Question about fills rates and HDTV resolutions, etc... (1 Viewer)

[Jason Harbaugh]

I was talking with someone about Soul Caliber II and the Xbox 720p version vs the other consoles.

Some things this person said:

I was only saying 1080 runs at 24fps-no matter what the game does, or what kind of HDTV you use; that's just protocol- Xbox games can't suddenly turn a 24fps television signal into a 30fps one, let alone 60.

Dragon's Lair lags, and Halo/JSRF lag, regardless of the native 480p support. I was saying here that the progressive scan feature standard with all Xbox games must be affecting the final game's framerate overall.

I was under the assumption that whether it is 480i or 480p you are rendering the same amount of information, just like how 1080i and 1080p do not take up any more space if they were being broadcast.

Also is it true that 1080i only runs at 24fps?

 

[James_tango]

No, in video games (graphics) 480i, and 480p is totally different animals.
Even the best deinterlacer isn't able to get the same detail out of the 480i signal that is present in the 480p.

Moving pictures (video, film) on DVDs can be deinterlaced to 480p.
If the source is film (24fps), it goes through a weave type interlacing algorithm, aka 2:3 inverse-telecine thus almost a perfect reconstruction is possible. This means there are only 24 actual 720x480 frames contained, the rest is repeated redundacy. The interlace output also contains all of these frames, you simply need to 'fit the fields together' properly. So an almost perfect reconstruction is possible.

On video-based DVD, you have 60 interleaved fields of half resolution (720x240) in the 480i signal and you can use clever deinterlacing to minimize combing or bobbing artefacts.

But video game is totally different story.
The progressive output of the XBox does have 60 full fields of full resolution (720x480 or 640x480). So its twice as much data to begin with. No deinterlacer can reconstruct this information.


But the XBox progressive output differs from that DVD progressive output in that it really has 60 full 640x480 frames in it and NO redundacy. The interlace signal always only outputs HALF of that information (60 fields of 640x240), although everything is rendered.

This missing half of information can't be restored, no matter what, which makes the advantage of XBox progressive output a totally different animal from DVD progressive output.

Finally, 1080i isn't always 24fps. Only film-based 1080i runs at 24 fps (48 fields). Video game is not film.

Hope this sheds some light.

 

[Keith Frederick]

Great post! I think pretty much everyone gets confused about that and it was refreshing to have someone explain it in detail. I do however question your explanation about 480i versus 480p. Two 240px fields is the same as one 480px frame. The argument is that an interlaced scanned image doesn't look as good as progressively scanned image. This is true.

But there isn't more information per frame in 480p and their aren't more frames. It is just a superior rendering process.

 

[Jason Harbaugh]

Thanks for digging this back up.

So just to be clear, the Xbox or a PS2 for that matter is rendering the same amount of data reguardless if the final output is progressive or interlaced?

 

[Joe Szott]

Props for Lakewood J

I think he is saying that the Xbox natively does 480p for everything and just throws away 50% of that when it outputs 480i. Whereas a deinterlacer takes 480i and double it to make 480p which isn't really the same thing. As far as PS2 vs Xbox for 480p support, it depends on the programming for the PS2, but the Xbox already does 480p anyway, so it is likely to be done easier/better. For 720p and 1080i programming on Xbox, again I suspect the game's programming will affect the slowdowns and FPS more than the intrinsic Xbox hardware. ie - if you tried to do the Flood level of Halo in 1080i it is gonna lag like crazy, if you were to tackle say the control room you would probably be just fine.