DVD distribution - de-interlace or not?
 

Say I've shot and edited a project in HDV 50i. Now I need to make 50 PAL DVDs to be distributed. I have no way of knowing what screen types my DVDs are going to be displayed on (i.e. it will be a mixture of CRT, LCD, plasma, projector and computers). The question is: do I de-interlace the video before making the DVD? Do I author my DVDs as 50i or 25p?

Here are several issues which are on my mind:

Firstly, if I remember correctly, CRT displays are the ONLY displays capable of showing interlaced imagery natively. All other display technologies (LCD, plasma, projects and computers) must de-interlace the video before outputting it.

Secondly, not all de-interlacing algorithms are made equal. Some de-interlacing throws away half your vertical resolution. All other de-interlacing produces some form of artefecting.

So: given that maybe 70% of my DVDs will be displayed on non-CRT displays, should I de-interlace my footage before making my DVDs?

I guess this entire post boils down to one essential question: how good are the de-interlacing algorithms used on LCD and plasma TV sets?

Many thanks,
Jack

I think you answer your own question, but coming from HD to SD-DVD it shouldn't make mush of a difference.
If you choose to de-interlace, then do it before you down convert to SD.
I personally go from HD directly to Mpeg2. A progressive footage always looks better on non-CRTs, but de-interlacing is a different beast all together.

Tough question.

I'm first inclined to just say burn as is. No quality loss from your end and their players will do the best they can.

However, if you deinterlace, then you will get the same signal on all of the sets (a CRT displaying deinterlaced as interlaced will just show odd/even lines of 25p rather than 50i, half frames at a time, which will look almost identical to progressive). Plus, CRT monitors are the lowest quality and you can get away with more. Less vertical rez on a huge LCD or plasma might be very apparent.

It really depends on how good your deinterlacing algorithm is, I suppose. Do some tests with DVD players and your computer, and see what you like best.

If it was progressive, you wouldn't run into any weird issues, like when you pause and get a flicker, etc.

Hi guys,

Thanks loads for the feedback - plenty to mull over.

Thanks,
Jack

I would test it both ways.

I deinterlace when I down convert the Cineform files to SD format. I think they look a little better even on CRT displays.

I don't know if this is correct, but it seems like if it is done during the down conversion step a little less data is thrown away.

It depends on many factors. One of them is your content - if there is a lot of high speed motion, and given that you're in PAL land where you only have 25 frames per second (less temporal resolution): interlaced will look better, smoother, while deinterlaced will look a bit jittery (fake film look). On the other hand, a good deinterlacer will produce very decent blurring in the motion are, that will make it look almost as good as interlaced. I have experimented with VirtualDub with satisfactory results.

Either way, as already suggested, you need to do some tests and decide for yourself... there is no wrong or right way of doing it... it all depends.

Just a technical note: CRT standard definition monitors display a lower quality image versus high definition LCD and plasma displays. In this sense CRT would indeed be the lowest quality. CRT high definition displays, on the other hand, have generally been considered the highest quality HD monitor technology available, though LCD and plasma technology may finally be catching up.

Vague, sorry. I meant the standard CRTs that everyone has, as opposed to any newer HD displays. Also, it would still apply, as HD CRTs likely are either progressive (not sure here-- are they?), or at least have good deinterlacing, one would think.

I figured that's probably what you meant. Just wanted to clear things up for anyone who might have gotten confused.

My Sony HD CRT can display 480i, 480p, and 1080i. I believe those are the common native display modes available on HD CRTs.

Just wondering about interlace artefacts (I am thinking of horizonal lines). Do they normally show up on a projector as on a computer screen? I have shown much on projectors in interlaced format but have never noticed the lines. But since I don't own a projector I can't test it easily.

Interlace artifacts are only visible when viewed on computers that don't have proper player software. By "proper software" I mean one that can properly deinterlace the interlaced video in order to be viewed on the computer monitor. Projectors should be able to handle interlaced video properly.

Ok, thanks for the reply. I wonder if there is any "proper media player" for this, but at the same time it is good to see the artifacts as long as you see what your customer sees.