Patent ID: 8396311

Claim:
An image encoding apparatus comprising: a code data generator to transform and quantize an image block to generate code data; a variable length code encoder to encode the code data into bit-string data on the basis of applying variable length encoding; an arithmetic encoder to encode the code data into bit-string data on the basis of converting the code data into binary symbols and applying binary arithmetic encoding; a binary symbol number estimator to estimate the total number of the binary symbols that are converted from the code data generated from a plurality of image blocks of a target picture to be encoded; and an encoding selector to select, for the encoding of the code data, either the variable length code encoder or the arithmetic encoder on the basis of the total number estimated by the binary symbol number estimator, wherein the binary symbol number estimator: obtains, for the plurality of image blocks of the target picture to be encoded, any one of a sum of activities, a sum of standard deviations, or a sum of variances, and estimates the total number of the binary symbols by selecting a larger one of a first value and a second value, the first value is a value obtained by dividing an estimated bin number complexity of the target picture to be encoded by a quantization step size obtained by dividing a product of a picture rate and an average quantizing step size of macro blocks of a lastly encoded picture associated with the same picture type as that of the target picture to be encoded by an assigned picture rate of the target picture to be encoded, wherein the estimated bin number complexity is estimated according to the equation epic_bin_x=α×pic_W+β, wherein: epic_bin_x is the estimated bin number complexity of the target picture to be encoded, pic_W is the any one of a sum of activities, a sum of standard deviations, or a sum of variances, α is a gradient of a regression line of I picture bin number complexity for the one of a sum of activities, a sum of standard deviations, or a sum of variances, the I picture bin number complexity being, a product of a bin number and an average quantizing step size of macro blocks of an I picture, β is an intercept of the regression line of the I picture bin number complexity for the one of a sum of activities, a sum of standard deviations, or a sum of variances, and the second value is a product of an assigned picture rate of the target picture to be encoded and a symbol-to-bit ratio, wherein the symbol-to-bit ratio is a value obtained statistically from a plurality of pictures having a same type as that of the target picture to be encoded or a value obtained from a lastly encoded picture having a same picture type as that of the target picture to be encoded.