In image coding for production, there is a strong demand for all-intra picture code quantity-fixed encoding focusing on editability, and control (quantization value control) for strictly suppressing the code quantity to be equal to or smaller than a given amount, that is, the picture fixed-length coding is necessary. For example, a system or the like which performs recording in a video tape recorder (VTR) is exemplified from long ago. In a file-based system which records an image in a hard disk, a flash memory, or the like, there is a strong demand for picture fixed-length coding from the viewpoint of each of random access to each picture.
Simultaneously, there is a demand for suppressing image quality deterioration due to the repetition of encoding and decoding in an edition process. In the picture fixed-length coding, as a method of maintaining dubbing image quality, in the related art, precoding is performed multiple times by binary search or the like, an optimum quantization value satisfying the conditions is found, a quantization parameter during previous encoding in back search is estimated from among quantization values greater than the optimum quantization value, and the quantization parameter is introduced or the code quantity is confirmed by precoding again after back search, thereby suppressing the code quantity to be equal to or smaller than a given value (see Japanese Patent No. 3561962).
However, since multiple times of precoding result in an increase in the processing amount, it is desirable to reduce the number of times of precoding from the viewpoint of the processing amount (circuit scale)/power consumption/price. In a coding scheme, such as advanced video coding (AVC) which performs compression using an intra-screen correlation, when realized by hardware, such as large scale integration (LSI), parallelization or pipeline processing cannot be performed in a macro block (MB) unit, and it is difficult to perform binary search of the related art.
Accordingly, as described in Pamphlet of International Publication WO 2009/157577 and Pamphlet of International Publication WO 2009/157579, the applicant has suggested that code quantity control by simple code quantity estimation for AVC and a dubbing image quality maintenance technology.