Converting 720p to 720 interlaced???
 

I was reading through the HD100 brochure and came across this: "the progressive signal can be easily converted to interlaced." Ummm... how? I know Final Cut can deinterlace footage, but how do you "interlace" progressive footage?

You just take each progressive frame and eliminate either the even or odd lines. You would do this for NTSC 30i broadcast of 720p material, scaling the progressive frames down to 480p before interlacing them. It's far easier than 1080i->480i downconversion, which I suspect is why most broadcast networks chose 720p as their HD standard instead of 1080i.

If you don't scale it down to 480p before interlacing, what do you wind up with? 720i? How would you do it in an NLE?

There is no interlaced 720-line standard, so you would never need to do it. The only way a 720-line image will ever be interlaced is if it's cross-converted to 1080i or downconverted to 480i. What the brochure is referring to is that a progressive signal is more easily converted to an interlaced standard than an interlaced signal can be converted to a different interlaced standard or a progressive standard.

I suspect any decent NLE would automagically handle interlacing the footage if you ever dropped a progressive clip into a timeline that was using an interlaced standard.

turn progressive into interlace
 

Hello,

I thought you have to shoot your footage at twice the frame rate before you can turn it into fields. I can choose an option in the timeline "interlace consecutive frames" but you keep half your f/s (because 2 fields are 1 frame).
So if i want to turn 25p progressive material into interlace and just export a movie at 50i I see no difference.

That's correct, 25p can't magically turn into 50i because the temporal resolution isn't there in the first place. You have to shoot 50p.

How about turning 50p into 25p? How does the NLEs/converters do the pulldown/conversion?

Will 50p footage converted to 25p have the exact same look as if it was shot in 25p?

Sure you can turn 25p into 50i. It doesn't suddenly gain temporal motion, but will look just like the 25p material, except on an interlaced TV. Just like watching a movie on your TV. Films are shot at 24fps and watched on your 50i/60i TV. No need to shoot 50/60p if you need to interlace, that is just silly.

There certainly is a need for it if you want it to look like native 50/60i material, and that's what I'm talking about here. The ability to pull down frames really goes without saying.

Quite right, if you want all the 'advantages' of interlaced (i.e. smoothness) you'd need to shoot in 50p.

What is actually meant by the phrase that is is easy to convert should be read as: "you can save your progressive video as an interlaced one without loosing to much quality" - of course you won't gain any smoothness that is there with the interlaced originated footage - the data in 2 fields will be of 1 image, taken at 1 point in time (instead of 2 fields for 2 moments in time as is the case with original interlaced footage).

It is especially easy if you compare it to the conversion of interlaced in progressive. There you'll loose quite some of your image quality (in the worst way you'll cut your vertical resolution in half. Obviously there are better ways, but there's always some strain on the original image quality).

How about turning 50p into 25p? That depends on the method you'll be using. You can show 2 frames at once with 50% opacity, creating (more or less) the same effect as the 'motion smoothing filter' in the JVC cam or you can choose to show just 1 of the 2 frames originally recorded. In that way you'll have the same as what's shot in 25p. The only thing that xould be different in the last one is that you might have shot it with a shutter of 100 in stead of 50, so after converting it to 25p, it'll look like 25p shot whit shutter 100, instead of the more 'normal' look of 25p shot with shutter 50...

I didn't understand the nature of the discussion of getting the footage to look like it was shot on an interlaced cam, but simply converting to interlaced. There still is no need to shoot at a high frame rate in my opinion, just shoot properly in the first place. Like any of the millions of film that we watch on our TV's.

You're making the rather large assumption that everything we shoot will lend itself naturally to slow and controlled camera moves and subject motion. Remember that this is an ENG camera as well and it's not limited to shooting indie films and interviews, but also fast-moving unpredictable events in the field. Also bear in mind that HDxxx footage may be required to cut seamlessly with other interlaced or high frame rate progressive footage, especially in a broadcast setting. I've seen someone try to cut an interview shot on an HD100 in 30p into a 60i SD broadcast and it simply looked bad. Even with a fairly stationary subject the lower temporal resolution was clearly visible.

If you can't shoot properly, don't shoot with a progressive cam. I have seen more then a few interview type films shot at a mere 24fps film never mind 30fps and of course they look fantastic. How odd. Hmmm. Of course if you must shoot in an ENG fashion, with random cam swings and simply in a way that suits interlaced video there is always the 50p/60p SD mode to fall back on. Otherwise don't use a progressive cam. I have shot lots of interviews in 30p and I simply don't have a clue as to why you say it looks inferior. It simply looks filmic instead of video-ish. If your interview is temporal resolution limited, I would simply have to ask, what the hell is the interview subject doing?

I have to agree to both of you. No matter how fast the action is, you can shoot it and make it look great in 25p or 30p. Even shot from the shoulder ENG-style. Once, I've made a 2 minute clip of some badminton just to show that, for those that didn't believe 25p could be smooth. You need to be able to handle the cam, but with the rules in mind and some dedication to your work it's fine, even in ENG circumstances.

On the other hand Stephan has a point when he says it's visible when you intercut it with 50i or 60i. That is quite true as well. You'll spot that a mile away.

I've shot a videoclip in Pal 25p. Now they want to broadcast it interlaced from a DVCam recorder. Will I loose resolution?
Thanx.

Even sports can look good at 24p if done the right way. Any Hollywood movie that deals with sports is shot at 24p. "We are Marshall" and the new "Rocky" movie are prime examples of new sports movies.

