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Render does not match RAM preview. Totally baffled...

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Ross Newton
Render does not match RAM preview. Totally baffled...
on Nov 18, 2008 at 6:02:51 pm

Apologies in advance if this is already covered on the forum, I searched for about an hour and half with no luck...

I'm working on a large project that is due shortly and I'm now at the export phase. I've only been working with AE for about a year and so far I've never had this problem. I've been working from the RAM preview screen on several comps and all my work looks perfect in those views. It's all visual effects work with lots imported CG images sequences, AE motion tracking, and hand-keyed position changes on top of that tracking (to fix things).

EVERYTHING is image-sequences. My plates are DPX sequences set at 23.98fps (they originated from the RED ONE camera). My CG is 32-bit TIFF sequences rendered at 23.98 fps.

So after spending months working on these comps, tracking and manually correcting things, I'm ready to export. The problem is on several of my comps, the exports do not match the RAM preview. I'm exporting to DPX image sequences at 32bpc. For example, my motion tracked CG layer will look perfect in the RAM preview, but in the render files, it's jumping around all over the place. I've checked to make sure all the right layers are checked to be on and everything looks right. I tried turning off multi-processing. I verified framerate settings on all layers and in the project settings, composition settings, and render settings. I tried dialing everything down to 8pbc, same problem. I tried outputting to TIFF sequences, same problem. For some reason, my CG layers are "off" on certain frames compared to the RAM preview.

On other comps, I'm getting weird gradient shifts on certain layers that I don't see in my RAM preview. And on another comp, an entire track matte layer will be a solid color in the render, but will matte appropriately in the RAM preview. Not all the comps appear to be messed up, but I'm afraid to export any of them for fear that my very, very nuanced and labored motion-tracking/keying will be off even the slightest.

I thought it might have something to do with layers getting offset by a couple of frames somehow (even though everything is image sequences), so I tried setting the "Preserve frame rate when nested or in render queue" checkbox in the Advanced tab under the Composition settings, but that crashed my render with like "Render Graph too complex" error. So I unchecked it. Would it have anything to do with OpenGL settings versus Adaptive Resolution? I've been RAM previewing everything with "Adaptive Resolution". OpenGL is not enabled under the "Previews" settings in the preferences. Also, these comps do not use any 3D layers or cameras.

I'm using AE CS3 and it happens on both Mac and PC. I'm completely baffled and frustrated. And I looked like a fool yesterday at meeting after reporting that work was coming along well, only to not be able to show up with any exported drafts.... please help.



Thanks!

Ross Newton


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Jimmy Brunger
Re: Render does not match RAM preview. Totally baffled...
on Nov 18, 2008 at 8:48:59 pm

Hmmm...is Open GL checked in your RENDER settings? Make sure 'render with open GL' is off and see if that helps...

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Ross Newton
Re: Render does not match RAM preview. Totally baffled...
on Nov 18, 2008 at 9:15:20 pm

I checked and it's off. I tried a render with it on just for kicks, but it didn't help. I get the same result whether it's on or off.

Does Adobe have a tech support number? And can you get to advanced people who really know the program in and out?



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Ross Newton
Re: Render does not match RAM preview. Totally baffled...
on Nov 19, 2008 at 1:08:44 am

Something else that's bizarre, I can do a RAM preview using the button in the "Time Controls" and it looks perfect in the Composition window. But when I go to "Save RAM Preview" under the Composition menu, it will reiterate through the whole composition, rendering it out and I can see the frames messing up as it renders.

Basically, ANY kind of export is messed up because it cycles through the render queue process where I can see the frames having issues. But just a plain RAM preview, looks perfect.



