Nicholas S-A wrote:
A number of you are very keen on having a "graphics card" with some
kind of CPU or DSP on it.
not to be nagging or anything, but isn't that just what oga is? We
might be using a small micro, but it is still integral to the DMA
transfer, VGA, etc. or are you referring to a prebuilt ones like I
suggested?
While I don't think that that's necessarily the most effective
approach, there are reasons why it might be AN approach quicker
than some others.
I agree. In general, prebuilt devices are not the most effective.
This is especially true of 3d, but not as much so for video
processing.
What is needed for 3D (at the most basic level) is 4 ALUs controlled by
a LIW. To some extent, MMX, 3D-NOW, SSE, AltiVec, & etc. (SPARC has the
equivalent) provide this. Problem is that we could use more than one
of the FPUs and they don't come separately any more. :-(
So here's my suggestion: If you all want to have a card like this,
we are capable of building one. We just don't have the resources
to design it. So you design it.
ooh, I like this attitude ;-)
Obviously, there are gaps that we can fill in. But going from what
you see in the OGD1 schematic, BOM, and artwork, you can see what
level of detail we need. Provide that. The more you provide, the
greater the likelihood we can make it. Really, the best thing
would be a complete PCB design in Veribest or gEDA.
I have almost no experience designing high speed multilayer boards,
but I want some. Is there some good source of information on laying
them out that I can look at? Up until this point I have only tried
google searches, which invariably turn up empty, or datasheets, which
invariably only describe via routing, noise considerations, etc of
the chip in question. I just want a doc that has general guidelines.
While Howard, Andy, and I can't do this work (any time soon), we
can guide others through the process. Time to get grease on your
hands, folks.
Oh, and don't shoot yourselves in the foot by trying to pack in too
many features. Figure out what is the minimum to make it work and
design that. If you can get that to work, then make another
version with more stuff.
Well, some basic questions to ask ourselves: 1) What will it do? I
personally think that a reasonable aim is decoding video, hopefully
even 720p/i or possibly 1080p/i, in real time (30+ fps), while also
providing a simple framebuffer and possibly audio. If video is the
way to go, what formats?
If you mean TV video, we need to support all common SDTV & HDTV formats.
2) What should we use?
It appears that there are three possible ways to go for the basic functions.
1 Either an x86 or POWER-PC processor. A northbridge chip could
be used if the processor doesn't have VGA hardware built in.
2 A media processor chip designed for set-top boxes and/or HD-DVD
or Blu-Ray players.
3 A floating point DSP. Then you need something for VGA hardware.
In all three cases, it might also be possible to use other existing
chips and/or an I/O processor to supply part of the needed functions.
I have no idea on this one. I like the idea of an FPGA, since I at
least understand a little verilog and it makes for a compact board
due to almost complete integration. Any sort of DSP should also work.
How much RAM? Do we need RAM?
We would probably need some programmable logic. Yes we need RAM on
the board. The amount of video RAM should be in line with other
currently available boards. This will need to be increased in order to
hold the software. It is possible that a northbridge chip would be less
expensive than custom for the memory controller and the video controller
-- an advantage is that we would have a full hardware VGA.
3) What sort of > interface? PCI? PCIe? USB? Ethernet? There are a
myriad of possibilities, and they all have advantages and
disadvantages.
I would suggest that we make a PC expansion card which means that we
would need to support PCIe, PCI, PCI-X, and/or AGP depending on what we
thought the market needed.
4) What sort of output? DVI, s-video, S/P-DIF, etc.
We need to consider how much old stuff we need to support. New stuff is
going to have DVI or HDMI. A VGA connector (sub miniature 15 pin D) is
optional since an adapter can be used with DVI. OTOH, if we have VGA
then you don't really need DVI since you can get a cable that converts.
Should we support older SDTV-video interfaces? If we have audio on
board, we would probably need outputs other than HDMI, but these could
be an add on since we will probably run out of room.
5) What is the purpose? Is it designed as a media center, linux video
"savior", or what?
A media center board is a viable product. This would be based on a
set-top box chip. If there is no way for system software to turn off
encryption, we might be able to get the needed licenses.
A medium priced video board to take the place of those now available
which are fully supported by open drivers is also a possibility.
6) Should the functionality be split into e.g. audio processing,
colorspace transform, ... or integrated into one behemoth?
If we use a set-top box chip, it will include audio so we should use it.
Then the question is whether this should only be for TV or if it should
be a general purpose sound card?
--
JRT
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