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Question for Frame Rate/Codec Wizards! :-)

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Charlie Austin
Question for Frame Rate/Codec Wizards! :-)
on Mar 21, 2014 at 9:51:52 pm

Had an issue, solved it, but wonder if anyone had an idea WYF was going on... So..

received a bunch of VFX shots. 1080p ProRes HQ 23.976 fps. They are all about a second long, with each frame numbered. Here's the issue, one clip as an example, but this happened on all of 'em...


It's a 24 frame clip, 1 frame of slate, and then frames 1-23. In QT player (7 and 10), Compressor, and PrCC frame 23 is visible. In FCP 7 and FCP X, the last frame is 22 frame 23 is not there at all. (same with the last frame of all clips.not there in Fcp 7 or X) Changing field settings, interlace settings.], *any* settings makes no difference. The 24 frame clips, is 23 frames long. Anyway...

Brought all original clips into compressor. Exported them at the same frame rate, same codec, same everything.

The re-exported clips from compressor now show all the frames in Fcp7 and X. Nothing changed, just ran them through Compressor.

So, my question is... WTF? :-) Anyone?

-------------------------------------------------------------

~ My FCPX Babbling blog ~
~"It is a poor craftsman who blames his tools."~
~"The function you just attempted is not yet implemented"~


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Al LeVine
Re: Question for Frame Rate/Codec Wizards! :-)
on Mar 21, 2014 at 10:08:53 pm
Last Edited By Al LeVine on Mar 21, 2014 at 10:09:27 pm

Just a bunch of questions and statements. I don't have a solution, but maybe things to think about:

You shouldn't have to worry about field settings or interlace, etc… That doesn't apply here.

Are you taking into consideration that :00 of each second counts as a frame (technically frame 1, but timecode wise frame 00)? Maybe the VFX house didn't export the last frame.

Do the clips have timecode on them? I'm talking metadata TIMECODE, not just time. Compressor could be adding timecode to your clips, correcting some sort of corruption when shots are imported.

How does After Effects see the raw clips compared to the converted clips? To me, After Effects always seems to interpret footage 100% correctly when other programs don't.

I had this problem a few years ago when I was capturing video from an HDCAM-SR deck. My setting was accidentally set to 1080p, not 1080psf. Not sure this is applicable to you though...


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Charlie Austin
Re: Question for Frame Rate/Codec Wizards! :-)
on Mar 21, 2014 at 10:21:40 pm

[Al LeVine] "Just a bunch of questions and statements. I don't have a solution, but maybe things to think about:"

Yep. :-) As I said, running through compressor "fixed" it. Odd thing is, for example, the original 24 frame clip - (and yes the first frame is frame 0. Slate on that frame, then 23 frames of pic, one of which just disappears) - shows as 23 frames duration in the 7/X timeline (missing frame 23), and the same clip run thru compressor is 24 frames, and contains frame 23.

Weird, I'll check the TC on both...

-------------------------------------------------------------

~ My FCPX Babbling blog ~
~"It is a poor craftsman who blames his tools."~
~"The function you just attempted is not yet implemented"~


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Charlie Austin
Re: Question for Frame Rate/Codec Wizards! :-)
on Mar 21, 2014 at 10:31:43 pm
Last Edited By Charlie Austin on Mar 21, 2014 at 10:32:37 pm

[Al LeVine] "Do the clips have timecode on them? I'm talking metadata TIMECODE, not just time. Compressor could be adding timecode to your clips, correcting some sort of corruption when shots are imported"

I think that's it. Original clips have no TC track/metadata, Running through Compressor adds it. Odd that 7 and X lose the last frame when there's no TC though...

Compressor clip on Left, Original on Right



-------------------------------------------------------------

~ My FCPX Babbling blog ~
~"It is a poor craftsman who blames his tools."~
~"The function you just attempted is not yet implemented"~


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Al LeVine
Re: Question for Frame Rate/Codec Wizards! :-)
on Mar 21, 2014 at 10:37:17 pm

Cool. Not sure what your VFX house is using, but definitely make them aware that you need TC for delivery. That way you won't get generation loss. (ProRes HQ to ProRes HQ is likely 99.9999% identical, ...but you know…)


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Jeremy Garchow
Re: Question for Frame Rate/Codec Wizards! :-)
on Mar 21, 2014 at 11:16:00 pm

[Charlie Austin] "So, my question is... WTF? :-) Anyone?"

