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• FFmpeg : Combine video files with different start times

  18 mai 2016, par Fabian

  I have two webm files with audio and video recordings of a video conference session. Both files only contain one side of the conversation. They are not of the same length (someone has joined before the other one), but I have the unix timestamp in milliseconds of the start time of each video file.

  On a timeline they look like this :

  webm 1:   -----------------------------------------------
  
  webm 2:                 -----------------------------

  or like this :

  webm 1:   -----------------------------------------------
  
  webm 2:                          -----------------------------

  I would like to combine these two video files into one file so that :

  1. They appear next to each other (using the hstack option), and
  2. That they are mixed with taking the time stamps of the start times
     into account. The final video should then look like this :

  Target result : --------------===========================----

  The beginning and the end of the new video would show a black placeholder for the video file that has no data at this time of the mixed stream.

  At the moment I use this command :

  ffmpeg -i 1463408731413703.webm -i 1463408880317860.webm -filter_complex \
  
  "[0:v][1:v]hstack=inputs=2[v]; \
  
   [0:a][1:a]amerge[a]" \
  
  -map "[v]" -map "[a]" -ac 2  -c:v libvpx output.webm

  This creates a video like this :

  Not good result : =====================------------------

  i.e. the conversation is out of sync.

  How can I combine two video streams with different length and different start times using ffmpeg so that I will end up with "Target result" above ?

  Thanks a lot !

• Live Smooth Streaming in IIS from webcam using FFMPEG

  13 mai 2016, par tearvisus

  I’m trying to do a live stream of video captured by my webcam and host it on IIS using Live Smooth Streaming. Here are the steps I’m taking :

  1. In the IIS manager’s MIME Types add a new extension : .isml with type : application/atom+xml
  2. In the IIS manager add a publishing point (filename : myStream.isml).
  3. Start the publishing point.
  4. Run the following command :

  ffmpeg -hide_banner -y -f dshow -rtbufsize 100000k -i video="Lenovo EasyCamera":audio="Microphone (Realtek High Definition Audio)" -movflags isml+frag_keyframe -s 854x480 -f ismv http://localhost/myStream.isml/Stream(video)

  5. Play the stream from the location http://localhost/myStream.isml/manifest using VLC.

  The problem is that the playback stops a few seconds before the moment in which I opened the stream with VLC. If I reopen the stream again, it will play from around the moment the first playback stopped to the moment the second playback started.

  What I’m trying to achieve is to make the clients see the video from the moment they open the stream to the moment they disconnect. A delay up to a few seconds is acceptable. Obviously, the playback should not end regardless of the connection moment.

  How can I do this ? Should I change something in the FFMPEG’s command or in the IIS ?

  Note : A solution using tools other than FFMPEG is acceptable, as long as they are free (as in beer).

  EDIT : Changed the description of problematic playback.

• rails streamio-ffmpeg does not find uploaded video files

  26 avril 2016, par Felix

  I try to make a screenshot as thumbnail of a movie while uploading.

  My code looks like this at the moment

  require 'rubygems'
  
  require 'streamio-ffmpeg'
  
  
  
   def uploadMovie
  
     @channels = Channel.all
  
     @vid = Movie.new(movies_params)
  
  
  
     @channel = Channel.find(params[:vid][:channel_id])
  
     @vid.channel = @channel
  
  
  
     if @vid.save
  
       flash[:notice] = t("flash.saved")
  
       movieFile = FFMPEG::Movie.new(@vid.video.to_s)
  
       screenshot = movieFile.screenshot("uploads/screenshot", :seek_time => 10)
  
       render :add
  
     else
  
       render :add
  
     end
  
   end

  But when I do this I got this error :

    No such file or directory - the file 'http://.s3.amazonaws.com/uploads/movie/video/7/2016-04-24_16.26.10.mp4' does not exist

  That should be okay because I upload the movies to Amazon S3 with carrierwave ...

  What’s going wrong in this case ?