Abstract:
The invention relates to a method of linking metadata to a data stream, the data stream having time-based navigation data and play list data, the play list data being indicative of play items of one or more play lists, the time-based navigation data mapping play items to the data stream, the method including the steps of: using the time-based navigation data for mapping of metadata to the play items, storing a metadata link being descriptive of the mapping of the metadata to the play items.

Description:
FIELD OF THE INVENTION  
       [0001]     The invention relates to the field of storage and transmission of packetized data, and more particularly to the linking of metadata to a data stream.  
       BACKGROUND OF THE INVENTION  
       [0002]     Streaming is a technology which is used for storing, transmitting, and broadcasting of packetized digital data, e.g. for audio and video broadcasting services. Often additional information is provided as an added value accompanying the audio and video data stream. For example, video summaries, story boards, cast background information, advertisement etc. are transmitted together with the streaming media as so-called metadata.  
         [0003]     When recording such a broadcast audio and video (AV) data stream together with metadata on storage media like Blue-ray Disc (BD) it becomes necessary to link the metadata to the AV stream. This is also true for manually added metadata. As an example, a user may want to link a short biography about James Dean pulled from the internet to the AV of the movie “East of Eden”. The link may be desirable to point to a special scene within the movie when James Dean is starting the car race ending at the cliffs.  
         [0004]     The linking of metadata to a data stream is as such known from the prior art.  
       SUMMARY OF THE INVENTION  
       [0005]     However, metadata and data streams are often stored independently and on different storage media. When a prior art data stream is edited the linkage of the metadata to the data stream is thus easily lost and the metadata might become unusable due to the editing operation. There is therefore a need to provide an improved method of linking of metadata to a data stream.  
         [0006]     The invention provides for a method of linking metadata to a data stream which relies on time-based navigation data associated to the data stream as a reference for mapping the metadata to the data stream. The advantage of this approach is that the original time-based navigation data which is referenced by the meta data remains unchanged and allows for a meaningful change detection and even adaptation when a PlayList containing the program data items or the stream data itself are edited. This way the original assignment of metadata to PlayList items is preserved and survives the editing operation.  
         [0007]     In accordance with a preferred embodiment of the invention system time clock (STC) clip file navigation data is used as the time-based navigation data for the mapping of the metadata. STC clip file information is data concerning the number, start and position of the monotonous system time clock sequences of the data stream. The entirety of the navigation information is often referred to as ‘clip’ or ‘clip information’ which comprises the STC sequence information and various other layers of navigation information such as program information and arrival time clock (ATC) sequence information.  
         [0008]     In accordance with a further preferred embodiment of the invention the mapping of the metadata is stored as an XML file. Usage of XML is advantageous as it is a generic format which can be used for various applications and hardware devices.  
         [0009]     A problem to be solved by the invention is to provide improved linking of metadata to a data stream.  
         [0010]     In principle, the inventive method is suited for linking metadata to a data stream, the data stream having time-based navigation data and play list data, the play list data being indicative of play items of one or more play lists, the time-based navigation data mapping play items to the data stream, the method including the steps of: 
        using the time-based navigation data for mapping metadata to the play items,     storing a metadata link being descriptive of the mapping of the metadata to the play items.        
 
         [0013]     In principle the inventive apparatus links metadata to a data stream, the data stream having time-based navigation data and play list data, the play list data being indicative of play items of one or more play lists, the time-based navigation data mapping play items to the data stream, the apparatus including: 
        means for mapping the metadata to the play items, whereby the time-based navigation data is used as a reference for the mapping;     means for generating a metadata link file being descriptive of the mapping of the metadata to the play items.        
 
         [0016]     Advantageous additional embodiments of the invention are disclosed in the respective dependent claims. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0017]     Exemplary embodiments of the invention are described with reference to the accompanying drawings, which show in:  
         [0018]      FIG. 1  Mapping of PlayList items to a data stream and mapping of metadata to the PlayList;  
         [0019]      FIG. 2  Navigation data and a metadata link before editing;  
         [0020]      FIG. 3  The navigation data of  FIG. 2  after editing. 
     
