Digital still camera

Abstract

There is provided a digital still camera which is capable of performing fixed-length compression to image data at high speed while suppressing dispersion in size of compressed data by including; a first compression unit which compresses inputted image data using a predetermined first compression parameter, a second compression unit which compresses the inputted image data using a second compression parameter different from the first compression parameter, an evaluating unit which evaluates compression results of the first compression unit and of the second compression unit based on a relationship with a predetermined range including a target size of compressed data, and a selecting unit which selectively performs recording processing to a compression result highly evaluated by the evaluating unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The nature, principle, and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings in which like parts are designated by identical reference numbers, in which:

FIG. 1 is a view showing a first embodiment of a digital still camera according to the present invention;

FIG. 2 is a view showing a detailed structure of an image data compressing part;

FIG. 3 is a flowchart representing an operation of the image data compressing part;

FIGS. 4A to 4C are views explaining an operation of managing compressed data;

FIG. 5 is a view showing another structural example of an image data compressing part; and

FIG. 6 is a view explaining a reference value for a scale factor.

Claims

1. A digital still camera which compresses image data for recording, the image data representing a digital still image photographed by a photographing unit, the digital still camera comprising: a first compression unit which compresses inputted image data, using a predetermined first compression parameter;a second compression unit which compresses said inputted image data, using a second compression parameter different from said first compression parameter;an evaluating unit which evaluates compression results of said first compression unit and of said second compression unit based on a relationship between the compression results and a predetermined range including a target size of compressed data; anda selecting unit which selectively performs recording processing to a compression result highly evaluated by said evaluating unit.

2. The digital still camera according to claim 1, wherein: said first compression unit performs compression processing to image data obtained by said photographing unit, using a standard compression parameter with which image data of a standard image with a standard amount of information is compressed to obtain compressed data of said target size; andsaid second compression unit performs compression to image data obtained by said photographing unit, using a compression parameter corresponding to a predetermined auxiliary scale factor, the auxiliary scale factor being equal to or larger than a standard scale factor corresponding to said standard compression parameter and smaller than a maximum scale factor which corresponds to a compression parameter with which said standard image is compressed to obtain compressed data of a size corresponding to a lower limit of a predetermined range including said target size.

3. The digital still camera according to claim 1, wherein: said first compression unit performs compression processing to image data obtained by said photographing unit, using a plain compression parameter with which image data of a typical plain image with an amount of information smaller than the standard image is compressed to obtain compressed data of said target size; andsaid second compression unit performs compression to image data obtained by said photographing unit, using an upper limit compression parameter with which said typical plain image is compressed to obtain compressed data of a size corresponding to a lower limit of a predetermined range including said target size.

4. The digital still camera according to claim 1, wherein: said first compression unit performs compression processing to image data obtained by said photographing unit, using a compression parameter for complicated images with which image data of a typical complicated image with an amount of information larger than the standard image is compressed to obtain compressed data of said target size; andsaid second compression unit performs compression to image data obtained by said photographing unit, using a lower limit compression parameter with which image data of said typical complicated image is compressed to obtain compressed data of a size corresponding to an upper limit of a predetermined range including said target size.

5. The digital still camera according to claim 1, further comprising: a parameter calculating unit which calculates, in response to a mode setting instruction, a first compression parameter to be used in said first compression unit for image data of a current frame, based on a compression parameter for compressed data of a previous frame selected by said selecting unit and on a size of the selected compressed data and said target size, and provides the first compression parameter to said first compression unit for the compression processing, the mode setting instruction indicating a continuous shooting mode in which images are shot continuously by said photographing unit; anda parameter determining unit which determines a value of a second compression parameter based on the first compression parameter calculated by said parameter calculating unit, and provides the second compression parameter to said second compression unit for the compression processing.

6. The digital still camera according to claim 1, wherein said selecting unit comprises:two memories which store therein compressed data obtained by said first compression unit and said second compression unit, respectively;a purging unit which purges compressed data evaluated low by said evaluating unit, out of two compressed data of an image of a current frame, the two compressed data being written in parallel to said two memories; andan assigning unit which assigns one of said memories storing the compressed data purged by said purging unit, as a storage of compressed data of a next frame to be generated by one of said first and second compression units which has generated compressed data of said current frame highly evaluated by said evaluating unit.