Interlacing artifacts or whatever they're called

[Chris Harding]

Hi Jeff

I remember getting the exact same thing when I tried to resize interlaced 4:3 footage to 16:9 ...My workflow with 50i is to match the media with Vegas and I always use BLEND as the de-interlacing method...I was told that use INTERPOLATE only if you have a lot a high speed movement (which doesn't happen at weddings at all!!) If I'm wrong then anyone can correct me but tell me why???

The other neat trick is to drop the Sony Sharpen plugin on all video tracks BUT leave it at zero (I have no idea why but it certainly makes a huge difference to your SD footage ..logic says it shouldn't but it does)

When you transcode with Cineform the footage will go in interlaced BUT does Cineform do anything to the interlacing??? I remember with Upshift I had an option to de-interlace in the transcode software (I don't use it any more as the i7 handles the AVCHD perfectly!!)

Chris

[Gerald Webb]

Out of interest I just did a conversion on an old mpg 2 tv capture I had,
Uff 720x 576
I tried a few different ways but the best by far was HDlink.
It upscaled to 720p and deinterlaced at the same time. As another bonus the dynamic range also increased, would the 4.2.0 to 4.2.2 color space do that?
Out of interest, if time wasn't a factor, what is the most lossless way to turn interlaced footage progressive?
I used to think Yadiff was pretty good but my tests today suggest otherwise.

[Jeff Harper]

Chris/ Gerald: HDLink (Cineform) is amazing, It definitely deinterlaces beautifully. I had started to convert the files yesterday but when I found I could just up the bit rate to smooth things out I went with that. The DVDs are in the mail and they look fine.

Vegas can do the job, but it's truly just a matter of figuring things out.

Last year I used HD link to convert every wedding, and the results were always stunning for DVD, and I had no issues lowering bit rates to fit projects to discs.

Now I've got 1080i footage from all cameras for a couple of projects, and I didn't want to convert everything, it's just too time consuming and eats up too much space.

[Leif Skoglund]

I’ve got the exact same problem as Jeff when rendering to DVD. My footage is 1920/50i – PAL . When rendering to PAL-DVD it looks horrible. Then after a few days, trying to solve this problem, I rendered from 1920/PAL to a NTSC format-DVD. This looks much better than rendering to PAL-DVD(I can't use this anyway). How can this be explained?

[Leif Skoglund]

I solved this problem by rendering a HQ *.mp4-file(included audio). Imported this MP4-file into Pinnacle Studio 15 and downconverted(rendered) this file to 720*576 DV-quality. Then burned my DVD in DVDA. The quality looks very good and I'm impressed of this result.....

Leif

[Jeff Harper]

Good thinking Leif, good job.

[Laurence Kingston]

This is a problem I am well aware of and I can tell you exactly what is going on.

Vegas resizes interlaced footage and progressive footage differently (as it should). The proper way to resize a progressive image is obvious: you just resize each frame like you would a still photograph.

Interlaced footage is a bit more tricky, especially if you are resizing an interlaced image at one size and outputting interlaced footage at another.

What you need to do is separate the even and odd fields, resize each independently, then fold them back together alternately by even and odd lines. In other words, every even line gets taken from one resized field, every odd line from another.

In Virtualdub or AVI Synth, the way to do this is with a chain of filters:

1: a separate into fields (either side by side or one over top of the other instead of alternating lines).
2: a resize filter that will resize these two side by side (or one over top of the other) fields.
3: a "refold" filter that will take every even line from one image, every odd line from the other, then "refold" them into a new interlaced image at the new size (SD DVD instead of HD for instance).

Vegas actually is very cool in that it does all this transparently in the background. That's the good news. The bad news is that Vegas is easily confused and that is exactly what is happening in this instance. The interlaced frames are being resized frame by frame with no regard to the interlace or even and odd fields. What you are seeing is a resizing of the interlace comb which is aliasing into a new frequency and thus is forming a resized interlace comb that is no longer happening at even and odd line points. Yeah, it looks terrible.

The reason this is happening is because you are resizing from one interlaced size to another, but you chose "none" for your deinterlace method instead of "blend fields" or "interpolate". For some strange reason, when you select no deinterlace method (which would make sense since you don't actually want to deinterlace) and you render to a new interlaced size, you get very strange looking aliased interlace comb artifacts. This is exactly what I am seeing in your posted screen captures.

