[mythtv-users] 0.21 buffering not as good as 0.20? (Stuttering...)

Brian Foddy bfoddy at visi.com
Wed Apr 9 01:39:12 UTC 2008

On Tuesday 08 April 2008, Mark Knecht wrote:
> Hi,
>    Just an observation here. This is not an apples to apples
> comparison as I've changed backend servers in the process of doing
> this but since going to 0.21 I'm seeing far more small delays when
> viewing material across my network than I ever say using 0.20. Is
> anyone else experiencing this sort of issue? Are there any
> optimization instructions/ideas that I should pay attention to WRT
> this issue?
>    Observations:
> 1) While watching material - none of it 'transcoded', it's all just
> the output of the PVR's MPEG encoder - I see and hear little delays
> that are probably anywhere from 0.1 to 0.5 seconds long. Stuttering...
> 2) When I skip a commercial I get a fairly standard start-up that goes
> something like this:
> - Material starts
> - Immediately get a 1 second delay
> - Material runs again
> - Get a 1/2 second delay
> - Material runs
> - Get a 1/4 second delay
> - Material runs fine from here...
>    The new server doesn't seem taxed at all. It's a low-end Semphron
> machine using less than 2% CPU when a single frontend is attached and
> operating. The hard drive gives approximately 50MB/S using hdparm -tT
> as a test.
>    The existing frontends have run for 2 years and haven't changed
> except for the Myth-0.21 updates. CPU usage is certainly higher on my
> 0.21 frontend. A 3GHz AMD64 Gentoo box is using 15-20% CPU to run a SD
> program. I believe that with 0.20 this was more like 10-12%. Still,
> it's not that bad.
>    There have been no changes to the network and in fact all the
> frontends are dual boot and can play the NetFlix streaming service for
> hours without stuttering. However NetFlix's video quality is lower so
> I expect that is probably a far lower data rate. Additionally they do
> a LOT of local buffering before they start playing.
>    Any comments or ideas about how I might improve this?

I'm not sure you're completely on the mark with your diagnosis.  I too 
sometimes see a stutter here or there, and many times is while playing
SD shows, or lower-res HD, not the full 7GB/hr CBS shows which
play fine.  I think sometimes its picking a little too small a buffer for 
the lower-res shows.  

Then there is another symptom that really bugs me.  The past two weeks
American Idol on HD won't play at all, massive stutters on my normal FE
( know the recording is fine cuz it plays fine on a faster machine).
Other FOX HD shows play fine.  Now tonight AI plays fine.  I have the old
shows and I'm going to study the info from mplayer to see if there is
anything different in resolution, bit-streams, or anything else between the
shows.  It may all be related...


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