Mailing List Archive: MythTV: Mythtvnz

jumpy video

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steven.mulvay at slingshot

Sep 2, 2008, 1:53 AM

Post #1 of 8 (662 views)
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jumpy video

Hi All, how are you?
I've finally got mythbuntu tuned up and running but the video is
extremely jumpy, audio clips a little bit too, but nowhere near as bad
as video. Live TV and TV recordings are as bad as each other.
My CPU shouldn't be drained very much because I'm using a PVR-150 which
is a hardware MPEG-2 encoder. I am wondering whether Mythbuntu is
having trouble using the encoder, although there are no errors shown on
start-up. (I have splash turned off)
A guy on the myth-users IRC channel says that there might be a PCI
latency issue, but I am unsure how to test this. Altering the bitrate
did not have any effect on the problem. The card works fine in Windows.
Machine info:
CPU: Intel 2 core duo
RAM: 4 Gig
Hard Drive: Approx 230 gig (virtually empty)
Kernal version: 2.6.24-19-generic
Mythbuntu version: Unsure, but I think it is the latest

Any help would be greatly appreciated.

Cheers,
Steve :)

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stevehodge at gmail

Sep 3, 2008, 4:13 PM

Post #2 of 8 (635 views)
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Re: jumpy video [In reply to]

On Tue, Sep 2, 2008 at 8:53 PM, Steven Mulvay <steven.mulvay[at]slingshot.co.nz
> wrote:

> Hi All, how are you?
> I've finally got mythbuntu tuned up and running but the video is
> extremely jumpy, audio clips a little bit too, but nowhere near as bad
> as video. Live TV and TV recordings are as bad as each other.
>

It shouldn't be CPU, but what does top say when you're watching?

> My CPU shouldn't be drained very much because I'm using a PVR-150 which
> is a hardware MPEG-2 encoder. I am wondering whether Mythbuntu is
> having trouble using the encoder, although there are no errors shown on
> start-up. (I have splash turned off)

It's not having problems using the encoder - if it was it wouldn't record at
all. But just in case try copying one of the recordings to another machine
to rule out the recordings as an issue.

Have you tried watching anything with mythvideo? Does that have the same
issue?

If that's not a SATA drive it might be drive performance - make sure DMA is
on (hdparm -d /dev/hd...)

Is X setup correctly? Try playing something using Xine or mplayer. If they
work ok then the problem is Myth, otherwise the problem is something in your
system and X would be a prime candidate at that point.

Cheers,
Steve

nick.rout at gmail

Sep 3, 2008, 5:24 PM

Post #3 of 8 (634 views)
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Re: jumpy video [In reply to]

On Thu, Sep 4, 2008 at 11:13 AM, Steve Hodge <stevehodge[at]gmail.com> wrote:
> On Tue, Sep 2, 2008 at 8:53 PM, Steven Mulvay
> <steven.mulvay[at]slingshot.co.nz> wrote:
>>
>> Hi All, how are you?
>> I've finally got mythbuntu tuned up and running but the video is
>> extremely jumpy, audio clips a little bit too, but nowhere near as bad
>> as video. Live TV and TV recordings are as bad as each other.
>
> It shouldn't be CPU, but what does top say when you're watching?
>
>>
>> My CPU shouldn't be drained very much because I'm using a PVR-150 which
>> is a hardware MPEG-2 encoder. I am wondering whether Mythbuntu is
>> having trouble using the encoder, although there are no errors shown on
>> start-up. (I have splash turned off)
>
> It's not having problems using the encoder - if it was it wouldn't record at
> all. But just in case try copying one of the recordings to another machine
> to rule out the recordings as an issue.
>
> Have you tried watching anything with mythvideo? Does that have the same
> issue?
>
> If that's not a SATA drive it might be drive performance - make sure DMA is
> on (hdparm -d /dev/hd...)
>
> Is X setup correctly? Try playing something using Xine or mplayer. If they
> work ok then the problem is Myth, otherwise the problem is something in your
> system and X would be a prime candidate at that point.
>
> Cheers,
> Steve

Saw someone comment on the main mythtv list recently that moving from
ext3 to xfs fixed a lot of prebuffering pauses and similar glitchy
things.

http://www.gossamer-threads.com/lists/mythtv/users/347976#347976

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barryc at bcsystems

Sep 3, 2008, 9:45 PM

Post #4 of 8 (627 views)
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Re: jumpy video [In reply to]

Isn't the downside of xfs that it needs to be defragmented occasionally?
With a mythbox always on, when would you be best to do that?

