How to denoise animations using Blender's Temporal Denoiser? I've been diving into the secret Blender Animation Denoiser function mentioned in February of 2019 by Pablo and documented on the Developer Site.
Here are some things I figured out after digging around:

When you render for the animation denoiser you have to use OpenEXR Multilayer.
I then enabled denoising within the Blender view layer settings panel, like instructed.

My code looks like this:
bpy.ops.cycles.denoise_animation(output_filepath=&quot;//Render\Denoised Sequence\Denoised_Images_&quot;)

After hitting enter on the above command, it worked!!!!.... except it didn't.

It went through the process of creating the images of the new denoised sequence.  But when I open the files... they are not denoised.  Simply exact copies of the original noisy images.
So close, yet I don't know where to go from here. Any ideas?
How to use the Temporal Denoiser

Step 01: Pack Denoising Data

Enable denoising data in View Layer &gt; Passes &gt; Denoising Data
Set file format to OpenEXR Multilayer (so Blender packs the denoising data)
Render your animation



Note:
Blender 2.8 needs to be used in the pipeline to pack the denoising data. Simply open your .blend with Blender 2.8, set up the denoising data and save. Then you can reopen the file and render with any version.






Step 02: Denoising
import bpy
import os 
import glob

inputdir=&quot;D:/Animation/&quot;
outputdir=&quot;D:/Animation/Denoised_&quot;
os.chdir(inputdir)
myfiles=(glob.glob(&quot;*.exr&quot;))
for file in myfiles:
   print(inputdir + file + &quot; to &quot; + outputdir + file)
   bpy.ops.cycles.denoise_animation(input_filepath=(inputdir + file), output_filepath=(outputdir + file))
 


Copy the above script into Blender's Text Editor (and backup your animation files :)
Change the location to where your rendered files are. The default location is D:/Animation/
Run the script by pressing the Play button ►






Notes: The used code is from this Reddit thread. All credits to toadfury.