Method and apparatus for vc-1 to mpeg-2 video transcoding

Abstract

A method for transcoding from a VC-1 format to an MPEG-2 format is disclosed. The method generally comprises the steps of (A) decoding an input video stream in the VC-1 format to generate a picture; (B) determining a first mode indicator for the picture; and (C) coding the picture into an output video stream in the MPEG-2 format using one of (i) an MPEG-2 field mode coding and (ii) an MPEG-2 frame mode coding as determined from the first mode indicator.

1 . A method for transcoding from a VC-1 format to an MPEG-2 format, comprising the steps of:
 (A) decoding an input video stream in said VC-1 format to generate a picture having a plurality of macroblocks;   (B) combine a plurality of macroblocks having a first partition into a second partition larger than said first partition; and   (C) coding said picture into an output video stream in said MPEG-2 format using said second partition.   
     
     
         2 . The method according to  claim 1 , wherein step (B) comprises the sub-step of:
 combining said macroblocks having an 8×8 partition with a VC-1 frame mode into a 16×16 partition with an MPEG-2 frame mode.   
     
     
         3 . The method according to  claim 1 , wherein step (B) comprises the sub-step of:
 combining said macroblocks having an 8×8 partition with a VC-1 field mode into a 16×8 partition with an MPEG-2 field mode.   
     
     
         4 . The method according to  claim 1 , further comprising the step of:
 combining a plurality of VC-1 motion vectors from a VC-1 macroblock partition in said picture to generate a seed motion vector for an MPEG-2 partition.   
     
     
         5 . The method according to  claim 4 , further comprising the step of:
 using said seed motion vector as a motion compensation center for an MPEG-2 motion vector.   
     
     
         6 . The method according to  claim 4 , wherein the step of said combining said VC-1 motion vectors comprises the sub-step of:
 calculating a median among said VC-1 motion vectors for each of said second partitions to generate a respective MPEG-2 motion vector for each of said second partitions.   
     
     
         7 . The method according to  claim 6 , wherein said median comprises one of (i) a vector median and (ii) a vertical median and a horizontal median. 
     
     
         8 . The method according to  claim 4 , wherein the step of said combining said VC-1 motion vectors comprises the sub-step of:
 utilizing one of said VC-1 motion vectors occupying a largest area within each of said second partitions to generate a respective MPEG-2 motion vector for each of said second partitions.   
     
     
         9 . A method for transcoding from a VC-1 format to an MPEG-2 format, comprising the steps of:
 (A) decoding an input video stream in said VC-1 format to generate a picture;   (B) determining that said picture had a VC-1 picture adaptive field/frame coding in said input video stream; and   (C) coding said picture into an output video stream in said MPEG-2 format using an MPEG-2 frame mode coding.   
     
     
         10 . The method according to  claim 9 , further comprising the step of:
 determining a VC-1 scan order for said picture, wherein said coding of said picture into said output video stream is seeded using said VC-1 scan order.   
     
     
         11 . The method according to  claim 9 , further comprising the step of:
 determining a VC-1 motion compensation mode for each of a plurality of macroblocks of said picture in said input video stream, wherein said coding of said picture into said output video stream uses an MPEG-2 motion compensation mode for each of said macroblocks in said output video stream based on a respective one of said VC-1 motion compensation modes.   
     
     
         12 . The method according to  claim 9 , further comprising the step of:
 calculating a plurality of seed motion vectors from a plurality of VC-1 motion vectors of said picture.   
     
     
         13 . The method according to  claim 12 , further comprising the step of:
 using said seed motion vectors as a plurality of motion compensation centers for a plurality of MPEG-2 motion vectors.