Video encoding apparatus and method, video encoding program, and storage medium which stores the program

Abstract

A video encoding apparatus and a corresponding method for applying orthogonal transformation to a prediction error signal between a video signal of an encoding target area and a predicted signal for the video signal, and quantizing an obtained orthogonal transformation coefficient by using a preset quantization step size so as to encode the coefficient. A prediction error power which is a power of the prediction error signal is computed. For input information such as the computed prediction error power, the preset quantization step size, and an upper limit of an amount of code generated for the encoding target area, it is determined whether or not an amount of code generated when performing quantization using the preset quantization step size exceeds the upper limit. An encoding process is changed based on a result of the determination.

The invention claimed is:  
     
       1. A video encoding apparatus for applying orthogonal transformation to a prediction error signal between a video signal of an encoding target area and a predicted signal for the video signal, and quantizing an obtained orthogonal transformation coefficient by using a preset quantization step size so as to encode the coefficient, the apparatus comprising:
 a determination circuit that receives information indicative of a prediction error power, the preset quantization step size, and an upper limit of an amount of code generated for the encoding target area, and determines whether or not an amount of code generated when performing quantization using the preset quantization step size exceeds the upper limit; and 
 a change circuit that changes an encoding process based on a result of the determination by the determination circuit, 
 wherein the determination circuit applies a permissive power for the prediction error power based on the upper limit and the preset quantization step size, and compares the permissive power with the prediction error power so as to determine whether or not the amount of code generated when performing the quantization using the preset quantization step size exceeds the upper limit. 
 
     
     
       2. The video encoding apparatus in accordance with  claim 1 , wherein:
 the determination circuit applies the permissive power for the prediction error power by setting variables of a function, which are the upper limit and the quantization step size, to the values of the upper limit and the quantization step size, where the value of the function is the permissive power. 
 
     
     
       3. The video encoding apparatus in accordance with  claim 1 , wherein:
 the determination circuit applies the permissive power for the prediction error power by referring to a table in which a relationship between data values of the upper limit, the quantization step size, and the permissive power is defined. 
 
     
     
       4. A non-transitory computer-readable storage medium which stores a video encoding program by which a computer executes an operation for implementing the video encoding apparatus in accordance with  claim 1 . 
     
     
       5. A video encoding method for applying orthogonal transformation to a prediction error signal between a video signal of an encoding target area and a predicted signal for the video signal, and quantizing an obtained orthogonal transformation coefficient by using a preset quantization step size so as to encode the coefficient, the method comprising:
 a determination step that receives information indicative of a prediction error power, the preset quantization step size, and an upper limit of an amount of code generated for the encoding target area, and determines whether or not an amount of code generated when performing quantization using the preset quantization step size exceeds the upper limit; and 
 a change step that changes an encoding process based on a result of the determination, 
 wherein the determination step applies a permissive power for the prediction error power based on the upper limit and the preset quantization step size, and compares the permissive power with the prediction error power so as to determine whether or not the amount of code generated when performing the quantization using the preset quantization step size exceeds the upper limit.