Regards

Barry

On Thu, 2008-09-04 at 12:24 +1200, Nick Rout wrote:
> Saw someone comment on the main mythtv list recently that moving from
> ext3 to xfs fixed a lot of prebuffering pauses and similar glitchy
> things.
>
> http://www.gossamer-threads.com/lists/mythtv/users/347976#347976
>
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stevehodge at gmail

Sep 3, 2008, 10:30 PM

Post #5 of 8 (625 views)
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Re: jumpy video [In reply to]

On Thu, Sep 4, 2008 at 4:45 PM, Barry Clearwater <barryc[at]bcsystems.co.nz>wrote:

> Isn't the downside of xfs that it needs to be defragmented occasionally?
>

I haven't heard that before, have you got any links?

> With a mythbox always on, when would you be best to do that?
>

I ran xfs for a couple of years without any problems. I would imagine that
the large files mythtv creates would not produce a lot of fragmentation. I'm
using jfs now, just to try something different, and I'm not seeing any
advantages to that.

Cheers,
Steve

noel at igrin

Sep 3, 2008, 11:39 PM

Post #6 of 8 (625 views)
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Re: jumpy video [In reply to]

The problem is with the ati card drivers in mythbuntu - even the
un-supported drivers won't do it. Streaming the file to a 450 Mhz
windoze machine using xming & putty there is no jumping, or hesitations,
it just plays smoothly, as it should.

Steve Hodge wrote:
> On Thu, Sep 4, 2008 at 4:45 PM, Barry Clearwater
> <barryc[at]bcsystems.co.nz <mailto:barryc[at]bcsystems.co.nz>> wrote:
>
> Isn't the downside of xfs that it needs to be defragmented
> occasionally?
>
>
> I haven't heard that before, have you got any links?
>
>
> With a mythbox always on, when would you be best to do that?
>
>
> I ran xfs for a couple of years without any problems. I would imagine
> that the large files mythtv creates would not produce a lot of
> fragmentation. I'm using jfs now, just to try something different, and
> I'm not seeing any advantages to that.
>
> Cheers,
> Steve
> ------------------------------------------------------------------------
>
> _______________________________________________
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>

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rob at robreid

Sep 5, 2008, 2:45 PM

Post #7 of 8 (607 views)
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Re: jumpy video [In reply to]

Barry Clearwater wrote the following on 04/09/2008 16:45:
> Isn't the downside of xfs that it needs to be defragmented occasionally?
> With a mythbox always on, when would you be best to do that?
>
Just playing around with an install of mythbuntu here and noticed that
under the Control Centre>Advanced Management there is an option for
'Enable daily defragmentation of your XFS files systems'.

cheers

rcr

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david at thistledown

Sep 7, 2008, 2:02 PM

Post #8 of 8 (571 views)
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Re: jumpy video [In reply to]

My understanding of XFS is that is does not write new files in fragments in
the first place (unlike, say, DOS) because of the clever way it does lazy
writes. Therefore, the only way a file can become fragmented is if you
change it's size significantly. This tends not to happen with media
recordings - the file is created and that's pretty much it until you delete
it. (unlike documents and spreadsheets that get updated.)

Consequently, I woudn't think there's going to be much to gain from
fragmenting XFS.

And there are some gotchas - people report losing files. So I'd use it with
some considerable caution and only after appropriate research.

- D

On Sat, Sep 6, 2008 at 9:45 AM, Rob Reid <rob[at]robreid.co.nz> wrote:

> Barry Clearwater wrote the following on 04/09/2008 16:45:
> > Isn't the downside of xfs that it needs to be defragmented occasionally?
> > With a mythbox always on, when would you be best to do that?
> >
> Just playing around with an install of mythbuntu here and noticed that
> under the Control Centre>Advanced Management there is an option for
> 'Enable daily defragmentation of your XFS files systems'.
>
> cheers
>
> rcr
>
> _______________________________________________
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>

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