Method and apparatus for transcoding coded picture signals from object-based coding to block-based coding

A transcoder for transcoding a coded object-based picture signal representing a picture to a coded block-based picture signal representing the picture, the transcoder comprising:

• a culling module that receives the coded object-based picture signal, wherein the object-based picture signal includes, for each of the objects, an object descriptor comprising a coded amplitude descriptor including interior tiles and boundary tiles, and culls therefrom signal portions that represent objects not visible in the picture, signal portions that represent objects that are not present in the picture and signal portions that represent objects that are present in the picture but are hidden to generate a culled object-based picture signal, the culling module additionally includes a tile culling module that culls, from the object-based picture signal, signal portions that represent interior tiles and boundary tiles that are hidden in the picture;
• a picture composer that receives the culled object-based picture signal and partially decodes selected portions thereof to generate blocks of a partially-coded block-based picture signal, the blocks having differing coding states;
• and
• a partial encoder that receives the partially-coded block-based picture signal and encodes the blocks thereof to generate the block-based picture signal in which the blocks have a uniform coding state.

A computer-readable medium in which is fixed a computer program that instructs a computer to perform a transcoding operation in which a coded object-based picture signal representing a picture is transcoded to a coded block-based picture signal representing the picture, the transcoding operation comprising:

• culling, from the coded object-based picture signal, signal portions that represent objects not visible in the picture to generate a culled object-based picture signal wherein the object-based picture signal includes, for each of the objects, an object descriptor comprising a coded amplitude descriptor including interior tiles and boundary tiles, in which culling signal portions that represent objects not visible in the picture includes:
• culling signal portions that represent objects that are not present in the picture;
• and
• culling signal portions that represent objects that are present in the picture, but are hidden includes culling, from the object-based picture signal, signal portions that represent interior tiles and boundary tiles that are hidden in the picture;
• partially decoding portions of the culled object-based picture signal and generating therefrom blocks of a partially-coded block-based picture signal, the blocks having differing coding states;
• and
• re-encoding the partially-coded block-based picture signal to generate the coded block-based picture signal in which the blocks have a uniform coding state.