Patent ID: 8155203

Claim:
The method for transcoding a data stream containing at least one coded digitized image, comprising: converting an input data stream of first intra-blocks coded using H.264 into an output data stream of second intra-blocks coded using H.263, where the first intra-blocks are each coded in a first prediction mode among a plurality of first intra-prediction modes in a local area and the second intra-blocks are each coded in a second prediction mode among a plurality of second intra-prediction modes, different from the first intra-prediction modes, in a frequency domain; and determining the second intra-prediction modes based on the first intra-prediction modes prior to selecting the second prediction mode used in coding the second intra-blocks by assigning, if a macro block is coded in H.264 using INTRA16 prediction mode HOR, the INTRA16 prediction mode HOR to corresponding four pixel blocks in H.263; assigning, if the macro block is coded in H.264 using INTRA16 prediction mode DC or PLANE, the INTRA16 prediction mode DC to the corresponding four pixel blocks in H.263; assigning, if the macro block is coded in H.264 using INTRA16 prediction mode VERT, the INTRA16 prediction mode VERT to the corresponding four pixel blocks in H.263; and determining, if pixel blocks of the macro block are coded in H.264 using INTRA4 prediction modes, a frequency of macro block prediction modes in the macro block and assigning the second prediction modes as a function of a most frequently occurring one of the macro block prediction modes as follows assigning, if one of INTRA4 prediction modes HOR and HorU occurs most frequently, the INTRA4 prediction mode HOR to corresponding four pixel blocks of the macro block in H.263; assigning, if one of INTRA4 prediction modes DC, HorD, VerR and DiagDR occurs most frequently, the INTRA4 prediction mode DC to the corresponding four pixel blocks of the macro block in H.263; and assigning, if one of INTRA4 prediction modes DiagDL, VERT or VerL occurs most frequently, the intra-prediction mode VERT to the corresponding four pixel blocks of the macro block in H.263.