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• Allowing downloads of partial video files from Django

  18 janvier 2019, par DataVis

  I have a Django app that allows users to make/save ’clips’ of video files, that is keep timestamps of start and end times of video files to save in playlists. I would like users to be able to download clips (and playlists as well) they have saved.

  I have done quite a bit of research on the topic and have gotten ffmpeg working from my terminal to save partial clips (though I’ve struggled to figure out pathnames for using subprocess.call with ffmpeg), and I have also gotten moviepy working via the terminal to save partial clips.

  I’m struggling to figure out how to incorporate this into my Django app so that users can click a link and subsequently begin a download of a specific clip (or playlist). I believe I will want to use celery to avoid tying up the server but I’m not even to the point where I can offload a task as I can’t figure out how to :

  1. ’Clip’ the original, longer video file to make it shorter (do I need to make a local copy of a new file first ?).
  2. Send a response as a download to the user.

  Here is my models.py :

  class Match(models.Model):
  
      game_id = models.IntegerField(primary_key=True,
  
          validators=[MinValueValidator(1)],db_column="game_id")
  
      wide = models.FileField(upload_to='games/2018/',blank=True,null=True)
  
  
  
  class Playlist(models.Model):
  
          name = models.CharField(default='',null=True,blank=True,max_length=200)
  
          created_by = models.ForeignKey(User,related_name="playlists",on_delete=models.CASCADE)
  
          created =   models.DateTimeField(editable=False)
  
          modified =  models.DateTimeField()
  
  
  
  
  
          def save(self, *args, **kwargs):
  
              ''' On save, update timestamps '''
  
              if not self.id:
  
                  entries = Playlist.objects.order_by('-id')
  
                  try:
  
                      self.id = entries[0].id + 1
  
                  except IndexError:
  
                      # we don't have any PlaylistEntries yet, so we just start @ 0
  
                      self.id = 0
  
                  self.created = timezone.now()
  
              self.modified = timezone.now()
  
  
  
              return super(Playlist, self).save(*args, **kwargs)
  
  
  
  
  
      class Clip(models.Model):
  
          name =  models.CharField(default='',null=True,blank=True,max_length=200)
  
          game_id = models.ForeignKey(Match,related_name="clips",on_delete=models.CASCADE,
  
              db_column="game_id",null=True,blank=True)
  
          clipstart = models.IntegerField(null=True,blank=True)
  
          clipend = models.IntegerField(null=True,blank=True)
  
          playlist = models.ForeignKey(Playlist,related_name="clips",on_delete=models.CASCADE,
  
              db_column="playlist",null=True,blank=True)
  
          created_by = models.ForeignKey(User,related_name="clips",on_delete=models.CASCADE)
  
          created =   models.DateTimeField(editable=False)
  
          modified =  models.DateTimeField()
  
          duration = models.IntegerField(null=True,blank=True)
  
  
  
          def save(self, *args, **kwargs):
  
              ''' On save, update timestamps '''
  
              if not self.id:
  
                  entries = Clip.objects.order_by('-id')
  
                  try:
  
                      self.id = entries[0].id + 1
  
                  except IndexError:
  
                      # we don't have any PlaylistEntries yet, so we just start @ 0
  
                      self.id = 0
  
                  self.created = timezone.now()
  
              self.modified = timezone.now()
  
              self.duration = int(self.clipend) - int(self.clipstart)
  
              return super(Clip, self).save(*args, **kwargs)

  And views.py where I’m struggling (I’m not sure if I’m working with FileField properly etc) :

  from moviepy.editor import *
  
  def ClipDownload(request,pk,*args,**kwargs):
  
  
  
      this_clip = models.Clip.objects.filter(pk=pk)
  
      file_name = this_clip[0].game_id.wide
  
  
  
      p = VideoFileClip(file_name,audio=False).subclip(this_clip.clipstart,this_clip.clipend)
  
  
  
      response = HttpResponse(p, content_type='application/force-download')
  
      response['Content-Disposition'] = 'attachment; filename=%s' % this_clip.name
  
      response['Content-Length'] = os.path.getsize(file_name)
  
      return response

  The current code is not working, I’m getting the proper Clip but I’m not able to make a subclip of the FileField as I’m getting an attribute error :

  AttributeError: 'FieldFile' object has no attribute 'endswith'

  I would be very appreciative if someone can point me in the right direction to get the file downloading so I can move on to trying to incorporate it into celery ?