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Chris Wright
Re: Render does not match RAM preview. Totally baffled...
on Nov 19, 2008 at 5:59:40 am

remove preference folder should do the trick, they often get corrupted and do weird things to preview windows and templates etc and since you're using Tiff's, DO NOT use LZW compression, it is not lossless, uncheck that option and use 32 NOT 24 bits, which is only 8 bits/pixel. :)




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Ross Newton
Re: Render does not match RAM preview. Totally baffled...
on Nov 19, 2008 at 4:52:57 pm

I cleared both of the preference files, this didn't work (thanks for trying though).

I can identify the problem layers. So I tried precomposing them and proxy-rendering them ahead of time. Didn't work.

However I have a new discovery on one of my problem comps with the track that goes out of whack. I thought that the tracked CG element was becoming "untracked" or something in the render, but actually what's happening is the plate/footage is duplicating a frame, thus throwing the CG element off track. My comp is 224 frames and about four times in the final render, it duplicates a frame.

I've seen some posts about this problem, but most of them deal with codecs of imported video files. My plate is a DPX image-sequence set at 23.98fps. And as mentioned, it RAM previews fine and doesn't duplicate any frames... any ideas?



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Troy Murison
Re: Render does not match RAM preview. Totally baffled...
on Nov 19, 2008 at 5:09:43 pm

Hi Ross,

You say your comp settings are at 23.98? If so, try changing them to 23.976, otherwise transformations (ie tracking) may 'jump around' when rendered to 23.976 as the keyframes aren't lining up perfectly with the footage. I have seen this before a long time ago. I can't remember if we had to redo tracking, etc. or just change the framerate to make it right. We didn't start the project, we were just rendering it for output and we assumed for a long time that it was a problem on our system vs. the artist's, so it took a long time to work out. I never found out why the RAM preview didn't match the render though.

I just re-read your post- our comp's sources were QT's not file sequences, so in my mind if you've interpreted your file sequence at x fps and rendered at x fps, things should match, but I've never tried.

-Troy Murison
Seattle, WA


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Ross Newton
Re: Render does not match RAM preview. Totally baffled...
on Nov 19, 2008 at 5:16:23 pm

I just did another test. I tried just rendering the DPX sequence by itself with no other layers in a new comp at 23.98fps. It is rendering fine with no frame doubling.

So maybe there's a problem in my effects comp, although I've double checked its frame rate. I'm going to make a new comp and copy my layers over. I'm also going to replace the existing plate layer in my effects comp for kicks. Will report shortly, I have a meeting now.



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Dave LaRonde
Re: Render does not match RAM preview. Totally baffled...
on Nov 19, 2008 at 6:32:56 pm

[Ross Newton] "I tried just rendering the DPX sequence by itself with no other layers in a new comp at 23.98fps. It is rendering fine with no frame doubling."

There's just one problem with that particular frame rate: it doesn't exist in NTSC-land. 23.98 is just a nickname for the actual frame rate, 23.976. So if you have footage in AE interpreted as 23.98, or conformed to 23.98, or if you render at 23.98, you need to change EVERYTHING to 23.976.

When it comes to frame rates, AE doesn't believe in nicknames. It calls a spade a spade.

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


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Ross Newton
Re: Render does not match RAM preview. Totally baffled...
on Nov 19, 2008 at 9:20:02 pm

Problem solved! Everything looks good. Wow, thanks Dave and Troy. Your suggestions made sense as soon as I read them.

The director of this film, before he gave me DPX images sequences, was giving me QT preview movies and they were all showing as 23.976 fps. We just assumed it was wrong or something because he assured me that the RED camera and Final Cut were showing the plates as 23.98 fps! Funny.

I have two questions then, now that I've conformed the plate and CG to 23.976. Should I re-render my CG elements as 23.976? I used Lightwave and I set the frame rate to 23.98. I supposed if it looks good I should leave it alone, but I hate things not being perfect. Second question is, why did the RAM preview show it correctly before!? Does it use a different rendering method?

So now that the tracking-comp is correct, I'm still working on fixing the other comps... I think those may have something to do with rendering at 32bpc... I'm going to play with those.