*shrug*







Jeremy


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Jeremy Garchow
Re: Question for Frame Rate/Codec Wizards! :-)
on Mar 21, 2014 at 11:19:45 pm

Actually, this reminds of a problem where the footage was rendered 23.98 instead of 23.976.


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Charlie Austin
Re: Question for Frame Rate/Codec Wizards! :-)
on Mar 21, 2014 at 11:27:31 pm
Last Edited By Charlie Austin on Mar 21, 2014 at 11:30:06 pm

[Jeremy Garchow] "Actually, this reminds of a problem where the footage was rendered 23.98 instead of 23.976."

I think that may have something to do ith it. As i said, the original 23.976 clips, with no TC, show as 23.976 in QT Player(s), Compressor, and PrCC. FCP 7 and X show them as 23.98, and lose the last frame. Adding the TC with compressor though, and the last frame reappears, even though they still show them both as 23.98 Here's a pic of the 2 clips, both have the exact same settings/info in the inspector, but as you can see, the clip with TC (on top) is 1 frame longer.
(if you look at the duration metadata from these 2 clips posted above, it's exactly the same) weird...



-------------------------------------------------------------

~ My FCPX Babbling blog ~
~"It is a poor craftsman who blames his tools."~
~"The function you just attempted is not yet implemented"~


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Oliver Peters
Re: Question for Frame Rate/Codec Wizards! :-)
on Mar 22, 2014 at 12:29:40 am

This has always been a problem with Apple. It boils down to a rounding error in how frame rates are calculated. If you look at Adobe-generated versus Apple-generated 23.976/23.98 footage, they are stamped differently. Way back when, Apple manuals for FCP "legacy" actually stated that a frame of QT media was not guaranteed to actually cover the exact duration of 1 frame of time. Remember, even though you are working with I-frame codecs, the video engine is not a frame-based architecture, like Quantel or Autodesk.

- Oliver

Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com


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Charlie Austin
Re: Question for Frame Rate/Codec Wizards! :-)
on Mar 22, 2014 at 12:43:23 am

Yeah, I was actually remembering something about that as i was wondering where my frame went. :-) Good to know that, if there is TC, it will interpret it correctly...

-------------------------------------------------------------

~ My FCPX Babbling blog ~
~"It is a poor craftsman who blames his tools."~
~"The function you just attempted is not yet implemented"~


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Franz Bieberkopf
Re: Question for Frame Rate/Codec Wizards! :-)
on Mar 22, 2014 at 2:08:59 pm

[Oliver Peters] "Remember, even though you are working with I-frame codecs, the video engine is not a frame-based architecture ..."

Oliver,

How is the architecture best described then, if not frame-based?

Is AV Foundation any different in this respect? What about MXF, etc.

Franz.


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Oliver Peters
Re: Question for Frame Rate/Codec Wizards! :-)
on Mar 22, 2014 at 2:58:02 pm

[Franz Bieberkopf] "How is the architecture best described then, if not frame-based?"

By frame-based, I mean that each and every frame is separately accounted for. QT and MXF (I think) look at the header and calculate from the first frame based on duration of the clip. So they are clip-based and not frame-based. This is why you cannot lop off the beginning and end of a media file when you consolidate. You have to make a shorter copy.

Quantel, Assimilate and Autodesk use a frame-based media architecture, since their internal workings are based on image sequences. Quantel calls this "Frame Magic", I believe. It allows you to shorten a media file simply by eliminating the unwanted head and tail frames without making a copy. I believe the old Leitch/DPS Velocity used a similar approach with their Virtual File System. This applies to their own internal media formats, though. I'm not sure if it applies to "soft-imported" compressed codecs, like when they directly access a QT media file.

[Franz Bieberkopf] "Is AV Foundation any different in this respect?"

I don't know.

- Oliver

Oliver Peters Post Production Services, LLC
Orlando, FL
http://www.oliverpeters.com


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Keith Koby
Re: Question for Frame Rate/Codec Wizards! :-)
on Mar 25, 2014 at 6:57:33 pm

Did you try QT Edit or good old fashioned cinema tools to conform the frame rate without transcoding? That might work..


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