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• How to access microphone using FFMPEG with C++

  14 juin 2014, par Godspped

  I want to be able to access a microphone on the computer using ffmpeg in C++, I can not find any example to do so. Do I have to use "avformat_open_input", but how do I know the list of audio capture devices on the computer ?

  Does anyone have some sample code or a tutorial they came by so that I can get started.

  Thanks in advance !

• Combine multiple videos into one

  10 janvier 2012, par StackedCrooked

  I have three videos :

  • a lecture that was filmed with a video camera
  • a video of the desktop capture of the computer used in the lecture
  • and the video of the whiteboard

  I want to create a final video with those three components taking up a certain region of the screen.

  Is open-source software that would allow me to do this (mencoder, ffmpeg, virtualdub..) ? Which do you recommend ?

  Or is there a C/C++ API that would enable me to create something like that programmatically ?

  Edit
  There will be multiple recorded lectures in the future. This means that I need a generic/automated solution.

  I'm currently checking out if I could write an application with GStreamer to do this job. Any comments on that ?

  Solved !
  I succeeded in doing this with GStreamer's videomixer element. I use the gst-launch syntax to create a pipeline and then load it with gst_parse_launch. It's a really productive way to implement complex pipelines.

  Here's a pipeline that takes two incoming video streams and a logo image, blends them into one stream and the duplicates it so that it simultaneously displayed and saved to disk.

    desktop. ! queue
  
             ! ffmpegcolorspace
  
             ! videoscale
  
             ! video/x-raw-yuv,width=640,height=480
  
             ! videobox right=-320
  
             ! ffmpegcolorspace
  
             ! vmix.sink_0
  
    webcam. ! queue
  
            ! ffmpegcolorspace
  
            ! videoscale
  
            ! video/x-raw-yuv,width=320,height=240
  
            ! vmix.sink_1
  
    logo. ! queue
  
          ! jpegdec
  
          ! ffmpegcolorspace
  
          ! videoscale
  
          ! video/x-raw-yuv,width=320,height=240
  
          ! vmix.sink_2
  
    vmix. ! t.
  
    t. ! queue
  
       ! ffmpegcolorspace
  
       ! ffenc_mpeg2video
  
       ! filesink location="recording.mpg"
  
    t. ! queue
  
       ! ffmpegcolorspace
  
       ! dshowvideosink
  
    videotestsrc name="desktop"
  
    videotestsrc name="webcam"
  
    multifilesrc name="logo" location="logo.jpg"
  
    videomixer name=vmix
  
               sink_0::xpos=0 sink_0::ypos=0 sink_0::zorder=0
  
               sink_1::xpos=640 sink_1::ypos=0 sink_1::zorder=1
  
               sink_2::xpos=640 sink_2::ypos=240 sink_2::zorder=2
  
    tee name="t"

• 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 !