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• Getting video metadata in ruby script using ffmpeg, ffprobe or rvideo

  24 janvier 2013, par alex

  I want to get metadata of videos referenced by a URL using Ruby. At this point, I found many related posts, but could not find out how to solve my problem.

  I tried to use RVideo, but when I do :

  file = RVideo::Inspector.new(:file => 'http://www.agreatsite.com/avideo.mp4' ;)

  It throws

  'ArgumentError : File not found (http://www.agreatsite.com/avideo.mp4)...

  So I can't get the information using RVideo (but it works well when I have the file hosted on my local computer).

  I then tried to use ffprobe, but I don't know how to read the output.
  So far, I have the following method, which "shows" the information I want when I run it in the console, but it actually returns "true" and I can't find out how to capture the output I need...

    def media_info
  
      source = self
  
      command = <<-end_command
  
        ffprobe -v quiet -print_format json -show_format -show_streams  #{source}
  
      end_command
  
      command.gsub!(/\s+/, " ")
  
      system(command)
  
    end

  Would love some help, to make this work with either ffprobe or RVideo !

  UPDATE :
  I found a way to get what I needed. Not sure this is the best way to do it :

  def get_media_duration

  source = self.media[0][:url]    
  
  
  
  command = <<-end_command
  
    ffprobe -v quiet  -show_streams  #{source}
  
  end_command
  
  command.gsub!(/\s+/, " ")
  
  
  
  duration = ""
  
  IO.popen(command) { |io| while (line = io.gets) do
  
                          puts "++ "+line.inspect
  
                          duration = line.split("duration=")[1].gsub("\n", "") if line.split("duration=").length > 1
  
                        end
  
                    }
  
  duration   

  end

  I guess I could make it work that way, but doesn't seem very elegant to me. Better suggestions would be greatly appreciated !

• Blender VSE Audio out-of-sync when animation (video) is rendered

  21 août 2021, par Siddhant Shenoy

  Ok, so I found out that Blender has this really cool video-editing interface and I was beginning to love it. Until, I created this awesome project composition and when I exported the animation as a video file, the audio was out of sync :(.

  



  Actual Problem

  



  Audio is in-sync with video when the animation is played in Blender but is out-of-sync in the rendered video.

  



  Solutions I tried out and failed

  



  

  • I used the 'Audio-Sync' option in the sequencer but that made no difference.

  


  • Then I thought that my scene audio frequency might have been an issue since it was initially 48kHz and my videos were at 24kHz, so I changed the scene audio frequency to 24kHz, this still failed to solve the issue.

  


  • Initially, I was combining videos with different frame rates and thought that might have been an issue (although animation played as expected in Blender), so I recreated the source videos to ensure all videos I was using in my project had the same frame rate, but this also did not work.

  


  • Someone online suggested exporting the video and audio separately and then combining them using a command-line tool like FFMPEG, this also failed.

  


  



  What's really frustrating

  



  


  • This lag (audio is a few frames ahead of the video) is noticeable only in longer videos (>12 mins, my video is 1 hr long) suggesting a very small rendered rate difference between the video and the audio.

  


  • Also, note that the animation plays absolutely fine in Blender, so all I could figure out was that this was a rendering issue.

  


  



  So if anyone figured this out please let me know. I am a noob in video/audio codecs so please forgive me if I used some incorrect nomenclature above.

  


• Use a video editing library (not executable) via Node [on hold]

  25 septembre 2018, par Merc

  I need to edit clips using node. I am looking around, and most (if not all) libraries seem (like Fluent FFMpeg) seem to be based on the fact that they run FFMPEG as an executable and get the resulting output.

  That’s not what I want. I worked with FFMPEG executable in the past, and I know how flaky it is in terms of return codes and error codes.

  Ideally, I would love to find a native library for video editing and make calls using node.

  In terms of libraries :

  • Gstreamer
  • FFmpeg/LibAV (does they come with C libraries to bind to ?)
  • libVLC

  In terms of binding with them :

  • node-gir. Gstreamer seems to have updated git files

  • native bindings. For example Gstreamer has gstreamer-superficial. I couldn’t find any javascript bindings forFFMPEG — only "run the executable and hope for the best" libraries

  • VLC has a bindings library that is quite old and had its last commit years ago.

  Am I getting this all wrong ?
  My ideal outcome is to have a nice, robust library that I use directly using node, but my lack of experience in terms of using native libraries, and the somehow fragmented world of video editing libraries.