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS  
       [0021]      FIG. 1  shows a data stream  100 . For example data stream  100  is a digital audio and video (AV) stream comprising MPEG compressed packetized data. Data stream  100  includes a sequence of data packets  102 ,  104 ,  106 , . . . , which carry the packetized data. When data stream  100  was received the recording did generate navigation data comprising PlayList  110  and time-based navigation data  108 .  
         [0022]     The time-based navigation data  108  can be organized into various layers such as arrival time clock (ATC) sequence information and system time clock (STC) sequence information. Further data stream  100  has at least one PlayList  110  comprising a number of PlayItems  112 ,  114 ,  116 , . . . . For example, a PlayItem is a recorded program, a recorded song, an advertisement or an other sequence of audio and video data. Each PlayItem of the PlayList  110  is mapped onto data stream  100  for identification of the data packets of data stream  100  belonging to a particular PlayItem by means of time-based navigation data  108  as illustrated in  FIG. 1 . Such mapping technique is as such known from the prior art and used for digital recording on DVR and BD.  
         [0023]     In addition the recorded data stream  100  can contain metadata. This metadata can be extracted from the stream and stored beside it in a database on the recording medium  118 . Another method for metadata generation is automatic or manual generation of metadata.  
         [0024]     A prior art metadata link is referencing on stream data by means of the PlayList navigation data. For assigning a certain time period (range) of a data stream to the metadata, the link stores the number of the PlayList and the start and end time within the PlayList, and playback of the data stream can be started by using this top-layer navigation information.  
         [0025]     In contrast, in accordance with the principles of the invention, metadata  118  is linked to the PlayList  110  by including PlayItem data and time-based navigation data  108  as a reference for the mapping. For example, metadata  118  contains a metadata link which specifies a link range  120  using time-based navigation data  108  as a reference. By means of link range  120  metadata  118  is mapped to the PlayItem range  122  which partly covers PlayItem  112  and PlayItem  116  and completely covers PlayItem  114 .  
         [0026]     Mapping metadata  118  through the intermediary of time-based navigation data  108  to PlayList  110  rather than directly to PlayItems of the PlayList  110  has the advantage that the metadata link information is preserved when PlayList  110  is edited. This is because time-based navigation data  108  remains unchanged when PlayList  110  is edited. The comparison of the metadata link containing the original intermediary of time-based navigation data as a reference against those valid after the stream editing allows for detecting and metadata link adaptation.  
         [0027]      FIG. 2  shows a more detailed example. PlayList# 1  has three play items  200 ,  202  and  204 . PlayList# 1  is identified by universal unique identifier (UUID) uuid# 1  (cf. ISO-11578, ISO/IEC 11578:1996, Information technology—Open Systems Interconnection—Remote Procedure Call (RPC), “UUIDs and GUIDs”, Leach, Paul J., Salz, Paul, Network Working Group—Internet Draft—Feb. 4, 1998 (draft-leach-uuids-guids-01.txt)).  
         [0028]     In the embodiment considered here the STC information of the data stream  206  is used as a time-based navigation data reference. Navigation data clip# 1  contains STC sequences  208  and  210 . Clip# 1  is identified by uuid# 2 . Clip# 2  contains STC sequence  212  and STC sequence  214 . Clip# 2  is identified by uuid# 3 .  
         [0029]     Metadata  218  is assigned to a range of PlayItems within PlayList# 1  by means of metadata link file  220  which belongs to metadata  218 . Metadata link file  220  is an XML file which specifies link range  222 . Link range  222  covers portion  224  of STC sequence  208 , STC sequence  210  and portion  226  of STC sequence  212 . Portion  224  is identified by entry  228  in metadata link file  220 , STC sequence  210  is identified by entry  230  and portion  226  is identified by entry  232 .  
         [0030]      FIG. 3  illustrates the effect of an editing operation by way of example. PlayList# 1  was changed by switching the order of PlayItems  200  and  202  and cutting off PlayItem  204  which now belongs to PlayList# 2 . uuid# 1  has been replaced by new uuid# 1 . 1  and new uuid# 4  has been assigned to PlayList# 2 . In the example the editing of original PlayList# 1  has changed the PlayList only but has left unchanged clip# 1  and clip# 2  as well as metadata  218  and in particular metadata link file  220 . The effect of the editing of the PlayList is that the mapping of the PlayItems onto data stream  206  through time-based navigation data, i.e. clip# 1  and clip# 2  has changed. As metadata link file  220  still contains the complete original link information it can be re-adjusted in accordance with the editing of the PlayList. This re-adjustment is required for entries  230  and  232  in the example considered here. The process of re-adjusting metadata link file  220  can be performed as follows: 
        checking whether reference PlayList UUID is available;     checking whether the clip order is the same;     checking whether the clip parameters are available and have not been modified;     adapting the metadata link file  220  by using all available PlayLists with all parts thereof.          
         [0035]     The result of this re-adjustment process is a new link range  234  as depicted in  FIG. 3 .  
         [0036]     Alternatively, the metadata link file  220  can be used to suggest various alternatives to a user for the re-adjustments.  
         [0037]     A further alternative is the generation of a new and additional PlayList to restore and keep the original PlayList information.