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Understanding FPS and Workflow Implications

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charlie broon
Understanding FPS and Workflow Implications
on Oct 23, 2011 at 1:18:21 pm

Hello all,

Hours of search, still unclear.

i'm using panasonic tm900 which records:

1. 1080i60 (29.97 fps)
2. 1080p60 (60fps)
3. digital cinema mode 24p, but its not a true 24p, its wrapped in 60i, so its really 29.97 fps.

that alone took some time to confirm.
my goal is to get the motion feel and look of traditional film but that has involved a lot more variables than I could imagine.

1.
Recording at 1080i60
firstly, while 29.97 fps, the result still has the very 'live' look because it has 60 motion samples / images per second. but these images are interlaced. so while its 29.97 fps for a full frame, the motion and movement is still the same as actual 60 fps.

i tried just simply converting to 24p, but of course, it comes out quite jerky, so my conclusion is, basically avoid going from 60i to 24 if possible

here, deinterlacing is required. If doing Log and transfer thru FCP, then there is no option to deinterlace at this point. this means that taking still frames are no go.
as i am doing now, i deinterlace all the original footage before hand with 3rd party .mts file converter before going to FCP.
the question is are there any quality differences/arguments to doing it before or after other than seeing the line artifacts while editing?


2.
recording at 1080p60
highest quality, highest frame rate.
concerning convering 60p to 24p, i haven't tested this yet, but as far as "motion" is concerned, it should be the same, because both still have 60 motion samples a second


3. digital cinema mode 24p wrapped in 60i...
a. firstly, what is actually happening in this "wrapping" how does it stuff with extra frames and from where? i was unable to find a sufficient answer.

b. more importantly, i have noticed that the quality in this mode is much less than the other modes. does this have something to do with the wrapping in 60i?

c. And if so, then recording in this mode REQUIRES that I first pulldown to native 24p. As far as I can tell, this is done, simply by converting to 24fps, but is that it?
do I have to tell the converter something about how to pulldown or remove whatever excess frames, etc...
It would be great to just record in this mode, but the quality is not sufficient unless I am not treating it correctly.


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

conclusion is that all the FPS talk is misleading. the film look when referring to motion aesthetic, is based on number of "image samples" or images a second,
so 24p or 30p will look completely different than 60i or 60p, even though, the fps to 60i and 30p are the same.

please, if anyone can confirm and clarify.

thanks!


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Walter Soyka
Re: Understanding FPS and Workflow Implications
on Oct 23, 2011 at 5:31:34 pm

I suggest you base your shooting frame rate on your required deliverable frame rate. If you are required to deliver 60i, don't shoot 24p.


[charlie broon] "3. digital cinema mode 24p wrapped in 60i...
a. firstly, what is actually happening in this "wrapping" how does it stuff with extra frames and from where? i was unable to find a sufficient answer."


See the Wikipedia article on telecine 2:3 pulldown [link] to see how a 24p video is "wrapped" in a 60i signal.

If you want to deliver 24p, you should shoot in this mode, then remove pulldown to get true 24p media from your 60i 2:3 originals. Edit, finish, and deliver in 24p (probably really 23.976 fps).

If you use a frame rate conversion tool to go from 2:3 60i to 24p, it will be wrong and look terrible. If you remove the pulldown, it should look pristine.

What software are you using, and how are you trying to remove the pulldown now?

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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charlie broon
Re: Understanding FPS and Workflow Implications
on Oct 24, 2011 at 10:20:35 am

To remove pull down, this was the only thing I could find on how, I used the compressor method

http://www.dvxuser.com/V6/showthread.php?170717-GH1-Pulldown-Removal-using-...


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

also, i did a test, with compressor method, and compared to the original footage (24p wrapped in 60i) and I could not tell a difference quality wise. So then all this pulldown removal and frame rate conversion is not an issue of image quality, but final delivery, frame rate...?

I could just leave the 24p in 60i wrapper, and edit to 29.97fps.
My output is Vimeo, where they accept both 24 and 30 fps. So there really is no reason for me to do pulldown removal?

i THINK i am slowly understanding... hopefully


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Walter Soyka
Re: Understanding FPS and Workflow Implications
on Nov 2, 2011 at 5:27:52 pm

[charlie broon] "i did a test, with compressor method, and compared to the original footage (24p wrapped in 60i) and I could not tell a difference quality wise."

There is no difference in quality, per se. Removing pulldown should not alter the image in any way; it just removes the extra telecine fields which must be inserted to make 24p work within a standard 60i signal.


[charlie broon] "So then all this pulldown removal and frame rate conversion is not an issue of image quality, but final delivery, frame rate...?"

That's correct -- although if you don't remove the pulldown, you will see the judder frames (which include half of one frame and half of the next on alternating line).


[charlie broon] "I could just leave the 24p in 60i wrapper, and edit to 29.97fps. My output is Vimeo, where they accept both 24 and 30 fps. So there really is no reason for me to do pulldown removal?"

I would do the removal. If you do not, you will very likely get a broken cadence (the 2:3 pattern will become irregular at edit points). That can be a bit jarring for viewers and is technically incorrect.

Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog - What I'm thinking when my workstation's thinking
Creative Cow Forum Host: Live & Stage Events


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charlie broon
Re: Understanding FPS and Workflow Implications
on Nov 2, 2011 at 9:23:26 pm

excellent.

i think i'm clear on it now.
this type of info should really be included in the manual. -_-

thanks!


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