JP3115373B2 - Image decoding apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image decoding apparatus and method, and more particularly, to an image decoding apparatus and method for shortening image data search time.

[0002]

2. Description of the Related Art Conventionally, there is a DCT (Discrete Cosine Transform) coding method as a data compression coding method using orthogonal transform of an image signal.

FIG. 3 is a block diagram showing a schematic configuration of an encoding system using DCT transform, and FIG. 4 is a diagram for explaining processing of the encoding system shown in FIG.

In FIG. 3, a digital image signal is inputted from an input terminal 2 and inputted to an 8 × 8 block forming circuit 4, where it is two-dimensionally divided into 8 × 8 pixel blocks. Sent out. 6 converts the image signal from the block forming circuit 4 into a DCT signal.
This is a circuit for converting and outputting an 8 × 8 data matrix for the frequency domain as shown in FIG. Here, X11 indicates a direct current (DC) component in the horizontal and vertical directions of the pixel block, that is, the average value of the pixel block.

[0005] The data matrix output from the DCT transform circuit 6 is linearly quantized in the linear quantization circuit 8 by a quantization step determined by the quantization step size generation circuit 16, as shown in FIG. The data is output as data G11 to G88. The quantized conversion data is supplied from a DC component to a variable length coding circuit (hereinafter referred to as “VLC”) 12 in order from a DC component by a zigzag scanning circuit 10 as shown in FIG. Output to

[0006] If the image coded signals thus obtained are sequentially recorded on a recording medium, the image information is coded and stored.

When a certain screen is searched for and displayed from a plurality of screens stored by the above technique, the original image signal is sequentially converted by performing inverse conversion and decoding in the reverse order of the encoding. Can be played.

[0008]

However, in the reproduction by the above-mentioned method, the original image can be reproduced almost faithfully, but the retrieval speed is slow when used under a constant reproduction speed which is the purpose of screen retrieval. There were drawbacks.

The present invention has been made to solve the above-described problem, and has as its object to search for an image to be decoded from encoded image data at various search speeds desired by a user.

[0010]

The present invention has the following configuration as one means for achieving the above object. An image decoding apparatus according to the present invention includes: an input unit that inputs image data that is encoded by converting image information into a frequency domain; a decoding unit that decodes input image data; and a search for input image data. It is characterized by comprising setting means for setting a speed, and control means for variably controlling a screen region and a frequency region for decoding the image data according to the set search speed.

An image decoding method according to the present invention converts image information into a frequency domain, inputs coded image data, decodes input image data, and sets a search speed of the input image data. Then, a screen region and a frequency region for decoding the image data are variably controlled according to the set search speed.

[0012]

Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

FIG. 1 is a block diagram showing the configuration of an embodiment of an image signal processing apparatus according to the present invention. In this embodiment,
1 shows an example in which an image signal processing device is applied to a search and reproduction circuit.

In FIG. 1, 22 is a recording medium, 24 and 32
Is a decoding circuit, 26 is a read position / amount control circuit, 28 is a search speed setting circuit, 30 is a memory, 34 is an output terminal, 36 is a CPU that controls the entire apparatus, and 38 is a program stored by the CPU 36. ROM 40 indicated indicates a RAM used as a work area of the CPU 36. The programs stored in the ROM 38 include programs for controlling the timing of various signals in the procedure shown in the flowchart of FIG. 2 described later.

The operation according to the above configuration will be described.

FIG. 2 is a flowchart for explaining an image signal processing procedure according to this embodiment.

First, an image signal is read out in units of a block composed of a plurality of pixels, transform data obtained by transforming the image signal into a frequency domain by orthogonal transform is quantized, and the quantized transform data is subjected to variable-length coding. The generated code is stored in the recording medium 22 (Step S1). From the recording medium 22, data is output in parallel at a speed sufficient for the search speed, one to a decoding circuit 24 for detecting the code length in a predetermined time (step S2), and the other to the decoding circuit 24. Is supplied to the memory 30 for holding data until the code length is detected (step S3). The code length detected by the decoding circuit 24 is input together with the search speed information from the search speed setting circuit 28 to a read position / amount control circuit 26 for controlling the read position and read amount of the memory 30. The memory 30 stores data from the recording medium 22 or the read position / amount control circuit 26.

The read-out position / amount control circuit 26 calculates the amount of readout of a DC component in which power is concentrated by orthogonal transformation from all the codes in a predetermined period and a subsequent high-frequency component.
Control is performed so as to change according to the search speed (step S4). That is, when the search speed is high, only the DC component that can be grasped while the entire image is coarse is read out from the memory 30, and when the search speed is low, the high-frequency component representing detailed information is also read. The read data is the decoding circuit
Sent to 32. The decoding circuit 32 receives the output from the memory 30 controlled to an appropriate amount by the read position / amount control circuit 26, performs a decoding process as an image signal, and outputs it to the output terminal 34 (Step S5).

According to the above configuration, it is possible to search the stored image contents at high speed by changing the decoding contents in accordance with the search speed.

As described above, according to the image signal search method of the present embodiment, the image signal is read out in units of blocks consisting of a plurality of pixels, and the transformed data obtained by transforming the image signal into the frequency domain by orthogonal transformation is quantized. In an image storage / playback apparatus having a function of storing a code generated by performing variable length coding on the quantized conversion data and reproducing the code,
High-speed retrieval of images becomes possible, and it is very useful to employ a retrieval method for a device such as a still image file device or a VTR (video tape recorder) as the image storage / reproduction device.

In the above-described embodiment, a control is considered in which only the DC component is decoded in order to cope with the high-speed search. However, in order to perform a higher-speed search, data is thinned out at a fixed rate from the DC component. It is also possible to perform decoding by decoding, or to decode only the vicinity of the center of the screen and perform corresponding control.

As described above, according to the present invention, an image to be decoded from encoded image data can be searched at various search speeds desired by the user.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an embodiment of an image signal processing device according to the present invention.

FIG. 2 is a flowchart illustrating an image signal processing procedure according to the embodiment.

FIG. 3 is a block diagram showing a schematic configuration of a DCT conversion method.

FIG. 4 is a diagram for explaining processing of the DCT conversion method shown in FIG. 2;

[Explanation of symbols]

 2 Input terminal 4 Blocking circuit 6 DCT conversion circuit 8 Quantization circuit 10 Zigzag scanning circuit 12 VLC 14 Output terminal 16 Quantization step size generation circuit 22 Recording medium 24 First decoding circuit 26 Control circuit 28 Search speed setting circuit 30 Memory 32 second decoding circuit 34 output terminal 36 CPU 38 ROM 40 RAM

Continued on the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 5/76-5/956 H04N 1/41 H04N ^7/ 24-7/68

Claims (2)

(57) [Claims] 1. An input unit for inputting image data converted by converting image information into a frequency domain, a decoding unit for decoding input image data, and a search speed of input image data are set. Setting means for decoding the image data according to the set search speed
An image decoding apparatus, comprising: a control unit that variably controls a screen area and a frequency domain. 2. An image data which is obtained by converting image information into a frequency domain, receives encoded image data, decodes input image data, sets a search speed of the input image data, and sets the set search speed Decoding the image data according to
An image decoding method characterized by variably controlling a screen area and a frequency domain.