[mythtv-users] hardware questions for HD to SD playback

Johnny jarpublic at gmail.com
Tue Sep 1 06:29:35 UTC 2009


> 1. All the discussion about VDPAU talks about which DE-interlacers will work
> with which cards. What about interlacing? Is this process just as
> processor-intensive as de-interlacing? Is it handled by VDAPU or is it done
> by some other part of the card/driver? Is VDAPU even needed?

If you don't set up any deinterlacer in your playback profile then
would be sending an interlaced signal to you interlaced display when
playing interlaced content. So no you don't need to worry about this
case as far as processor/GPU power is concerned. Some people have some
issues getting their video card to have the right modeline to send a
proper 1080i signal to their HDTV, but this is a configuration issue
not a computation power issue.

> 2. What about down-sampling? How much extra effort is that? Is it something
> that any card can do without a problem or is it something I need VDAPU or a
> fast CPU to do?

No, downsampling is simple it will be done automatically on the fly by
any video card. Scaling the output for a given display is one of the
basic things that all video cards do. The processing power is needed
for decoding the HD video and deinterlacing it if needed.

> 3. My current setup suffers from the bug in the nVidia driver that makes it
> only output 1/2 the interlaced fields. The picture is sharp and clear but
> only 1/2 the vertical res it should be. Has this been fixed yet? Does it
> effect the HD resolutions or just the SD ones? (Is 1080i output as 720i)

I haven't heard of this bug or ever had this problem with any of my
nvidia cards in the time I have been doing this for the last 3 or 4
years.

> Depending on the answers to the above questions, I'm thinking about getting
> a gigabyte GA-73PVM-S2H motherboard.
> http://www.newegg.com/Product/Product.aspx?Item=N82E16813128072
> This is an intel 775 socket board with an on-board nVidia 7100 GPU. I was
> thinking that with a Core 2 Duo CPU this might be fast enough to do what I
> want, and I could add a VDPAU capable card later, once myth .22 is out. The
> 7100 does not support Xvmc but with that CPU I figure it won't be a problem.
>
> 4. The choice of boards with Intel GPUs is much bigger than those with
> nVidia GPUs. I have seen the advice about nVidia GPUs working better with
> MythTV, but I was wondering if that is only of benefit if I'm actually using
> the GPU? If I get an add-in nVidia video card, such as a 9500, does it
> matter if the built-in GPU is from Intel? In other words, is the advice of
> using an nVidia GPU only for the GPU or does it apply to the rest of the
> chip set as well? Also, does it mean "get nVidia" or does it mean "don't get
> ATI or VIA" and Intel is OK.
> 5. If intel is OK, which one? They have so many. I've heard that some of the
> newer ones aren't well supported.

Intel generally has good support/drivers in Linux. But as with any
hardware and Linux I always google around with the exact hardware I am
considering to see if others are having issues. Nvidia is the main
recommendations because they are the only game in town currenty if you
want hardware acceleration for decoding and deinterlacing in Linux.
When get a discrete video card it should be irrelevant what your on
board video is. When you get your nvidia card you would simply disable
the onboard video in the bios. Many motherboards will even disable the
onboard video automatically when a discrete video card is inserted.

> 6. The aforementioned board, and ones like it, seem to be a few years old.
> They seem to all have DDR 2 800 memory and PCIe v1. Is this fast enough?
> Does VDPAU need faster RAM or PCIe v2?

Any PCIe should be fine for mythtv purposes. You may want to make sure
you can use a new PCIe 2.0 video card in an older PCIe 1.0 slot. If I
recall correctly, I think that PCIe 2.0 is supposed accept 1.0 cards,
but for a PCIe 2.0 card supporting 1.0 slots is optional. VDPAU
doesn't need faster RAM or PCIe 2.0.


More information about the mythtv-users mailing list