[mythtv-users] Deinterlacing Methods

James Buckley xanium4332 at googlemail.com
Sat Jan 13 23:31:32 UTC 2007

Hmm, for me kernel deint is just rubbish, I don't know how anybody could
watch it! News tickers are so jumpy it's hard to track the text moving, and
frequently someone can say a word and I not even see their lips move. I
don't think this is normal though, can anyone confirm this?

On 13/01/07, Daniel Kristjansson <danielk at cuymedia.net> wrote:
> On Sat, 2007-01-13 at 12:32 +0000, James Buckley wrote:
> >
> > TV
> > Type: LCD
> > Model: LG 37LP1D
> > Inputs: DVI (PC), DVI (TV), Componet, HDMI
> > Working Modelines: 1280x720p, at 50Hz with a little overscan
> >
> > People have told me that you can get perfect TV using Kernel
> > deinterlacing, with a framerate that's as good as standard TV
> > (and doesn't have any flicker), however for me this method
> > just doesn't have enough FPS.
> >
> > I don't know whether my problems are related to an incorrect
> > setup (using Gentoo), buggy hardware, or just my incompetence,
> > but could someone tell me what I *should* get from each of the
> > deinterlacing methods, as I've never had anything to compare
> > too!
> You will never get a perfect picture with a progressive display..
> The Freeview STB is probably not doing any deinterlacing, it
> just sends an interlaced frames to the monitor and the monitor
> does the deinterlacing. And apparently the monitor does a good
> job.
> So your best option would probably be to feed the monitor a
> PAL signal without any deinterlacing instead of 1280x720p.
> MythTV allows you to use different video modes for the GUI
> and video playback, so you can get the both of both worlds.
> If you can't feed the monitor a PAL signal for some reason,
> then bob will give you the closest approximation to the
> deinterlacing the LCD is doing. It is however prone to
> "bobbing" as it's name would indicate. The smaller your
> video resolution, the more pronounced is the bobbing.
> The vertical resolution needs to be a multiple of 2 of the
> video source vertical resolution for the bobbing to
> completely disappear. Bob deint also requires the frame
> rate of the display to be twice that of the source video
> (true in your case). Flicker also happens with bobdeint
> when you have a single pixel high horizontal line, this
> is because it is only present in every other frame shown.
> Dimming the lights in the viewing room will make the
> flicker less pronounced. (It is more pronounced with PAL
> than NTSC, which is one reason bob is much more liked here).
> Kernel deint is prone to ghosting, but gives a decent picture
> with PAL sized frames. It also uses a lot of CPU, but your
> processor should be able to handle it.
> Linear blend deint is also prone to ghosting, but not as
> much as kernel deint. But it also considerably more likely
> to fail to deinterlace a frame. It only uses a little more
> CPU than bobdeint.
> oneline deint just throws away half the vertical resolution,
> it never fails to deinterlace but it is inappropriate for
> low resolution material like PAL.
> For your video card I would make sure to disable all the auto
> vsync in nvidia-settings, and then enable MythTV's OpenGL
> vsync method. If this doesn't work, re-enable the vsync in
> nvidia-settings, and then enable RTC vsync by running this
> as root:
>    echo 1024 > /proc/sys/dev/rtc/max-user-freq
> Good luck!
> -- Daniel
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