[mythtv-users] 0.19, XvMC, and Prebuffer pause

[Brandon Stoll]

> On 2/26/06, Joe Silver <devils.taco at gmail.com> wrote:
> > So it looks like there has been a trouble ticket opened on this issue:
> > http://svn.mythtv.org/trac/ticket/1361
> > http://www.gossamer-threads.com/lists/mythtv/commits/185733
> >
> > However, it doesn't really look like it's being investigated further.  I
> > could be mistaken, but it sounds like this is being passed off as a
> > performance issue instead of an internal issue.  Hopefully one of the
> > developers has the same issue and can provide the appropriate performance
> > settings to the rest of us to correct this issue.  It sounds like the rest
> > of us are stumped!  Perhaps it's something to do with differences between
> > default settings between 0.18 and 0.19.  Why these defaults would be changed
> > to break something as important as HD playback is a real mystery...
> >
> > -Joe
> >
On 2/27/06, Steve Malenfant <smalenfant at gmail.com> wrote:
> My system plays back HD now with some hiccups.
>
> - Disabled OpenGL Sync
> - Mounted the /mnt/store directory with NFS to my remote backend
> (backend streaming isn't the greatest in 0.19).
> - Enabled Real time priority.
>
> Some channel (WGCL atlanta 18 mbits stream, 1080i) I can play and to
> anything to my machine (Browsing web, monitoring my frontend) without
> getting pre-buffering pause.  But when I play FOX 720p at 13
> mbits/sec, I can't do anything with the system...  Always results in
> prebuffering.
>
> I'm not sure why the playback isn't consitent.  30 fps vs 60 fps?
>
> Steve M.

  I was getting constant prebuffering pauses (at least one per minute)
for the longest time, but I've pretty much got rid of them all now. 
I'm running a sempron 3100 with software RAID5 and a FX5200 (using
xvmc).  Tickers don't look bad, although they still have a choppiness
[why is this?]
  I'm fairly sure enabling IO-APIC in the kernel is what did it, but I
also upped the SATA controller PCI latency and lowered the other
device latencies respectively. My myth compile optimizations are
OPTFLAGS=-O2 -pipe -fomit-frame-pointer -finline-functions and
ARCHFLAGS=-march=athlon-xp -mmmx -msse2 .  I'm not very familiar with
compilers so those probably aren't ideal at all, but its working well
for me.
  When playing back a single HD(xvmc) stream I'm using about 40-60%. 
I don't get prebuffering with recording HD+SD and playing back HD, but
it does go downhill from there.  vmstat pretty much confirms its a
CPU/software raid problem- WA times are 50+ and idle CPU is mostly 0
when remote frontend playback and commercial flagging gets tossed in.
  I don't know if this will help anyone since all my problems have
been revolving around the RAID, but I figured it was worth mentioning
since my myth setup (finally) works perfectly.