Hello
I use this spec for all my different animation and it works great,
but in this scene I always have a noise moving between each frame in darker area.
The render time for all the frame is very long so I use a renderfarm, I don’t want to push everyting to the max because my bank account will explode 
but to find the right solution 
What’s your point of view 
Look up Super Image Denoiser (Temporal), it might help
Is the floor reflective? Is this an interior scene lit through windows? Those are difficult scenarios to render. Your settings work in most scenes, but they break in a difficult lighting case like this one.
First, make sure you aren’t using an animated seed (in the advanced tab). This is something that people sometimes tell you to do, but it’s really only good if you aren’t using the denoiser.
Now, let’s talk about the sampling settings
The problem is likely the lack of a “min samples” value. If you leave that number at 0, Cycles will pick a value for you based on the “max samples” and the value it will pick might not be adapted to your scene. For a case like this, you might easily need 128 min samples or more.
Meanwhile, your noise treshold of 0.002 is so low (high in quality) that it probably does almost nothing. You probably reach the max samples before the treshold has had the chance to do much, making the render take longer than needed. You could try to set it to 0.01, as your quality is most likely being bottlenecked by the 2 other settings anyway.
Here is a thread where I explain what the sampling settings do if you are interested.
Is there an HDRI or sky background coming through windows? Make sure you are using light portals in the windows. It won’t help with the direct sunlight, but the diffuse sky light coming from every direction will be a lot cleaner.
Also, make sure your windows have their shadows disabled or use a glass material with the shadow disabling trick.
Having a scene lit mostly by sharp beams of sunlight on a floor is a really noisy thing to render. Raytracing renderers like Cycles have a hard time finding those narrow patches of light on the floor.
I don’t know if your skills are at that level yet, but if I had to render an interior scene, I would bake the indirect light of the walls and ceilings to textures. This massively accelerates a render, because it makes the bouncing light cleaner across the whole scene.
Here is an example and explanation, if you have the knowledge to follow.
Something else that can help with this problem is the double resolution render trick.
This also has the benefit of better conserving texture detail through the denoising process.
Wow, a lot of creat info there thank you!
Yes you are right it is through window, with a reflective floor, an hdri evironment + a sun.
If you are curious I can share the blend file tomorrow (midnight here 
)
My bro I don’t even see what you could possibly be talking about. Your frames look good.
On the video, look at the floor shadow area on the left side, it is flickering like crazy.
I use a renderfarm so an addon is not a solution for this case, but I keep it for my own renders 
So like you mentioned I checked for the animated seed, it was unchecked.
I tried to double the size of my scene with a threshold 0,01 and 2048 sample, but 
The renderfarm indicates me the amount for 200 hundred frame, ouch it will cost me an eye 
In case there is a solution I join here the blend file and a short rendered animation. (that’s a bit heavy because all is packed, 300Mo)
Ok, I do see it now, thanks. Frankly… the eye is drawn to the moving foliage shadow front and center, I wouldn’t worry about flickering in this particular case. Of course the issue stands in other situations, but here, it’s completely camouflaged by other moving parts.
Yes but here it is a very short part of the animation, and in the full version your eye see very well the bad quality and flickering parts
If you are going to do the doubling trick, you can reduce the quality even more than that, until it takes the same time as before. It can be hard to give an exact number because of the way the noise treshold works.
Anyway, after looking at your scene, I don’t think this is the solution. Your scene is overall just very noisy, so that’s the thing I would focus on solving. You have made a scene that’s hard for Cycles and it’s going to need some optimizations.
In addition to the things I said in the previous post, your scene also has light sources hidden in deep holes. That’s a sure way of generating noise. In general, Cycles fears any light that’s hard to find (like lights coming in through a narrow opening).
I would use the light path node to deactivate the light coming from those emissive surfaces and instead use area lights with a low spread angle. This will give you the same result as before, but the narrow beam will ensure Cycles can find those lights easier and with less noise.
This setup makes a material emissive to the camera but without emitting light in the scene:
Then, I use area lights with low spread for a more controlled beam.
You could use light portals in the windows. This will guide the light towards the openings and help Cycles find the sky light easier. Portals work only for the sky (HDRI or other background).
It doesn’t make a very big difference in this case because the windows are large, but it’s generally a good practice and it costs very little time to setup.
Here is a file where I have made the changes.
Your scene is a perfect case for my light baking trick, like I mentionned earlier, so I have included it on some of the main surfaces (feel free to remove it from the materials if you don’t want or understand it). It greatly helps with noise and allows me to lower the quality of the sampling settings a bit.
However, the bake would have to be removed or redone if you ever wanted to change the lighting or remodel the scene’s layout.
WOW, I don’t know what to say 
I spent one full day on it without solving it
You are amazing 
I have learn so much here!
There is a so great community here, love it so much 
