This is why the Slim has video-out problems

[Ceraphis]

Hey, I posted this in the slim security hack thread but I wanted it to get more exposure as I think I figured it out. Feel free to either call me lamezorz or point out that I ride the short bus if everyone (or at least the devs) knows this already. Alternate theories and discussion highly welcomed and encouraged! :)

I think the problem with the games only going over progressive component and taking up a really small area on the tv screen is that the psp can't go back in time and make all games compatible before this feature came out. If you notice, with a 480p signal the pixels are 720x480, and the psp screen is 480x272. This means that, unless I'm mistaken, there are 104 pixels on each of the left and the right sides that are black, and 120 pixels on each of the top and bottom that are dead area.

So my guess is that the chip they put on the slim to do tv out doesnt have a scaler built in, it just pipes the signal to another display. Which would mean that they probably created new PRXs for the xmb that create a 480i (320x240, interlaced) XMB and decode video into 480i when you have the composite cables in or the component cable with the interlace option + 4:3 display.

Then of course, with progressive component plugged in, the XMB is able through sony's code to output a 720x480p picture which looks great. BUT, when you launch a UMD, homebrew, or ISO, the code that created these (some of the time) magnificent games and apps is only built to output a total of 480x272 progressive lines. With the lack of a scaler chip (e.g. the 360 has one called ANA/HANA), the only possibility is to output a 480x272p image to a 720x480 display. At this point it is up to the TV to scale it if it can. My TV has some zoom functions, but they suck because they only stretch the top and bottom of the image which ends up looking like crap.

Anyway, I fear (not that its the worst fate) that we might never see (at full speed) psp-driven scaling of games and such either to a full 720x480p or (not that its remotely possible for all I know) 720p or 480i through composite/interlaced component. From what I know about electronics and what have you, I think the only solution would be for a hacked or additional prx, which would likely only give us a basis to start developing homebrew that specifically makes use of it. This would still not be perfectly ideal because, if my understanding is correct, it could only be software-based, which could in turn cause noticeable slowdowns especially with games and homebrew that don't expect such a function to exist. If this is all we could expect to surface, I imagine the best we could hope for is fullscreen GBA or GB/C emulation or similar. I suppose you could think of it as similar to the reason why the PS3s with PS2 software emulation are less compatible than launch U.S. PS3s with the hardware built in.

Am I off my rocker or does this all make complete sense and is likely the entire reasoning behind all this video-out hubbub? Considering if I'm in fact ON my rocker, am I just teh stoopid? :D

[B2K24]

good info there but I can't find a damn video output cable for sale so cannot test

[Chilly Willy]

Close - here's my take on it. The video chip in the PSP can be programmed for a number of modes - they just happen to run it in 480x272 mode all the time on phat PSPs. For the slim, when you're playing videos and on the XMB, they just rewrote the libs to use a 720x480 interlaced (for SVideo and composite out) or progressive (for component out) screen. This was simple - just change a couple lines in the VSH and video player and you're done.

So why can't they do the same for games? Memory - specifically, embedded DRAM. The VPU in the PSP has 2MB of EDRAM for use by the video. If you do the calculations, 720x480 takes more than twice the memory of 480x270. Games are written expecting the screen to be 480x272, leaving X amount of memory left over for storing textures and such. If the screen suddenly jumps to 720x480, there's less EDRAM left over for use by the game.

Now, new games could be written expecting the loss of EDRAM in larger screens, but the current group of games are stuck at 480x272.

[Ceraphis]

lol I knew it had something to do with the hardware not being able to handle it I wonder how much it would have seriously cost them to put a scaler chip in the PS3, and now the PSP?

However, I'll riddle your brain with this: does the same thing apply to downconverting the signal to interlaced 480i? Last I checked 480i could be theoretically construed as 320x240p, which by the same comparison would be below the existing expectations of a 480x272p output.

With your added info, I have two possibilities that come to mind. I would guess although it might have been possible, the interlaced signal may look trashy compared to the 480x272 expectation or whatever (lower) resolution would have been chosen, and so for quality reasons it was left out. Either that or the process of transcoding the progressive signal into interlaced would have put unexpected (to the first two years worth of games) pressure on the hardware, causing an instability that could crash unsuspecting games. In the same way that remotejoy or usb/nethost functionality only has limited compatibility.

[Chilly Willy]

lol I knew it had something to do with the hardware not being able to handle it I wonder how much it would have seriously cost them to put a scaler chip in the PS3, and now the PSP?

However, I'll riddle your brain with this: does the same thing apply to downconverting the signal to interlaced 480i? Last I checked 480i could be theoretically construed as 320x240p, which by the same comparison would be below the existing expectations of a 480x272p output.

With your added info, I have two possibilities that come to mind. I would guess although it might have been possible, the interlaced signal may look trashy compared to the 480x272 expectation or whatever (lower) resolution would have been chosen, and so for quality reasons it was left out. Either that or the process of transcoding the progressive signal into interlaced would have put unexpected (to the first two years worth of games) pressure on the hardware, causing an instability that could crash unsuspecting games. In the same way that remotejoy or usb/nethost functionality only has limited compatibility.

720x480i uses the same bandwidth as 720x240p, but it still uses the same amount of memory as 720x480p. Remember, it's the reduction of free video mem that is the issue here.

Yes, a video scaler would have (mostly) solved the problem, but would have added to the price, and maybe delayed the release a few more months. I would expect that when Sony does the next revision of the hardware to defeat the Pandora battery, it will probably also add a scaler to the video encoder.