JP3555457B2 - Encoding device and decoding device for television signal - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television signal encoder and decoder for superimposing and providing character information such as advertisements and warnings in digital television broadcasting.
[0002]
[Prior art]
In television broadcasting, text information such as extraordinary news is broadcast by superimposing a subtitle image on the broadcast station side with respect to the original image which is the original program, and the superimposed image on the receiving side is displayed as it is. Is displayed. For this reason, when the receiver records the broadcast content on a VTR (video tape recorder) or the like by timer reservation, even the subtitle information related to extraordinary news, which is hardly necessary at the time of playing the recorded image, is lost. At the same time, it was recorded on the VTR. Even now, in analog television broadcasting, there is a method by which a receiver can selectively display character information by means such as character multiplex broadcasting using a vertical blanking period. Japanese Patent Application Laid-Open No. 6-237423 has proposed a method in which information such as extra news can be selectively displayed by a viewer using this method.
[0003]
[Problems to be solved by the invention]
In this method, information such as extraordinary news is sent as data such as character multiplexed information in a superimposed manner during the vertical blanking period, and the superimposed information is restored as necessary on the receiving side. The technique of superimposing is adopted. However, it is difficult to satisfy the condition that all the decoding devices have this function. Therefore, if the broadcasting station determines that it is necessary to inform all the receivers of the information, the broadcasting station naturally The side selects a method of superimposing subtitles such as extra news on the original image in advance. Therefore, in the above case, it is difficult to reproduce the original image before the subtitle is superimposed on the receiving side and record it on the VTR.
[0004]
Therefore, the present invention provides a method for transmitting an image in which subtitles such as extra news are superimposed in digital television broadcasting while maintaining compatibility with a normal decoding device and responding to the selection of a receiver. It is an object of the present invention to provide an encoding device and a decoding device which can obtain an original image before superimposing subtitles by a decoding device and can record only the original image on a VTR or the like.
[0005]
[Means for Solving the Problems]
To achieve the above object, the invention according to claim 1 relates to an apparatus for encoding a television signal, comprising: a subtitle synthesizing means for superimposing a subtitle image on an original image to generate a main image; Area extracting means for extracting a portion corresponding to an image area to generate a partial image, main image coding means for encoding a main image to generate a main image code, and coding a partial image to generate a partial image code And a code multiplexing unit that multiplexes the main image code and the partial image code to generate transmission data.
[0006]
According to a second aspect of the present invention, in the television signal encoding apparatus according to the first aspect, the starting coordinates of the partial image on the screen are based on the starting coordinates of the effective encoding area of the main image in the main image encoding means. The size is specified in units of eight pixels, and the size of the partial image is also specified in units of eight pixels.
[0007]
The invention according to claim 3 relates to a television signal decoding apparatus, in which only a subtitle image insertion area is extracted and encoded from a main image code obtained by superimposing and encoding a subtitle image in an original image and an original image. Code classification means for classifying a main image code and a partial image code from received data including a partial image code; main image code decoding means for decoding a main image code obtained by the classification to generate a main image; Image decoding means for decoding the partial image code obtained by the above and generating a partial image, and reproducing the original image by superimposing the decoded partial image on the decoded main image and outputting the image output signal And a superimposing means.
[0008]
According to a fourth aspect of the present invention, in the television signal decoding apparatus according to the third aspect, the main image decoding unit, the partial image decoding unit, and the superimposing unit are configured by a single image decoding unit. The image decoding means is characterized in that the decoding of the main image code and the decoding of the partial image code separated by the code separation means are processed in a time-division manner.
[0009]
In digital broadcasting using a transmission path such as a satellite, a terrestrial wave, or a cable, a single commissioned broadcaster can easily broadcast on multiple channels. Therefore, as means for solving the above problem, an image before superimposing subtitles, that is, data obtained by compression-encoding the original image is generated, and the main image after superimposing subtitles is multiplexed with data obtained by compression-encoding. And transmit it. Thereby, when the receiving side selects the original image from the transmitted data, an image without captions can be obtained.