Intercutting progressive and interlaced is a big no no in my opinion. Unless it is being done for an clear effect such as a MTV type piece. One of the reasons why movies work at 24p for us is because everything from the beging including the titles is 24p so our minds get used to the motion and view it as normal. As soon as you add just a few seconds of interlaced you throw the brain off and it triggers that something is odd about the progressive footage.

Learn to shoot with care. Wipping the camera around like a rabid dog is not good shooting even if interlace is forgiving of it. If you keep trying to compare 24p/25p/30p to interlaced TV then you will never be happy with it.

You will. Theoretically you don't need to, but practically you will and you have to. the lines are somewhat averaged, thus causing loss of resolution.

That is not such a bad thing in itself - it is just a necessety. If it would be converted to interlaced and the total sharpness of the progressive footage would be kept, that would mean that details and lines that are just 1 line thick would start flickering if you saw 'em on an interlaced TV-set. To avoid that you need to drop resolution a little, thus softening those 1-line details but retaining a flicker-free image.

try e.g. putting a high-res picture of a tree in the fall on interlaced video(when all the indiviual branches are in plain sight - some of them are bound to be very thin lines) - the tree will seem to shake right out of the image.

thanks a lot for the info. And if I turn it into 50p and then print it to tape, will this also be a way to get rid of details flickering when broadcasting interlaced? And is the frame rate of PAL always 25?

Hey Marijn, It won't make no difference. but I'm not sure what you mean with print it to tape. Take a look at my website and send a mail, I can answer you in dutch, that might be a little easier. (Thursday I'm close to Amsterdam, by the way. If you have some time we can discuss it over a beer...)

For now: the flickering will only be reduced if the averaging is done (that is the drop in resolution). The 'frame-rate' of PAL is always 25. But that means 2 things: PAL progressive will be 25 frames (true and whole frames), PAL interlaced will be 50 fields (and thus 25 'frames')

And now I can't shoot properly? Funny, they keep hiring me back...

I never said that 24/30p looked bad by itself. I said it looked bad when cut with high temporal resolution footage at 60i/p in a broadcast setting. Read my post before responding kthx.

I hardly regard 50/60p mode as something to "fall back on," but rather as the primary mode to shoot in when shooting for a broadcast environment where the dominant standard has a scan rate of 50/60 Hz. Shooting 30P for a show that's 60p on the air is like shooting SD for an HD show. And I resent the implication that I'm simply randomly swinging the camera around. Have you ever shot sports?

I will use whatever equipment that suits my needs. Just because your end product requirements are different than mine doesn't mean the same product can't fit both of our needs. JVC's made a great camera for both indie film and ENG styles of shooting, yet you seem to think there's no need for its ENG side. You should visit pro.jvc.com sometime. Right on the front page is a graphic for the HD250 that says "HD ENG SPORTS." They're not marketing this thing toward indie film guys, they're marketing this toward broadcasters who broadcast in 50/60p. The fact that it makes a good indie film camera is a side effect of the features that also make it a good broadcast/ENG camera.

You say that like "video" is a bad thing. It's not. It's just a different look for a different purpose. I don't spend all my time obsessing over how I can make my picture look like "film." I spend my time trying to shoot good-looking video. Sometimes that means the same thing, sometimes it doesn't. What you need to learn is how to respect different shooting styles than your own.

No need to take it personally - I'm sure it wasn't meant that way. All I can say is that when I first shot in 25p all action looked bad. But once I adapted to filming in 25p (instead of 50i) all things look good. Even sports. Haven't got any complaints on that one.

I'm so much accustomed to it by now, that I would only want the 50p because it gives me a super smooth full res slow motion. For all other shooting, 25p is fine for me.

I shoot a lot of handheld ENG-style - sports too, but I'm not missing the 50i higher temporal resolution. The only thing that bugs me with the HD101 is that while shooting you see 50p in the viewfinder, instead of 25p as it is recorded. Furthermore you just need to accustome yourself with the style of shooting 'low-framerate' progressive. Only slow pans or very fast ones. Perferrably following a subject while panning or making high impact camera moves, ... that sort of thing. If you're used to that, shooting sports in 25p will look just fine.

I don't deny that 25/30p can look good when done properly. My argument for using 50/60p is that if you have a camera that's capable of it and your footage is going to be airing in a 50/60p broadcast, it's really a waste to not use that capability, especially when 25/30p footage is going to look noticably jerkier when shown next to 50/60p footage in the same broadcast.

Now they can broadcast 25p, they say it has nothing to do with the PAL system we have here.

In the world of standard def broadcast there is only PAL/SECAM and NTSC. 25P, 30P, 24P do not exist as broadcast formats. DV 25P really only refers to the acquisition format of the material.

When you look at the tape on a technical level for broadcast it is still 50i but those two fields just happen to have been captured at the exact same moment in time - not 1/50th of a second apart from each other.

The same is true for 30P in the NTSC broadcast areas. The only exception is 24P which uses 2:3 pulldown to spread the 24 progressive frames over 1 second and make up the 59.94 fields per second.

The ATSC digital broadcasting standard allows for 24p and 30p framerates (as well as "NTSCized" equivalents like 23.976 and 29.97). In practice broadcasters are still using the old NTSC field rates and using pulldown to show 24p and 30p content, but the capability is there in the standard.

I think Tim has summed it up quite well here. Well said Tim.