Image coding apparatus and image coding method

Abstract

An image coding technique and image decoding technique capable of preventing degradation of picture caused by the extremely insufficient number of bits to be allocated to residual frames, and enabling coding to reproduce high-quality picture, in a case that scenes difficult to be coded are continued. A deriving part 31 for deriving the frame constellation target number of bits which can be assigned reads out from a memory 36 the total number of bits of frame constellation units to remaining frames, subtracts the generating number of bits used by coding the previous frames and updates, and transmits it to a deriving part 32 for deriving the following frame target number of bits. The deriving part 32 for deriving the following frame target number of bits computes the target number of bits assigned to the following frames based on the remaining frame number in consideration of the received total number of bits and frame rate values Rf. A deriving part 33 for deriving the mean or average frame number of bits computes the mean rate of the number of bits assigned to the former frames. An operation part 34 multiplies the mean rate of the computed number of bits by considered factors, compares this with a target value of the number of bits, and selects a greater one of values and transmits it to a deriving part 35 for a quantization step.

Description

technical field [0001] The present invention relates to an image encoding technique and an image decoding technique, in particular to an image encoding technique using a variable bit rate method or a variable frame rate method. Background technique [0002] Conventionally, a variable bit rate (Variable Bit Rate) method is one of methods for controlling bit rates in image coding technologies such as the MPEG (Moving Picture Expert Group) standard. This is mainly because the bit rate is allowed to locally vary with the complexity of the coded image, and the length of time is specified in order to comply with constraints such as the capacity of the buffer memory that stores the encoded data, or the constraints of the image recording time when recording on the recording medium. (For example, 1 second) The control method suppresses the number of occurrence bits within a certain number. That is, by generating more encoding bits (increasing the bit rate) for difficult-to-encode pi...

AI Technical Summary

Problems solved by technology

In the example of FIG. 6, the difficult-to-encode frames are consecutive, and since many bits are allocated to the encoding of these frames, the result of gradually reducing the frame rate is that the interval between frames is widened, resulting in an image with slow motion, and the display as an image state of deteriorating quality

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