Denoising Animations in Cycles I've made a simple animation in blender 2.81a and am now trying to render it.  

My system specs: CPU i7-6500U; GPU Nvidia Geforce GTX 950M; RAM 16gb DDR4
So far, I've done two test renders (both in cycles):


8 samples, 8 light bounces, denoising on, 60fps (240 frames). Total render time was about 3 hours. Looking at single frames, they were flawless, but if you play the animation, you see that the denoiser is producing some kind of jitter (like in this video).
256 samples, 4 light bounces, denoising on. I set the framerate to 24fps and used time remapping to maintain animation speed (96 frames). The jitter has become far less, but is still there. However, the time remapping made the animation look kind of not-fluent.
So I figured that I probably need 512 samples to reduce the jitter and render at 60fps. However, this will probably take about 16 hours to render.
Are there any other ways to  
change the framerate without changing the animation speed? (except for manually repositioning keyframes)
decrease general render time/reduce the jitter (aka denoising for animations)
Thanks in advance!




Edit: I heard that Blender 2.83 and 2.90 (which is not yet oficially released) have improved the denoising system, e.g. AI-accellerated denoise, adaptive sampling and optix viewport denoising. Do any of these also apply to video or is there now any option for better denoising for animations?
The default denoise options currently offered in blender (AI, Optix and the original blender denoiser) produce jittering because they do only Spatial Denoising, meaning that they use only one frame for input, so all images are denoised separately. The main problem with this approach is that noise patterns might not be consistent or homogeneous from one frame to the next. Sometimes this kind of denoising might actually create more problems than using no denoising at all.

Edit
For proper temporal denoising in blender read:
How to denoise animations using Blender&#39;s Temporal Denoiser?

In case of animation, you could also use denoise tools created specifically for video. Those tools not only can do Temporal Noise Reduction, by analysing several frames to understand how noise is transforming from frame to frame, but also use some spatial noise reduction as well.
Some suggested tools:
Neat
This denoiser can remove noise from video sequence, and it uses information from neighboring frames to denoise images. The best use for this plug-in - render animation without denoising, then remove noise from sequense in Natron (for example). Unfortunately, this Ofx plugin is commercial.
Deflicker
This Ofx  plug-in can remove jittering from denoised sequence. Instead  Neat, it can not remove noise, only flickering. As Neat, this plug-in can work in Natron and, unfortunately, it is also commercial.
Resolve
This video editor also has sophisticated noise reduction tools (only in studio version) and it is also commercial.