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-   -   Mixing 720p and 1080i footage, and (https://www.dvinfo.net/forum/jvc-gy-hd-series-camera-systems/68344-mixing-720p-1080i-footage.html)

Scott Shuster May 28th, 2006 11:56 AM

Mixing 720p and 1080i footage, and
Hi everybody — Greetings again to the great Chris Hurd, whose guidance has been so valuable to us through repeated purchases...Hi, Chris!!

We create dance and fitness DVDs...and we are very excited about the progressive option now available from JVC. We shot progressive in the pre-HD days (Panasonic) and were blown away by the image quality.

BUT: We already have a Sony Z1U, which is interlaced, not progressive. We have been shooting in 1080i, not 720p like the JVC. There may also be some differences in the 'transport stream,' the MPEG standards used, & other stuff that we-don't-understand-'cuz-really-all-we-want-to-do-is-press-"record" - y'know what I mean?

Question: Can we use a Sony Z1U and a JVC GY-HD100 side-by-side on the same shoot and mix video from both of them in Final Cut Pro-HD to create our DVD productions?

Second question: Can you describe the visual difference we will see between 720p and 1080i. "1080" is a bigger number than "720" - one of our staff says "It can't be good to switch to a lower number.." Is this correct thinking?

Third question: (The last one, I promise!) Will shooting in 720p instead of 1080i limit us somehow when the time comes to issue our DVDs as HD-DVDs, or when Mark Cuban wants to license our content for his all-HD TV channel — :)

Many thanks,

Nate Weaver May 28th, 2006 12:51 PM

There's a lot of issues here to consider, but I'll try to break them apart:

1-Higher numbers don't mean better image quality: The HD100 is actually a higher res camera than the Z1. This is not opinion or conjecture, it's real numbers from resolution charts I've been witness to on a couple occasions now.

The Sony records slightly less real resolution to a tape format (1080i) that can hold MUCH more. In other words, the numbers on the tape formats mean diddly in this matter.

2-You can edit the two together, but it'll likely be a huge PITA. Only Avid Xpress Pro to my knowledge can mix formats in a single timeline. That means to do it in FCP you'll have to first convert one format to the other before editing. This is time-intensive..HD format conversion in software takes a while.

3-Aesthetic considerations: The JVC and Sony look different. With a good HD monitor you'll be able to tweak the two to meet in the middle, but it'll be tricky.

4-Framerate considerations: You've been shooting 1080i on the Sony, which records 60 separate fields per second. The best the JVC can do is 30 full frames per second, which looks very different. Cineframe 30 mode on the Z1 would give you the closest approximation of framerate to match the JVC, at the cost of vertical res. which will make it look even yet more soft compared to the JVC.

In short, I'd say don't do it. It'll be a lot of work and trouble for a compromised final product. Buy another Z1 or buy another JVC, but trying to use both will give you gray hairs.

Stephan Ahonen May 28th, 2006 03:33 PM

1080i60 and 720p60 cross-convert pretty well, actually. The fact that 720 is a progressive format really helps out, one 1080 field can easily become a 720 frame and vice versa due to the very manageable 3/2 size ratio between the two. However, 1080 doesn't downconvert to standard def very well at all due to an awkward resize ratio (4/9) and the fact that both formats are interlaced. Interlacing makes any kind of resizing operation a major PITA unless you're dealing with an exact 2/1 ratio.

As for your second question, 1080 may have more pixels in a frame, but only half as many frames per second. In practice you're only getting 12.5% more pixels getting thrown at you at any given moment.

Third question, most major broadcasters are using 720 at the moment. I'm not sure which format will "win" ultimately, but I feel that 720 is the superior format. Even if 1080 wins out, like I said before 720 will cross convert to 1080 very nicely, so I wouldn't worry.

Nate Weaver May 28th, 2006 03:41 PM


Originally Posted by Stephan Ahonen
1080i60 and 720p60 cross-convert pretty well, actually.

They can and do given the right gear or sodtware, but my argument was that it's not very practical. It was incredibly slow to convert 1080i to 720p on my dual 2.0 G5. Like 5x-7x realtime.


Originally Posted by Stephan Ahonen
As for your second question, 1080 may have more pixels in a frame, but only half as many frames per second. In practice you're only getting 12.5% more pixels getting thrown at you at any given moment.

Not with the Z1 :-)

I've posted large projects in both 1080i and 720p in Final Cut Pro...and was just trying to say that if I had to do both in the same project, I'd cry.

If there's an easy way to get to a common codec with the two, then the other hurdles are much easier. Bring in via Kona 2 and DVCPRO HD?

Steve Mullen May 28th, 2006 04:28 PM


Originally Posted by Nate Weaver
Buy another Z1 or buy another JVC, but trying to use both will give you gray hairs.

I agree fully -- but if you do it, be sure you use a 60i interlaced timeline and convert the progressive to interlace. Essentially, you'll have a 30 Frames/s timeline into which 30p will go into. (30p can go to 60i with zero problems.)

The 1280x720 will be scaled to 1440x1080 -- which is not a big deal with progressive. Since the Sony really is 960x1080 scaled to 1440x1080, they could wind up "equally" sharp -- especially if you tune both camcorders.

But, you'll have to CC everything to get them to match.

But, it's a lot of work as Nate points out.

Craig Donaldson May 29th, 2006 03:08 PM

ok, i know we're talkin HD here but if you needed a second camera to the gy-101e and couldnt get one, what would you use?

Shoot dv? Keep the formats the same? Or shoot main camera in HD and second camera in SD?

I often find i am wishing for a second camera on shoots but the thought of mixing formats just does my head in.....

In answer to the first question in this post- you could buy a new HD-100/200 and the BRD-50 (?) deck and 'up'convert from it to 1080i. No more timeline worries.

On another note- it always amazes me how many people (esp. other cameramen) are ignorant to the differences between 1080i and 720p. I know more than one who has made a camera purchase purely for the biggest number...... also producers/ production managers...... try telling them that 720 can be better than 1080. I wonder if the Sony will ultimately win out over the
JVC because people just dont get it.....!

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