[mythtv-users] Choppy Video Problems

Darren Black lists.drdaz at gmail.com
Sun May 22 20:14:33 UTC 2005


On 5/22/05, <SB> Childe Roland <rolandchilde at gmail.com> wrote:
> I get slow framerates all the time tho.  It's worst when I change
> channels, but I usually get about 20-25 fps just watching a recorded
> show or watching live TV.  Could that be due to my HDD?
> 
> On 5/22/05, Darren Black <lists.drdaz at gmail.com> wrote:
> > On 5/22/05, <SB> Childe Roland <rolandchilde at gmail.com> wrote:
> > > I am having a problem with my new KnoppMyth box.
> > >
> > > 1. Everytime I change the channel the video and sound skip some.
> > > Sometimes this continues, but can be fixed by pausing the video and
> > > waiting a few seconds
> > > 2. Both Live tv and recorded seem to have extremely low frame rates.
> > > The video is much more choppy than it should be
> > >
> > > I don't think it is my system (see specs below) and the TV Tuner
> > > should have hardware encoding.
> > >
> > > I think these problems are both related to the HDD. When I run the
> > > "hdparm -Tt" test I get a cached read in the 400's (MB/sec), but the
> > > timing buffered disk reads only gives me between 9 and 20 MB/sec.
> > > The drive is extremely old and only supports ATA 33.
> > >
> > > Could this be the problem?? I'd like to upgrade to get more space, but
> > > it won't be worth it if it's not going to give me a full 30 fps. Also,
> > > is it perhaps a setting in MythTV that I have missed?
> > >
> > >
> > > My specs -
> > > Athlon Sempron 2400+
> > > 512 MB DDR 333
> > > 20 GB ATA-33 HDD
> > > Hauppauge PVR-150 (non MCE)
> > >
> > > Machine Status:
> > > Load: 1.30, 0.61, 0.23
> > > RAM: 501MB, 396 MB used, 105 MB (20%) free
> > > Swap: 490 MB, 0 used
> > > --
> > > =============================
> > > <SB> Childe Roland
> > > "I will show you fear in a handful of jellybeans."
> > > _______________________________________________
> > > mythtv-users mailing list
> > > mythtv-users at mythtv.org
> > > http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users
> > >
> >
> > **Crossposting to ivtv-devel**
> >
> > I am experiencing the same problems. We have similar setups, but my
> > harddisks are fairly new and really not slow. I've crossposted to
> > ivtv-devel because I think the issue is related to the ivtv driver.
> > Mythfrontend outputs 'prebuffering pause' whenever the video stutters.
> > As you say, this only happens when I change channel, and is cured by
> > pausing a couple of seconds.
> >
> > From my browsing in the ivtv posts, I get the idea this has something
> > to do with vbi code (given when this error started occuring) and what
> > people are talking about generally ;) Is there anything that people
> > who really arent looking to use CC/TXT can do to the driver to make
> > this error go away? I perhaps have the wrong idea here... feel free to
> > let me know if I have ;)
> >
> > Regardless... Any suggestions would be welcome.
> > /drdaz
> >
> 
> 
> --
> =============================
> <SB> Childe Roland
> "I will show you fear in a handful of jellybeans."
> 

Possibly... I'm not sure where you live, but if you live in a PAL
country (I do), the framerate should be 25fps. I have noticed that
compared to normal TV my video looks like its running at a lower
framerate... But I had just kind of accepted that.

The amount of data that needs to be written and read to record and
playback one video stream at a time just isnt that high... My
guesstimation says DVD video would require approximately 1
megabyte/sec to be written and read concurrently. Not sure of the spec
of ata33, but I've got a feeling it can handle that. You could try
reducing the bitrate of the video in recording profiles to check I
guess.

/drdaz


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