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• How to make FFMPEG video grayscale ?

  15 octobre 2018, par Aang

  In my program I am using the subprocess Python module in my script to call on FFMPEG to turn a sequence of images into a video (grayscale). It works and a video is created, but upon further inspection I see that the video itself has encoded the different intensities incorrectly.

  Here is my code :

                  subprocess.call(['/usr/local/bin/ffmpeg', '-framerate', \
  
                               framerate, '-f', 'image2','-pattern_type', \
  
                               'glob', '-i', self.directory + '/orbit_*.png', \
  
                               '-r', '10', '-s', '620x380', '-flags', 'gray', self.directory + 
  
                               ".avi"])

  Here is a link to the video that’s created : https://drive.google.com/open?id=0Bxt1siua2KQma0JaMVBMcE9TOEE

  If you’ll look at the scale bar on the right in the video, which normally looks like this
  in color, you’ll see that the same color shows up twice on the scale bar. I think it’s because FFMPEG is reading colors with the same intensities (for example, yellow and blue) the same way and therefore when the photo is encoded into grayscale it looks like this.

  What can I do ? Is this a matter of changing the "-flags", "gray" parameters of my subprocess call ?

• Does the incoming codec or audio-video sync matter when encoding from Xvfb using FFMPEG ?

  15 décembre 2022, par Nav

  How I'm capturing :
  
I'm using Xvfb on Linux, to capture a video and audio from an app that is also running on Linux. I'm using -f x11grab when capturing that video headlessly from Xvfb's frambuffer using FFMPEG, and encoding it using a few other parameters like -c:v libx264 -pix_fmt yuv420p.

  


  The questions :
  
Since I'm reading from Xvfb framebuffer :

  


  

  1. Would it matter that the app uses SVC to encode the video, and I'm using H.264 ?

  


  2. Would it matter if I use a different framerate than the app is using ?

  


  3. Would it matter if I use a different pix_fmt than what the app is using ?

  


  


  Reason for asking :

  


  
  
As shown in the image (blue is the app, red is FFMPEG, green is Xvfb) ;

  


  

  • The CPU percentage consumed by FFMPEG shoots up when the app's CPU percentage shoots up. I've also encountered audio being ahead of video for some participants, but I'm unable to figure out whether it's due to network lag or due to FFMPEG's encoding.

  


  • Also, the aim is to reduce CPU consumption, so I was looking to see if I could do FFMPEG encoding in the same format as the app.

  


  


• FFmpeg and Jupyter Notebooks

  12 mai 2022, par Clerni

  I'm getting the error RuntimeError: Requested MovieWriter (ffmpeg) not available when trying to run this simple example of creating and displaying an animation in a Jupyter Notebook.

  


  ---------------------------------------------------------------------------&#xA;RuntimeError                              Traceback (most recent call last)&#xA; in <module>&#xA;      8 &#xA;      9 # Define the meta data for the movie&#xA;---> 10 FFMpegWriter = manimation.writers[&#x27;ffmpeg&#x27;]&#xA;     11 metadata = dict(title=&#x27;Movie Test&#x27;, artist=&#x27;Matplotlib&#x27;,&#xA;     12                 comment=&#x27;a red circle following a blue sine wave&#x27;)&#xA;&#xA;/usr/local/lib/python3.8/dist-packages/matplotlib/animation.py in __getitem__(self, name)&#xA;    164         if self.is_available(name):&#xA;    165             return self._registered[name]&#xA;--> 166         raise RuntimeError(f"Requested MovieWriter ({name}) not available")&#xA;    167 &#xA;    168 &#xA;&#xA;RuntimeError: Requested MovieWriter (ffmpeg) not available&#xA;&#xA;</module>

  


  Running !pip install ffmpeg didn't help, as ffmpeg is already installed, apparently :

  


  Requirement already satisfied: ffmpeg in /home/username/.local/lib/python3.8/site-packages


  


  How can I make this work ?