Moving-picture encoding apparatus and moving-picture decoding apparatus
According to one embodiment, an encoding apparatus includes a prediction unit, a classifying unit, a first transformer, a second transformer, an order controller, and an entropy coder. The prediction unit obtains a predictive residual signal to be encoded, by using a mode selected from intra-prediction modes. The first transformer obtains first transformation coefficients by subjecting the signal to an orthogonal transformation by use of a first transformation basis if the selected mode is classified into a mode having a prediction direction. The first transformation basis is preset so that a coefficient density after the orthogonal transformation is higher than a coefficient density.
1. A moving-picture decoding apparatus, comprising:
an entropy decoder configured to obtain a prediction mode and transformation coefficients from coded data;
an intra-prediction image generator configured to generate a prediction image signal according to the prediction mode;
a classifying unit configured to classify the prediction mode into a first prediction mode preset in intra-prediction modes or a second prediction mode preset in the intra-prediction modes;
an order controller configured to rearrange the transformation coefficients according to scanning order corresponding to the prediction mode from among scanning orders predetermined for intra-prediction modes;
a first inverse orthogonal transformer configured to obtain a predictive residual signal by subjecting the rearranged transformation coefficients to an inverse orthogonal transformation by use of a first transformation basis if the prediction mode is classified into the first prediction mode;
a second inverse orthogonal transformer configured to obtain a predictive residual signal in the second prediction mode by subjecting the rearranged transformation coefficients to the inverse orthogonal transformation by use of a second transformation basis different from the first transformation basis if the prediction mode is classified into the second prediction mode; and
an adder configured to add the predictive residual signal and the prediction image signal, thereby generating a decoded image signal.
2. The apparatus according to claim 1 , wherein the order controller rearranges the transformation coefficients according to scanning order corresponding to information about a prediction direction for intra-prediction indicated by the prediction mode.
3. The apparatus according to claim 2 , wherein the order controller rearranges the transformation coefficients according to scanning order corresponding to a horizontal direction from among the scanning orders if the prediction direction for the intra-prediction indicated by the prediction mode corresponds to horizontal prediction.
4. The apparatus according to claim 2 , wherein the order controller rearranges the transformation coefficients according to scanning order corresponding to a vertical direction from among the scanning orders if the prediction direction for the intra-prediction indicated by the prediction mode corresponds to vertical prediction.
5. The apparatus according to claim 1 , wherein the prediction mode includes information about a block size.
6. The apparatus according to claim 1 , wherein the prediction mode includes information about luminance and color-difference.
7. The apparatus according to claim 1 , wherein the inverse orthogonal transformation performed by the second inverse orthogonal transformer is an inverse discrete cosine transformation.
8. The apparatus according to claim 1 , wherein the second inverse orthogonal transformer uses the second transformation basis if an inter-prediction is performed.
9. A moving-picture decoding method, comprising:
obtaining a prediction mode and transformation coefficients from coded data;
generating a prediction image signal according to the prediction mode;
classifying the prediction mode into a first prediction mode preset in intra-prediction modes or a second prediction mode preset in the intra-prediction modes;
rearranging the transformation coefficients according to scanning order corresponding to the prediction mode from among scanning orders predetermined for intra-prediction modes;
obtaining a predictive residual signal by subjecting the rearranged transformation coefficients to an inverse orthogonal transformation by use of a first transformation basis if the prediction mode is classified into the first prediction mode;
obtaining a predictive residual signal in the second prediction mode by subjecting the rearranged transformation coefficients to the inverse orthogonal transformation by use of a second transformation basis different from the first transformation basis if the prediction mode is classified into the second prediction mode; and
adding the predictive residual signal and the prediction image signal, thereby generating a decoded image signal.