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Mixing interlaced footage in progressive timeline

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Paul StrettonMixing interlaced footage in progressive timeline
by on Mar 1, 2015 at 9:17:23 am

I've searched the web for a while now and can't seem to find a difinitave answer so I'm hoping this thread can help
I have a big editing job in a couple of days and I'll be working with 2 shooters - one will be giving me 1080 50i footage and the other 1080 25p. The final export is to be
1080 25p. I need to know how to conform the interlaced footage to 25p - do I use the Modify - interpret footage option, right click each clip in the timeline and select Always Deinterlace for the field option, or another way? I have tried both these already but my interlaced footage still looks interlaced (on my computer screen at least).
Any advice on this greatly appreciated!


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Tim KolbRe: Mixing interlaced footage in progressive timeline
by on Mar 2, 2015 at 9:33:20 pm

I might try to edit on a 1080p50 sequence just to see if the result would work for you…

The 25p material will simply run each frame for a duration of two and the interlaced stuff should end up effectively running a field on each frame (you'll need to decide if the interlaced footage is compromised for your purposes since each 'frame' would effectively represent a 'field').

You could then export to 25p, which will simply drop every other frame. You may or may not see a compromise in clarity on the interlace material, but you won't see the sawtooth edges on action like you would with a simple deinterlace step. You also wouldn't have to handle/process/convert the files prior to editing with this method.

Obviously I'm advocating a test to see if this yields an acceptable result in your eyes before setting off to edit the project.

Maybe next time all the contributors could be convinced to agree on a format...

TimK,
Director, Consultant
Video Producer at I-CAR




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Ht DavisRe: Mixing interlaced footage in progressive timeline
by on Sep 27, 2015 at 3:05:57 am

I've run across situations where you have several shooters with vastly different equipment and very different footage. While premiere does allow me to control a lot, I cannot tell them all I need them to buy new equipment.

While testing is fun, it's a huge time-suck. 50i and 25p have the same general frame rate, but different field dominance values. 50i actually has a rolling value, while 25p has a simultaneous one. Some say deinterlacing "drops half your resolution". Technically (by number) it does. But worse, interlacing drops half the photographic information. How do we get this back?

I've seen some AVISYNTH tutorials that show how you can get great results without losing your frame rate. Since 50i is 25 FrPS, just like 25p is also 50FiPS, just rolled differently, you can surmise that a progressive video rate of agreement between the two is 25 frames per second. Using this as your new frame rate, you have some options.

First, you can interpret the 50i as 25p. Unfortunately, this gets a little funky with some cameras and it pixelates badly. The alternative is to "De-interlace", which "drops half your resolution" (correction, it removes intermittent areas of the photograph and blurs things a bit). Both of these really stink. Some plug-ins actually allow you to pass video in, and run it through to get progressive footage. Only a few are any good, and I'd stick close to RedGiant, if you can fork over a few hundred $$$.

another option is to pass it through programs like AVISYNTH that RECURSIVELY blend the fields in a few different mashups, Compare to the original field\frames, and "Find" a *close* rendition of the frame in progressive fashion. Using them also allows you to remove excess frame-age to have the video match your desired frame rate. This is your most preferable option. It adds an extra step, but it works.

The last option is to prep your video by placing each clip in it's own sequence, and export both to the same frame rate. In premiere or AME, you can also render with maximums for quality and bit-depth, and turn on frame blending, exporting to 25p. This will tend to maintain your resolution, as using the frame blending on a FIELD ROLLED video actually does FIELD blending to create an intermediate frame before comparing fields and building the new frames. It's not as recursive as AVISYNTH, but it works alright.

Yes you can test your options and waste hours doing it. Only the last two options here are worth using if you don't have a lot of time to learn the niceties of the plugins. The last one is best if "Good enough" fits what you need, and the AVISYNTH is alright if you have a front-end for it. Personally I like using product based on it:
JES Movie Tools v1.0

for the mac


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Tim KolbRe: Mixing interlaced footage in progressive timeline
by on Sep 27, 2015 at 2:54:41 pm

"50i and 25p have the same general frame rate, but different field dominance values. 50i actually has a rolling value, while 25p has a simultaneous one."

I'm not certain what you mean by 'rolling value'...50i has upper field dominance in everything but perhaps DV, which has lower in NTSC versions. It's constant and does not change. 25p (progressive) has no field dominance...there are no fields.

"Some say deinterlacing "drops half your resolution". Technically (by number) it does. But worse, interlacing drops half the photographic information. How do we get this back?"

'Some' are referring to the resolution you refer to as photographic information... but deinterlacing can be done several ways, and not all of them include simply dropping one field and duplicating the other to fill in the gaps. What you are referring to as resolution is the temporal rate (instances of image change in a second).

The industry's use of '50i or 59.94i is really kind of deceiving as these are 'field rates'. Since both require 2 fields to create a frame, the framerate should be noted as 25p/25i or 29.97p/29.97i to actually make sense comparitively.

TimK,
Director, Consultant
Video Producer at I-CAR




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