Why does everyone say don't deinterlace?

[Onceler2]

The videos I have taken from dvds that were interlaced and were kept in their original format just extracted look terrible on my LCD TV. The ones that I have deinterlaced look pretty good compared to them.

[Selur]

no clue, 'everyone' here is cursing interlacing and using:
a. a deinterlace filter
b. a IVTC filter
c. a field blender filter
to get progressive output, since progressive is the more 'natural' state of things.

When people are against deinterlacing, this is normally because:
a. they don't know how to do it properly (or don't think the one the recommend it to doesn't know how to do it properly)
b. they normally deal with content which is badly mastered and hard to deinterlace properly (mixed content)
c. they are creating intermediate content and their target is to be interlaced again
d. they want interlaced content because they need it

Cu Selur

[Richard_G]

Do the original DVDs look as terrible on your TV? If you are extracting the video properly, and keeping it in the original format as you say, they should look no different. What are you actually doing with them?

[Onceler2]

yes the original videos are terrible.
my TV is 120Hz
I will stick to deinterlacing then since that seems to produce watchable output.
But I was just wondering as to why they are so adamant about not doing it.

[manono]

yes the original videos are terrible.

Then maybe the problem isn't the interlacing but something else like a very poor quality DVD. Maybe you just have a crummy TV with a lousy deinterlacer in it. Can you then also say you've never seen a decent interlaced DVD on your television set? Because, if so, that's not the experience of others.

Maybe a small sample from the source DVD, one with steady movement, might help to get to the bottom of this.

But I was just wondering as to why they are so adamant about not doing it.

Because if reencoding for DVD, by deinterlacing you lose the fluidity of movement because it's, in effect, 60fps for NTSC and you've deinterlaced it down to 30fps. And because the deinterlacer/bobber in the TV set is most likely better than whatever you did to it.

[sanlyn]

Because even the best deinterlace (QTGMC as of now) or IVTC entails data loss, depending on the condition of the source. Sometimes the original interlace or telecine/blend is just crummy to begin with. If your LCD doesn't play properly interlaced video correctly, guess what? Many LCD's don't play interlace or pulldown well at all. Not all LCD's are equal. Almost all film-based DVD and BluRay issues are telecined in some form or other. They seem to play OK on my TV's. Always have.

[enim]

why they are so adamant

Because they are so adamant. When I went to continental restaurant for the lunch with my friends today and being asked Which food, Japanese, Korean or Chinese? Which beer, domestic or imported? I simply replied, it does not really matter, which ever taste better.

[Cornucopia]

no clue, 'everyone' here is cursing interlacing and using:
a. a deinterlace filter
b. a IVTC filter
c. a field blender filter
to get progressive output, since progressive is the more 'natural' state of things.

When people are against deinterlacing, this is normally because:
a. they don't know how to do it properly (or don't think the one the recommend it to doesn't know how to do it properly)
b. they normally deal with content which is badly mastered and hard to deinterlace properly (mixed content)
c. they are creating intermediate content and their target is to be interlaced again
d. they want interlaced content because they need it

Cu Selur

I disagree. In media, a golden rule is: one should "do the least harm". This also translates to "leave well enough alone, unless it's necessary". And since ALL progressive TVs have built in deinterlacers, it's likely NEVER (or RARELY) necessary to do it yourself, unless the model of TV/device you have is SO CRAPPY that it ruins the image using the built-in deint algorithm. Another part of that rule also ought to be that when one intends to make changes, it's usually better to make the change ONCE, and if possible, at the END.

From someone who has knowledgeably dealt for decades with WELL PRODUCED/MASTERED and HIGH QUALITY interlaced footage (both in leaving it as such and in deinterlacing or ITVC'ing)...

Scott

[Budman1]

In this same anti-deinterlace theme... I notice when I use FFMpeg to convert a video it seems to always change to progressive. What would I add to the script to keep it interlaced?

[poisondeathray]

In this same anti-deinterlace theme... I notice when I use FFMpeg to convert a video it seems to always change to progressive. What would I add to the script to keep it interlaced?

It depends on which ffmpeg build and what library is being used for the encoding

Older versions used -top 1 or -top 0 for TFF or BFF respectively for field order
Newer versions tend to use -tff or -bff
also -flags +ildct+ilme

[jman98]

Other than this

yes the original videos are terrible.

the OP has said absolutely nothing useful.

I am wondering if he is doing a variation on what I, as an IT worker, will call "the old blame Linux trick" where someone wants to know how to do something under Linux and can't find out how to do it. The members of a Linux forum are jerks and tell newbies to "read the freakin' manual". So the guy posts in the forum about how Linux really sucks because he could easily do this under Windows/Solaris/AIX/whatever but the task just cannot be done at all under Linux because it sucks. This is inevitably followed by the same guys who earlier refused to help posting in excruciating detail exactly how to do the task under Linux and defending Linux and pointing out how that OS he can easily do the task under is far worse than Linux is. I've seen this trick used here before and many of our members fall for it.

Then again the OP could be a bit on the dumb side and he's either confusing this forum with some other one or he's exaggerating about what one person told him here and acting like 100% of the members told it to him.

[Cornucopia]

The videos I have taken from dvds that were interlaced and were kept in their original format just extracted look terrible on my LCD TV. The ones that I have deinterlaced look pretty good compared to them.

Yeah, right away I would be cautious about the "taken from my DVDs". Taken, HOW? With what app & what settings?

And, played HOW? via your PC to TV? (and HOW CONNECTED?) or via a settop media player box to TV? or something else?

Too many unknown variables to blame it on any one thing like deint.

Scott

[sanlyn]

To add to the confusion, film-based DVD's are usually not interlaced. They're progressive with pulldown applied and shouldn't be deinterlaced in the first place. People play interlaced/telecined DVD's 24/7/365 without the problems described here, except for aforementioned players or TV's that just don't interpolate or upsample very well. Or...the O.P. has his playback system configured improperly. Or...the DVD sources really are crap, probably blended or field-decimated stuff or some other oddball processing of the originals.

With no sample of the sources before the O.P. or someone else processed them, it's anybody's guess what's going on.