Deinterlace = quality loss?

[Eileron]

When you deinterlace a video that needs it, is there a loss in quality (ie: image becomes less smooth, etc)? I've been wondering.

[rhester]

Yes, there is degradation any time you deinterlace, whether the source material is interlaced or not.

Please see http://en.wikipedia.org/wiki/Deinterlace for exacting details.

Rodney

[jbrjake]

There's a pretty good thread about interlacing in the support section of the forum, with a couple of visual examples of the loss of image quality deinterlacing entails:

http://handbrake.m0k.org/forum/viewtopic.php?t=200

[Eileron]

Thanks guys - anyone know how Quicktime deinterlaces, and whether that deinterlacin gcan be activated from Front Row? I'm making all this with a iTV plan, and animated movies just don't quite live up to the quality that I'm going for.

[sidechain]

I have a few DVD's that I recorded on my Panasonic DVD from a TV or others DVD's (that were encrypted to hard)
All of these had white lines in them using de-interlace cleaned them up a lot.
Also several music DVD's ( Not Shot on Film ) needed de-interlaced as well.
The white lines that you will see are real obvious.
The simple rule is do use it unless you need it.

[MySchizoBuddy]

how to tell if the source is interlaced or not
DVD are progressives
Digital Cameras ?

[jbrjake]

DVD are progressives

No, all DVDs are interlaced. Some are hard interlaced, and some are soft interlaced. The latter category includes most films on DVD. They have a 2:3 cadence applied first, so the interlacing can be removed without deinterlacing in the strict sense. Read up on telecine and IVTC and 3:2 pulldown.

http://www.hometheaterhifi.com/volume_7 ... -2000.html
http://www.theprojectorpros.com/learn.p ... nterlacing

If you go about thinking all DVDs are progressive, you're eventually going to rip a tv series or low-quality movie or documentary or concert video that isn't. Figuring out if a source is interlaced is a simple matter of stepping through the frames in any video editor, or using any number of video analysis tools to detect the mixture of progressive and interlaced content on any given disk. mencoder is great at this.

rhester could probably explain it better than me, but he already pointed you guys to wikipedia...

[rhester]

The explanation given is great. mplayer is the weapon of choice I use to detect interlaced frames - the mplayer documentation online (not the man page) gives excellent theory and practical implementation advice on this (for end-users).

Rodney

[deckeda]

Rodney, would you mind posting a link to what you refer? I'm only familiar with MPlayerOSX http://mplayerosx.sourceforge.net/

****

But personally, at the moment, all I have is an analog CRT television ... I suppose it doesn't ever make sense for me to de-interlace. My understanding is that an interlaced signal is what that type of TV expects?

Seems I never read about what the intended display device is in these de-interlacing discussions, only what the source is.

[jbrjake]

mplayer os x is outdated. batmanppc has current binaries available here:

http://www.haque.net/software/mplayer/m ... sx/builds/

Regardless, what you want is the documentation of the actual mplayer project:

http://www.mplayerhq.hu/DOCS/HTML/en/me ... ecine.html

You're not hearing about output device because it *doesn't matter*. If you don't deinterlace you flatten fields to get progressive output with interlacing artifacts. If you store this on a computer to play on a CRT tv over an svideo connection, your computer will be taking that progressive image with all its interlacing artifacts and interlacing it again. This means you'll now have an interlaced image with interlacing artifacts, the worst of all possible worlds. Trust me, I ripped several seasons of Futurama like this and it sucked.

[deckeda]

Thanks, that answers a few questions as to why, how and where interlacing is (re)introduced prior to landing at a CRT TV's input jack.