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Dave LaRonde
Re: Render does not match RAM preview. Totally baffled...
on Nov 19, 2008 at 10:14:03 pm

[Ross Newton] "...he assured me that the RED camera and Final Cut were showing the plates as 23.98 fps!"

And wouldn't you know -- the two biggest offenders in the 23.98/23.976 mixup are people who make camera and editing software!
Lesson learned, huh?


[Ross Newton] "Should I re-render my CG elements as 23.976? I used Lightwave and I set the frame rate to 23.98."

I would first try this: highligt the footage, then go File>Interpret> Main and CONFORM the footage to 23.976. See how it looks.


No clue on why the RAM Preview looked okay.


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


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Ross Newton
Re: Render does not match RAM preview. Totally baffled...
on Nov 19, 2008 at 11:25:48 pm

Yeah conforming the CG elements to 23.976 looks good. I guess I shouldn't try to fix it if it's not broken. I was thinking about going back and re-rendering the CG at 23.976... maybe Lightwave assumes 23.98 is 23.976 too, because they look right.

So I figured out what the other issues were that I mentioned in my first post. Basically in a couple of the comps, I pre-comped some Particular layers and rendered proxies for them so I could move them to other AE machines that don't have Particular installed. So the method I used was to pre-comp the Particular layer, set it to render with Alpha to a TIFF sequence, set to Enable Proxy, then render. Then the proxy automatically worked and looked good in my RAM preview. The alpha layer was working appropriately and only showing the particles. However, in the final render of the comp, the pre-rendered proxies were ALL rendering without any alpha. And they were also using the keyframes (like opacity) of the original Particular layer in the pre-comp. So I had all these layers of color fading in and out and no idea why, because the RAM preview looked perfect!

So to fix it, I just imported the pre-rendered proxy files (the TIFF sequences) and dragged them into the comp where the pre-comped Particular layers were, then I turned off the pre-comped layers. Problem solved and the alpha of the pre-rendered files worked great in the RAM preview and final render.

The question is, why weren't they working the first way (is my method wrong)? And why was the RAM preview showing them work as they should?



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Troy Murison
Re: Render does not match RAM preview. Totally baffled...
on Nov 20, 2008 at 12:57:17 am

Ross,

Glad to hear you're in a better place right now! The 'looking-correct-on-RAM-preview' issue threw us for a loop too, I never revisited the problem to investigate further. "Moving on!" 'ya know...

Thanks for updating us!

-Troy Murison
Seattle, WA


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Alex Wallach
Re: Render does not match RAM preview. Totally baffled...
on May 28, 2014 at 10:54:50 pm

Dave, thank you SO MUCH. I was stuck on for a couple of hours with masks that were perfect in RAM preview and then moved around on me when rendered. I couldn't find a solution to the problem anywhere online until I read your comment. I registered an account here JUST to thank you. So, again...THANK YOU!!

Alex


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tjoeme snamedraab
Re: Render does not match RAM preview. Totally baffled...
on Oct 27, 2015 at 5:14:07 pm

Hi there,

I know this specific problem has been resolved, however I had the same problem and the answers in this thread did not help my specific problem. (I live in a PAL region so 25 fps really is 25 fps)

My problem:

When using a motion tracker the RAM preview showed me a perfectly tracked picture.
However when I rendered the object that used the motion tracker was off by multiple pixels in every direction.

My solution: (probably not the best solution but it worked)

Import the After Effects composition into Premiere (Premiere -> File -> Adobe Dynamic Link -> Import After Effects compostion)and export from there.

This fixed it and the render looks perfect.
I hope someone might find this info usefull.

Bye!


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Ryan Donahue
Re: Render does not match RAM preview. Totally baffled...
on Jun 14, 2017 at 11:59:43 am

Often, multiple layers/effects get ‘corrupted’ timing-wise - Solution: Right click multi layers and ‘pre-compose’ !


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