[mythtv-users] Standard PCI VDPAU-capable Video Cards vs. PCIExpress
Brad Templeton
brad+myth at templetons.com
Sun Nov 28 22:32:00 UTC 2010
On 11/28/2010 11:52 AM, Robert Longbottom wrote:
>
> On 28 Nov 2010, at 06:07 PM, Brian Wood<beww at beww.org> wrote:
>
>> On Sunday, November 28, 2010 10:57:50 am Robert Longbottom wrote:
>>
>>>> How about the OSDs? Are they OK?
>>> Yes, the osds were fine - I assume you mean during playback?
>>> Everything just worked.
>>>
>>>> May I ask what mobo you are using? Most of them have a BIOS setting
>>>> to tell it what graphics card to use first, this might correct the
>>>> booting problem.
>>> No idea. It's a small form factor HP business pc that I got from work
>>> when they were selling them off for £30 as part of an upgrade.
>>>
>>> I did have a fiddle around with the various settings in the bios but
>>> never managed to find a combination that worked. I think I ended up
>>> wit the on board graphics disabled, an old-ish nvidia agp card and
>>> the Sparkle pci card in it. That's the only way it would boot! The
>>> bios and text console display on the agp card and I configured X to
>>> run on the pci card.
>>>
>>> Sadly the agp card wasn't new enough to do vdpau and I couldn't find
>>> a low profile agp card that would. Thankfully the pci slots were
>>> turned on their side it would take a full height card.
>> I'm not aware of any AGP card that will do VDPAU. If I could find one I'd
>> jump on it immediately. The only ones I have found are either PCIExpress
>> or PCI.
>>
>> If I've missed one I'd love to hear about it :-)
> I don't think so. I'm fairly sure I looked for any vdpau capable agp card about a year ago and drew a blank. It was hard enough at the time to find a fanless pci card that I could get in the UK.
>
> Robert.
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This works -- I have a PCI 8400GS card in my old Pentium-4 frontend, but
there are some important caveats. It's a tradeoff, because the P4 is
able to decode mpeg-2 1080i in software, but not able to handle 1080
line mpeg 4 movies as you might download. The VDPAU is able to play
both types of video.
But you will *only* be able to play HD video in the 4 VDPAU supported
formats. Other videos, including the ones you made with mythtv's
transcode, will not play properly in software players, because the PCI
bus doesn't have enough bandwidth to shove 30 frames of 1920x1080x4
bytes every second into the card! In fact, I believe it does not have
enough bandwidth to even do 720p. PCI just isn't a very fast bus.
VDPAU works because you are sending partially compressed data into the card.
I've wondered if I might be able to hack it to bring up the on-board
video in the box and see if that can play software decoded HD, but that
would mean having to switch inputs on the TV while playing it. Messy.
I also found that in spite of speed reports, if you want to do things
like audio speed up and nice OSD, you can't use the fancy deinterlacers
in vdpau. You can use the more basic ones at 2x mode, so they still
look pretty good, but if you try to use the advanced ones, you will find
that any appearance of the the OSD makes the video skip a bunch.
(Right now, audio speed up isn't working at all in the TRUNK version I
compiled last week. It seg faults, and I don't know if VDPAU is to
blame as it doesn't do it on a different frontend compiled from the same
code.)
On the whole, I was not that happy with my decision to go to PCI 8400gs
with vdpau. The regular operation of Mythtv (playing mpeg2s) is only
modestly improved. Losing the ability to play other formats including
my old transcodes was annoying, though the ability to play downloaded
mp4s at HD was good. So I stayed with it, but I guess it's not
something I would go nuts to do.
If you can, the obviously answer is a new motherboard, since you can now
get a dual core chip and motherboard for peanuts with PCI-express. The
only reason I didn't go that way is my frontend is an Aopen cube SFF
computer, and you can't get new motherboards for this particular one as
far as I know. That's why I won't be buying any more SFFs with custom
sized motherboards. They are cute but they limit you.
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