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class="Paragraph" 30p or 60i

Published : 5th April 2004


Is the choice between 30p and 60i merely aesthetic?

I have just started meeting with a client about a documentary that should have international appeal. Japan was specifically mentioned. Am I forced to shoot in 60i if we want to have access to the Japanese market? Or are they only concerned with the delivery format, which would leave the acquisition format up to me.

This will be my first HD shoot of this scale.

We are most likely going to use a Sony HD camera, either a 900 or a 700a.

Alan A. Hereford * Cinematographer
Marin Co., CA USA



Alan Hereford wrote:

>Is the choice between 30p and 60i merely aesthetic?

The choice is not merely aesthetic. By any measure any interlaced imaging format throws away at least 40% of the available, stated vertical resolution and may be the biggest" bait-and-switch in HD imaging. That 40% (40x1080=432 lines of vertical resolution) in 1080 represents the resolution that simply cannot be processed by the human psycho-visual perception system because of the temporal time displacements of the line-to-line interleaving process used in the interlace process.

As to your business decision, if a client insists on the use of interlace, for commercial or nationalistic reasons, you need to do what you feel is appropriate to your business plan. They certainly will.

GEORGE C. PALMER
HDPIX, INC.
HD and Digital Imaging Services
www.hdpix.com



Oriental clients really like Interlace with lots of Detail. When you work for them ...Give them what they want.

B. Sean Fairburn
LA HD DP



>"Oriental?" Out of curiosity, does that mean just Japanese, or the Asian subcontinent in general?

Japanese clients usually prefer 1080i because NHK is 1080i. But I've worked on several Chinese shows that are 1080/25p. A couple of Thai music videos I posted were 23.98p, while a Malaysian corporate video was 720p.

Yes, give them what they want. But don't assume and don't generalize. It gets you into trouble.

Lucas Wilson

HD/2K Online
Los Angeles



>"As to your business decision, if a client insists on the use of interlace, for commercial or nationalistic reasons, you need to do what you feel is appropriate to your business plan. They certainly will"

George and Sean,

I knew I could count on you guys.

At this point, no one is insisting on anything (well, other than pretty pictures shot on HD). We all would prefer to shoot progressive but are wondering if this choice is going to bag us down the line.

Given the subject, the client feels that the Japanese market would be a natural choice. Although a major market, it would not be our only one. I have used Japan as an example because I have it in my mind that they require an interlace format for broadcast.

Alan A. Hereford * Cinematographer
Marin Co., CA USA



>"Oriental?" Out of curiosity, does that mean just Japanese, or the Asian subcontinent in general?

I also have some experience in the "Asian" market...and as Lucas said there is no "one standard" across the pacific rim, Ntsc/PAl/HD25P...you name it, there's a place that insists upon it.

In my experience NHK does insist upon 1080/60i

At the end of the day this is really a question for the show's producer's to answer, and if you are the producer, then check out the delivery requirements in the contract.....

As to whether they will except footage supplied @ 30P and transcoded to 60i is best answered by the producer's and NHK tech staff, but would not hold my breath

Good luck

Dermot Shane
Vfx guy ( and now a temporary post sup...)
Vancouver, Canada & Shanghai, China



Alan Hereford wrote :

>We all would prefer to shoot progressive but are wondering if this choice is going to bag us down the line.

Be assured that progressive is always better than interlace; your only downstream consideration should be the frame rate. If 30f is appropriate for all of your distribution and release technical requirement, then progressive is the only way to go. Whatever you do discuss those requirements with your post house/film out facility to confirm that appropriateness.

GEORGE C. PALMER
HDPIX, INC.
HD and Digital Imaging Services



You could always shoot and edit in a progressive format and then create a 1080/60i master for those markets that would prefer an interlaced HD master. Transmission and production standards do not have to match.

Robert Goodman
Filmmaker/Author
Philadelphia, PA



>In my experience NHK does insist upon 1080/60i

In the past, this was true. Recently, decisions seem to be made on how much they want the content. Even as far back as 1996, NHK took 1250/50i material and converted in the Atlanta Olympics for major portions of programming. Discussions with NASA/KSC concerning launch video indicated that NHK would accept 720p60 conversions for those cameras provided by NASA (which could be a significant number, assuming that we fly before HD is obsolete.)

