Method and device for sharing MPEG frame buffers

Abstract

A method and device for sharing MPEG frame buffers utilizes a shared bidirectional frame buffer, which is used for temporarily storing bidirectional predicted pictures, to reduce the quantity of bidirectional frame buffers. And, through monitoring and controlling the displaying units and the decoding units, the method and device avoids the decoded image data overwriting the image data, which has not yet been displayed, in the shared bidirectional frame buffer.

1 . A device for sharing MPEG buffer comprising: 
 a bidirectional frame buffer providing successive a first bidirectional frame and a second bidirectional frame with storing temporary data for writing during decoding and reading during displaying;    a display unit coupled with said bidirectional frame, said display unit sequentially reads said first bi-directional frame and said second bidirectional frame; and    a decoding unit coupled with said bi-directional frame, said decoding unit sequentially writes said first bidirectional frame and said second bidirectional frame, wherein said decoding unit writes said second bi-directional frame into a position in a storing unit, wherein said position is previously occupied by said first bi-directional frame that has been readout by said display unit.    
   
   
       2 . The device according to  claim 1 , wherein said decoding unit writes a plurality of bottom field row of said second bidirectional frame into a position that is previously occupied by a plurality of top field row of said first bidirectional frame.  
   
   
       3 . The device according to  claim 1 , wherein said decoding unit writes a plurality of top field row of said second bidirectional frame in a position that is previously occupied by a plurality of first half frame row of said first bidirectional frame.  
   
   
       4 . The device according to  claim 1 , wherein said decoding unit writes a plurality of bottom field row of said second bidirectional frame in a position that is previously occupied by a plurality of first half frame row of said first bidirectional frame.  
   
   
       5 . The device according to  claim 1 , wherein said display unit reads a position being corresponding to a specific position where said second bi-directional frame is stored in said storing unit.  
   
   
       6 . The device according to  claim 5 , wherein said decoding unit writes a plurality of frame row of said second bi-directional frame into a corresponding position that is previously occupied by both a plurality of top field row and a plurality of bottom field row of said first bi-directional frame that have readout by said display unit.  
   
   
       7 . The device according to  claim 5 , wherein said decoding unit writes a plurality of top field row of said second bi-directional frame into a corresponding position that is previously occupied by a plurality of top field row of said first bidirectional frame that has readout by said display unit.  
   
   
       8 . The device according to  claim 5 , wherein said decoding unit writes a plurality of bottom field row of said second bi-directional frame into a corresponding position that is previously occupied by a plurality of bottom field row of said first bidirectional frame that has readout by said display unit.  
   
   
       9 . The device according to  claim 5 , wherein said decoding unit writes a plurality of frame row of said second bidirectional frame into a corresponding position that is previously occupied by a plurality of frame row of said first bidirectional frame that has readout by said display unit.  
   
   
       10 . The device according to  claim 5 , wherein said decoding unit writes a plurality of top field row of said second bidirectional frame into a corresponding position that is previously occupied by a plurality of frame row of said first bi-directional frame that has readout by said display unit.  
   
   
       11 . The device according to  claim 5 , wherein said decoding unit writes a plurality of bottom field row of said second bi-directional frame into a corresponding position that is previously occupied by a plurality of frame row of said first bidirectional frame that has readout by said display unit.  
   
   
       12 . The device according to  claim 1  further comprising a forward reference buffer and a backward reference buffer, wherein said forward reference buffer is for storing a forward reference frame and said backward reference buffer is for storing a backward reference frame.  
   
   
       13 . A method for sharing MPEG buffer comprising: 
 storing a first bidirectional frame and a second bi-directional frame in a storage device; and    writing a plurality of row of said second bidirectional frame into a position that is previously occupied by a plurality of row of said first bidirectional frame that has been readout.    
   
   
       14 . The method according to  claim 13 , when frame display and first bottom field and second top field image data (FBST) structure are currently applied, said writing step comprising writing a plurality of bottom field row of said second bidirectional frame into a position that is previously occupied by a plurality of top field row of said first bidirectional frame that has been readout.  
   
   
       15 . The method according to  claim 13 , when frame display and first top field and second bottom field image data (FTSB) structure are currently applied, said writing step comprising writing a plurality of top field row of said second bi-directional frame into a position that is previously occupied by a plurality of frame row of first half of said first bidirectional frame that has been readout.  
   
   
       16 . The method according to  claim 13 , when frame display and first bottom field and second top field image data (FBST) structure are currently applied, said writing step comprising writing a plurality of bottom field row of said second bi-directional frame into a position that is previously occupied by a plurality of frame row of first half of said first bi-directional frame that has been readout.  
   
   
       17 . The method according to  claim 13 , wherein a position of read said first bidirectional frames is corresponding to a position of said storage device where said second bidirectional frame is stored.  
   
   
       18 . The method according to  claim 17 , when field display and frame structure are applied, said writing step comprising writing a plurality of frame row of said second bidirectional frame into a corresponding position that is previously occupied by a plurality of top field row and a plurality of bottom field row of said first bidirectional frame that has readout.  
   
   
       19 . The method according to  claim 17 , when field display and first top and second bottom field image data (FTSB) structure are applied, said writing step comprising writing a plurality of top field row of said second bidirectional frame into a corresponding position that is previously occupied by a plurality of top field row of said first bi-directional frame that has readout.  
   
   
       20 . The method according to  claim 17 , when field display and first bottom field and second top field image data (FBST) structure are applied, said writing step comprising writing a plurality of bottom field row of said second bidirectional frame into a corresponding position that is previously occupied by a plurality of bottom field row of said first bidirectional frame that has readout.  
   
   
       21 . The method according to  claim 17 , when frame display and frame structure are applied, said writing step comprising writing a plurality of frame row of said second bidirectional frame into a corresponding position that is previously occupied by a plurality of frame row of said first bidirectional frame that has readout.  
   
   
       22 . The method according to  claim 17 , when frame display and first top field and second bottom field image data (FTSB) structure are applied, said writing step comprising writing a plurality of top field row of said second bi-directional frame into a corresponding position that is previously occupied by a plurality of frame row of said first bidirectional frame that has readout.  
   
   
       23 . The method according to  claim 17 , when frame display and first bottom field and second top field image data (FBST) structure are applied, said writing step comprising writing a plurality of bottom field row of said second bidirectional frame into a corresponding position that is previously occupied by a plurality of frame row of said first bidirectional frame that has readout.