Recalbox sur TV CRT en RGB

[archimage]

Le HDMI a aussi l'avantage de procurer un DAC audio, ou laisser libre le GPIO pour utiliser quelque chose de plus qualitatif comme du Hifiberry. Pour ma part je trouve ça plus facile de commencer par là. En revanche j'ai constaté un défaut assez contraignant, des fois en sortant d'un émulateur, au retour à Emulation Station j'ai des pertes de synchronisation intempestives. Rebrancher le HDMI ou réinitialiser l'affichage avec la commande tvservice résoud le problème sur le coup. Mais je n'ai pas encore compris d'où ça vient pour l'éliminer entièrement et empêcher que ça revienne en sortant de Retroarch. Le passage du 240p au 480i a l'air d'être un peu chaotique...

[archimage]

Rendu sur un sony BVM .

[Scandy]

@gkralicek2 said in Recalbox sur TV CRT en RGB:

Le VGA n'est pas directement acquis auprès du GPIO puisqu'il faut un réseau de résistance (R-2R ladder) entre la sortie GPIO et le connecteur VGA. Par contre il est vrai que cette méthode n'induit, sur le papier, pas de latence d'affichage comme c'est le cas avec un convertisseur HDMI-VGA (DAC). Dans la pratique et pour avoir comparé les deux longuement, la latence est quasi imperceptible pour peu que le convertisseur HDMI->VGA soit de bonne qualité. Après l'usage du GPIO présente certaines limitations concernant le nombre de couleurs affichables simultanément (codage couleur sur 6 bits par canal donc 18 bits au total soit 262144 couleurs max). Pas vraiment gênant en soi pour des jeux retro utilisant rarement plus de 65536 couleurs à l'écran :=). Par contre l'adaptateur GPIO->VGA monopolisant un grand nombre de broches sur le GPIO, il n'en reste plus assez pour pouvoir connecter des sticks arcade en montage dans un bartop par exemple. La connexion de manettes en USB générant plus d'input lag dans les jeux qu'un stick arcade branché en GPIO (dans les jeux de type Vs fighter c'est flagrant), perso je préfère reserver l'usage du GPIO pour les contrôleurs jeux et sortir du RGB à partir d'un convertisseur HDMI-VGA de qualité avec une latence d'affichage quasi-nulle :=)

Il serait intéressant de faire des test "scientifique" dans le "monde réel", pour évaluer l'existence de:

• convertisseurs HDMI > VGA presque lagless
• arcade stick USB presque lagless (utilisés dans le tournois EVO?)

En outre, le retard induit par le port USB dépend souvent du OS et par l'UI. Je lis quelque part (Shmups forums?) que les ports USB en Linux sous CLI sont pratiquement lagless.

[Substring]

@Scandy let's see where lag can come from, depending on the input method :

• GPIO : the mechanics of sticks/buttons do not generate any lag. The clock scanning the gpio + the processing of the gpio information (which is inside the kernel, not in userspace), then udev or SDL2, is the only source of lag before the data is processed by the emulator
• USB : again, let'.s not bither with mechanics. The info has to be processed by the onboard chip, send the right info through the usb, then processed by the usb-hid kernel module, udev/sdl2 then emulator

I'd say the gpio is slightly faster as the processing preceding the emulator is a bit shorter.

A while ago i tried increasing the kernel rate (known as the Hz patch) + switch the context environment (server/desktop/realtime) ... I wouldn't say i found any miracle, but worse : ES constantly had micro stutters

[aTg]

@gkralicek2 I'm working on a GPIO JAMMA adapter with rgb565, 32 non-latency buttons and audio all through the GPIO.

[Scandy]

@Substring said in Recalbox sur TV CRT en RGB:

The info has to be processed by the onboard chip, send the right info through the usb, then processed by the usb-hid kernel module, udev/sdl2 then emulator

So, forced to only one choice, you'd rather use the GPIO for video or controls?
IMHO the delay generated by an HDMI>VGA converter is more sensitive than that induced by USB hardware.
I do not take into account the delay caused by the emulator/SDL because it would be present in both cases.

[Scandy]

@aTg a RGB-Pi with female SCART and one (or two) DB15 female controller ports would be definitive, IMHO.

[gkralicek2]

@aTg That's good news ! Something i could definetely put to good use in my candycab :=)
But as @scandy mentioned it, an RGB stereo SCART output with DB-15 connectors to plug in neo-geo type arcade sticks would be a definitive killer for CRT TV owners ! :=). Though i doubt there would be enough pins on the GPIO connector to achieve this...

[aTg]

@Scandy That already exists, the rpi2scart ... (A bit expensive the truth)
He thinks that I am alone, I can not launch so many projects at the same time.
I had an idea about this that you are telling me, so that it was not the same as everything I had thought of including in the design a box for the RPi in the form of a console, its connector scart on the back and the DB15 in front, with button of power and reset.
But it's just an idea.