[0010]
However, in order to compress and encode the entire area of the original image as it is and transmit it, almost the same amount of information as the main image is required, and both the original image and the main image are transmitted simultaneously in a limited transmission band. This leads to a significant reduction in the transmission quality of both. For this reason, of the original image, only the area where the subtitles are to be superimposed is encoded as a partial image, multiplexed with the code data of the main image, and transmitted. On the receiving side, it becomes possible to obtain the original image by decoding the main image and superimposing the decoded partial image thereon.
[0011]
According to the present invention, since the partial image has a smaller amount of information than the entire original image, by transmitting in a limited band, the quality of the main image is significantly impaired compared to the case where only the main image is transmitted. Without compression, encoding and transmission are possible. On the receiving side, a main image and a partial image are combined to generate an original image, which can be used for recording on a VTR.
[0012]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 shows a state in which an encoding device 10 on the transmitting side and a decoding device 30 on the receiving side are coupled via a transmission line 20. The encoding device 10 receives the partial image synthesis control signal 151, the subtitle image signal 152, the original image signal 153, and the partial image coordinate signal 154 and performs predetermined signal processing to generate transmission data 159. The transmission data 159 is transmitted from the transmission side to the reception side via the transmission path 20, and is input to the decoding device 30 as reception data 351. The decoding device 30 performs predetermined signal processing on the received data 351 to generate a desired image output signal 358.
[0013]
FIG. 2 shows the internal configuration of the encoding device 10. The internal configuration and operation will be described below with reference to FIG. When broadcasting extraordinary news, putting in advertisements, putting in logos that mean copy guard, or even issuing an alarm in the event of a disaster, the transmitting side activates the partial image composition control signal 151 to activate the code. The switch 101 is closed in the gasifier 10. As a result, the caption image signal 152 and the original image signal 153 are input to the caption synthesizing unit 102, and the main image signal 155 representing the main image 503 obtained by synthesizing the subtitle image 502 with the original image 501 is generated. The main image signal 155 is encoded by the main image encoding unit 103 configured as a compression encoding device such as MPEG, and is sent to the code multiplexing unit 108 as a main image code 156 from here. The original image signal 153 is also input to the rectangular area extraction unit 104, where a rectangular area wider than the combined subtitle image is extracted as the partial image 504. The partial image 504 to be extracted is specified by the partial image coordinates related to the partial image coordinate signal 154. In order to make the boundaries of the combined image inconspicuous, the starting coordinates of the partial image 504 are determined by the DCT (discrete cosine transform) used in MPEG from the starting coordinates of the effective coding area of the main image in the main image coding unit 103. It is specified by the number of pixels which is a multiple of the square unit of 8 × 8 pixels which is the minimum unit. Similarly, the size of the partial image 504 is designated by the number of pixels which is a multiple of the square area of 8 × 8 pixels. The partial image signal 157 representing the partial image 504 is encoded by the partial image encoding unit 105 using a compression encoding method such as MPEG, like the main image encoding unit 103. The partial image code 158 obtained by the encoding is sent to the code multiplexing unit 108 via the switch 106 which is closed by activating the partial image synthesis control signal 151. Further, the partial image coordinates 154 are also input to the code multiplexing unit 108 via the switch 107 closed by the partial image synthesis control signal 151. The code multiplexing unit 108 generates multiplexed transmission data 159 based on the input partial image synthesis control signal 151, main image code 156, partial image code 158, and partial image coordinate signal 154. Actually, information such as audio signals and data not shown here is also multiplexed by the code multiplexing unit 108.
