title: FFMPEG - Add (white, color-less, analog) grain to the video without desaturating video itself
body: <p>I am working on old videos where I am basically converting them to HVEC and sharpening, so i.e. my command can look like this</p>
  
  <pre><code>.\ffmpeg.exe -i F:\file.mkv -vf unsharp=3:3:1.5 -c:v hevc_nvenc -qp 27 -a:c copy file_new.mkv
  </code></pre>
  
  <p>inherent problem with this is, of course that with reducing bitrate and sharpening every now and then I can notice some nasty artifacts around the edges and on at plain-color objects.</p>
  
  <p>I noticed with some older, many times remastered movies/series that they have quite a lot of grain in the video, so I was thinking - what if I add grain and help it to mask the compression and sharpening artifacts?</p>
  
  <p>After bit of searching I got to 
  <a href="https://ffmpeg.org/ffmpeg-filters.html#noise" rel="nofollow noreferrer">https://ffmpeg.org/ffmpeg-filters.html#noise</a>
  and now I am using this command</p>
  
  <pre><code>.\ffmpeg.exe -i F:\file.mkv -vf unsharp=3:3:1.5,noise=alls=14:allf=t+u -c:v hevc_nvenc -qp 30 -a:c copy file_new.mkv
  </code></pre>
  
  <p>however this has one big problem, it is merely a digital RGB noise, is there a way to make it desaturated, analog-ish? I tried adding h=s=0, however this is applying 0 saturation to the video track as a whole. Is there an effect which would achieve this or is there a way that I can reduce the saturation only of the very effect which then gets to "overlay" the video track, so the track would not be touched?</p>