Do I have to De-Interlace?

[NotSoEasy]

I am going to be backing up a PAL DVD to XviD and know it will be interlaced.
Will I need to de-interlace it? I assume it wont matter if played later on PC but will it matter if played on Philips 642/37
If de-interlacing is needed, what is best.Should I do it by way of VdubMOD or AviSynth ( I will be cropping and resizing by way of AviSynth )

[zoobie]

The general theory here is to leave it interlaced. This helps retain quality.

[NotSoEasy]

Kinda thought that so left it.Thanks for the reply.

[manono]

Leave an XviD interlaced? I disagree, especially if you'll be resizing vertically. I recommend (for fast and good) using LeakKernelDeint in an AviSynth script.

Be darned sure it's really interlaced before you go deinterlacing it, though. Check the unfiltered frames first, to confirm the presence of interlacing.

[NotSoEasy]

How do you go about checking unfiltered frames?

[manono]

LoadPlugin("C:\Path\To\DGDecode.dll")
MPEG2Source("C:\Path\To\Movie.d2v")

Open it in VDub(Mod), scroll to a place where there's movement/action, advance a frame at a time, and look for interlacing, zooming the picture if necessary

[NotSoEasy]

Well I tried a few scenes and I never saw it jump back and forth when going frame by frame.Never saw any interlace lines either so I guess DGMPGDec DGIndex was wrong!
How can it not know or why would it even say it is interlaced if it is not?
I always let it run ( preview ) for a few minutes so it gets enough info to know about the movie.

[manono]

so I guess DGMPGDec DGIndex was wrong!

No! DGIndex is right. It tells you how it was encoded, and not what the source is like. Those are often 2 completely different things, especially where PAL DVDs are concerned. The only way to tell if it's interlaced or not is with your eyes.

Running the Preview at a slow speed is also another way to look for interlacing, but not as guaranteed as stepping through it frame by frame. The Preview video is sometimes too small to tell, for me anyway.

[NotSoEasy]

Im a little lost by what you mean.You say it is correct, but I just found out it was not interlaced as it said it was?
My source files are VOB I ripped with DVD Decrypter and those loaded into DGMPGDec and from there, I click preview and I see it says PAL interlaced.
I didnt encode anything at this point.

[manono]

Hi-

Well, you don't really have to understand it. You just have to know that the information that DGIndex gives you doesn't tell you whether the video itself is interlaced or not. Even if it says Progressive, while it usually is really progressive, some idiot could have done it wrong. Do as I said before. Load the D2V into VDub(Mod), step through it in a motion sequence and look for the interlacing.

Just know that it's perfectly OK and "legal" to encode progressive material as interlaced. It's true for the vast majority of PAL DVDs. But if they are movies, you can almost bet that they're really progressive. You already saw what I'm talking about, and as you examine more and more retail PAL DVDs, you'll see it more and more often. Most PAL DVDs that are encoded as interlaced, shown to have been encoded as interlaced by such apps as DGIndex and Bit Rate Viewer, really contain progressive content.

[NotSoEasy]

Ok, I read ya now.
I looked once again and zoomed in to 400% and saw no interlacing which is good I guess since that is one less filter to have to mess with.
I guess the real answer to all this though is that if you have something interlaced and are encoding it, de-interlace it?
We sure could use a good updated guide on encoding.Many are old with old software versions.A new updated one is needed bad.

[manono]

For AVI encoding, I certainly believe in deinterlacing. DVD is another story.

XviD does have an option to encode it interlaced. I just don't happen to believe in using it. Maybe zoobie does, unless he misunderstood your question.

[jagabo]

I'm pretty sure the DVP-642 doesn't play interlaced AVI files correctly.

[edit]

I take it back -- I encoded two short NTSC 640x480 videos, one TFF, the other BFF, and both played properly as long as the Xvid codec had then flagged properly.

[manono]

Yes, and you have enough sense to keep the original vertical resolution. That's one reason I don't suggest using interlaced encoding of XviDs. Sure as heck some idiot will just blindly resize to 512x384 and then wonder why he sees "lines" when playing it in his standalone. Either that or he'll do some kind of other filtering that messes up the field structure. That and the fact that interlacing is less compressible than is progressive content, and there are some pretty good AviSynth deinterlacers, and I don't mean FieldDeinterlace() or the VDub equivalent.

...and both played properly as long as the Xvid codec had then flagged properly.

My guess is that the flagging has nothing to do with it. Did you try not flagging it? If you have a standard interlaced CRT TV set, it's just playing the fields anyway, flagged or not. You might try encoding without setting the flag and seeing if it also plays OK That's just a guess though, as I've never played with interlaced encoding.

[jagabo]

...and both played properly as long as the Xvid codec had then flagged properly.

My guess is that the flagging has nothing to do with it. Did you try not flagging it? If you have a standard interlaced CRT TV set, it's just playing the fields anyway, flagged or not. You might try encoding without setting the flag and seeing if it also plays OK That's just a guess though, as I've never played with interlaced encoding.

I originally did the tests without setting the interlaced and field order flags in Xvid. The BFF video played properly. TFF did not (the fields played in the wrong order). Obviously, the DVD player has to send the fields one at a time to the TV (s-video cable) and it defaulted to sending the bottom field first.

[manono]

I'm not understanding. You did 2 tests, one with a BFF video and a different one using a TFF video? And only the native BFF video played properly, while the native TFF one didn't play properly (stuttery back and forth movement)?

If so, then you also seem to be saying that the DVD-642 (and maybe by extension just about any other DVD/MPEG-4 player) can play interlaced video without it having the interlaced and field order flags set IF they are all native BFF. So, in cases where the video is TFF, then changing the field order will also allow them to play properly.

Interesting. Thanks for the reports on your tests.

[jagabo]

I did four tests. One with TFF video encoded as progressive, one with BFF video encoded as progressive, one with TFF video encoded as interlaced with the Xvid TFF flag set, and one with BFF video encoded as interlaced with the Xvid BFF flag set.

The two interlaced encodings with field order flags played with the correct field order.

The BFF video with progressive encoding played with the correct field order.

The TFF video with progressive encoding played with the wrong field order.

I wouldn't count on other players behaving exactly the same (although my old Liteon 2002 does). Most software players under Windows don't.