[0014]
FIG. 3 shows the internal configuration of the transmission path 20. The transmission path 20 includes a modulation device 201 at a transmission end and a demodulation device 202 at a reception end. The transmission data 159 generated by the encoding device 10 is modulated by the modulation device 201, and transmitted from the modulation device 201 directly to the receiving side via the transmission line 203 or in the form of a terrestrial wave 251 or a satellite wave 252. , And is demodulated here and transmitted to the decoding device 30 as received data 351. In the case of transmission by the terrestrial wave 251, transmission data 159 modulated by the modulation device 201 is emitted as a radio wave from the transmission antenna 204, received by the reception antenna 205, and input to the demodulation device 202. In the case of transmission by satellite wave 252, transmission data 159 modulated by modulation device 201 is emitted as a radio wave from transmission antenna 206, received by reception antenna 207, and input to demodulation device 202.
[0015]
FIG. 4 shows the internal configuration of the decoding device 30. Hereinafter, the internal configuration and operation of the decoding device 30 will be described with reference to FIG. The decoding device 30 has a code classification unit 301 at its input end. Here, from the received data 351, a main image code 352 corresponding to the main image code 156, a partial image code 353 corresponding to the partial image code 158, a partial image coordinate A partial image coordinate 354 corresponding to the signal 154 and a partial image synthesis control signal 355 corresponding to the partial image synthesis control signal 151 are separated. The main image code 352, the partial image code 353, and the partial image coordinates 354 are input to the image restoration unit 40 provided in the decoding device 30, where the image is restored and an image output signal 358 is output. The partial image synthesis control signal 355 is input to the control unit 302, and the output signal is input to the image restoration unit 40 as a control signal. When the partial image synthesizing control signal 355 is active, the control unit 302 sends a mode control signal 356 that causes the receiver to output an original image through the operation of the operation unit 303 to the control unit 302, and selects an original image via the control unit 302. The signal 357 is input to the image restoration unit 40. Upon receiving the original image selection signal 357, the image restoration unit 40 restores the main image or the original image in which the caption is superimposed and outputs an image output signal 358. This image output 358 can be used, for example, for recording a VTR.
[0016]
The image restoration unit 40 will be described in more detail with reference to FIG. The image restoration unit 40 includes a partial image code decoding unit 402 separately from the main image code decoding unit 401. The main image code decoding unit 401 generates a decoded main image 450 by decoding the main image code 352 compressed by a compression method such as MPEG. On the other hand, the partial image code decoding unit 402 similarly decodes the partial image code 353 compressed by a compression method such as MPEG, and specifies the position of the partial image with the partial image coordinates 354. The obtained decoded partial image 451 is sent to the superimpose unit 404 via the switch 403 when the original image is selected by the original image selection signal 357. The superimposing unit 404 restores the original image 505 (= 501) by superimposing the decoded partial image 451 on the decoded main image 450, and outputs an image output signal 358.
[0017]
Then, by recording this image output signal 358 with a VTR or the like, an original image without captions can be recorded. At the same time, by outputting the decoded main image 450 output from the main image encoding / decoding unit 401 to a TV screen (display device), when viewing in real time, an image including subtitles such as extra news is viewed. be able to. In the case of a normal decoding device, only the main image code is decoded and output. Therefore, when the image is viewed on a display device, the same image as the conventional image is viewed, and the transmission data is compatible with the conventional device. The nature is also maintained.
[0018]
FIG. 7 shows another example of the configuration of the image restoring unit 40, and its operation will be described below with reference to FIG. In the image restoration unit 40a, the two decoding units, the main image decoding unit and the partial image decoding unit, are not physically separated. Here, a single image decoding unit 405 is provided, and decoding of each image is performed by time division. To process. This time division processing is realized by a software technique. Therefore, the image restoration unit 40a includes a single image decoding unit 405 and a memory 406 that temporarily stores the restored image.
[0019]
In the image restoration unit 40a shown in FIG. 7, first, the main image code 352 is taken into the image decoding unit 405, and the main image (see FIG. 5: main image 503) is decoded (FIG. 8: step 801). The decoded main image is written to the memory 406 (Step 802). Next, the state of the original image selection signal 357 is checked (step 803). If restoration of the original image is selected, the process proceeds to the next processing step 804. When the restoration of the main image is selected, the process returns to the first step 801 to adjust the timing with a video synchronization signal (not shown) and shift to the processing of the next main image. In step 804, it is determined whether or not the data includes the partial image code 353. If the partial image code 353 is included, the data is decoded (step 805), and the data of the decoded partial image 504 is converted according to the partial image coordinate signal 354. Overwrite the memory 406. These operations are repeatedly executed in synchronization with a video synchronization signal such as one field or one frame.
