Moving image encoding device

Abstract

A computation unit subtracts a prediction image from an input image. An orthogonal transformation unit applies orthogonal transformation to an output of the computation unit. A quantization unit quantizes an output of the orthogonal transformation unit. An encoding unit encodes an output of the quantization unit. A prediction mode determination unit determines a prediction mode from the input image. The prediction mode is different according to types of an I-picture, a P-picture and a B-picture.

What is claimed is: 
     
         1 . A moving image encoding device comprising:
 a computation unit subtracting a prediction image from an input image;   an orthogonal transformation unit applying orthogonal transformation to an output of the computation unit;   a quantization unit quantizing an output of the orthogonal transformation unit;   an encoding unit encoding an output of the quantization unit; and   a prediction mode determination unit performing an intra-prediction to the input image to determine an intra-prediction mode when the input image is an I-picture, and performing the intra-prediction and an inter- prediction to the input image to determine any one of the intra-prediction mode and an inter-prediction mode when the input image is a P-picture and a B-picture,   wherein the prediction mode determination unit calculates a flat area determination parameter for determining whether each pixel block of the input image is a flat area or not, calculates an offset value based on a threshold determination result of the flat area determination parameter of a block positioned around a coding target block of the input image, and selects and applies a prediction mode of the coding target block based on an evaluation value to which an error between the input image and the prediction image corresponding to the coding target block, header cost integrated with a weighting coefficient, and the offset value are added.   
     
     
         2 . The moving image encoding device according to  claim 1 , wherein the prediction mode determination unit calculates a mode offset value as the offset value, and selects and applies one optimal mode among the intra-prediction modes of the coding target block based on an evaluation value to which the error, the header cost, and the mode offset value are added. 
     
     
         3 . The moving image encoding device according to  claim 1 , wherein the prediction mode determination unit calculates an intra-offset value as the offset value, and selects and applies any one of the intra-prediction mode and the inter-prediction mode of the coding target block based on an evaluation value to which the error, the header cost, and the intra-offset value are added. 
     
     
         4 . The moving image encoding device according to  claim 2 , wherein the prediction mode determination unit performs a threshold determination by using multiple thresholds for the flat area determination parameter of the block positioned around the coding target block of the input image, and changes the mode offset value stepwisely so that the larger the flat area determination parameter is, the larger the mode offset value is set. 
     
     
         5 . The moving image encoding device according to  claim 3 , wherein the prediction mode determination unit performs a threshold determination by using multiple thresholds for the flat area determination parameter of the block positioned around the coding target block of the input image, and changes the intra-offset value stepwisely so that the larger the flat area determination parameter is, the larger the intra-offset value is set.