@gkralicek2 If there are, I already have a prototype working.

[Scandy]

@aTg said in Recalbox sur TV CRT en RGB:

@Scandy That already exists, the rpi2scart ... (A bit expensive the truth)
He thinks that I am alone, I can not launch so many projects at the same time.
I had an idea about this that you are telling me, so that it was not the same as everything I had thought of including in the design a box for the RPi in the form of a console, its connector scart on the back and the DB15 in front, with button of power and reset.
But it's just an idea.

@gkralicek2 If there are, I already have a prototype working.

A board with the same form-factor of RPi, placed on top of it (like a "shield") with female SCART and DB15 controllers... hmmmmmm!

[gkralicek2]

@aTg Now that's impressive ! Good job mate !

[Scandy]

Ok guys, I need your help.

RPi3 > HDMI to VGA > OK! (on a LCD monitor)

but

RPi3 > HDMI to VGA > VGA to SCART (from Retrocable.es)

...I get only a black picture.

My crt TV seems to recognize that there is some kind of signal, but I only get a black picture. What I'm doing wrong? :_(

Thanks.

[aTg]

@Scandy For the tv to be set to RGB mode you need 3v on pin 16 of the scart.

[Substring]

@Scandy said in Recalbox sur TV CRT en RGB:

So, forced to only one choice, you'd rather use the GPIO for video or controls?
IMHO the delay generated by an HDMI>VGA converter is more sensitive than that induced by USB hardware.
I do not take into account the delay caused by the emulator/SDL because it would be present in both cases.

D**n, i had hoped I2C pins would still be available in DPI mode, or that DPI can be used for DPI. Looks like not. Too bad

One test that could be done is use a HDMI multiple output, and compare HDMI vs HDMI2VGA at the same time.

Anywya, enugh of trolling stuff

[Substring]

@Scandy said in Recalbox sur TV CRT en RGB:

Ok guys, I need your help.

RPi3 > HDMI to VGA > OK! (on a LCD monitor)

but

RPi3 > HDMI to VGA > VGA to SCART (from Retrocable.es)

...I get only a black picture.

My crt TV seems to recognize that there is some kind of signal, but I only get a black picture. What I'm doing wrong? :_(

Thanks.

@archimage or @ian57 any clue ?

[gkralicek2]

@Scandy Have you plugged the USB connector from the "retrocable.es" cable into one of the Pi USB port or a USB power supply ? You need that +5v line to be connected so the TV can switch to RGB mode properly otherwise it will expect a composite signal by default and display a blank screen.
If you've done that already and still have a black picture then have you modified the config.txt and recalbox.conf files in order to output a video mode compatible with the TV @15khz (such as CEA mode 6 -> 480i or CEA mode 8 ->240p) ?

You could use :
hdmi_group=1
hdmi_mode=6

in your ./boot/config.txt file so that emulation station is displayed in 480i (640*480 interlaced mode)

and :
global.videomode=CEA 8 HDMI

in your ./recalbox/share/system/recalbox.conf file so that your emulators run at 240p (720x240 progressive). Note that you will have to adjust the aspect ratio in retroarch and activate the "smoothing" option in recalbox menus to get a proper 4/3 display in your games out from the 720x240 res.

[Scandy]

@gkralicek2 thank you very much for your feedback.
Yes, the USB was connected, but in config.txt I only set hdmi_safe=1.

I'll check with

hdmi_group=1
hdmi_mode=6

Thanks!

[ian57]

@Substring as gkralicek2, I was thinking of the +5V which force the tv to switch to the right mode.

[gkralicek2]

@Scandy Then that's for sure the source of your problem :=)... If you haven't configured the config.txt file with a proper output video mode compatible with what your CRT TV can display, all you'll get is a black screen. Default boot up res is 640*480 progressive @31khz which is compatible with a PC LCD screen but NOT with a TV set which is limited to resolutions using a 15khz horizontal frequency (240p, 480i or 576i).
Once you'll have applied the settings i gave you in my previous post, you should get a picture :=)

[Scandy]

@gkralicek2 @ian57 @Substring thank you for your help!
Adding a male - female VGA cable between the HDMI > VGA adapter and Retrocable VGA > SCART fixed it (of course I've also setup config.txt).
Now I have a perfectly clear RGB picture on my good old crt TV.

Unfortunately, it seems that real time resolution switch does not work in AdvanceMAME using the HDMI > VGA adapter (I only get a black screen... l'll write to Andrea).

So I still wait for the GPIO - VGA from Malaysia...

P.S. If someone's interested, I found how to use Unibios in AdvanceMAME.