When playing PSOne Classics on the PSP, were the games rendered in 320x240p (as far as I know this is the native resolution of PSX games, however the PS1, PS2, and PS3 all output this as 480i and up) or 640x480i then downscaled/deinterlaced and displayed on the screen?

In addition, when using the Video Out feature of the PSP, I notice that PSOne games are in 4:3 full-screen in contrast to window-boxed PSP games. Now what is going on with this mode? If set to Progressive, does it take the 240p native resolution of PSX games and simply upscale that to 480p, or does it take the 480i PSX/PS2 resolution style of the game and then deinterlace?

I believe PS1 games could be rendered at a variety of resolutions, not just 320x240. And all were restricted to 4:3 aspect ratio.

Okee doke, here we go!

The Playstation spit out 320x240 as 240p most of the time, as in 240 lines of progressive output. This is not 480i. Really only in menus did it ever switch over to 640x480 rendering, output as 480i, and even that was quite rare.

Also, when talking about 240p, 480i, or 480p, aspect ratio does not exist as aspect ratios are all handled by the display in question. If a dev wanted to spit out video intended for 16:9 display sources from a Playstation, or even an Atari 2600, it is simply a matter of rendering to the correct amount of horizontal squish.

To answer the original question, the PSP renders PSX games at whatever their native resolution is (mostly 320x240p) and then scales it to the PSP's screen resolution following whatever scaling rules you have in place.

Yeah, I remember there were a few games that had anamorphic modes. One of them was an EA baseball game. Of course, you didn't gain any resolution, you just stretched a squished image across a wider screen.

Thanks, darklordjames, for the detailed explanation!

Now, even though the Playstation spit out 240p, didn't most of the TVs back then just scale that signal into 480i for display?

It's not really the same as scaling as we know it today. CRTs don't have a native res.

BTW some games utilized "high definition" modes on PSX. I believe WipeOut 3 ran at 512x512.

What I don't understand though is, how did it output a progressive signal when TVs of the time couldn't accept it? Did it do 240p internally, and then that was converted for interlaced output over composite or s-video?

"Now, even though the Playstation spit out 240p, didn't most of the TVs back then just scale that signal into 480i for display?"

No.

SD CRT's will natively display both 480i and 240p. There was no such thing as display based scaling back then.

"What I don't understand though is, how did it output a progressive signal when TVs of the time couldn't accept it? Did it do 240p internally, and then that was converted for interlaced output over composite or s-video?"

No No No No and No.

Composite and s-video will both carry 240p, in it's 60fps, progressive form.

Okay, I was confused because TVs of the time were interlaced displays.

No, TVs of the time were not interlaced by nature. It's just that the vast majority of signals fed to them were interlaced. TVs of the time were analog, running at partcular frequencies. As long as the incoming signal complied with those frequencies, the analog displays didn't care if the signal was 240x4000000p, or 480x12i. The display showed the signal as it came in.

A final question.

Why do some HDTVs not properly display PS1 games over Component connections when they play just fine with RF, Composite, and S-Video? The signal output is the same no matter the connection type, 240p, so what would be the problem?

Because most of the time, HDTV's don't ever expect to see 240p, especially over component. In that case, they normally treat it as 480i, which makes it look really blocky in comparison to displaying proper 240p on an analog display. Alternatively, they think that the input is something like VGA 320x200 and totally screw up the image. My previous plasma choked on 240p as well. Trying to play ICO, which I think is the only 240p PS2 game, over component resulted in the image being pushed like 20% off the top of the screen and like 30% off the left. It was unplayable.

As for the reason the display gets messed up? My best guess is that it's because 240p relies on a bit of a timing trick. A vertical blank line gets skipped, causing the same 240 line to be redrawn each field, instead of alternating lines being drawn as in 480i. The blank skip probably trips up the displays scalers or ADC's. It's also quite possible that displays that show a problem with 240p over component, but not sub-s-video simply have two sets of ADC's. On for component inputs, on for sub-s-video inputs.