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• ffmpeg : How to replace a series of frames with a series of image files ?

  14 septembre 2020, par Arnon Weinberg

  Given a video file, start and end timestamps, there is a known number of frames between those timestamps in the video file, and I have an equal number of .png files in a directory to replace them with. The .png files are sorted as 001.png ... NNN.png. How would I go about updating the video file with the replacement frames using ffmpeg ?

  


  This is a followup to using ffmpeg to replace a single frame based on timestamp, but I'm asking about replacing multiple sequential frames based on 2 timestamps.

  


  Presumably something like :

  


  ffmpeg -i input.mp4 -i %3d.png -filter_complex "something including the timestamps 4.40,5.20" -c:a copy output.mp4


  


  I would also be okay with using frame numbers instead of timestamps if that makes things easier, and it's reasonable if start and end frames must be keyframes.

  


  Background :

  


  Many machine learning algorithms for video processing use ffmpeg to extract specific scenes from videos based on start and end timestamps, dump them into a sequence of .png files, process them in some way (denoise, deblur, colorize, annotate, inpainting, etc), and output the results into an equal number of .png files. The output frames are usually assembled into a new video file, but I would like instead to update the source video file so as to preserve audio, unedited video, and other video properties (fps, keyframes, etc).

  


  This approach will not work as-is for some categories of video processing algorithms. For example, interpolation results in more frames than were originally extracted, and upscaling results in higher-resolution images. As such, I would appreciate an explanation of any solution so that I can adapt it for such cases (or I will ask separate questions for those).

  


• Guidance on Implementing Custom Designs and Background Effects for Videos [closed]

  23 septembre 2023, par Joel Smith

  I am currently developing a web application that allows users to upload videos on the frontend. The primary goal of my project is to enable users to add custom designs to their videos and apply background effects. I'm using Python for the backend to handle video processing.

  


  I'm seeking advice on the appropriate technologies, libraries, or approaches to achieve the following :

  


  

  1. Custom Designs : I want to provide users with the ability to overlay custom graphics or text onto their videos. What Python libraries or tools can I use to achieve this ? Are there any best practices for adding graphics and text to videos dynamically ?

  


  2. Background Effects : I need to implement the feature to add background effects to uploaded videos. How can I achieve this, and what are the recommended methods or libraries for background replacement or manipulation ?

  


  3. Shadow Effects : Additionally, I want to enhance the visual appeal of the videos by adding shadow effects to elements like text or custom designs. What techniques or tools should I explore to achieve this effect ?
4.Combining Videos : To apply background effects, I need to merge the uploaded video with a background video or image seamlessly. What is the best approach to combine videos and maintain video quality during the process ?

  


  


  I have already implemented the frontend video upload to the backend and would appreciate any insights, code examples, or recommendations that can help me achieve these features effectively.

  


• avfilter/drawbox+drawgrid - add option to prevent overwriting of source pixels

  11 décembre 2017, par Gyan Doshi

  avfilter/drawbox+drawgrid - add option to prevent overwriting of source pixels
  If the user-supplied color in drawbox and drawgrid filters is non-opaque,
  
  the box & grid painting overwrites the input's pixels (including alpha).
  
  Users typically expect the alpha of the specified color to only act as a key
  
  for compositing on top of the main input.
  Added option allows users to select between replacement and composition.
  
  Tested and documented.
  

  • [DH] doc/filters.texi
  • [DH] libavfilter/vf_drawbox.c