Here is what you need to know.

1/ When you are working with interlaced HD and you want to make an SD DVD, the best looking option is to make an interlaced SD DVD out of your interlaced HD footage. Yes, you can deinterlace, but most of the time it will not look nearly as good as if you go interlaced to interlaced.

2/ When you are resizing from one size of interlaced to another, you need to to select a deinterlace method. It doesn't matter if you choose "blend fields" or "interpolate" because you are not going to actually deinterlace. It makes no difference which one you choose. You just can't select "none".

3/ With a deinterlace method selected, just render to one of the SD interlaced templates at the same frame rate (60i if you're NTSC, 50i if you're in one of the PAL countries).

4/ With the deinterlace method selected, go ahead and try rendering to an MPEG2 DVD widescreen template and it will look great.

What Vegas will be doing when you select a deinterlace method but render to a new interlaced size is the following: separate the even and odd fields, resize them separately, and fold them back by even and odd lines into the newly resized frames. Very cool once you figure this out.

I must say that when I ran into this, it took me a good six months to figure out, and nobody I talked to at the time had any clue what was going on. This has been an issue from even before HD. I first ran into this when I was trying to make 16:9 SD renders out of 4:3 interlaced footage. Since doing this is an interlaced to interlaced resize, I ran into exactly the same artifacts doing this as well.

[Laurence Kingston]

That was the long answer. The short answer is this:

When you are working with interlaced HD footage and you want to render out a DVD:

1/ Select a deinterlace method (it can be either "blend fields" or "interpolate", it doesn't matter since you aren't actually going to deinterlace).

2/ Render to the widescreen interlaced mpeg 2 template format to make your DVD.

This will give you a widescreen interlaced SD DVD that looks perfect.

If you don't select a deinterlace method, Vegas will do the resize from HD to SD without regard for the interlace comb. The result of this will be an aliasing of the interlace comb that will give you large resized comb artifacts that look absolutely terrible.

[Seth Bloombaum]

Laurence, thanks for this very clear description of Vegas' processes for resizing.

There's been so much talk of inferior and superior methods of deinterlace and resize, with opaque references to "Vegas doesn't do it the best way..."; your research and method very clearly show how to get Vegas' best possible results for this common process.

It also explains why some people have never seen these interlace artifacts in their resized projects.

[Tim Akin]

What if your working with progressive HD footage and are going to DVD? I've been getting some shimmering in brick and floors with horizonal lines. I have always selected none in project properties for deinterlace method.

[Gerald Webb]

I've done few the last few weeks, as mentioned previous, for best quality, I would export to Cineform and let HD link do the resize.
In Vegas though, this works,

1920x 1080 Progressive,
Project setting-Deinterlace = None (of course),
Render to -Elementary DVD streams, just use the DVD architect template but change the fields to None.
This gives you a progressive DVD .

1920x1080 Interlaced UFF
Project setting-Deinterlace = blend or interpolate.
Render to- same as above, dvd architect template, but set your fields the same as your source.
This gives you an interlaced DVD.

1920x1080 Interlaced UFF into Progressive (for web delivery)
Project setting-Deinterlace = blend or interpolate.
Render to- mp4 of your choosing , it will not have any image issues but the quality does go down.

Thanks to Laurence for a great explanation :)

[Gints Klimanis]

Anyone using the Yadif deinterlace plug-in?

[Gerald Webb]

Yep, have been over the last few months , have to say though, just using Vegas' own Deinterlace via project properties gives about same quality at about 10th of render time.
My opinion only, show me some frame grabs and prove me wrong
:)

[David Stoneburner]

I'm wondering if you get the same results when playing the DVD on a DVD player to a TV? The interlaced fields are noticeable on a PC monitor but usually not a DVD player. I'm still using Vegas 9 have jumped yet. Might need to wait for 12 now. That seems the hard part is trying to fool proof any project for all the different ways people can play them back.

[David Jimerson]

You won't see interlace artifacts playing a DVD to a regular interlaced TV, because that's what interlacing is designed for.