Mailing List Archive: MythTV: Users

Frame by frame playback - 3 good, 2 "ghosty"

Index | Next | Previous | View Threaded

dalequigg at gmail

Jan 2, 2008, 12:23 PM

Post #1 of 4 (657 views)
Permalink

Frame by frame playback - 3 good, 2 "ghosty"

Hi,

I'm new to MythTV but have been enjoying using it with my Mythbuntu
install. I'm very impressed with how well everything works.

I have a standard definition CRT TV, Comcast cable, HDHomeRun, and
PVR-150. I record all my shows in standard definition, mostly using
the HDHomeRun.
My computer is a BackEnd/FrontEnd with a ASUS M2NPV-VM motherboard,
2GB RAM, and a ~2 GHZ CPU.

I thought I saw my question in the forum archives, but I couldn't find
it again. I've noticed that when going "frame by frame" in a show,
that there seems to be a repeated pattern of 3 "good" frames" and 2
"ghosty" frames (especially if there is horizontal movement). This
happens whether I use "Default" or "Highest" recording quality. I've
also tried various settings for deinterlacing, but I've not seen any
change in the output.

My questions are;
1) Is this "frame by frame" viewing indicative of what is actually
happening during playback?
2) If so, what recommendations are there for improving the picture quality?

Thanks for any help.
_______________________________________________
mythtv-users mailing list
mythtv-users[at]mythtv.org
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users

jra at baylink

Jan 2, 2008, 12:31 PM

Post #2 of 4 (600 views)
Permalink

Re: Frame by frame playback - 3 good, 2 "ghosty" [In reply to]

On Wed, Jan 02, 2008 at 12:23:06PM -0800, Dale Quigg wrote:
> I thought I saw my question in the forum archives, but I couldn't find
> it again. I've noticed that when going "frame by frame" in a show,
> that there seems to be a repeated pattern of 3 "good" frames" and 2
> "ghosty" frames (especially if there is horizontal movement). This
> happens whether I use "Default" or "Highest" recording quality. I've
> also tried various settings for deinterlacing, but I've not seen any
> change in the output.

Yup, it's interlace you're seeing. 3:2 pulldown from 24fps source
interlace, to be specific. For comparison, record a local news
broadcast (preferably one that has *not* gone hi-def yet), and frame
through that.

Deinterlacing *can* help, though I don't know precisely which mode will
work best for you...

Cheers,
-- jra
--
Jay R. Ashworth Baylink jra[at]baylink.com
Designer The Things I Think RFC 2100
Ashworth & Associates http://baylink.pitas.com '87 e24
St Petersburg FL USA http://photo.imageinc.us +1 727 647 1274

Witty slogan redacted until AMPTP stop screwing WGA
_______________________________________________
mythtv-users mailing list
mythtv-users[at]mythtv.org
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users

mkh01 at earthlink

Jan 2, 2008, 5:41 PM

Post #3 of 4 (592 views)
Permalink

Re: Frame by frame playback - 3 good, 2 "ghosty" [In reply to]

On Wed, Jan 02, 2008 at 03:31:45PM -0500, Jay R. Ashworth wrote:
> On Wed, Jan 02, 2008 at 12:23:06PM -0800, Dale Quigg wrote:
> > I thought I saw my question in the forum archives, but I couldn't find
> > it again. I've noticed that when going "frame by frame" in a show,
> > that there seems to be a repeated pattern of 3 "good" frames" and 2
> > "ghosty" frames (especially if there is horizontal movement). This
> > happens whether I use "Default" or "Highest" recording quality. I've
> > also tried various settings for deinterlacing, but I've not seen any
> > change in the output.
>
> Yup, it's interlace you're seeing. 3:2 pulldown from 24fps source
> interlace, to be specific. For comparison, record a local news
> broadcast (preferably one that has *not* gone hi-def yet), and frame
> through that.
>
> Deinterlacing *can* help, though I don't know precisely which mode will
> work best for you...

The 3:2 pulldown is also commonly called "telecine", which might help if
you searching the web for information. Deinterlacing is unlikely to help
because the process creates one extra frame per each four in the
original source, though it may help with other playback problems.

The real question is this: do you notice it when you play it at normal
speed? If not, the answer is "play it at normal speed". If you're
watching ordinary NTSC TV the majority of the content you see has
probably gone through this process. For that matter, DVD players do it
on the fly most of the time.

If you're looking to archive the material you can often (mostly) undo
the process with an inverse telecine ("IVTC") or pullup filter.

--
Michael Heironimus
_______________________________________________
mythtv-users mailing list
mythtv-users[at]mythtv.org
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users

dalequigg at gmail

Jan 3, 2008, 8:02 AM

Post #4 of 4 (580 views)
Permalink

Re: Frame by frame playback - 3 good, 2 "ghosty" [In reply to]

On Wed, Jan 02, 2008 at 05:41:45PM -0500, Michael Heironimus wrote:
> On Wed, Jan 02, 2008 at 03:31:45PM -0500, Jay R. Ashworth wrote:
> > On Wed, Jan 02, 2008 at 12:23:06PM -0800, Dale Quigg wrote:
> > > I thought I saw my question in the forum archives, but I couldn't find
> > > it again. I've noticed that when going "frame by frame" in a show,
> > > that there seems to be a repeated pattern of 3 "good" frames" and 2
> > > "ghosty" frames (especially if there is horizontal movement). This
> > > happens whether I use "Default" or "Highest" recording quality. I've
> > > also tried various settings for deinterlacing, but I've not seen any
> > > change in the output.
> >
> > Yup, it's interlace you're seeing. 3:2 pulldown from 24fps source
> > interlace, to be specific. For comparison, record a local news
> > broadcast (preferably one that has *not* gone hi-def yet), and frame
> > through that.
> >
> > Deinterlacing *can* help, though I don't know precisely which mode will
> > work best for you...
>
> The 3:2 pulldown is also commonly called "telecine", which might help if
> you searching the web for information. Deinterlacing is unlikely to help
> because the process creates one extra frame per each four in the
> original source, though it may help with other playback problems.
>
> The real question is this: do you notice it when you play it at normal
> speed? If not, the answer is "play it at normal speed". If you're
> watching ordinary NTSC TV the majority of the content you see has
> probably gone through this process. For that matter, DVD players do it
> on the fly most of the time.
>
> If you're looking to archive the material you can often (mostly) undo
> the process with an inverse telecine ("IVTC") or pullup filter.

Jay and Michael,

Thank you for your responses.

Michael - Thanks for the pointer. Wikipedia explains telecine well.

> The real question is this: do you notice it when you play it at normal
> speed?
No, I don't really notice the blurred images. I was just wondering if the
picture would/could look better if this were "fixed".

Thanks again!
Dale
_______________________________________________
mythtv-users mailing list
mythtv-users[at]mythtv.org
http://mythtv.org/cgi-bin/mailman/listinfo/mythtv-users

Index | Next | Previous | View Threaded

Interested in having your list archived? Contact lists@gossamer-threads.com