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• How to create slideshow from images with ffmpeg ?

  7 novembre 2012, par Arsen Zahray

  I want to create a slideshow from images, where each image would be displayed for some period of time (several seconds).

  How do I do that ?

  Currently I was trying to encode short clips with ffmpeg and then stitch those together with mencoder :

          foreach (var item in filePattern)
  
          {
  
              var otpt = item.Key + ".mpg";
  
              Process.Start("ffmpeg",
  
                  string.Format("-y -r 25 -f image2 -vframes 75 -i {0} {1}", item.Value, otpt)//-loop 1
  
                  ).WaitForExit();
  
          }

  ffmpeg -y -r 25 -f image2 -vframes 75 -i input-pattern output does create a file with 1 frame in it, while ffmpeg -y -loop 1 -r 25 -f image2 -vframes 75 -i input-pattern output on windows never finishes (needs ctrl+c to stop) ; the second command worked on linux for me.

  I need to make this work primary on Windows. Which params should I use ?

• AVPacket not being processed during audio decode

  2 août 2013, par brad_c6

  I am attempting to refactor the decoding_encoding.c example provided in the FFMPEG documentation. Instead of using a array (as a buffer) and reading into the buffer. I already have the file in memory (via a std::vector). I ran a file diff over and found a pattern of data that seems to not be getting decoded (simply lost). Both the file outputted from their example and mine are of the same file length, mine is missing the last 112 bytes ?

  FFMPEG Example

  My Code

• Getting a poster frame(thumbnail) with ffmpeg

  3 juillet 2012, par Tyler

  I am trying to get a poster frame from a video file, using ffmpeg.

  I have been following this tutorial and come up with the following code(which is taken/adapted from the link I gave) :

  public bool GetVideoThumbnail(string path, string saveThumbnailTo, int seconds)
  
          {
  
              string parameters = string.Format("-i {0} {1} -vcodec mjpeg -ss {2} -vframes 1 -an -f rawvideo", path, saveThumbnailTo, seconds);
  
  
  
              if (File.Exists(saveThumbnailTo))
  
              {
  
                  return true;
  
              }
  
              else
  
              {
  
                  using (Process process = Process.Start(pathToConvertor, parameters))
  
                  {
  
                      process.WaitForExit();
  
                  }
  
                  return File.Exists(saveThumbnailTo);
  
              }
  
          }

  At the moment this code is successfully creating a file in the correct destination (saveThumbnailTo) only the picture is completely black. I have tried changing the seconds value in the code to ensure that I am not just getting a blank picture from the start of the video. The path refers to where my video is stored, by the way.

  I am currently calling the above code like so :

  GetVideoThumbnail(videoPath, folderPath + "/poster.jpg", 100)

  ..and then passing it out to my view to display the picture. I just wonder whether ".jpg" is the extension I should be giving to this file as I am not entirely sure ?

  Edit : When I run the same command from the command line I get the following errors :

  Incompatible pixel format 'yuv420p' for codec 'mjpeg', auto-selecting
  format 'yuvj420p'

  which appears in yellow, and

  [image2 @ 02S96AE0] Could not get frame filename number 2 from pattern
  'poster.jpg' an_interleaved_write_frame() : Invalid argument

  which appears in red.

  Could anyone help me with getting this working properly as I am completely unfamiliar with the ffmpeg command line and not sure what I am doing wrong. I have tried removing the vcodec parameter and get the same error message.