JPH0456520A - Coder - Google Patents

Abstract

PURPOSE:To reduce quantity of data almost without deteriorating picture quality by providing a dynamic range calculator and a compression rate controller to the coder so as to vary the compression rate depending on the dynamic range. CONSTITUTION:A dynamic range 5 of an input signal 1 is calculated by a dynamic range calculator 4 and the dynamic range 5 is calculated by the same function block as that for orthogonal transformation. When the dynamic range 5 is high, a compression rate controller 8 controls a compression parameter 9 so that the quantity of data is reduced with an increased compression rate and a coder 10 encodes an orthogonal transforming signal 3 with the compression parameter 9. Thus, the quantity of data is reduced almost without deteriorating the picture quality.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a means for reducing the amount of data required to transmit and store image signals in order to reduce communication costs and extend recording time. The present invention relates to an encoding device.

Conventional technology A block diagram of a conventional encoding device is shown in FIG.

In the figure, 1 is an input signal, 2 is an orthogonal transformer that orthogonally transforms input signal 1, 3 is a signal that has been orthogonally transformed by orthogonal transformer 2, 10 is an encoder that encodes signal 3, and 11 is a code This is an output signal encoded by the encoder 10.

In the conventional encoding device configured as described above, the input signal 1 is orthogonally transformed by the orthogonal transformer 2, and the input signal 1 is orthogonally transformed by the encoder 10.
encoded in By choosing an appropriate function for this orthogonal transformation, it is possible to make certain transformation components smaller than other components, and as proven in information theory, signals with strong correlations such as image signals can be significantly reduced. Data amount can be reduced. Furthermore, when DCT (discrete cosine transform) or the like is used as an orthogonal transform, the distortion for high frequency components is less visually noticeable than the distortion for low frequency components. can be reduced.

Problems to be Solved by the Invention However, in the configuration described above, the visual characteristics of images are not used, and there is still room for reducing the amount of data.

In view of this, it is an object of the present invention to provide an encoding device that further reduces the amount of data compared to conventional encoding devices without substantially impairing image quality.

Means for Solving the Problems The present invention provides dynamic range calculation means for calculating the local or block-by-block dynamic range of an input signal;
Compression parameter generation means for generating a parameter for controlling an encoding compression rate from the dynamic range calculated by the dynamic range calculation means, and encoding means for encoding the input signal using the compression parameter. This is an encoding device characterized by: Further, a dynamic range calculating means for calculating a dynamic range locally or for each block of an input signal, an edge detecting means for detecting an edge part of the input signal, and a dynamic range calculated by the dynamic range calculating means and the edge part. The present invention is characterized by comprising a compression parameter generation means for generating a parameter for controlling the compression rate of encoding from the edge information detected by the detector, and an encoding means for encoding the input signal using the compression parameter. This is an encoding device that performs

Effects According to the first aspect of the present invention, the dynamic range calculation means calculates the dynamic range of the input signal, and when the dynamic range is large, the compression ratio is increased by the compression ratio controller (reducing the amount of data). Generally, when the dynamic range is large, there is little visual deterioration in image quality even if encoding distortion increases somewhat, so it is possible to obtain the same level of reproduced image quality with a smaller amount of data than with conventional encoding devices. Furthermore, the second invention further adds an edge detection means to the first invention, thereby controlling the compression ratio using both the dynamic range and edge information.

Even if the dynamic range is large, the encoding distortion near the edge is visually noticeable, so even if the dynamic range is large, the compression ratio of the edge part is controlled so as not to be too large (to reduce the amount of data). Image quality can be slightly improved even with the same amount of data as in the invention of .

Embodiment FIG. 1 is a block diagram of an encoding device in an embodiment of the first invention. In the figure, 1 is an input signal, 2 is an orthogonal transformer that outputs an orthogonal transformed signal 3 obtained by orthogonally transforming the input signal 1, 4 is a dynamic range calculator that calculates the dynamic range 5 of the input signal 1, and 8 is a dynamic a compression controller for calculating compression parameters 9 for encoding from a range 5;
0 is an encoder that encodes the orthogonal transformed signal 3 using compression parameters 9 and outputs an output signal 11.

In the encoding device of this embodiment configured as described above,
The operation will be explained below. Input signal 1 is used to calculate dynamic range 5 using a dynamic range calculator. This dynamic range 5 may be calculated using the same block as the orthogonal transform, or may be selected for several orthogonal transform blocks or independently of the orthogonal transform blocks. When the dynamic range 5 is large, the compression rate controller 8 controls the compression parameters 9 to increase the compression rate and reduce the amount of data. The encoder 10 encodes the orthogonal transformed signal 3 using compression parameters 9. Orthogonal transformation is known as a pre-processing method for compression encoding, and is one of the methods that can reduce the amount of data with almost no loss in image quality. Therefore, by encoding the orthogonal transform signal 3 with the compression parameter 9,
It is possible to significantly reduce the amount of data. Next, compression parameter control using a dynamic range will be explained.

FIG. 2 is an example of an image, where the dynamic range is small inside a circle and the dynamic range is large inside a rectangle. The solid line in Figure 3(a) is the original signal inside the circle,
The solid line in Figure 3) represents the original signal inside the rectangle. The horizontal axis indicates pixel position, and the vertical axis indicates pixel value. For each, the dotted line indicates the encoded data. Generally, sign distortion is additively added to the signal, so the third
Compared to the signal in FIG. 3(b), the signal to noise ratio of the signal in FIG. 3(a) is degraded.

