Data rate conversion

Abstract

A method for converting frame data at a slower rate into field data at a faster rate in a video decoder comprises determining a basic field repetition rate such that a field is repeated an integer number of times in a frame period, calculating a ratio differential of the repetition rate by subtracting from the speed-up ratio of the faster to the slower rate, the ratio of the fields per frame period to the slower rate, comparing the ratio differential with the differential of the field repetition rate and adding or subtracting extra fields when the two are substantially at variance.

What is claimed:  
     
         1 . A method for use in converting input sets of data having an associated input rate into output sets of data, based on the input sets, for use at an associated output rate that differs from the input rate, comprising: 
 receiving at least one stored value indicative of the difference between the input rate and the output rate, performing at least one computation based on the at least one stored value, the result of the computation being used, in generating of the output sets of data, to control the insertion of additional sets of data or the deletion of sets of data.    
     
     
         2 . The method of  claim 1  in which the input sets and the output sets comprise video frames.  
     
     
         3 . The method of  claim 1  in which the input sets are based on compressed digital information.  
     
     
         4 . The method of  claim 3  in which the compressed digital information complies with a data compression standard for video information.  
     
     
         5 . The method of  claim 4  in which the standard comprises MPEG, JPEG, or H.261.  
     
     
         6 . The method of  claim 1  in which the output sets comprise video fields that satisfy a video broadcast standard.  
     
     
         7 . The method of  claim 6  in which the video broadcast standard comprises NTSC, SECAM, or PAL.  
     
     
         8 . The method of  claim 1  in which the input rate is one of 24, 25, or 30 frames per second.  
     
     
         9 . The method of  claim 1  in which the output rate is one of 50 or 60.  
     
     
         10 . The method of  claim 1  in which the at least one computation is based on Breshenham's algorithm.  
     
     
         11 . The method of  claim 1  in which the at least one stored value include a positive incremental value and a negative incremental value.  
     
     
         12 . The method of  claim 1  in which the at least one computation comprises a computation performed with respect to each of the input sets.  
     
     
         13 . The method of  claim 1  in which the insertion or deletion of sets of data occurs at regular intervals.  
     
     
         14 . The method of  claim 1  in which the ratio of the input rate to the output rate may be any arbitrary rate.  
     
     
         15 . The method of  claim 1  further comprising delivering the output sets of data at the output rate.  
     
     
         16 . The method of  claim 1  in which the additional sets of data that are inserted comprise copies of ones of the input sets of data.  
     
     
         17 . A method comprising: 
 receiving a succession of compressed digital video input frames that comply with a digital video standard, the input frames having an associated input frame rate in accordance with the standard,    decompressing the input frames,    using the decompressed input frames to generate a succession of output video frames that comply with a broadcast video standard, the output frames having an associated output frame rate that is different from the input frame rate, and    in connection with the generation of the output video frames performing a computation that controls the insertion of additional frames into the output frames or the deletion of frames from the output frames to achieve the output frame rate.    
     
     
         18 . A method comprising: 
 receiving MPEG video frames having an associated frame rate,    decompressing the MPEG frames,    based on the MPEG frames, generating a sequence of video frames for displaying at a frame rate different from the frame rate associated with the MPEG video frames, by performing a computation that controls insertion of additional frames into the display sequence.    
     
     
         19 . A video decoder associated with a displaying device and comprising stored values indicative of a difference in data set rates between input video data sets received by the decoder and a video data set rate associated with the displaying device, and 
 a logic unit controlled to generate video data sets at the frame rate associated with the displaying device by inserting or deleting data sets based on computations performed using the stored values.    
     
     
         20 . The video decoder of  claim 19  in which the logic unit comprises hardware.