[mythtv-users] Choppy Playback & prebuffering message

glen martin lists at locutory.org
Tue Apr 18 02:19:21 UTC 2006


Steven Adeff wrote:
> On 4/17/06, glen martin <lists at locutory.org> wrote:
>   
>> Scott Petler wrote:
>>     
>>> After reading more about your particular machine, I think the issue is
>>> even more likely due to
>>> a pci bus bandwidth issue.  This is because your video card is PCI
>>> rather than AGP.
>>>
>>> Having both the backend and frontend on the same machine is using up
>>> your PCI bandwidth.
>>> I would suggest a system with AGP video to keep your playback path off
>>> of the PCI bus.
>>>
>>>       
>> Interesting. What does this mean for 'modern' machines with PCI-E cards,
>> or those with onboard video? Or mine, which has both (onboard video that
>> can be overridden with a PCI-E16 card)? Is there something magic about
>> AGP, and I should preferably replace my frontend with a mobo that
>> supports AGP?
>>     
>
> PCIE!=PCI. PCIE is faster than AGP, its one of the AGP replacement bus designs.
>
>   
That's what I'd been thinking, too, but the earlier message in this
thread made me wonder. That message talked about network and video both
being PCI, so I inferred the same myth traffic goes across the bus twice
and saturates it. Now PCIE has more bandwidth than PCI, true, but it is
still one bus.
>   
>> lspci shows my onboard video and network and ide all on the same pci bus.
>>
>> My own situation is that I can playback analog content fine, but certain
>> HD streams (again, playback) cause some prebuffering messages as the
>> play starts up or when inserting onscreen menus or messages (eg. 'I'),
>> and if I switch aspect ratios ('W'), playback (and frontend) hangs with
>> incessant prebuffering messages.
>>
>> The issue seems bandwidth related. The streams for which I have problems
>> have very high bitrates.  My confusion has been that the cpu isn't
>> overly taxed, ticking along at perhaps 50% load.  XvMC, realtime, yadda
>> yadda.
>>     
>
> are you playing over a network?
>   
Nope, prerecorded, local disc. So onboard IDE, onboard video, both on
the pci bus per the lspci. Heck, the only actual cards in the box are
the tuners, both of which are idle as I'm testing.

FWIW, this is an Asus A8N-VM/CSM GeForce 6150 / nForce 430, with
Athlon64 3200+.



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