[0020]
The partial image data written in the memory 406 is read out in synchronization with a video synchronization signal (not shown) to generate an image output signal 358.
[0021]
【The invention's effect】
According to the present invention, a transmission image is transmitted to a reception side in the form of a main image obtained by superimposing subtitles on an original image on a transmission side in a limited transmission band while minimizing image quality deterioration. The original image before superimposition can be restored on the receiving side from the received data, and unnecessary subtitles can be deleted during the recording process of the receiver, and only the desired original image can be recorded.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram showing a state in which an encoding device and a decoding device according to the present invention are connected via a transmission line.
FIG. 2 is a block diagram showing an internal configuration of the encoding device in FIG. 1;
FIG. 3 is a block diagram showing an internal configuration of a transmission line in FIG. 1;
FIG. 4 is a block diagram showing an internal configuration of the decoding device in FIG. 1;
FIG. 5 is an explanatory diagram illustrating an image processing process of the encoding device in FIG. 2 with reference to an image example.
FIG. 6 is an explanatory diagram illustrating an image processing process of the decoding device in FIG. 4 with reference to an image example in FIG. 5;
FIG. 7 is a block diagram showing another embodiment of the image restoration unit in FIG. 4;
FIG. 8 is a flowchart for explaining the operation of the image restoration unit in FIG. 7;
[Explanation of symbols]
Reference Signs List 10 Encoding device 102 Subtitle synthesis unit 103 Main image encoding unit 104 Rectangular area extraction unit 105 Partial image encoding unit 108 Code multiplexing unit 151 Partial image synthesis control signal 152 Subtitle image signal 153 Original image signal 154 Partial image coordinate signal 159 Transmission data 20 Transmission path 201 Modulation device 202 Demodulation device 30 Decoding device 301 Code classification unit 351 Received data 357 Original image selection signal 358 Image output signal 40 Image restoration unit 40a Image restoration unit 401 Main image code decoding unit 402 Partial image code decoding Unit 404 superimpose unit 405 image decoding unit 406 memory

Claims (4)

Subtitle synthesizing means for superimposing a subtitle image on an original image to generate a main image; area extracting means for extracting a portion corresponding to a subtitle image area from the original image to generate a partial image; Main image encoding means for encoding the partial image, generating a partial image code by encoding the partial image, and multiplexing and transmitting the main image code and the partial image code. An encoding device for a television signal, comprising: a code multiplexing unit that generates data. 2. The television signal encoding apparatus according to claim 1, wherein a start coordinate of the partial image on the screen is specified in units of eight pixels with reference to a start coordinate of an effective encoding area of the main image in the main image encoding unit. And a television signal encoding apparatus in which the size of the partial image is also specified in units of 8 pixels. The main image code and the partial image from the main image code obtained by superimposing and encoding the subtitle image in the original image and the received image data including the partial image code obtained by extracting and encoding only the subtitle image insertion region from the original image Code classification means for classifying codes, main image code decoding means for decoding a main image code obtained by classification to generate a main image, and decoding of a partial image code obtained by classification to generate a partial image A television signal decoding apparatus, comprising: a partial image code decoding unit; and a superimposition unit configured to superimpose a decoded partial image into a decoded main image to reproduce an original image and output an image output signal. . 4. The television signal decoding apparatus according to claim 3, wherein said main image code decoding means, partial image code decoding means, and superimposing means are constituted by a single image decoding means, and said image decoding means is a code decoding apparatus. An apparatus for decoding a television signal, wherein decoding of a main image code and decoding of a partial image code classified by a classification unit is performed in a time-division manner.

Images