[MPlayer-users] XV performance with PCI graphics

[Alexander Roalter]

Jan Knutar wrote:
> On Tuesday 28 October 2008, RC wrote:
>> On Mon, 27 Oct 2008 23:30:02 +0200
>>
>> Jan Knutar <jknutar at nic.fi> wrote:
>>> This makes no difference, XV transfers the video as 12bpp (YV12)
>>> regardless of x11 colour depth.
>> Point taken.  I suppose with such a low BPP that would preclude
>> overwhelming the PCI bus at that resolution as well.
> 
> 
> Well it's not overwhelmed if it's keeping up ;) 
> 
> I've seen similar differences between PCI and PCIe myself. Maybe the Xv 
> driver doesn't DMA?

At least lspci shows busmaster capability for the PCI graphics, and with
 pictures that are not so big the speed is reasonable. I finished up
plugging in my old PCI-e card in the remaining 4x-slot (which is able to
retain a 16x-card since it is open on the back side - had I known this
earlier, I wouldn't have bothered to getting a decent PCI graphics card).

Point is, more than ~60MB/s on PCI are not that easy to achieve, PCIe
per lane offers 250MB/s. A 1280x720 video at 24bpp, 24fps has around
80MB/s, which are quite close to the theoretical maximum of PCI, but
less than a third of the theoretical maximum of a PCIe-1x (let alone 16x).

Complicating the fact is the nvidia closed source driver, where no-one
can be sure what happens internally... I'd be happy to switch to nv or
maybe nouveau, if it correctly supports XV and multi-head (and
perferrably twin-view on one card). 3d is of no interest to me whatsoever.

-- 
cheers,
Alexe