[mythtv-users] mpeg2 video stuttering

ojw at weilerfamily.com ojw at weilerfamily.com
Wed Sep 24 04:26:59 UTC 2008


Quoting "Michael T. Dean" <mtdean at thirdcontact.com>:

> On 09/23/2008 07:44 PM, ojw at weilerfamily.com wrote:
>> After having ditched the idea that a 1.8Ghz P4 can display
>> 1080i content, I invested in a dual core Wolfdale processor
>> (45nm) at 2.53Ghz and paired it with a Gigabyte GA-73PVM-2SH
>> motherboard (Nvidia 630i based mobo with a GeForce 7100 built
>> in).  I'm using two Pinnacle PCTV HD Pro USB capture devices
>> and am only tuning ATSC based terrestrial transmissions.  Both
>> mythfrontend and mythbackend are running on the same box.
>>
>> The problem I'm having is that when I try to view either a
>> recorded show or something live'ish (from the ringbuffer),
>> the view jitters.  What should be obviously smooth scene
>> pans turns into jerky stutter steps through the scene.
>>
>> I was thinking it might be the marginally supported PCTV
>> HD Pro USB stick but I found that when I transfer the
>> recorded MPEG file to a PC running windows XP (using
>> windows media player), the video playback is as smooth
>> as silk.  I checked the CPU utilization during playback
>> on my mythtv box using top and found that it's usage doesn't
>> go over 50%.  I also tried configuring for XvMC which results
>> in a good cpu usage drop (down to 30%) but the image still
>> stutters about the same amount.
>>
>> I also tried playing the resulting mpegs in mplayer on the
>> mythtv box.  At first, mplayer told me I didn't have enough
>> CPU power to play the file so I used the -ao null option to
>> negate sound.  After I did that, mplayer didn't complain but
>> it stuttered more than during playback in mythtv.
>>
>> I'm not sure where to go from here and was hoping you all
>> could direct me to further diagnostic efforts.  I'd be
>> happy to post whatever config information you think would
>> help diagnose this.  I'll start with the basics:
>>
>> Kernel: v2.6.26.3
>> MythTV: 0.21.20080304-1
>> NVIDIA: 173.14.12
>> Using HDMI out at 1920x1080
>
> http://www.mythtv.org/wiki/index.php/Troubleshooting:Prebuffering_pause
>
> And, if it turns out yours is not on there, but you are suffering from
> prebuffering pauses, please update the page once you find out the cause.  :)
>

The prebuffering pause troubleshooting page above seems to
suggest that in 100% of the prebuffering pause problems, I
should see a "NVP: prebuffering pause" in the output of
mythfrontend.  I restarted mythfrontend with a -v all, then
played a recorded show.  I then searched through the log
output by typing "grep -i prebuffering" and found no matches.

Is it possible that I'm still suffering from prebuffering
pauses?  If not, what else could I check?

Looking through the output, I did see many occurances of this:

Xlib:  extension "XVideo-MotionCompensation" missing on display ":0.0"

So I suppose if nothing else, I guess I figured out that the
on-motherboard 7100 doesn't support XvMC





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