[mythtv-users] Jerky video

HP-mini blm-ubunet at slingshot.co.nz
Sun Nov 17 21:19:47 UTC 2013


On Sun, 2013-11-17 at 13:03 -0800, DaveD wrote:
> On 11/17/2013 10:36 AM, HP-mini wrote:
> > On Sun, 2013-11-17 at 07:14 -0800, DaveD wrote:
> >> On 11/17/2013 01:32 AM, HP-mini wrote:
> >>> On Sun, 2013-11-17 at 20:06 +1100, Phill Edwards wrote:
> >>>> My video playback seems to be a bit jerky. It's not all that
> >>>> noticeable but it seems to play - very slight pause - play - very
> >>>> slight pause on a continuous basis. The video card is a Nvidia Geforce
> >>>> 1GB GT210 Silent Low Profile Graphic Card HDMI DVI VGA HD.
> >>>>
> >>>> Recordings are SD DVB-T format.
> >>>>
> >>>> Any suggestions for how I can get rid of the mild jerkiness?
> >>>>
> >>> Bring up the OSD playback data jitterometer when playing a problem
> >>> recording.. Check buffered data & frame timing jitter.
> >> "jitterometer?"  I thought this was a joke, so I googled it.  Like most
> >> thing Myth, nothing shows up in the wiki or other documentation, but it
> >> is obviously a feature because there are lots of hits on the source for
> >> it.  How does one invoke it?
> >>
> >> There was another post today from someone as frustrated as myself about
> >> where to get information.  Documentation is alway sorely out of date.
> >> I'm guilty.  The immediate requirements are always what one works on and
> >> catching up on the docs always seems to be the last priority and never
> >> gets done.  Posting to this list is GREAT (thanks to all!) for solving
> >> problems and getting info about how to do things, but it's
> >> after-the-fact.  There are tons of features that are not obvious that
> >> one could take advantage of if there were a CURRENT list of them somewhere.
> >>
> >> Anyway, I'm betting the jitterometer is referred to as something else in
> >> the docs and/or on screen.  What other features do I not know about?  (a
> >> rhetorical question)  Are there current docs that might answer these
> >> questions?  In addition to google, I tried grepping through the docs
> >> that came with my distro's package (Fedora 17, Myth 0.26) and found
> >> nothing.  Is the jitterometer a recent addition that's not in 0.26?
> >>
> >> Dave D.
> >>
> >> __
> > The jitterometer info is contained in the playback data OSD popup.
> > - play recording
> > - <M> to invoke menu
> > either under advanced or video or somewhere. There aren't too many
> > choices & you will find lots of useful/interesting features.
> >
> > Changing the de-interlacing settings could be enlightening.
> >
> > The playback jitter is also logged if you start the FE with:
> > mythfrontend -v playback
> Yep.  Lots of useful things, but jitterometer isn't one of them.  It 
> lets me change deinterlacing, picture settings, etc, but nothing about 
> buffered data, frame timing, etc.  I used to use that menu all the time 
> to adjust audio sync on 720p recordings (all others were ok), but that 
> got fixed in 0.26 (maybe 0.25) so I haven't been there, lately.  Maybe 
> not in 0.26 but added in 0.27?
> 
> I have a very subtle jitter, I think.  It's so subtle I'm not even sure 
> it's there, but I notice something when 1080i content pans across a 
> scene.  I just started noticing it a month or so ago, so maybe it's been 
> there all along, but I really don't think so (I'm pretty picky about 
> playback quality).  Doesn't seem to do it all the time, either.  My 
> guess was that my buddies at Comcast in their effort to squeeze another 
> couple of bucks out of their customers implemented a more aggressive 
> compression, since most customers wouldn't notice anyway.  I thought 
> perhaps the jitterometer would detect it, if present, and quantify it 
> for me.  I haven't changed anything in my (delightfully stable) 
> backend/frontend combo in some time, which is what makes me think of 
> Comcast (they charge more for less constantly).
> 
> Dave D.

hit <M> for playback menu
then select "Playback" --> "Playback Data"

Maybe your 1080i is actually progressive video mangled into interlaced
format without correct temporal encoding..
This looks like 24p video (no frame creation on TV).
This has been reported to be happening in UK.

You could be right about cable provider, 1080i is lower BW than required
for 720p.

The GT210 is not & never was recommended for any interlaced video
playback. Maybe SD resolutions are okay.




More information about the mythtv-users mailing list