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Interlacing/Aliasing Problem from FCP QT Export of HDCAM Footage

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Pat BrayInterlacing/Aliasing Problem from FCP QT Export of HDCAM Footage
by on May 11, 2011 at 11:00:26 am

Hi

My client has handed me a HDCAM (Pal) which has been digitised in fcp (which looks fine on the timeline) and a quicktime exported (uncompressed and animation codec versions) for me to use in AE. When I separate the fields (upper) I get bad aliasing, and when I leave it off it looks good static but once there's any movement I obviously get interlacing issues. Any solutions? Is there something wrong with the export settings from fcp? Any suggestions would be great...


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Tudor "Ted" JelescuRe: Interlacing/Aliasing Problem from FCP QT Export of HDCAM Footage
by on May 11, 2011 at 11:14:03 am

Other than making sure that you have the right field dominance selected in Interpret Footage(if you're not sure check both), the "Preserve Edges" checked, and that you're looking at the footage at full resolution and not half, my only suggestion would be to ask the client for the clips exported progressive and not interlaced from FCP.

Tudor "Ted" Jelescu
Senior VFX Artist


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Pat BrayRe: Interlacing/Aliasing Problem from FCP QT Export of HDCAM Footage
by on May 11, 2011 at 11:33:43 am

Hi Ted

Thanks for the advice, I've checked everything you've suggested, apparently it looks like the clients have shot progressive and laid off interlaced so I don't know if this has degraded things somewhat. I asked for a progressive export from FCP and it looks horrible so rendering out a version of my title and dropping it into the edit suit to view on a broadcast monitor, hopefully it might ok...

Cheers
Patrick


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Tudor "Ted" JelescuRe: Interlacing/Aliasing Problem from FCP QT Export of HDCAM Footage
by on May 11, 2011 at 12:42:01 pm

Quick thought- render a progressive and an interlaced version to have both when you go to the edit suite and check them.

Tudor "Ted" Jelescu
Senior VFX Artist


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Jon BaggeRe: Interlacing/Aliasing Problem from FCP QT Export of HDCAM Footage
by on May 11, 2011 at 3:29:11 pm

Turning on Separate Fields in After Effects will cause aliasing in the composition viewer whether the footage is actually interlaced or not.

The viewer will always show the image on a whole frame. When you separate fields, the first field will be placed on the whole frame (this is what you see), and the second field will be placed 0.5 frames later in time. When you then turn on field render in the render queue it will render a frame every 0.5 frames sampling the footage at these times. If you have separated the fields correctly and field render the same way the footage will look correct.

If you field render progressive footage, it will use a duplicate of the full frame every field. The footage may look like it stutters compared to any key framed animation.

If you progressive render interlaced footage (that have been correctly separated) it will only ever use the first field for rendering, and you will get aliasing in the render too.

You can use frame blending or pixel motion to fix some of these issues, but if you're going to render differently from your footage you should look into a plugin that properly deinterlaces/reinterlaces depending on what your final result should be.

As for your specific footage, if it was originally shot progressive and FCP has interpreted it as interlaced, that shouldn't really change the footage itself. (unless you've rendered deinterlacing or reinterlacing in FCP which I'm sure there is a plugin that can do)
You should be able to interpret as progressive in AE. If you get horizontal banding in areas of fast movement when you interpret progressive in AE that's a sign the original footage was in fact shot interlaced.

This is all a bit complicated, apologies in advance if I haven't made myself clear.

--------------
http://www.jonbagge.net
Jon Bagge - Editor - London, UK
Avid - FCP - After Effects


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Dave LaRondeRe: Interlacing/Aliasing Problem from FCP QT Export of HDCAM Footage
by on May 11, 2011 at 3:12:06 pm

Unless the camera shooting recording the 1080 video costs about the same as a brand-new Corvette, the chances are extremely remote that it's true progressive scan.

The progressive footage you have is recoded using a method called progressive segmented frame, where the camera scans a complete frame, then records the frame in... well, two fields. Video engineers may quibble on that point, but if the frame behaves like it's two fields, what's the difference? But if FCP and AE are set appropriately, it will also behave as a frame.

So: interpret the footage in AE as having a field order of None. Do your AE voodoo. Render a file from AE using a field order of None. In the FCP browser, your client may have to set the field order (erroneously called field dominance in FCP) to none, and change the field order in the edit timeline to None.

And if they don't have a proper video monitor -- not a computer monitor -- it will look like hell. The only way to judge the quality of an image in FCP is to look at it on a video monitor. They need to know that.

And yes, FCP has some troubles determining what's progressive scan footage and what's not. The problem's on their end, not yours.

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


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