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Help Diskless frontend

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ben_dash at yahoo

Nov 5, 2005, 7:20 PM

Post #26 of 31 (1813 views)
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Re: diskless xBox stuttering - was Help Diskless frontend [In reply to]

--- George Nassas wrote:
> On 5-Nov-05, at 8:23 PM, Ben Dash wrote:
> > Are you running at 640x480 or did you cut the
> > resolution down?
> 640x480. It doesn't look as bad as I expected. Also,
> during X startup
> there are a bunch of messages in the log about how
> it doesn't like
> something about the hardware. They're harmless but
> they do delay the
> start and the TV flickers quite a bit for about 5
> seconds. Just in case
> that was your next question.... :)

I used to get a load of errors about X resolution, but
since I changed to a 2.6 kernel I get no errors and
Xorg starts much quicker. With 2.4 there was a lot of
initial screen flicker before X came up. X still
takes a lot longer than my regular PCs. They
generally go from text mode to Evilwm X starting
mythfrontend within half second. My xBox takes at
least 5.

I wonder if I'll be able to solve all my problems by
going to the nvidia driver instead of nv?

I just don't understand why I'm getting stuttering
when my CPU utilization is so low, i.e. 50%. I had a
PII 400 which was experiencing similar stuttering but
its CPU was maxed out at 90-100% utilization. I can
understand that, but at 50%, it must be something else
surely?

Any advice?

Thanks,

Ben

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david.whyte at gmail

Nov 5, 2005, 7:37 PM

Post #27 of 31 (1772 views)
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Re: diskless xBox stuttering - was Help Diskless frontend [In reply to]

On 11/6/05, Ben Dash <ben_dash [at] yahoo> wrote:
>
> Any advice?
>

When I started with my myth BE/FE combo, I had severe stuttering. I
solved this by getting an old TNT2 dedicated video card rather than
the onboard thing I had with the crappy mobo I was running.

This improved things, but I did still have stuttering, which I solved
by using the nvidia drivers. Now, I can play Std Def at no more than
20-30% CPU, and all I have is a sempron 2400.

My advice, use the nvidia drivers if you can.

Whytey

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gnassas at mac

Nov 5, 2005, 8:45 PM

Post #28 of 31 (1788 views)
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Re: diskless xBox stuttering - was Help Diskless frontend [In reply to]

On 5-Nov-05, at 10:20 PM, Ben Dash wrote:

> since I changed to a 2.6 kernel I get no errors and

I'm running 2.4 because I read the 2.6 fatx driver isn't quite ready
for prime time. Do you do any updating of the xbox's filesystem while
you're in linux? Besides regular myth I'm also playing around with
xbmcmythtv and I want a reliable way to push out updates. Nothing to do
with your problem but I'm curious.

> I just don't understand why I'm getting stuttering
> when my CPU utilization is so low, i.e. 50%. I had a

Could it be something to do with syncing updates to the vertical
retrace? I've never had those kinds of issues on any of my FEs but I
think some past threads on this list that mentioned that. One of those
things you skim and file away for future use. Look for Use OpenGL VSync
in the TV Playback menus.

BTW, does the frontend log say anything?

- George

ben_dash at yahoo

Nov 7, 2005, 6:50 AM

Post #29 of 31 (1770 views)
Permalink

Re: diskless xBox stuttering - was Help Diskless frontend [In reply to]

--- George Nassas wrote:
> On 5-Nov-05, at 10:20 PM, Ben Dash wrote:
> > since I changed to a 2.6 kernel I get no errors
> I'm running 2.4 because I read the 2.6 fatx driver
> isn't quite ready
> for prime time. Do you do any updating of the xbox's
> filesystem while
> you're in linux?

No. The only thing I'm using the native HDD for is
swap and that seems fine with the fatX drivers for
2.6. I read somewhere that a major problem with FatX
for 2.6 was a lack of long filename support and swap
doesn't need that.

> > I just don't understand why I'm getting stuttering
> > when my CPU utilization is so low, i.e. 50%. I
> had a
>
> Could it be something to do with syncing updates to
> the vertical
> retrace? I've never had those kinds of issues on any
> of my FEs but I
> think some past threads on this list that mentioned
> that. One of those
> things you skim and file away for future use. Look
> for Use OpenGL VSync
> in the TV Playback menus.
>
> BTW, does the frontend log say anything?

The frontend log just says "prebuffering pause".

I had an interesting development this weekend, I would
have replied to this thread earlier but my PC was in
pieces for an upgrade. Anyway, my development was
that I found that if I run an xterm in the background
and run top on it, then I get hardly any "prebuffering
pause" stuttering.

