"240p" from composite

[bleck]

Hey guys,

Is it possible to get a 320x240 60Hz progressive signal (called "240p" in the retro gaming community) from the Raspberry Pi's composite output? I'm basically trying to get it to output the type of signal that would create an image with no flicker and
scanlines on a CRT TV (like the output from the NES, SNES, etc). So instead of alternating between odd and even lines at 60Hz, it should output at 60Hz to just even or just odd lines.

This mode seems to exist from the HDMI output, and I can get the pi to output 320x240 at 60hz interlaced (which I'm guessing is upscaled to 480i before outputting) by changing the framebuffer.

Any ideas?

Cheers

Sorry if this has already been asked.

[Raimu]

It's not a mode that outputs only odd or even, it's a mode that outputs about the exact same picture on both the odd and the even scanlines. That said, the composite TV output for Raspi seems like a slightly "loose" implementation... I think the best bet would be to configure your emulator to output at a resolution that scales neatly enough when it's sent to Raspi's TV-out system.

[-heisenberg-]

This is relevant to my interests.

I've been meaning to try this exact same thing. Unfortunately I don't have a CRT handy right now, but here's the theory: you need is a modeline for your resolution. Add it to /etc/fb.modes and then do something like

Code: Select all

fbset -a -v "320x200 60Hz 16bit"

(or whatever your mode is called).

[-heisenberg-]

Update: I've tried it, and it doesn't work. Apparently the interlace bit is set by the firmware. I've started a new topic here:

http://www.raspberrypi.org/phpBB3/viewt ... 63&t=27599