So even for NHK, don't assume that you know the answer. If your NHK contact wants the material, she can run interference for you (yes, there are a few women involved in NHK program acquisition.)

You never know. Like everyone else, the more money they put in, the more control they will want.

cheers,

Charles R. Caillouet, Jnr.

Vision Unlimited/LA
Atchafalaya Basin Documentary Project
HD production technical support since 1987



Alan,

From an information-theoretic standpoint, interlaced sampling is always worse than progressive sampling.

In interlaced sampling, pixels between fields within a frame are under sampled by at factor of at least two, and pixels between frames within a field are under sampled by a factor of at least two, yielding severe aliasing artefacts whenever and wherever there is interfield or interframe motion of more than one pixel.

To avoid these aliasing artefacts, an interlaced-scanning camera would need to smooth the pixels with a low-pass filter across fields within each frame and across frames within each field.

Information-theoretically, it can be shown that the result would contain no more information than scanning progressively at half the temporal rate and half the vertical resolution. in other words, the equivalent quality of, say, 1920 x 1080 p/f x 60 f/s interlaced, would be 1920 x 540 p/f x 30 f/s progressive.

On the other hand, where the interfield and interframe motion correspond to less than one pixel, Nyquist filtering yields excessive motion blur and vertical blur. Since the degree of motion varies both spatially and temporally, there is no feasible solution to this problem. Doing so would require the intelligence to identify corresponding regions of scan lines adjacent in space and time. The fact that, as George Palmer reported, interlaced scanning represents only a 40% rather than 50% information loss to the human visual system indicates that our eyes may be capable of more intelligent temporospatial integration than linear filters.

Andreas Wittenstein
Founder, BitJazz Inc.
http://www.bitjazz.com/sheervideo/



Goodman sensibly wrote:

>Transmission and production standards do not have to match.

Otherwise a lot more people would have film projectors at home!

Jeff "ah, that would be good!" Kreines



> Is the choice between 30p and 60i merely aesthetic?

No, as you've seen, it's highly religious/political as well!

One nagging technical issue to be aware of: 60i and 24p are both reasonably easily standards-converted for 50i distribution channels. 30P material does NOT convert easily to 50i; the motion update rate is too slow for clean motion interpolation compared to 60i, and unlike 24p there isn't a whole of pulldown-related, speed-changing jiggery-pokery in place to make it work.

If you have the potential to distribute the program in 50i countries (most of Asia outside of Japan and Korea), I'd suggest considering both 60i or 24p ahead of 30p.

Adam Wilt / Video Geek / Menlo Park CA USA



Adam Wilt wrote :

>Is the choice between 30p and 60i merely aesthetic? If you have the potential to distribute the program in 50i countries (most of Asia outside of Japan and Korea), I'd suggest considering both 60i or 24p ahead of 30p.

I hate to bring up the whole frame rate thing again, but do you mean 59.49i and 23.978p?

Ian Ellis DP
600 op/f-900 owner
Austin TX
512-751-5690
www.texashighdef.com



Ian Ellis wrote :

> but do you mean 59.49i and 23.978p?

What, even more new speeds from our friends at Sony???

Should be 23.976 (i.e. 24 less 1/10 of 1%) and 59.94 (i.e. 60 less 1/10th of 1%).

Jeff Kreines



>"I hate to bring up the whole frame rate thing again, but do you mean 59.49i and 23.978p?"

Ian,

If you are asking me, then yes. I was using 30, (24), and 60 for the sake of simplicity.

Alan A. Hereford * Cinematographer

Marin Co., CA USA



Alan Hereford wrote :

>If you are asking me, then yes. I was using 30, (24), and 60 for the sake of simplicity.

Yes, I was asking. Of course, it would help if I quoted the correct frame rates in my post! Thanks Jeff.

Ian Ellis DP
600 op/f-900 owner
Austin TX
512-751-5690



Adam Wilt writes:

>30P material does NOT convert easily to 50i...

Nor does it convert easily to 24p.

Dan Drasin
Producer/DP
Marin County, CA