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How to keep hdv 50i as 50i?

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ninetto makavejevHow to keep hdv 50i as 50i?
by on Aug 12, 2009 at 8:55:54 am

OK, here we go again, I have read a few posts on how AE handles fields but I am none the wiser.
So I will be very happy to just get a simple answer to what I feel is a simple problem.

In FCP I have captured material shot as 1080 hdv 25p, and yes I know FCP handles this as 1080 hdv 50i. As I understand it, this is the same thing as 25p, or no?

Now to add some lens blur I pull the 25p (50i) HDV into AE and this is where the confusion starts:

do I leave the fps as 25, set interpet with NO FIELDS and drop into a composition also with 25 fps? Then render out as 1080 HDV 50i?

or:

do I force AE to interpret the 25p at 50fps, set the composition at 50fps and then render out at 1080 HDV 50i?

Would be very grateful to hear how I can input HDV 50i into AE and get it out as HDV50i... or at least that FCP handles the AE-material as 50i like the original?


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Dave LaRondeRe: How to keep hdv 50i as 50i?
by on Aug 12, 2009 at 4:44:59 pm

[ninetto makavejev] "I know FCP handles this as 1080 hdv 50i. As I understand it, this is the same thing as 25p, or no? "

No. Pretty much all 1080 video is INTERLACED. HDV is definitely interlaced... EVEN IF YOU SHOOT IT AS 25P. Why?

When you shoot interlaced (50i), the camera scans one field... THEN it scans the other field. The two fields are recorded as a frame, but the two fields are separated in time. In the case of PAL, the separation is 1/50 sec.

When you shoot 25p, the camera scans the entire frame... and then it records that frame as two fields. The big difference: those two fields are NOT separated in time -- they're from the same instant in time. So it LOOKS like 25p, but it's really 50i. Kapiche?

So for HDV 1080 video, separate the fields as Upper field first and life will be good.



[ninetto makavejev] "Would be very grateful to hear how I can input HDV 50i into AE and get it out as HDV50i... or at least that FCP handles the AE-material as 50i like the original?"

DON'T work in AE in HDV!!! AE doesn't like HDV!!! Experiment with a text HDV clip before you commit to doing an entire AE project with HDV!!! Here's why:


Dave's Stock Answer #1:

If the footage you imported into AE is any kind of the following -- footage in an HDV acquisition codec, MPEG1, MPEG2, mp4, m2t, H.261 or H.264 -- you need to convert it to a different codec.

These kinds of footage use temporal, or interframe compression. They have keyframes at regular intervals, containing complete frame information. However, the frames in between do NOT have complete information. Interframe codecs toss out duplicated information.

In order to maintain peak rendering efficiency, AE needs complete information for each and every frame. But because these kinds of footage contain only partial information, AE freaks out, resulting in a wide variety of problems.


Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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ninetto makavejevRe: How to keep hdv 50i as 50i?
by on Aug 12, 2009 at 6:53:22 pm

Thanks for clearing up some of the confusion. I probably shouldn't open up the can of worms "why must 25p be packed in a 5oi wrapper with 2 fields"... but nevertheless when exporting the material out of FCP into a lossless codec, then the question arises:

How can I get full vertical resolution out from this 25p (50i) material? Which progressive, lossless codec DOES AE like?

hiside, ninetto



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Dave LaRondeRe: How to keep hdv 50i as 50i?
by on Aug 12, 2009 at 7:34:46 pm

That depends on your machine. Since I'm a Mac guy, I prefer Quicktime's Animation codec set to best quality: it's lossless. If I know I'll be working on a Mac with both FCP 6+ and AE, I might use the Apple ProRes codec.

If you're on a Windows box, you're on your own.

Dave LaRonde
Sr. Promotion Producer
KCRG-TV (ABC) Cedar Rapids, IA


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ninetto makavejevRe: How to keep hdv 50i as 50i?
by on Aug 14, 2009 at 7:58:23 am

Quicktime Animation is super-duper, the render times in AE are not even longer compared to using native HDV as raw material.

But yes, there is still one last question. Since your original (VERY clear, thanks) description that 25p DOES have fields, i.e. is interlaced, but with both fields recorded at the same time... I have to wonder, when do I tell AE to interpret the material as "NO FIELDS", if in fact HDV progressive material also has fields? This question comes up e.g. when using the QT-Animation material for effects, but rendering out to HDV 50i.

Or am I just beating a very dead horse, let the render presets decide?

thanks and
buona fortuna, ninetto


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