Answers.Body: <p>Without knowing the video properties, my generic answer is</p>
  
  <pre><code>ffmpeg -i in.mp4 -vf geq=lum='p(X,Y)':cb=128:cr=128 out.mp4
  </code></pre>
  
  <p>This will reset the color information, but pass the luma plane intact. Add <code>-crf 0</code> for truly lossless re-encoding.</p>
  
  <hr>
  
  <p>This is the faster way,</p>
  
  <pre><code>ffmpeg -i in.mp4 -vf extractplanes=y,format=yuv420p out.mp4
  </code></pre>
  
  <p>The luma plane is extracted, and then neutral chroma planes are added in the pixel format conversion. This 2nd step is added because otherwise ffmpeg will auto-convert pixel format to yuv444 which isn't widely compatible.</p>
  
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2018-03-18T00:37:14.683Z
Answers.Text: Awesome, that works. Is this the quickest way? If not, what information would need to know for a faster/better solution?
Answers.UserDisplayName: Stefan Popp
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2018-03-18T08:18:02.480Z
Answers.Text: There's one potentially quicker way but I have to check whether it alters the luma.
Answers.UserDisplayName: Gyan
Answers.ContentLicense: CC BY-SA 3.0
Answers.CreationDate: 2018-03-16T19:00:51.413Z
Answers.LastActivityDate: 2018-03-19T12:57:51.923Z
Answers.LastEditDate: 2018-03-19T12:57:51.923Z
Answers.UserDisplayName: Gyan
Body: <p>I need to reduce the file size of an mp4 video. I don't need color information at all but pixel brightness resolution must be preserved. Videos consist of white background with a few (important) black dots of about 5px diameter. I am confused about what the best method/output would be.</p>
  
Tags: <ffmpeg><codec><file-formats><colorspace>
Title: Lossless color compression
UserDisplayName: Stefan Popp
ThreadText: # Lossless color compression
  
  (Asked by: username_0 on 2018-03-16)
  
  I need to reduce the file size of an mp4 video. I don't need color information at all but pixel brightness resolution must be preserved. Videos consist of white background with a few (important) black dots of about 5px diameter. I am confused about what the best method/output would be.
  
  **Tags:** ffmpeg, codec, file-formats, colorspace
  
  
  ---
  
  ## 1 answers
  
  ### Answer by username_1 on 2018-03-16. Score: 3 | Accepted answer
  
  Without knowing the video properties, my generic answer is
  
  ```
  ffmpeg -i in.mp4 -vf geq=lum='p(X,Y)':cb=128:cr=128 out.mp4
  
  ```
  
  This will reset the color information, but pass the luma plane intact. Add `-crf 0` for truly lossless re-encoding.
  
  ---
  
  This is the faster way,
  
  ```
  ffmpeg -i in.mp4 -vf extractplanes=y,format=yuv420p out.mp4
  
  ```
  
  The luma plane is extracted, and then neutral chroma planes are added in the pixel format conversion. This 2nd step is added because otherwise ffmpeg will auto-convert pixel format to yuv444 which isn't widely compatible.
  
  > **Comments:**
  > **username_0**: Awesome, that works. Is this the quickest way? If not, what information would need to know for a faster/better solution?  
  > **username_1**: There's one potentially quicker way but I have to check whether it alters the luma.  
  
  ---
  
  