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• OpenCV4 (python 3.9) VideoCapture failing to open .mp4 file on osx

  15 juin 2021, par Ender

  I am trying to read an mp4 video frame-wise with OpenCV4 installed with brew. The following snippet, though, fails to open the file :

  


  v_path = os.path.join(v_dir, v_title + ".mp4")
v = cv2.VideoCapture(v_path)


  


  resulting in the following error :

  


  OpenCV: Couldn't read video stream from file []


  


  v_path is an absolute path. Some advise searching for the opencv_ffmpeg.dll file and copying it to the root python folder but its not in /usr/local/Cellar/opencv/4.5.2_4/lib and I would rather not download it directly from a site. If this is crucial, how should I reinstall opencv (ideally still using brew) ? The thing is brew include ffmpeg with the opencv installation. Others say converting to .avi with ffmpeg is the trick but there should be a solution for .mp4, right ? Other questions focus on issues where VideoCapture opens the video but is unable to load any frames, this seems like a less severe problem.

  


  brew doctor


  


  reveals no serious issues.

  


• What options I should use to rescale video without skewing them in FFMPEG Rails ?

  5 juin 2019, par ADMAT Bandara

  The main issue happens when it processes the recalling

  All videos uploading from Apple iOS will process nicely.
  But all videos uploading from Android devices are getting skewed.

  In my rails app, I am using Carrierwave:Video and FFMPEG to process videos with the help of delayed jobs.

  class VideoUploader < CarrierWave::Uploader::Base
  
  
  
    include CarrierWave::Video
  
    include CarrierWave::Video::Thumbnailer
  
  
  
    # For carrierwave_backgrounder
  
    include ::CarrierWave::Backgrounder::Delay
  
  
  
    version :rescaled do
  
      process encode_video: [
  
        :mp4,
  
        resolution: "640x480", # Aspect ratio is preserved automatically
  
        audio_codec: "aac",
  
        custom: "-strict experimental -q:v 0 -preset slow -g 30",
  
        callbacks: { after_transcode: :set_success }
  
      ]
  
    end
  
  
  
  
  
    version :thumb do
  
      process thumbnail: [{format: 'png', quality: 10, size: 400, strip: true, logger: Rails.logger}]
  
      def full_filename for_file
  
        png_name for_file, version_name
  
      end
  
    end

  This is correct videos screenshot

  https://drive.google.com/open?id=1D0aNWcVxtL6DbTwBmWWIGzUUuyEyWNOG

  This the video screenshot after video process with FFMPEG

  https://drive.google.com/open?id=1vilExHoan2UuRPH9RbiZig58H1TwyewA

  (It’s like vertically pressed)

  ---

  Please help me, if you know a solution

• Double decoding with same bitrate android

  3 mars 2016, par Bee

  How to do double decoding with same bit rate android ? I mean I want to play 2 videos in 2 different views but syncronisedly. I found this grafika double decoder. But it is not with same bitrate.
  The documentation says that.
  Any one know any sample project or guideline that I can follow ? Or maybe just can illustrate the steps I have to do ? May be used ffmpeg or something else ?