated. Would be great to get Space Invaders and the RetroPie front end all working when used with a mirror.

I'm using a Raspsberry Pi 3B+ with RetroPie 4.4 and Pi2Scart.

OneSwitch

I know self-bumping is a bit rude. Would love to find out if anyone has had luck flipping/mirroring an upright RetroPie Raspberry Pi 3B+ image using Pi2Scart. This would be so nice for anyone with a broken Space Invaders machine, struggling to get the ancient hardware working, at least as a stop gap.

mitu

@OneSwitch I don't think that mirroring can be done globally - like rotating the screen can be done - , but only with a shader - as noted in https://retropie.org.uk/forum/topic/20566/.

OneSwitch

@mitu You can on an HDMI monitor, but I'm not smart enough to work out how to do it (if possible) on a CRT monitor. I've heard recalbox can do it, but I'd rather stick with RetroPie if I can at this stage. This works right now in my Space Invaders...

disable_overscan=1

hdmi_ignore_edid=0xa5000080
hdmi_drive=2
hdmi_group=2
hdmi_mode=69
display_hdmi_rotate 0x20000

# Enable audio (loads snd_bcm2835)
dtparam=audio=on
gpu_mem_256=128
gpu_mem_512=256
gpu_mem_1024=256
overscan_scale=1

This works well in Pi2Scart for everything but for being a flipped image:

# For more options and information see
# http://rpf.io/configtxt
# Some settings may impact device functionality. See link above for details

# uncomment if you get no picture on HDMI for a default "safe" mode
#hdmi_safe=1

# uncomment this if your display has a black border of unused pixels visible
# and your display can output without overscan
disable_overscan=0

# uncomment the following to adjust overscan. Use positive numbers if console
# goes off screen, and negative if there is too much border
#overscan_left=32
#overscan_right=32
#overscan_top=0
#overscan_bottom=16

# uncomment to force a console size. By default it will be display's size minus
# overscan.
#framebuffer_width=1280
#framebuffer_height=720

# uncomment if hdmi display is not detected and composite is being output
#hdmi_force_hotplug=1

# uncomment to force a specific HDMI mode (this will force VGA)
#hdmi_group=1
#hdmi_mode=1

# uncomment to force a HDMI mode rather than DVI. This can make audio work in
# DMT (computer monitor) modes
#hdmi_drive=2

# uncomment to increase signal to HDMI, if you have interference, blanking, or
# no display
#config_hdmi_boost=4

# uncomment for composite PAL
#sdtv_mode=2

#uncomment to overclock the arm. 700 MHz is the default.
#arm_freq=800

# Uncomment some or all of these to enable the optional hardware interfaces
#dtparam=i2c_arm=on
#dtparam=i2s=on
#dtparam=spi=on

# Uncomment this to enable the lirc-rpi module
#dtoverlay=lirc-rpi

# Additional overlays and parameters are documented /boot/overlays/README

# Enable audio (loads snd_bcm2835)
dtparam=audio=on
gpu_mem_256=128
gpu_mem_512=256
gpu_mem_1024=256
overscan_scale=1

# pi2scart only
dtoverlay=vga666

# crt settings
disable_audio_dither=1
enable_dpi_lcd=1
display_default_lcd=1
dpi_group=2
dpi_mode=87
hdmi_timings=320 1 10 20 54 240 1 6 8 10 0 0 0 60 0 6400000 1 
display_rotate=1 #UNCOMMENT THIS LINE FOR HORIZONTAL GAMES

Obviously, a CRT TV would look far more original, in a reliable way in my Space Invaders, as for other people too trying to bring life back to these 40 year old machines. And other mirrored games of which there are quite a lot.

youxia

It's quite a specific request. You can try to ask on Arcade Forge's facebook page.

OneSwitch

@youxia I don't use Facebook, but I have sent them an e-mail. If I get any luck, I'll post it back here.

youxia

Yeah, I got similar problem. Don't use fb but have some questions for them. I think I will need to use my aunt's account :)

OneSwitch

Space Invaders mirrored effect

I'll pass this thread onto Jochen at Arcade Forge too by e-mail. Basically, the hope is to be able to flip the image, as seen in this image of a Space Invaders machine in the bottom-most CRT screen. But not just for the game, but the entire Raspberry Pi display. So the RetroPie menu screens are the correct way around in a mirror, as well as the games, vertically, on a CRT screen through Pi2Scart. That would be fantastic.

OneSwitch

Had this from Jochen at Arcade Forge:

"I have digged the SDL 1.2 and SLD 2 libs. I think it's not possible to get with standard libs to solve this task. So this will be a real head scratcher for the front end developers. I doubt that someone will write a piece of code to support that. Its difficult."

grant2258

there is code in mame2003_plus and mame2003 that does this it would need to be done per core though you can certainly add a bit of code yourself to mame2003 or plus to get space invaders output like this.

OneSwitch

@grant2258 Top post explains it a bit more. I can already get the game flipped on a CRT TV. I can't get Emulation Station flipped too. Flipped to work if viewed in a mirror.