• CMake on Ubuntu, Requested 'libavdevice' >= 56.4.100 but version of libavdevice is 53.2.0

  5 mars 2019, par user1830386

  I am trying to get into plug in writing for Gazebo but keep running into an error when compiling my programs.

  Requested 'libavdevice >= 56.4.100' but version of libavdevice is 53.2.0
  
  CMake Error at /usr/share/cmake- 
  
  3.10/Modules/FindPackageHandleStandardArgs.cmake:137 (message):
  
  Could NOT find AVDEVICE (missing: AVDEVICE_FOUND) (Required is at least
  
  version "56.4.100")

  but when I do ffmpeg -version I get :

   libavdevice    57. 10.100 / 57. 10.100

  Yet CMake seems to think I’m on version 53. Trying to update ffmpeg or libavdevice-dev returns that I am on the latest version.

  Here is my make file :

  cmake_minimum_required(VERSION 2.8 FATAL_ERROR)
  
  
  
  find_package(gazebo REQUIRED)
  
  include_directories(${GAZEBO_INCLUDE_DIRS})
  
  link_directories(${GAZEBO_LIBRARY_DIRS})
  
  list(APPEND CMAKE_CXX_FLAGS "${GAZEBO_CXX_FLAGS}")
  
  
  
  add_library(model_control SHARED model_control.cc)
  
  target_link_libraries(model_control ${GAZEBO_LIBRARIES})
  
  
  
  list(APPEND CMAKE_CXX_FLAGS "${GAZEBO_CXX_FLAGS}")

  and the cc file :

  #include <functional>
  
  #include <gazebo></gazebo>gazebo.hh>
  
  #include <gazebo></gazebo>physics/physics.hh>
  
  #include <gazebo></gazebo>common/common.hh>
  
  #include <ignition></ignition>math/Vector3.hh>
  
  
  
  namespace gazebo
  
  {
  
    class ModelPush : public ModelPlugin
  
    {
  
      public: void Load(physics::ModelPtr _parent, sdf::ElementPtr /*_sdf*/)
  
      {
  
        // Store the pointer to the model
  
        this->model = _parent;
  
  
  
        // Listen to the update event. This event is broadcast every
  
        // simulation iteration.
  
        this->updateConnection = event::Events::ConnectWorldUpdateBegin(
  
            std::bind(&amp;ModelPush::OnUpdate, this));
  
      }
  
  
  
      // Called by the world update start event
  
      public: void OnUpdate()
  
      {
  
        // Apply a small linear velocity to the model.
  
        this->model->SetLinearVel(ignition::math::Vector3d(.3, 0, 0));
  
      }
  
  
  
      // Pointer to the model
  
      private: physics::ModelPtr model;
  
  
  
      // Pointer to the update event connection
  
      private: event::ConnectionPtr updateConnection;
  
    };
  
  
  
    // Register this plugin with the simulator
  
    GZ_REGISTER_MODEL_PLUGIN(ModelPush)
  
  }
  
  </functional>

  Thanks !

• handling subprocess file output

  14 janvier 2019, par Sandip Kumar

  I am working on a project in which at some point user uploads a video and in backend i have to generate thumbnail for that video. I preferred ffmpeg for this purpose and the system is in django environment.
  This is my view function

  def upload(request):
  
      if request.method == 'POST':
  
          form = DocumentForm(request.POST, request.FILES)
  
          if form.is_valid():
  
              newdoc = Document(docfile=request.FILES['docfile'])
  
              filename = str(request.FILES['docfile'].name)
  
              newdoc.save()
  
              op = subprocess.call(['ffmpeg', '-i',"media/private/"+up, '-ss', '00:00:03.000', '-vframes', '1', 'abc.jpg']) // Generates thumbnail
  
              newdoc.thumbnail = op
  
              newdoc.save()
  
              return HttpResponseRedirect(reverse('list'))
  
      else:
  
          form = DocumentForm()

  The Document has the thumbnail field. I know that subprocess.call() returns returncode not any object so using op variable is useless. So my query is how do i save generated thumbnail in model.