The stuttering goes from once every 10 seconds,
without the xterm runing top, to once every 10 minutes
with the xterm running top. Interestingly, when a
stutter occurs the CPU utilization appeared to go down
not up. Clearly the CPU isn't the limiting factor in
this case.

I have a gigabit switch so I doubt that I have a
network bandwidth problem. My myth backend server is
a different machine than my NFS root server (note that
the xBox frontend is diskless with an NFS root except
for a local fatX swap).

So, the current status is that I, and more importantly
my wife, can experience stutter free live TV and
recorded shows at 640x480, which is GREAT. All I have
to do is start up an xterm running top in the
background.

This seems more than a little wierd though.

Does anyone have any idea why this solution is able to
mask the problem and, if so, what a real solution
could be?

Thanks!

Ben

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ben_dash at yahoo

Nov 7, 2005, 6:59 AM

Post #30 of 31 (1755 views)
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Re: diskless xBox stuttering - was Help Diskless frontend [In reply to]

--- David Whyte wrote:
> On 11/6/05, Ben Dash <ben_dash [at] yahoo> wrote:
> >
> > Any advice?
> I can play Std Def at no more than
> 20-30% CPU, and all I have is a sempron 2400.
> My advice, use the nvidia drivers if you can.

Hardware MPEG 2 decoding is definitely the way to go
if it's an option. Since the video card does all the
work you can use more or less any slow, and hence cool
and quiet, CPU. I had a 400mhz PII at one point but
traded up for a 1ghz Celeron.

I found that if I run an xterm in the background and
run top in it then I get hardly any stuttering
problems. The incidence of stutters go from once
every 10 seconds to once every 10 minutes.

Very strange.

Any idea why this would help?

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cymenvig at gmail

Nov 7, 2005, 7:03 AM

Post #31 of 31 (1785 views)
Permalink

Re: diskless xBox stuttering - was Help Diskless frontend [In reply to]

On 11/7/05, Ben Dash <ben_dash [at] yahoo> wrote:
>
> --- George Nassas wrote:
> > On 5-Nov-05, at 10:20 PM, Ben Dash wrote:
> > > since I changed to a 2.6 kernel I get no errors
> > I'm running 2.4 because I read the 2.6 fatx driver
> > isn't quite ready
> > for prime time. Do you do any updating of the xbox's
> > filesystem while
> > you're in linux?
>
> No. The only thing I'm using the native HDD for is
> swap and that seems fine with the fatX drivers for
> 2.6. I read somewhere that a major problem with FatX
> for 2.6 was a lack of long filename support and swap
> doesn't need that.
>
> > > I just don't understand why I'm getting stuttering
> > > when my CPU utilization is so low, i.e. 50%. I
> > had a
> >
> > Could it be something to do with syncing updates to
> > the vertical
> > retrace? I've never had those kinds of issues on any
> > of my FEs but I
> > think some past threads on this list that mentioned
> > that. One of those
> > things you skim and file away for future use. Look
> > for Use OpenGL VSync
> > in the TV Playback menus.
> >
> > BTW, does the frontend log say anything?
>
> The frontend log just says "prebuffering pause".
>
> I had an interesting development this weekend, I would
> have replied to this thread earlier but my PC was in
> pieces for an upgrade. Anyway, my development was
> that I found that if I run an xterm in the background
> and run top on it, then I get hardly any "prebuffering
> pause" stuttering.
>
> The stuttering goes from once every 10 seconds,
> without the xterm runing top, to once every 10 minutes
> with the xterm running top. Interestingly, when a
> stutter occurs the CPU utilization appeared to go down
> not up. Clearly the CPU isn't the limiting factor in
> this case.
>
> I have a gigabit switch so I doubt that I have a
> network bandwidth problem. My myth backend server is
> a different machine than my NFS root server (note that
> the xBox frontend is diskless with an NFS root except
> for a local fatX swap).
>
> So, the current status is that I, and more importantly
> my wife, can experience stutter free live TV and
> recorded shows at 640x480, which is GREAT. All I have
> to do is start up an xterm running top in the
> background.
>
> This seems more than a little wierd though.
>
> Does anyone have any idea why this solution is able to
> mask the problem and, if so, what a real solution
> could be?

That is definately bizarre -- I don't have any idea why that is
happening. I did wonder if you had run "chmod a+s mythfrontend" and
selected the option to have realtime priority in MythTV (I think it's
in Settings->Play TV) and verified it is using realtime priority by
looking at the frontend log? I realize the CPU usage goes down when it
occurs but I am curious all the same. If you don't want to deal with
the above you could also start playback and then adjust the priority
of the specific playback process to see if it changes anything.
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