Method and apparatus for encoding video pictures, and method and apparatus for decoding video pictures
The H.264 standard has introduced a new coding method for intra-coded pictures, which is named “intra prediction”. The basic idea of intra prediction is to predict a block using reconstructed neighbour pixels. Thus, only the residual information needs to be encoded. Scalable video coding adds some scalable extension to H.264, in terms of spatial, temporal and SNR scalability. An improved encoding method for scalable video comprises generating from a video picture a first and a second picture with higher resolution than the first picture, wherein each macroblock in the first picture has a plurality of corresponding macroblocks in the second picture, intra-coding the first picture on macroblock level, wherein for each macroblock a prediction direction is determined, generating a first residual picture, intra-coding the second picture on macroblock level, wherein for each macroblock the prediction direction of the corresponding macroblock of the first picture is reused, and generating a second residual picture.
1. Method for encoding video pictures using an encoder, the method comprising the steps of
generating from a video picture a first and a second picture, wherein the second picture has a higher resolution than the first picture and each macroblock in the first picture has a plurality of corresponding macroblocks in the second picture;
intra-coding the first picture on macroblock level, wherein macroblocks are intra predicted and for a first intra predicted macroblock an intra prediction direction is determined; and
intra-coding the second picture on macroblock level, wherein for macroblocks corresponding to said first macroblock, instead of determining the intra prediction direction, the intra prediction direction of the first macroblock of the first picture is reused, wherein no intra prediction direction search is performed for the macroblocks that correspond to said first macroblock, and wherein intra-coding of a picture on macroblock level comprises the steps of
defining a plurality of subblocks of a macroblock;
selecting a first subblock from the defined subblocks or from subblocks of a neighboring macroblock;
defining a prediction direction within the macroblock;
performing a prediction for a second subblock within the macroblock using the selected first subblock and the prediction direction; and
generating residual information, the residual information being the difference between the predicted subblock and the actual second subblock.
2. Method according to claim 1 , wherein the intra prediction direction is scaled according to the resolution difference between the first and the second picture.
3. Method according to claim 1 , further comprising the steps of
generating a first residual picture being the difference between the first picture and the intra-coded first picture; and
generating a second residual picture being the difference between the second picture and the intra-coded second picture.
4. Method for decoding video pictures, the method comprising the steps of
decoding an encoded first video picture, wherein the encoded first video picture is intra-coded and contains encoded macroblocks, and for each encoded macroblock prediction direction information and residual information;
decoding an encoded second video picture, wherein the encoded second video picture also contains encoded macroblocks, and wherein the decoding of the encoded second video picture comprises steps of
extracting from the encoded second video data first macroblock data including first subblock data and first residual update data;
extracting from the encoded first video picture first prediction direction data referring to the first macroblock data;
decoding a first subblock of the first macroblock from the encoded first macroblock data;
predicting from the first subblock and the first prediction information a second subblock of the first macroblock, wherein no further directional information is added to the prediction direction information; and
updating the predicted second subblocks of the first macroblock with the extracted first residual update data.
5. Method according to claim 4 , wherein the intra prediction direction information is scaled according to the resolution difference between the first and the second picture.