DaVinci misinterpret frame rate source footage

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issue-88

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DaVinci misinterpret frame rate source footage

PostFri Oct 19, 2018 6:31 pm

Hello Guys,

I am a very fresh, excited new Davinci Resolve user.
I'm running the latest DaVinci Resolve 15.1.2, on the latest Windows 10 version.

All works well, except for my current project.
All the supplied content is mp4, H.264 50FPS 4096X2160 progressive.
The footage is identified as such by: windows, VLC, adobe premiere, handbrake and mediacoder.

But when I import it in DaVinci it says it's 25 FPS. No matter what I do.
I can change it to 50fps in clip attributes but it just plays it double the normal speed.
Can import it in the 50fps timeline but its will become half as long, so plays double the speed. :o
It also looks a bit choppy when playing it in the program and exporting it from davinci, something's not right.
Also tried it on a different computer, and different versions of Davinci but the problem stays the same.
Also the content consists of 8 different clips, all having the same thing.

If I export/render it from any program, davinci will recognise it as 50fps, and it will look proper.

Who has any idea how I can solve this mystery? :?:
Its not as fun anymore if I first have to pull all content true another render first before being able to use davinci.

Thanks in advanced
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Ole Kristiansen

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Re: DaVinci misinterpret frame rate source footage

PostFri Oct 19, 2018 7:03 pm

Do you have a clip we can download ?

Best,
Ole
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issue-88

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Re: DaVinci misinterpret frame rate source footage

PostFri Oct 19, 2018 8:27 pm

Ole Kristiansen wrote:Do you have a clip we can download ?

Best,
Ole


Sure, I posted one of the clips on a wetransfer.

https://wetransfer.com/downloads/39e2c4 ... 425/b8c2b3

This is a copy of original file I got, don't have contact with the original creator so I cant quickly verify with him, but as you see it is in dire need of some correction and balancing.

But like I said, every program tells me 50fps except davinci

Caution, its video content for a child theater show and in dutch so dont mind the specific content ;)
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Cary Knoop

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Re: DaVinci misinterpret frame rate source footage

PostFri Oct 19, 2018 9:05 pm

The metadata described the frame rate as 50p while the original frame rate is 25p.

However, ffprobe reports 3654 frames while Resolve reports half of that which seem to indicate it is indeed 50p.
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issue-88

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Re: DaVinci misinterpret frame rate source footage

PostFri Oct 19, 2018 9:26 pm

Cary Knoop wrote:The metadata described the frame rate as 50p while the original frame rate is 25p.

The actual framerate is 25p so I would assume the file got remuxed incorrectly ( frame rate of 50p is only at the container level).

There does not seem to be a problem playing the video at 25p (so you really did not get 50p).


Ah, oke.
I probably looked at it with a very biased vision :?: since all other programs said 50fps.

So its Davinci that was right and all other programs wrong :shock:
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issue-88

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Re: DaVinci misinterpret frame rate source footage

PostFri Oct 19, 2018 9:40 pm

Cary Knoop wrote:The metadata described the frame rate as 50p while the original frame rate is 25p.

However, ffprobe reports 3654 frames while Resolve reports half of that which seem to indicate it is indeed 50p.


Ah, so it seems something is still off. almost thought I was imagining things. :D
Also I just looked at it frame by frame in premiere, and it really seems to be 50 individual unieke frames per second.

Sorry that my replies take a long time, since i am new posts needs to go tru moderation. :?
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Cary Knoop

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Re: DaVinci misinterpret frame rate source footage

PostFri Oct 19, 2018 9:53 pm

issue-88 wrote:Ah, oke.
I probably looked at it with a very biased vision :?: since all other programs said 50fps.

So its Davinci that was right and all other programs wrong :shock:

Yes, ignore the original comment, it probably got remuxed incorrectly but the framerate is indeed 50p.

Transcoding the file to for instance ProRes solves the problem.

Waar heksen zijn gebeuren rare dingen! :)
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issue-88

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Re: DaVinci misinterpret frame rate source footage

PostFri Oct 19, 2018 10:01 pm

Waar heksen zijn gebeuren rare dingen! :)
[/quote]

Hahaha it does indeed :lol:

Is it sommething davinci incorrectly reads from the metadata?
So strange it would just ignore half of all frames.

