interlaced image sequences

[Steve Roberts]

It all looks good at first glance. Details:

1. Please get a DVD burner. They’re cheap. Seriously. If you can’t burn and play a DVD that you author, you’re working blind.
2. You’re using NTSC non-square pixels when working at 720×480 right? If not, you should. Sorry, had to ask. 🙂
3. Why use interlaced if you don’t have to match something interlaced? I and others find interlacing too much of a hassle with little or no benefit.
4. Did you confirm that your interlaced renders are indeed interlaced?
5. When you re-render, you should only render interlaced if you have something moving (keyframed motion) in your comp and you want an interlaced result. Otherwise, don’t render interlaced, because rendering progressive just leaves your interlaced sources unchanged.
6. Regarding the pillarboxing, when I’m simulating a 16:9 DVD, I see no pillarboxing. Can’t speak for 4:3. Maybe the DVDsp COW can help.

Hope that helps…

[Kasey Spayman]

1. My computer has a dvd burner but all available ports on my motherboard are in use for a RAID array that i installed after buying it.

2.) Yes I’m using .9 pixels

3. The comps that I’m rendering have a lot of moving text and shapes and stuff that would probably look better interlaced.

4. “Did you confirm that your interlaced renders are indeed interlaced?” the PNG sequence LOOKs interlaced and so does the quicktime final. Whether or not they are correctly done I can’t say because I can’t preview them on a TV.

5. “When you re-render, you should only render interlaced if you have something moving (keyframed motion) in your comp and you want an interlaced result. Otherwise, don’t render interlaced, because rendering progressive just leaves your interlaced sources unchanged.”

— this is the most alarming thing I’ve read so far. Are you telling me to… render the PNG sequence intermediate interlaced, then render the final quicktime progressive? I can’t wrap my head around that maybe explain more? I thought Encore would want an interlaced source (the final quicktime)…

[Steve Roberts]

Hey Kasey,

I’m one of those guys who likes the look of progressive instead of interlaced. To each his own.

If it looks interlaced, it is interlaced. To check the field order of an interlaced movie, import it into AE, make sure fields are separated (interpretation) and opt-double-click on it. In the window that comes up, use the PageDn key to step through the file. If it plays normally, the interpretation (upper or lower first) is correct. If it jerks pack and forth, the interpretation is incorrect.

Regarding Number 5, if you have stuff flying around in your comp over interlaced footage, render interlaced in the same field order as your BG footage. This way the flying stuff will be interlaced properly.

Imagine an interlaced movie (sequence, whatever) as a series of comb-like images. Programs that are just used to progressive frames can only see them that way — as comb-like images. However, AE can be told to take the alternating lines and make a sort-of frame, then take the other alternating lines and make the next sort-of frame, and so on. Thing is, it only shows every other sort-of frame, because there are two of those for every real frame in a comp. This is what happens when you separate fields on interpretation. When you take a comp with a field-separated movie and render interlaced, it remembers the extra sort-of frames and interlaces them back into the frame.

I hope that makes sense.

Big caveat: never scale an interlaced image or movie. It makes irredeemable crapola. You can spot these by interlacing lines of varying width. If you see that, you’ve made an interlaced movie incorrectly, possibly by scaling it in the output module, or by scaling without separating fields. If somebody gives you one of those, you need the unscaled source to make anything with it. Anyway, if your interlacing lines are of constant width, you’ve made them correctly. Use the PageDn tip to check field order.

Render progressive if you’re just, say, color-correcting interlaced footage that you interpreted fields-off. This way, each frame in the comp is a comb-like image (you know, the interlaced look), and it gets rendered exactly as it came in – as a comb-like image. If you render that sort of comp “interlaced”, you would get the same result Each field will be an identical comb-like image.

Encore doesn’t need an interlaced source. Nobody needs an interlaced source. Things that can display interlaced can handle progressive: they just treat a progressive frame as two identical fields! 🙂

Regarding the alarmingness, if you want an interlaced final, render the comp with flying stuff interlaced. The final can be rendered with fields or without, but if there’s no movement, scaling, whatever, the footage will not be altered if you’ve interpreted it “no fields”. If however, you had interpreted it with fields, you should render with fields, otherwise AE will only render frames, losing half the temporal info … sort of.

Hope that helps …