CRT on Raspberry Pi3 - overscan issue

[madbrain]

I'm using a Pi 3B+ with the composite output cable. I had to set

[pi3]
temp_soft_limit=70
dtoverlay=vc4-kms-v3d,composite=1
include crt/recalbox-crt-config.txt

in config.txt in order to be able to get a picture on bootup.

This dtoverlay line containing "composite=1" is not mentioned in the article on CRT at https://wiki.recalbox.com/en/tutorials/video/crt/crt-screen-with-composite , but probably should be.

Unfortunately, there is massive overscan, not sure how many pixels, but it seems huge. overscan is supposedly disabled by default.
I tried to play with the settings mentioned at https://wiki.recalbox.com/en/tutorials/video/display-configuration/image-size-settings-overscan-tft but they unfortunately did not improve things.

Does anyone have a suggestion ? I would rather have black bars on the sides than have the picture seemingly cropped.

[poppadum]

@madbrain This Pi firmware issue thread suggests inserting into /boot/cmdline.txt:

video=Composite-1:720x480@60,margin_left=32,margin_right=32,margin_top=32,margin_bottom=32

Replace the 720x480@60 with 720x576@50 if you're using PAL, and the margin values as you see fit.

[madbrain]

@poppadum said in CRT on Raspberry Pi3 - overscan issue:

video=Composite-1:720x480@60,margin_left=32,margin_right=32,margin_top=32,margin_bottom=32

Thanks. Unfortunately, this had no effect on the overscan - the image is still vastly cropped. The values for margin_xxx seem to be ignored. The resolution is not ignored. I tried to switch to 640x480 (a 4:3 resolution, as my CRT is 4:3) and ended up with a blank screen on boot. unfortunately. But at least I know the OS is doing something with to the video from the config and not just ignoring it. Sigh.

[madbrain]

I'm still looking for a solution to this. I can't use Recalbox at all due to this problem. Too much of the display is off-TV.

[Huskion]

@madbrain

Hi there, I had the same problem as you. I couldn't get the Pi3 composite output working with overscan for Recalbox. I've spent quite a while figuring this out on my Pi3 but I think I've got it.

It may be contradictory in some places, but please set your config.txt in the following way, making sure that each line is in this exact order:

[pi3]
# Raise the first security limit up to 70   instead of 60   for pi3
temp_soft_limit=70
enable_tvout=1

#NTSC-480i
sdtv_mode=0

#NTSC-240p
#sdtv_mode=16

#PAL-576i
#sdtv_mode=2

#PAL-256p
#sdtv_mode=18

#4:3
sdtv_aspect=1

#16:9
#sdtv_aspect=3

disable_overscan=1 #this is on purpose
hdmi_force_hotplug=0
hdmi_ignore_hotplug=1
dtoverlay=vc4-fkms-v3d #fkms not kms
overscan_top=32
overscan_bottom=32
overscan_left=32
overscan_right=32
include crt/recalbox-crt-config.txt

Uncomment (delete #) from the start of the line for the resolution and mode you need. It is also important that you have 'fkms' instead of 'kms'. You will likely need to adjust the overscan values to the desired amounts after testing a few times. For me (Sony Trinitron) I used -14, -5, 13, 25 respectively. You can also use overscan_scale=0 instead of the four individual values and see if that's better for you.

Additionally, you have to edit the file cmdline.txt. The entry is a single line and must stay that way. At the end of the existing text, add:

video=Composite-1:720x480@60ie

for NTSC-480i.

For NTSC-240p you will need to keep 720x480 but the end should say @60e (no i means no interlacing). Setting 720x240p here will cause the image to only appear across the upper half of the screen.

Likewise, for PAL-576i, it's 720x576@50ie. For PAL-256p it's 720x576@50e.

I hope this helps you and anyone else with this issue.
P.S. I think updating Recalbox will reset all this. Might be better to put it into recalbox-crt-config.txt but I'll cross that bridge when I get to it.