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• FFMPEG exported video is all black

  5 mars 2024, par Kartikey

  I am trying to generate a video wall of 4 videos using ffmpeg like the given image

  


  

  


  I am exceuting this below script to get the desired result

  


  def merge_videos(output_file):
    command = [
        'path_to_ffmpeg/ffmpeg.exe',
        '-i', 'path/playblasts/front.mp4',
        '-i', 'path/playblasts/side.mp4',
        '-i', 'path/playblasts/persp1.mp4',
        '-i', 'path/playblasts/persp2.mp4',
        '-filter_complex', '[0:v][1:v][2:v][3:v]xstack=inputs=4:layout=0_0|w0_0|0_h0|w0_h0[v]',
        '-map', '[v]',
        output_file
    ]
    subprocess.run(command)


  


  where as passing output file path as argument, but I am getting below result

  


  

  


  Any help would be appreciated.
Thanks & Best Regards

  


• FFMPEG thumbnail image gives black image

  24 mars 2015, par user3772344

  I am trying to get the thumbnail image of video using ffmpeg. but for some of the video it shows the black image. I have done the following code.

   KxMovieDecoder * decoder = [[KxMovieDecoder alloc] init];
  
  [decoder openFile:videoURL error:nil];
  
  gHistory = [[NSUserDefaults standardUserDefaults]objectForKey:[decoder.path lastPathComponent]];;
  
  
  
  NSArray *ar =  [decoder decodeFrames:1.0f];
  
  KxMovieFrame *frame;
  
  
  
  for (KxMovieFrame *frames in ar)
  
  {
  
      if (frames.type == KxMovieFrameTypeVideo) {
  
          frame =  ar.lastObject;
  
          break;
  
      }
  
  }
  
     KxVideoFrameRGB *rgbFrame = (KxVideoFrameRGB *)frame;
  
  UIImage *imageKX = [rgbFrame asImage];

  I don’t know whats the wrong in this method

• Cutting HEVC video results in parts stating with no video (black image) but correct audio for a few seconds

  8 juin 2020, par Oliver

  i have large HEVC video files and want to cut out parts of them. I use ffmpeg for that with the following command :

  



  ffmpeg -i input.mp4 -ss 01:18:47.040 -c:v copy -c:a copy -to 01:18:42.640 output.mp4


  



  i know that there can be problems when copy is used and no re-encoding, that is why i checked before that the frames specified in the -ss and -to parameters where keyframes (i-frames).

  



  So iam expecting to get a clean cut at the beginning and at the end. But what i get is 10 seconds of black image with normal audio in the beginning until the video starts. To make this clear : 10 seconds of video are missing in the beginning but the audio is fine.

  



  Btw : when moving the -ss part before the -i there seem to be no problems with the video (at least in the beginning). I know about the differences of putting -ss before and after the -i, but i also know, that using -ss after the -i should be slower (and was more accurate in the past) but should not make any differences in the final result. That is why I am so irritated.