Explain 1080P

braw

braw

Well-known member
This may just be speculation, but does anyone know how 1080p will work on this camera? I have read that it will be like the DVX since DVCPRO HD doesn't provide for 1080p inherently. 720p works without having to use pulldown so 24p will be 40Mbps, but will 1080p have the same bandwidth?

Example:

720 24p = 40Mbps
720 60p = 100Mbps
1080 60i = 100Mbps

So will 1080 store only useable frames with a header for when you import, so that 1080 30p will have each frame using 100mbps or 24 using 80Mbps? Or does it need to actually store the redundant frames so that 24p will be 40Mbps? My concern is that with the increased resolution there is also increased compression. It seems like it could be a catch 22. Does this even matter all that much?
 
No it really dosen't matter that much. But the stream will be interlaced 1080. And yes there will need to be some sort of pulldown removal for 24P 1080. There will be a standard and advanced mode just like the DVX.
 
Okay, let's start from scratch -- there is no wasted resolution, no increased compression, nothing like that. DVCPRO-HD stores each and every frame individually, and each and every frame gets the exact same amount of compression. It's not like HDV where what happens in one frame can affect what happens in another. In DVCPRO-HD, every frame gets exactly the same bandwidth as every other frame.

In 1080 mode, it works like the DVX. The progressive stream is carried within a 60i data stream. So, NTSC DV could be thought of as 480i, and the DVX delivers 480/24p, 480/30p, and 480/60i, but on tape they're all recorded as 480/60i.

Same with the HVX -- it records 1080/60i only. So the progressive-scan footage will be carried within a 1080i data stream: 1080/24p, 1080/30p, and 1080/60i are all recorded within a 1080/60i data stream. Just like with the DVX, 24p will be recorded using either 3:2 or 2:3:3:2 pulldown, your choice.

There are no header flags or only-used-frames flags in the 1080i/p version; only in the 720p version. So when recording 1080 mode, it's always 100 megabits all the time. There's not much "wasted space", because a 1080/30p stream will require 100 megabits, just like 1080/60i does. If 1080/24p was possible to be stored as only the active frames (with no pulldown) it would still require 80 megabits, but it doesn't have that capability, so it requires 100 megabits.

Increased resolution does not mean increased compression. 720p mode uses exactly half the pixels per frame as 1080 mode. 720p mode uses twice as many frames per second as 1080 mode, so they both net out at 100 megabits. A 720p mode frame has half as many pixels, and compresses at the exact same compression ratio, so that the compressed frame takes up half as much space as a 1080 frame does.
 
Excellent, Thanks Barry. That makes sense. 1080 has a max of 30p and 720 has a max of 60p, so 1080 allocates twice the bandwidth for twice the resolution (roughly speaking).

That's exactly what I was wondering. I wasn't sure exactly how that pulldown technique worked.
 
That's good news. I was wondering how that would work.

Now if only the 1080p mode had that nifty variable framerate action going for it.
 
In 1080 mode, it works like the DVX. The progressive stream is carried within a 60i data stream.
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Is there not a provision for progressive flagging? Compressing a progressive image as 60 fields has a downside, as each field is compressed separately, mucking up spatial compression... not to mention colour sampling.

-Spiff
 
In other compression formats, yes. But in a DV-based compression system, no.

DV (and its variants, DVCPRO-50 and DVCPRO-HD) all employ two modes of compression, based on how much difference the codec sees between the fields. If there's a lot of temporal offset, the codec will compress as fields. But if it doesn't detect much offset, it'll instead compress the entire frame at once.

Which results in better, more efficient compression on progressive footage! It works that way in regular DV, even though up until the DVX there pretty much hadn't been such a thing as actual progressive CCDs recording data in DV. It was more of an optimization for when the camera was locked-down, etc., but it comes in very handy in handling 24P and 30P footage.

So no, expect no mucking up of spatial compression or colour sampling.

Now if only the 1080p mode had that nifty variable framerate action going for it.
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Well, it does, sort of. I mean, how variable is "variable"? You should be able to get the same rates out of it that you can get from a DVX, so you should get 3P, 4P, 6P, 8P, 12P, 15P, 24P, and 30P, as well as 60i... pretty nifty, eh?
 
Well, I think he meant the "Varicam"-style frame rate control you get in 720p ... but I'm not complaining. :)
 
Yeah. I was hoping to shoot at 22 FPS in 1080p. But it is amazing that you can do it at all.
 
Just out of curiosity, what would you shoot at 22fps for? (I only ask out of ignorance.)
 
Lots of action sequences (particularly in martial arts films) shoot at 22 FPS so when it's played back at 24, it's got that extra-quick feel to it, without looking very "sped-up".
 
No. In the Bourne Identity they borrowed a jack-hammer from a road construction crew and strapped it onto their camera.

-Spiff
 
Sorry - but fight scenes are close to my heart, and the ones in the Bourne series have made attrocious use of high shutter speeds, jittery cameras, and quick edits to hide whatever merit the fights may have had. They could have undercranked as well, but the whole combination violates so many principles as to how to do it "right", it's just not even funny... and I'm not the only one who felt sea-sick watching them.

Like Ryan said, undercranking is very common - in particular in a lot of old kung-fu flicks. It's use in Hollywood has been slightly more careful. It has the tendency to make the fighters look "light" (as movement of cloth etc. is sped up as well).

I prefer the opposite technique - overcranking shots with absolutely crazy stunts so you can see exactly what happens - Ong Bak for example.

-Spiff
 
mmm said:
Cheers Barry! Great, clear explaination

Are you paid by Panasonic?

If not, you should be!
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Glad it made sense. And for clarification, no, I am not on the Panasonic payroll. They are a customer of mine, in that they buy DVX Book/DVDs from me (and I am a customer of theirs, since I have to buy anything I want from Rush, no special "hookups" for gear here...), but I don't draw any sort of paycheck or have any sort of contract/relationship with them.
 
Ah, sucks no special discounts.

I thought about coming to Vegas and have you order the HVX for me, for the special Barry Green price of $59.95 oops, that's $5,995.

Oh forgot to add that includes extra 6 8g P2 cards.

LOL
 
Spiff,

I'm 100% with you on the Bourne Supremacy. I have never attended any other movie in which the cinematography was more distracting and obtrusive. I should have bought a bucket of dramamine pills with my popcorn and soda to conteract the nausea of watching a 2 hour movie with about 2 minutes of stable camera footage. Who outlawed the tripod and dollly rig on that shoot?

Too bad. Writing, story, and acting were all good. But yikes, what an unwatchable piece of crappola visually. Imagine what Woo, Rodriguez or Tarantino could have done with those action scenes.
 
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