[mythtv-users] Stutter issues with HDTV

[Brandon Beattie]

I have a few concerns about the system, memory, and pci busses.  I have
seen many symptoms that these may be causing problems that are being
difficult to debug.  Every half hour, or hour, when I have a card that
starts to record I have a second or so long pause as the card is being
set.  At hour intervals when I have 3 cards stopping, changing channels,
and starting back up my system basically locks up for about 6-10
seconds.  (Including when watching a movie with mplayer).  

As another side, non-XvmC stutter issue, I have also
been able to get the backend to crash several times when moving ripped
movies from one partition to another on raid 5 and 1 configurations.  If
I copy one movie at a time I am usually fine, if I do 2 about 1/3 times
mythbackend just hangs, complains about not being able to write to file
handlers, and if I do 5 mythbackend dies in a few minutes).  Playback,
even with XvMC makes video pause if I do more than 1 copy at a time,
and even 1 being copied causes noticible stutter in playback.  I can
move 60MB/s write and 90MB/s read on my raid setup, CPU is not pegged
either.

Throwing CPU at the stutter problem may not make it perfect.  It can
help, and especially if you are transcoding or commercial detecting on
the same box that you are watching the video on.  Stuttering is not that
bad on my athlon 2600 when using XvMC unless I'm moving a lot of data
around the system.  My system load is often up to 7 and I don't notice
bad stuttering.

Perfect motion on a HTPC is tough, I would be curious if you think DVD
playback on your system is smooth.  If you say yes, then it's something
you can probably solve easily.  If no, then you should do some
research on tvtime and see how they are trying to get around an
imprefect display hardware.  I personally cringe when watching DVD's on
computers, and lately in theaters I am very aware of stuttering of film
and it's almost a disease because once you know what to look for it can
be very distractive and can ruin a movie for me. :)

I also mention some of the problems with getting smooth video in general
on a PC on the Linux HTPC howto.  (I also finished reviewing the
SilverStone LC01 loaded with 6 drives and 2 optical drives, put in a
stereo cabinet and tested how well it can cool the hardware.. No
comparison between it and the Antec Overture...  Anyone want a modified
Overture case?  :)  )

--Brandon


On Tue, Aug 17, 2004 at 12:54:03PM -0500, john roberts wrote:
> 
> Hi - me again - the HDTV stutter guy. :)
> 
> The only way I've been able to get my HDTV 1080i content not to stutter is with using XvMC enabled.  Ane I've confirmed the quality of the picture is less then "software" enabled de-interlacing support.
> 
> So - I'm thinking of buying a new CPU and I'm wondering what speed I should get.
> 
> I currently have a 2.6G P4 HT 800 FSB.  I've heard from others (Wendy on the list) who has had stutter issues with a 3.0 P4 HT.
> 
> Do I need to go to 3.2G?  Is this not a CPU issue?  I've had this HDTV stutter issue with 0.15.1 and the latest (as of 8/16/04) CVS tree.
> 
> Any thoughts before I go my a new processor?  I'm not crazy about the idea of doing so - the darn things are expensive.  I thought by getting a FX5500 (which would do XvMC) I wouldn't have had to do this.
> 
> Thanks,
> 
> -John
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