Grain Overlay and Generate functions for Vapoursynth

Requirements

• vs-fgrain-cuda (optional, not needed for overlay)

Setup

Put the vs_grain.py file into your vapoursynth scripts folder.
Or install via pip: pip install git+https://github.com/pifroggi/vs_grain.git

Generate Realistic Film Grain

Simple helper function for the very realistic grain generator fgrain that animates the grain, adds opacity option, and support for YUV. Requires an Nvidia GPU.

import vs_grain
clip = vs_grain.fgrain(clip, iterations=800, size=0.5, deviation=0.0, blur_strength=0.9, opacity=0.1)

clip
Clip to apply grain to.
Must be in YUV444PS or GRAYS format.

iterations
Higher values look more realistic. Lower values speed up the processing time but result in grain that looks less natural.
Originally called "num_iterations" in fgrain.

size
Average size of the grain particles.
Originally called "grain_radius_mean" in fgrain.

deviation
Standard deviation of size, which dictates how much variation there is in the size of the grain particles.
Originally called "grain_radius_std" in fgrain.

blur_strength
Generates smoother grain. This is not really a blur, but it has a similar effect.
Originally called "sigma" in fgrain.

opacity
Opacity of generated grain.

Overlay Grain Clip

Set your own grain clip and overlay it on top of your base clip. This automatically loops the grain clip, crops it if it is too large and repeats it if it is too small.

import vs_grain
clip = vs_grain.overlay(clip, grain, blend_mode='overlay', size=1.0, blur_strength=0, opacity=1.0)

clip
Clip to apply grain to.
Must be in YUV format.

grain
Grain clip to overlay.
Must be in YUV format.

size
Multiplicator to resize grain clip. Will automatically crop if too large or repeat if too small.

blur_strength
Smoothes the grain by blurring the grain clip.

opacity
Opacity of grain clip.

blend_mode
Method used to blend the grain clip with the base clip. Blend functions are from havsfunc by HolyWu.
Available blend modes:

• overlay
• hardlight
• linearlight
• softlight
• vividlight
• grainmerge
• grainextract
• average
• normal

Tips & Troubleshooting

If fgrain is too slow for you, try generating a short grain clip on gray background and then use vs_grain.overlay with blend_mode="grainmerge" to apply it to the whole clip.