Source Code for Module advene.model.core.media

  1  """ 
  2  I define the class of medias. 
  3  """ 
  4   
  5  from advene.model.consts import ADVENE_NS_PREFIX 
  6  from advene.model.core.element import PackageElement, MEDIA 
  7  from advene.util.autoproperty import autoproperty 
  8   
  9  FOREF_PREFIX = "%s%s" % (ADVENE_NS_PREFIX, "frame_of_reference/") 
 10  DEFAULT_FOREF = FOREF_PREFIX + "ms;o=0" 
 11   
 12 -class Media(PackageElement): 
 13   
 14      ADVENE_TYPE = MEDIA 
 15   
 16      # attributes that do not prevent medias to be volatile 
 17      _url = None 
 18      _frame_of_reference = None 
 19      _unit = None 
 20      _origin = None 
 21   
 22      @classmethod 
 23 -    def instantiate(cls, owner, id, url, frame_of_reference, *args): 
 24          r = super(Media, cls).instantiate(owner, id, *args) 
 25          r._url = url 
 26          r._frame_of_reference = frame_of_reference 
 27          r._update_unit_and_origin() 
 28          return r 
 29   
 30      @classmethod 
 31 -    def create_new(cls, owner, id, url, frame_of_reference, *a): 
 32          owner._backend.create_media(owner._id, id, url, frame_of_reference) 
 33          r = cls.instantiate(owner, id, url, frame_of_reference) 
 34          return r 
 35   
 36      @autoproperty 
 37 -    def _get_url(self): 
 38          """ 
 39          The URL from which the media can be fetched. 
 40          """ 
 41          return self._url 
 42   
 43      @autoproperty 
 44 -    def _set_url(self, url): 
 45          self.emit("pre-modified::url", "url", url) 
 46          self._url = url 
 47          self.__store() 
 48          self.emit("modified::url", "url", url) 
 49   
 50      @autoproperty 
 51 -    def _get_frame_of_reference(self): 
 52          return self._frame_of_reference 
 53   
 54      @autoproperty 
 55 -    def _set_frame_of_reference(self, frame_of_reference): 
 56          self.emit("pre-modified::frame_of_reference", 
 57                    "frame_of_reference", frame_of_reference) 
 58          self._frame_of_reference = frame_of_reference 
 59          self.__store() 
 60          self._update_unit_and_origin() 
 61          self.emit("modified::frame_of_reference", 
 62                    "frame_of_reference", frame_of_reference) 
 63   
 64      @autoproperty 
 65 -    def _get_unit(self): 
 66          """The time-unit of this media if known, else None. 
 67   
 68          The unit is known if the frame of reference is in the default Advene 
 69          namespace. 
 70   
 71          NB: this is specific to the cinelab application model. 
 72          """ 
 73          return self._unit 
 74   
 75      @autoproperty 
 76 -    def _get_origin(self): 
 77          """The time-origin of this media if known, else None. 
 78   
 79          The origin is known if the frame of reference is in the default Advene 
 80          namespace. 
 81   
 82          NB: this is specific to the cinelab application model. 
 83          """ 
 84          return self._origin 
 85   
 86 -    def _update_unit_and_origin(self): 
 87          foref = self._frame_of_reference 
 88          if foref.startswith(FOREF_PREFIX): 
 89              foref = foref[len(FOREF_PREFIX):] 
 90              self._unit, params = foref.split(";") 
 91              params = dict( i.split("=") for i in params.split("&") ) 
 92              self._origin = params.get("o", 0) 
 93          else: 
 94              self._unit = None 
 95              self._origin = None 
 96           
 97   
 98 -    def __store(self): 
 99          o = self._owner 
100          o._backend.update_media(o._id, self.id, self._url, 
101                                  self._frame_of_reference) 
102