Apparatus, method, and computer program for image encoding with intra-mode prediction
An image encoding apparatus includes: a prediction preparing section which prepares a prediction for each intra-prediction mode by using at least ones of pixel signals of pixels lined horizontally in an upper end of an encoding target block and pixel signals of pixels lined vertically in a left end of the encoding target block among pixel signals of the encoding target block; and a prediction mode derivation section which execute an intra-prediction operation by using an image of the encoding target block in an encoding target image and the prediction prepared by the prediction preparing section.
1. An image encoding apparatus comprising:
a processor configured to
prepare a prediction for each of a plurality of intra-prediction modes of an encoding target block by using at least one of pixel signals of pixels of the encoding target block lined horizontally in an upper end of the encoding target block and pixel signals of pixels of the encoding target block lined vertically in a left end of the encoding target block; and
execute an intra-prediction operation of the encoding target block by using an image of the encoding target block in an encoding target image and the prepared prediction,
wherein
when the preparing step uses pixel signals of the pixels of the encoding target block lined horizontally in the upper end of the encoding target block, the preparing step prepares the prediction by further using pixel signals of pixels lined vertically in a right end of a block adjacent to a left side of the encoding target block in the encoding target image, and
when the preparing step uses pixel signals of the pixels of the encoding target block lined vertically in the left end of the encoding target block, the preparing step prepares the prediction by further using pixel signals of pixels lined horizontally in a lower end of a block adjacent to an upper side of the encoding target block in the encoding target image.
2. The image encoding apparatus according to claim 1 , wherein depending on a direction of processing order of a macroblock formed by one or more encoding target blocks, the preparing step uses the pixel signals of the pixels of the encoding target block lined horizontally in the upper end of the encoding target block or the pixel signals of the pixels of the encoding target block lined vertically in the left end of the encoding target block.
3. The image encoding apparatus according to claim 2 , wherein
when the direction of the processing order of the macroblock is horizontal, the preparing step uses the pixel signals of the pixels of the encoding target block lined horizontally in the upper end of the encoding target block in the intra-prediction operation of the encoding target block in the macroblock, and
when the direction of the processing order of the macroblock is vertical, the preparing step uses the pixel signals of the pixels of the encoding target block lined vertically in the left end of the encoding target block in the intra-prediction operation of the encoding target block in the macroblock.
4. The image encoding apparatus according to claim 3 , wherein
when the direction of the processing order of the macroblock is horizontal, the preparing step uses the pixel signals of the pixels of the encoding target block lined horizontally in the upper end of the encoding target block in the intra-prediction operation of the encoding target block in an upper end of the macroblock, and
when the direction of the processing order of the macroblock is vertical, the preparing step uses the pixel signals of the pixels of the encoding target block lined vertically in the left end of the encoding target block in the intra-prediction operation of the encoding target block in a left end of the macroblock.
5. The image encoding apparatus according to claim 1 , wherein the executing step comprises:
calculating an encoding cost of each intra-prediction mode for the encoding target block by using the encoding target image and an encoded image, and
setting a mode with the smallest encoding cost as a selected intra-prediction mode of the encoding target block.
6. The image encoding apparatus according to claim 5 , wherein
when the preparing step uses one of the pixel signals of the pixels of the encoding target block lined horizontally in the upper end of the encoding target block and the pixel signals of the pixels of the encoding target block lined vertically in the left end of the encoding target block, the preparing step prepares the prediction by using the pixel signals and pixel signals adjacent to the encoding target block in the encoding target image, and
the executing step calculates the encoding cost by performing an offset adding operation in accordance with the prediction mode where the pixels of the encoding target block are used.
7. The image encoding apparatus according to claim 1 , wherein the intra-prediction operation related to one or more encoding target blocks forming a macroblock is performed in parallel.
8. An image encoding method comprising:
preparing a prediction for each of a plurality of intra-prediction modes of an encoding target block by using at least one of pixel signals of pixels of the encoding target block lined horizontally in an upper end of the encoding target block and pixel signals of pixels of the encoding target block lined vertically in a left end of the encoding target block; and
executing an intra-prediction operation of the encoding target block by using an image of the encoding target block in an encoding target image and the prepared prediction,
wherein
when the preparing step uses the pixel signals of the pixels of the encoding target block lined horizontally in the upper end of the encoding target block, the preparing step prepares the prediction by further using pixel signals of pixels lined vertically in a right end of a block adjacent to a left side of the encoding target block in the encoding target image, and
when the preparing step uses the pixel signals of the pixels of the encoding target block lined vertically in the left end of the encoding target block, the preparing step prepares the prediction by further using pixel signals of pixels lined horizontally in a lower end of a block adjacent to an upper side of the encoding target block in the encoding target image.
9. A non-transitory computer readable medium having computer readable instructions thereon that when executed by a computer cause the computer to perform an image encoding method comprising:
preparing a prediction for each of a plurality of intra-prediction modes of an encoding target block by using at least one of pixel signals of pixels of the encoding target block lined horizontally in an upper end of an encoding target block and pixel signals of pixels of the encoding target block lined vertically in a left end of the encoding target block among pixel signals of the encoding target block; and
executing an intra-prediction operation of the encoding target block by using an image of the encoding target block in an encoding target image and the prepared prediction
wherein
when the preparing step uses the pixel signals of the pixels of the encoding target block lined horizontally in the upper end of the encoding target block, the preparing step prepares the prediction by further using pixel signals of pixels lined vertically in a right end of a block adjacent to a left side of the encoding target block in the encoding target image, and
when the preparing step uses the pixel signals of the pixels of the encoding target block lined vertically in the left end of the encoding target block, the preparing step prepares the prediction by further using pixel signals of pixels lined horizontally in a lower end of a block adjacent to an upper side of the encoding target block in the encoding target image.