Visually, grainy noise is noticeable in areas with a small dynamic range, but is hardly noticeable in areas with a large dynamic range.

Therefore, by increasing the compression rate when the dynamic range is large, it is possible to reduce the amount of data with almost no loss in image quality.

As described above, according to this embodiment, by providing a dynamic range calculator and a compression rate controller and changing the compression rate depending on the dynamic range, it is possible to reduce the amount of data with almost no deterioration in image quality.

FIG. 4 is a block diagram of an encoding device that is an embodiment of the second invention. In the figure, 1 is an input signal 1, 2 is an orthogonal transformer that outputs an orthogonal transformed signal 3 obtained by orthogonally transforming the input signal 1, 4 is a dynamic range calculator that calculates the dynamic range 5 of the input signal, and 6 is an input signal. An edge detector detects edge 7 of signal 1, 8 is a compression controller that calculates encoding compression parameter 9 from dynamic range 5 and edge 7, and 10 encodes orthogonal transform signal 3 with compression parameter 9 and outputs the signal. This is an encoder that outputs 11.

The operation of the encoding apparatus of this embodiment configured as described above will be explained below. Since the components other than the edge detector 6 and the compression ratio controller 8 operate in the same manner as in the embodiment shown in FIG. 1, their explanation will be omitted. If the input signal 1 contains edge information, the dynamic range 5 is wide (but the compression ratio controller 8
Try not to increase the compression rate too much. Coding distortion is more noticeable in edge areas than in flat areas, so even if the dynamic range is large, increasing the compression rate too much will cause a significant deterioration in image quality. FIG. 3(C) shows the state of the edge portion. In the figure, solid lines represent original signals, and dotted lines represent encoded data. Pixel values vary greatly at edge boundaries. In areas other than edges, the pixel value of the original pixel changes greatly even in the vicinity where the pixel value changes sharply, so the encoding distortion is not noticeable, but the area near the edge is flat, which is why the encoding distortion is noticeable. Become. Furthermore, in moving images, unnatural motion causes a significant deterioration in image quality. Therefore, image quality can be improved by lowering the compression rate near the edges and reducing encoding distortion.

As described above, according to this embodiment, by providing a dynamic range calculator, an edge detector, and a compression ratio controller, and changing the compression ratio depending on the dynamic range and edges, the amount of data can be reduced even at the edges without deteriorating the image quality. can be reduced.

FIG. 5 is a block diagram of an encoding device according to another embodiment of the second invention. This figure has almost the same configuration as the embodiment of FIG. 4, except that the output signal 11 is fed back to the compression ratio controller.

The operation of this embodiment configured as described above will be explained below. In order to keep the average data amount of the output signal 11 constant, the compression ratio is controlled by feeding back the output signal 11. That is, when the average amount of data is large, the compression rate is increased to reduce the data amount, and when the average data amount is small, the compression rate is decreased to reduce encoding distortion. Such a coding method already has a compression rate controller, and when the present invention is applied to this, this compression rate controller can be used as is.

Therefore, the encoding apparatus of the present invention can be easily applied by adding only the dynamic range calculator 4 and edge detector 6. Conversely, the amount of data that can be reduced by compression control using the dynamic range 5 and edge 7 can be used to improve image quality by using a feedback mechanism that keeps the average amount of data constant. The benefits of control are great.

As described above, according to this embodiment, the image quality can be improved by providing a dynamic range calculator, an edge detector, and a compression ratio controller and changing the compression ratio depending on the dynamic range and edges.

In addition, although the encoding means using orthogonal transformation was demonstrated in the 1st to 3rd Example, encoding means other than orthogonal transformation, such as predictive encoding, may be used. Further, in the first embodiment, the compression ratio control 8 may be controlled by the output signal 11, and furthermore, in the second and third embodiments, the dynamic range 5, the edge 7
, a compression ratio controller 8 is independently provided for the output signal 11,
Encoding control may be simplified.

As described in detail, according to the present invention, the amount of data can be reduced with almost no loss in image quality, and its practical effects are great.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the encoding device in the first invention, FIGS. 2 and 3 are explanatory diagrams of the encoding method of the present invention, and FIG. 4 is a block diagram of an embodiment of the encoding device in the second invention. FIG. 5 is a block diagram of another embodiment of the encoding device according to the second invention, and FIG. 6 is a block diagram of a conventional encoding device. 4...Dynamic range calculator, 6...
...Edge detector, 7...Compression rate controller, 1o
・・・・・・Encoder. Name of agent: Patent attorney Shigetaka Awano (1 person)

Claims (1)

[Claims] (1) Dynamic range calculation means for calculating the local or block-by-block dynamic range of an input signal, and controlling the encoding compression rate from the dynamic range calculated by the dynamic range calculation means. An encoding device comprising: compression parameter generation means for generating a parameter; and encoding means for encoding the input signal using the compression parameter. (2) The encoding apparatus according to claim (1), further comprising compression parameter generation means for generating a parameter that reduces the amount of data when the dynamic range is large. (3) a dynamic range calculation means for calculating a dynamic range locally or for each block of an input signal; an edge detection means for detecting an edge portion of the input signal; and a dynamic range calculated by the dynamic range calculation means and the A compression parameter generation means for generating a parameter for controlling a compression rate of encoding from edge information detected by an edge detector, and an encoding means for encoding the input signal using the compression parameter. An encoding device that does (4) The encoding apparatus according to claim (3), further comprising compression parameter generation means for generating a parameter that reduces the amount of data when the dynamic range is large and there is no edge.