Re: [Xbox-linux-user] Any hope for a 1.6 XBox?

[David P. <dm...@da...>]

> Okay, I thought NTSC was 525 lines of resolution, as in what comes out
> of your standard cable box.  I was also under the impression that
> 640x480 was VGA, but I could be wrong.

Right, let's try this as an explanation ;)

VGA is 640x480.

Normally (on <1.6 xboxes) we are able to use the encoder to SCALE the
video output of the GPU, so it fits inside the VISIBLE area of the TV
picture you see.  If it's not scaled properly, it overflows the visible
area of the TV picture. This is called 'overscan'. Normal broadcast TV is
overscanned - it's just that the subtitles etc are positioned to fit into
the 'safe' visible area.
However, for Xbox linux, overscan isn't so good, as it means part of your
desktop (several inches each way) gets missed off the side of your TV.
However, on 1.6, without having any docs on the encoder, we aren't able to
utilise it to scale our picture.  The settings we are using are dumped
from those the MS bios uses, and IT uses overscanned video, so we're stuck
with that, until someone works out (assuming this encoder *can* actually
scale) how to program the encoder, rather than just load values into it. 
We know some values, but not what they MEAN. Some we can deduce easily,
some (scaling) are harder to deduce, as the MS bios doesn't use them at
all.
> Soo....let me ask for opinions here.  What do you think are the
> chances of getting an X driver for a 1.6 XBox to output a composite,
> 525-line, fit-for-a-TV NTSC picture in the near future?

It's not the X driver that's relevant, actually. On xbox linux, X uses the
fb device. The intelligence is done in xboxfb (the linux kernel
framebuffer driver). The X driver we have does not need updating for newer
xbox encoder hardware, as the framebuffer driver handles it.
> Is anyone
> working on it at the moment?

In opensource projects, it's very hard to answer that. I'm personally not
(I did the work for the Focus chip).  Trying to get true scaling working,
without having an appreciation of what all these values mean is very hard.
Simple things we can reverse engineer, but scaling (and adjusting the PLL)
is not always that simple.
>Would I be better off just dumping the
> machine and trying to get an earlier release?

If you're reasonably impatient, yes. I don't think it's sensibly possible
to give you a 'due by' date for the functionality you're after, sadly. 
eBay is often a good place to start, but I'm sure you might find more luck
in a 'swap' or pawn shop, maybe.
David

> Thanks again,
> -Jon