JPH06152983A - Image encoding method - Google Patents

Abstract

PURPOSE:To improve encoding efficiency by executing encoding suitable to an image pickup picture and a character image. CONSTITUTION:An input image signal is separated to a camera image pickup picture signal, a character image signal and a character position signal to show each character position by an input separation circuit 12. The camera image pickup picture of the same part a preceding frame is inserted to a part of the camera image pickup picture signal from which the character image signal is omitted. These of the camera image pickup picture signal, the character image signal, and the character position signal are encoded in encoding circuits 13, 14, 15 respectively by encoding rules suitable to each of them, and further, a signal to show a synthesizing method is encoded by the encoding circuit 16, and these encoded outputs are multiplexed by a multiplex circuit 17.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of encoding an image signal containing a character image.

[0002]

2. Description of the Related Art In order to efficiently transmit or store an image signal, there is an image coding method in which image redundancy is removed by using a digital technique. For example, in CCITT, an international standard image coding method applied to 64 kbit / sec xp (P = 1 to 30) is recommended. In this image coding method, an input digitally coded image signal is used as it is as a coding input, the redundancy of the signal is removed, and transmission and storage are performed. In such a system, a single image coding system is considered as a camera-captured image even for an image in which an artificial character image other than the image captured by the camera, such as time display and telop, is superimposed. Applied.

[0003]

However, the coding method suitable for the image picked up by the camera is different from the coding method suitable for the artificial character image, and the coding efficiency is apt to decrease. In addition, when different character information is superimposed on the decoding side (reception side) at the position where it is superimposed on the encoding side (for example, the transmission side), a superimposed image is created after agreement between the encoding side and the decoding side in advance. There is a need.

An object of the present invention is to enable efficient coding of one image signal composed of such image signals having different characteristics, and to determine the superimposed position of character information only by the processing on the receiving side and the reproducing side. The present invention is to provide an image encoding method.

[0005]

According to the present invention, a character image portion is separated from an input image signal, and the input image signal in which these character images are separated and each character signal of the separated character image portion are respectively applied to it. Encoding is performed by a suitable encoding method, information indicating the position of each character in the character image portion is encoded, and these three pieces of encoded information are multiplexed and transmitted or stored.

[0006]

The image information input to the input terminal 11 includes camera-captured image information obtained by replacing the character image portion with an image that is not a character image at the same position in the previous frame in the input separation circuit 12, and a black level except for the character image information. The character image information and the character image position information indicating the position of each character are separated, and character image combining method information relating to the method of combining the character image and the camera image is created. Although a conventionally proposed method can be used to separate the camera-captured image and the character image, the camera-captured image and the character image have different signal statistics, and both are different due to the difference in the statistics. The signals can be separated. For example, the signal value of a character image has a constant and high brightness, and continuously exists. Utilizing this property and knowledge of character patterns,
It is possible to separate the camera-captured image and the character image, which are the background. The separated character image has its starting scan line number,
Horizontal pixel position number is added as character image position information,
This character image position information is, for example, position information of the upper left corner of each character area.

A camera-captured image from which character images are separated is
Although the frequency band is wide and the range of signal values (levels) is wide, in the image coding circuit 13, for example, the CCITT
Coding is performed by a high compression coding method such as a standard coding method that utilizes the height of temporal correlation and spatial correlation of an image. In the character image encoding circuit 14, the separated character image uses a character code instead of the character image by character recognition, or when the character expression font is important, the character image is referred to for each character by referring to the character image position information. Compression encoding is performed to encode the signal value and the signal duration for each scanning line. Since the separated character image position information represents the position of each character that constitutes the character string, it can be expected that these also have similar values, and the absolute value of each position information is Instead, a relative value, that is, a difference value between character positions is obtained by the character position information encoding circuit 15, and further encoded by variable length encoding based on the probability distribution of signals. In the character image synthesizing method encoding circuit 16, the character image synthesizing method information is
A method of synthesizing a character image and a camera-captured image as the background,
For example, a predetermined code is generated according to replacement, simple addition, inversion, or the like. The outputs of the image coding circuit 13, the character image coding circuit 14, the character position information coding circuit 15, and the character image synthesizing method coding circuit 16 are matched with the video frame timing and multiplexed by the transmission multiplexing circuit 17. And is transmitted to the partner device via the transmission line 18.

The receiving side performs the reverse operation of the transmitting side. The transmission / separation circuit 19 causes the image captured by the encoded camera to the image decoding circuit 21, and the encoded character image to be the character image decoding circuit 22.
In addition, the encoded character image position information is the character position information decoding circuit 2
3, the character image synthesizing method information is the character image synthesizing method decoding circuit 2
4 are input respectively. In the image decoding circuit 21, the camera-captured image is decoded by the decoding method determined by the encoding method of the image encoding circuit 13. The character image decoding circuit 22 decodes the character image according to a decoding method determined by the encoding method of the character image encoding circuit 14, and based on the character image position information output from the character position information decoding circuit 23, the character image is decoded. It is placed on the screen and outputs the image signal with the others black. The character position information decoding circuit 23 decodes the character position information by a decoding method determined by the encoding method of the character position information encoding circuit 15. In the character image synthesizing method decoding circuit 24, the synthesizing method is determined by the encoding method determined by the character image synthesizing method encoding circuit 16 and output to the output synthesizing circuit 25. Image decoding circuit 21
And the output of the character image decoding circuit 22 are combined in accordance with the character image combining method decoded by the output combining circuit 25 in accordance with the video frame timing and output as an image signal.

Although the image signal coded according to the present invention is transmitted in the above description, it may be stored. The character image combining method information may be omitted, and the decoding side may combine the decoded character image with the decoded camera-captured image by simple replacement.
A plurality of character image information and a plurality of character image position information regarding the character image information may be encoded, and one of them may be selected on the decoding side and combined with the camera image.

[0010]

As described above, according to the present invention, a large code can be obtained by executing the encoding by the encoding method suitable for separating the image picked up by the camera and the character image for encoding. The efficiency of conversion can be obtained. In addition, since the camera-captured image and the character image are handled separately, the character information that needs to be displayed on the receiving side or the stored image reproducing side is affected by the superimposed character information on the transmitting side or the stored image recording side. It can be displayed without overlapping. For example, on the receiving side, a (customized) screen configuration that suits the user's convenience, for example, using the screen configuration showing the date of the day in the upper left of the screen and the plan of the day in the lower right of the screen, the transmitted image is displayed and transmitted. The character image superimposed from the side can be easily moved to a position that does not disturb the screen configuration. When multiple screens are available, the transmitted character information can be displayed on other screens.

In the embodiment, an example between two remote points is shown, but the present invention can be applied to transmission between multiple points and recording / reading via a storage device.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

Claims (1)

[Claims] 1. A character image portion is separated from an input image signal, the input image signal separated from the character image is encoded, and the separated character image portion includes information indicating a character position on the screen, and An image encoding method characterized by encoding each character image signal of a character image portion and multiplexing these three pieces of encoded information.