[mythtv-users] HDHomeRun like device for analog?

Brian J. Murrell brian at interlinx.bc.ca
Fri May 14 14:57:27 UTC 2010

On Fri, 2010-05-14 at 08:38 -0600, Brian Wood wrote: 
> If you use a standard PCI card, be aware that the PCI bus may become a 
> bottleneck under some circumstances.

Indeed.  This is a concept I have been struggling with.  The mobo in my
FE/BE has 5-6 PCI slots and an AGP slot.  I liked the idea of VDPAU
until I heard PCI was going to be my only option.

> If you are playing back something that 
> VDPAU can't help with (feature set "B" only helps with MPEG2 and h264, feature 
> set "C" can do more, like VC-1, I think), you may have to move more data than 
> the bus can cope with, especially if you are using multiple PCI capture 
> devices at the same time.

That's me.  Well, the multiple PCI capture cards part, anyway.  I have 3
cards, which amounts to 4 tuners.

> So the PCI VDPAU cards work fine, as long as you are using VDPAU, but if you're 
> not, it's just a slow old video card. VC-1 HD with a feature set "B" card, for 
> example, might be problematical.

What is VC-1 and when might I run into it?  And how much bus bandwidth
does it need to carry it to a video card, post-decoding (i.e. if your
VDPAU card cannot handle it)?

But to get back on topic, just how much PCI bus bandwidth are we talking

Let's say I have 4 (Hauppage MPEG-2 encoder card) recordings all going
on at once and an MPEG2 playback (i.e. the result of a recording from an
Hauppage PVR card) using VDPAU all going at the same time.  Where am I
in terms of bus saturation?

My recorded files are 2.17GiB/h, which by my math equals 633KiB/s or
4.9Mib/s.  So, my guess is that to have 4 recording and 1 playing, I am
using 24.7Mib/s.

According to http://en.wikipedia.org/wiki/Conventional_PCI PCI is
capable of 133MB/s.  So am I as in the clear as I think I am?  Only
using about 1/5 of the bandwidth available?


-------------- next part --------------
A non-text attachment was scrubbed...
Name: not available
Type: application/pgp-signature
Size: 198 bytes
Desc: This is a digitally signed message part
URL: <http://mythtv.org/pipermail/mythtv-users/attachments/20100514/c6087bf0/attachment.pgp>

More information about the mythtv-users mailing list