[mythtv-users] XvMC Prebuffering Pauses

[Steven Adeff]

On 7/23/06, Brian Foddy <bfoddy at visi.com> wrote:
> I know this is probably one of the most beaten issues, but
> I'd like some input.
>
> My machine  is able to play 1080i content from
> CBS/NBC without too much difficulty.  There are occasionally
> streams of pauses, especially with fast  forwarding but they
> don't cause too much problem and its easy to just jump back
> 15 seconds and it picks up fine.  Once its running, playback
> is fine without pauses.
>
> The problem has always been ABC (720p).  A program like the
> Lost will play for about 5-10 seconds fine, then stream prebuffering
> pauses, hanging the playback with really no way to ever get
> it playing correctly.  Fox is also the same way.
>
> Which is why its strange.  I've been browsing the code, putting
> some variable dumps, etc.  In Ringbuffer.cpp, the 1080i is
> a higher estimated bitrate (>18000) and uses a larger block size,
> the 720p is about 13000, and standard tv is about 10000.
> Also, when played on a faster frontend that is able to play
> smoothly, the 720p content regularly takes less CPU load than
> 1080i.  So why is 720p such a problem?
>
> I've also tried changing NvAGP from 0, to 1, to 3, no change.
>
> What resource is actually short when
> Prebuffering pauses occur?  Originally I thought it was the
> XvMC internal buffers that weren't getting released fast enough.
> But then I wondered why most often occurs starting up and fast forward
> so I began to wonder if the player is starved of frames from the
> disks?  Playing the content from local drives doesn't seem to help tho either.
>
> System details:
> Frontend:
> P3-1400, 768MB ram, Nvidia 5600 or 5700 Ultra video (I've tried both).
> FE NFS mounts video filesystem via 1Gb network, nfs mount options:
> rsize=8192,wsize=8192,hard,intr,nfsvers=3,actimeo=0,tcp
> Linux 2.6.16.23 kernel, 1000Hz CONFIG_HZ (I've tried lower also),
> all preemption options.
>
> Backend
> Dual Xeon 2400 P4, 2GB ram, 5 raid0 160MB scsi disk drives, 1Gb network
> to frontend.
>
> I've also tried this from a dual P3-1000 machine, and even tho it can't
> quite play any HD content smoothly, it doesn't ever get the streams like
> the 1400 does.
>
> I'm looking for guidance here, even if its making personal tweaks to
> the source.  But so far nothing is making any difference at all.
>
> Thought?
> Brian

I had a similar issue a while back, updating the nvidia drivers to one
of the recommended two and running .19-fixes ended up getting me
going, though i had other issues with XvMC so I don't use it. Will
this work for you? dunno, XvMC is very very finicky.

-- 
Steve
Before you ask, read the FAQ!
http://www.mythtv.org/wiki/index.php/Frequently_Asked_Questions
then search the Wiki, and this list,
http://www.gossamer-threads.com/lists/mythtv/
Mailinglist etiquette -
http://www.mythtv.org/wiki/index.php/Mailing_List_etiquette