And could i fix it with a simple remux? i believe i already tried that first, but came to a conclusion it did not help and only a re-render would fix it for davinci :|
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Cary Knoop

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Re: DaVinci misinterpret frame rate source footage

PostFri Oct 19, 2018 10:10 pm

issue-88 wrote:So do you have any idea why davinci identifies it incorrectly?
Is it sommething davinci incorrectly reads from the metadata?

It seems so.

issue-88 wrote:So strange it would just ignore half of all frames.
And could i fix it with a simple remux? i believe i already tried that first, but came to a conclusion it did not help and only a re-render would fix it for davinci :|

The original frame rate is written in the stream header, so perhaps if you demux into raw video (might give issues with H.264) and then set the framerate and mux. I would simply transcode, that solves the problem.
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issue-88

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Re: DaVinci misinterpret frame rate source footage

PostFri Oct 19, 2018 10:21 pm

So the best way is to re encode to a ''lossless'' format so davinci recognises the frame rate properly?

Still it bothers me a bit that all other programs did not encounter any problems and a transcoding pass is needed before its usable. :(

But to end on a positive note, i'm very thankful for you're insight and clarification.
Really kept me in doubt, since there is also a lot of other content from different sources in different FPS, and of course everything needs to be blended and faded during live show. :o

So trying to tune and align everything as optimally as possible. :D
But this was a strange one
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Cary Knoop

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Re: DaVinci misinterpret frame rate source footage

PostFri Oct 19, 2018 10:25 pm

Another alternative is to kick the files back and tell them it did not pas your QA stage due to conflicting fps descriptions. :)
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issue-88

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Re: DaVinci misinterpret frame rate source footage

PostFri Oct 19, 2018 10:34 pm

Cary Knoop wrote:Another alternative is to kick the files back and tell them it did not pas your QA stage due to conflicting fps descriptions. :)


Since the first 3 try-out shows are already passed, and the premiere in 1,5 weeks its a bit to little time for that :lol:

But thats how it goes, got most of the content the day's before the first show, so its been a bit last minute work :P

Also I hate the poor encoding already done in the video, in moving parts the compression is very visible.
4k, 50fps, 20mbs on h.264 is a bit on the very low end when not done very thoroughly.
Its clearly the creator is an artistic type, and I am a technical type :D

My big benefit is that I don't have a 4K touring projector so i'm downsampling to the native projector resolution, that gives me some extra room for a crisp image. Some level corrections and a final HEVC render pass and its good as new :D
But I love the super sampling function with sharpen and denoise :D
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Cary Knoop

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Re: DaVinci misinterpret frame rate source footage

PostSat Oct 20, 2018 1:06 am

issue-88 wrote:4k, 50fps, 20mbs on h.264 is a bit on the very low end when not done very thoroughly.

That is already a substandard delivery quality for 4kp50 let alone a quality suitable for any kind of post-processing.
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issue-88

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Re: DaVinci misinterpret frame rate source footage

PostSat Oct 20, 2018 4:13 pm

Cary Knoop wrote:That is already a substandard delivery quality for 4kp50 let alone a quality suitable for any kind of post-processing.


I'm painfully aware of that, unfortunately as a engineer who runs shows i am always involved way to late and content is often done and like it is.
Often times there are way to many links/people in the chain for me to have any influence on content quality by then.
Always try but most of the time its like it is, just have to make due.
In audio its the terrible MP3 :cry:
with video its the substandard MP4 :cry:

So I always try to optimise the content as much as I can for the projector/system on that particular show.
By doing much post-processing work i can avoid the need of unnecessary scaling and processing during live show by all the devices in the chain, running native resolution without any steps in between really is a big deal for the overall quality perception.
Also I try to balance the brightness, contrast, color and levels as much as I can when touring with the same projector to really make the most out of it.

The saying is that you can't polish a turd. :?
But,......
I'f become very skilled at polishing turds :P

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