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TOPIC: 3 Clips With Framerates 29.73 25 30.01 And Time is not real time.

3 Clips With Framerates 29.73 25 30.01 And Time is not real time. 06 Oct 2020 21:29 #110378

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I have 3 clips, synchronized into a compound clip.
My project is 23.98 (only because I read that's the best setting).
I have found that 2 minutes are longer. If I speed it up by 101% it's about right.

Here is another way to describe it. If I look at the properties of the clip it's 2:04 (or something higher than what it should be), I only found this out because I actually placed a 2 minute timer on the timeline and they don't match up.
I have no idea what's going on or how to prevent this. I've had this with other videos too. I am assuming it has something to do with the frames of the project and that of the clips. The problem is, I will always have clips from different cameras with different frame rates.

I would appreciate it very much if someone could enlighten me on what's going on and how to fix it.

I am also confused by the fact that it seems the clips are slower but I can't hear it or see it. Perhaps 1% to 2% slower is not noticeable.

The attachment shows what I am trying to explain. The highlighted clip is 2 minutes long, the video clip it's placed over contains a part that is 2 minutes long, so it's supposed to end where the highlighted clip ends, but it ends where the needle is located.
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3 Clips With Framerates 29.73 25 30.01 And Time is not real time. 07 Oct 2020 00:43 #110379

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What is the frame rate of those clips?

I retime stuff to fit TV broadcast times. You can go 94% - 104% and not notice any difference. Depending on the content, you can put that slightly further.

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3 Clips With Framerates 29.73 25 30.01 And Time is not real time. 07 Oct 2020 05:57 #110381

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Hi, the frame rates were in the title, sorry, forgot to put them in the description.
"3 Clips With Framerates 29.73 25 30.01 And Time is not real time."
I'd like to get it where I don't need to mess about with any retiming. I'd also like to understand why it happens.

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3 Clips With Framerates 29.73 25 30.01 And Time is not real time. 07 Oct 2020 11:00 #110384

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taco.fleur wrote: "I will always have clips from different cameras with different frame rates....Frame rates 29.73 25 30.01 And Time is not real time...I'd like to get it where I don't need to mess about with any retiming. I'd also like to understand why it happens...


Whenever you have mixed frame rates it can cause complications. Some are more straightforward to handle in post production and others are difficult. It is vital when planning and executing video production that extreme emphasis be conveyed to all contributors that everyone should only use the designated frame rate. In post production that frame rate should be used for the timeline, and the final exported product should normally be that frame rate.

Exceptions include cameras shooting an even multiple of the chosen frame rate, e.g, 59.94 fps for a 29.97 fps timeline, or 50 fps for a 25 fps timeline. Those can be "rate conformed" smoothly and with no artifacts. If the contributed material comes from different world regions where the cameras or smart phones have no capability to achieve a common frame rate, then you must accept that -- but only after strenuous efforts to communicate ahead of time to everybody and achieve the least variation and most compatible frame rates possible.

In the modern era of contributed footage from smart phones, it may not be as easy. However my iPhone built-in camera app has settings for 24, 30 and 60 fps. It's a simple config setting.

If someone captures and contributes a sudden news event with their cell phone (plane crash, tornado, etc), the news org. has to accept it. That person had no warning and wasn't part of a planned effort. But oftentimes even informal loosely-planned events shot on smart phones can be coordinated ahead of time to use a designated frame rate.

Re why did your material seemingly change timeline durations, when a NLE "rate conforms" different frame rates, there are various algorithms. When conforming 25 and 24 (or 23.98) material the algorithm is an automatic speed change. You designated a 23.98p timeline and to conform 25p fps material requires it be speeded up or shortened slightly.

By contrast when rate conforming 23.98p and 29.97p material it's possible to discard or duplicate certain frames, thereby reducing the mis-match. However it introduces a motion cadence issue where subject or camera motion is less smooth. This in turn can sometimes be lessened by using optical flow rate conforming (not optical flow retiming).

To use optical flow rate conforming, select a clip in the timeline with a non-matching frame rate, then in the FCPX video inspector, scroll to bottom and under Frame Sampling select Optical Flow. Then select that clip in the timeline, render with CTRL+R, and examine the playback smoothness. If that works, do all the clips with frame rates that differ from the timeline rate.

This normally improves smoothness at the cost of significant CPU time. But in some cases it can cause morphing artifacts so you must check for those on every clip.

Typically 29.97 to 23.98 is a more difficult conversion than the opposite direction. I think 25 is handled similarly. You might get better results from using a 29.97 timeline, that way the 29.97 and 30.01 material would closely match and rate conversions from 25 to 29.97 might be better. It would likely not retime the 25 fps material but use some frame duplication algorithm which you might be able to smooth using optical flow rate conforming.

Gerald Undone discusses mixing frame rates in this video:

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3 Clips With Framerates 29.73 25 30.01 And Time is not real time. 07 Oct 2020 11:16 #110385

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taco.fleur wrote: Hi, the frame rates were in the title, sorry, forgot to put them in the description.
"3 Clips With Framerates 29.73 25 30.01 And Time is not real time."
I'd like to get it where I don't need to mess about with any retiming. I'd also like to understand why it happens.


I was making a point. You're trying to sync different frame rates, that's the problem. Really bad idea. Then if you have different audio sample rates, you're hosed.

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3 Clips With Framerates 29.73 25 30.01 And Time is not real time. 08 Oct 2020 15:29 #110395

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Thank you for your detailed reply.

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