KR100462448B1 - Television system with provisions for displaying an auxiliary image of variable size - Google Patents

Abstract

The present invention provides a compressed auxiliary video signal derived by an auxiliary image to selectively reduce the size of the auxiliary image, such as that which can be displayed in the main image in a so-called "picture in picture" or "PIP" operating mode of a television system. And to crop a predetermined amount of auxiliary image from the auxiliary image without changing the compression ratio of.

Description

TELEVISION SYSTEM WITH PROVISIONS FOR DISPLAYING AN AUXILIARY IMAGE OF VARIABLE SIZE

The present invention relates to a television system having a device for displaying an auxiliary image together with a main image, and more particularly to a television system having a device capable of changing the size of the auxiliary image.

Many modern television systems have an apparatus for displaying a main image corresponding to the main video signal source as well as an auxiliary image corresponding to the auxiliary video signal source. Such a device allows a viewer to watch one program while watching another. The auxiliary image may be displayed in the main image in the form of a so-called "PICTURE-IN-PICTURE" or "PIP". The auxiliary image may also be displayed next to the main image in the form of a so-called "PICTURE-OUTSIDE-PICTURE" or "POP".

The auxiliary image converts an analog video signal provided from an auxiliary signal source into a digital video signal, subpixels the digital video signal by removing pixel samples and scan lines from the digital video signal, and the resulting compression. And store the stored digital signal from the memory in synchronization with the horizontal and vertical synchronization components of the video signal from the main video signal source. So-called anti-aliasing filters are used to reduce the bandwidth of the digital signal before compression to avoid side effects in the secondary image due to subsampling. The digital signal recovered from the memory is converted into an analog signal, and the resulting analog video signal corresponding to the auxiliary image is synthesized with the analog signal corresponding to the main image to form a synthesized analog video signal. The synthesized analog video signal is coupled to a display device. The compositing operation is performed by a switching unit or " multiplexer " which selectively separates the main video signal from the display during a predetermined portion of the predetermined horizontal scan lines of the main video signal, and instead couples the auxiliary video signal to the display. do.

The secondary image is generally formed considerably smaller than the main image. For example, the secondary image may be 1/3 of the main image size. However, it is desirable to reduce the size of the auxiliary image even more selectively, such as 1/3 to 1/4, so that the auxiliary image does not cover the main image. One way to achieve this is to change the compression ratio of the secondary image. However, this requires a relatively large and complex circuit that changes the subsample rate and the associated antialiasing filtering and changes the form of management of the memory that stores the subsampled digital signal. Moreover, additional compression tends to make the details of the secondary image and the characters and graphics embedded in the secondary image more difficult to see.

1A and 1B show screens of a television system in various PIP modes of operation.

2 is a block diagram of a television system having a PIP processing section constructed in accordance with the present invention;

3 is a graphical representation of a method for reducing the size of an auxiliary image in accordance with the present invention.

4 is a waveform diagram of various signals that also indicate a method that may reduce the size of an auxiliary image in accordance with the present invention.

5 is a block diagram showing an embodiment of a portion of the PIP processing section of the television system of FIG. 2 constructed in accordance with the present invention.

The present invention allows to selectively reduce the size of the auxiliary image by cropping a predetermined amount of the auxiliary image from the auxiliary image without changing the compression ratio of the compressed auxiliary video signal from which the auxiliary image is derived.

FIG. 1A shows a screen of a typical 4: 3 aspect ratio television receiver with a relatively small secondary image corresponding to 1/3 video compression ratio inserted in the full size main image in the PIP mode of operation. FIG. .

The third size secondary image tends to obscure the main image. Therefore, it is desirable to allow the user to selectively reduce the size of the auxiliary image to, for example, a quarter size of the auxiliary image. FIG. 1B shows a screen that appears when the size of the auxiliary image is reduced by increasing the video compression ratio to 1/4. The main image is more visible, but the secondary image is compressed until the details in the secondary image are difficult to see. Also, any characters or graphics inserted in the auxiliary image in the studio, such as closed caption text, or characters inserted in the receiver itself, such as channel numbers, are hardly visible.

Reduction of the size of the auxiliary image according to the present invention is achieved by cropping a predetermined portion of the original auxiliary image without changing the video compression ratio. Such a result is shown in FIG. 1A as a quarter size secondary image labeled “CROPPED”. Such reduction in size makes the main image more visible. Part of the secondary image is lost, but the details of the image and the characters or graphics are relatively good to see because the image is not compressed.

In addition, the circuit required for reducing the size of the auxiliary image when employing the cropping method is much less complicated than the circuit required for employing the compression method. Compression methods require a significant number of complex circuits to change the compression subsampling rate and associated antialiasing filtering and to change the form of management of the memory that stores the subsampled digital signals. Hereinafter, the present invention will be described with reference to FIG. 2 from a structural point of view.

Briefly, in the PIP processing unit of the television system shown in FIG. 2, a composite video signal corresponding to an auxiliary image including a luminance component and a chromaticity component is processed to obtain a luminance signal and two color difference signals or three color difference signals. Form the same baseband components. Each of the component signals is compressed, synchronized with the video signal corresponding to the main image, and synthesized with the corresponding component of the main video signal to form a synthesized component signal. The synthesized component signals are coupled to a display device such as a picture tube. At least, only one PIP processing channel is shown in FIG. 2 because the PIP processing channels for the various components are similar to one another in the context of the present invention. In the following description, the terms "secondary video signal" and "main video signal" correspond to one of the component signals.

As shown in FIG. 2, the analog auxiliary video signal received at the input terminal 1 is converted into a digital video signal by the A / D converter 3. The digital auxiliary video signal is subsampled in the compression device 5 to remove a predetermined number of scan lines and a predetermined number of pixels per scan line. The compression device 5 is equipped with an anti-aliasing filter which reduces the bandwidth of the sub-video signal before sub-sampling in order to reduce side effects in the reproduced auxiliary image due to the sub-sampling process. The compressed auxiliary video signal is also stored (recorded) in a memory provided in the compression device 5 and retrieved from the memory in synchronization with the vertical and horizontal synchronization components of the main video signal. The digital video signal read out from the memory of the compression device 5 is coupled to a digital multiplexer ("MUX") or switch 7. The function of the multiplexer 7 and the associated "boundary" device 9 will be described below. First, assume that the multiplexer 7 couples the digital video signal read out from the memory to the D / A converter 11. The D / A converter 11 converts the digital video signal into an analog signal. The resulting compressed auxiliary analog signal is synthesized by the analog multiplexer or switch 15 with the main analog video signal received at terminal 13. The resulting synthesized video signal is coupled to the display device 17 so that an image including an auxiliary image in the main image is displayed.

The clock device 19 generates clock signals for various parts of the PIP processor, and the control device 21 generates various control signals for the PIP processor. The control device 21 responds to horizontal (H) and vertical (V) sync components of the main video signal and PIP and crop (CROP) command signals initiated by the user. The PIP command signal initiates a PIP mode of operation. The CROP command signal initiates a crop operation to reduce the size of the secondary image.

The multiplexer 15 operates to replace the main video signal with the compressed auxiliary video signal at a desired position of the auxiliary image in response to a switching signal. The multiplexer 15 is sometimes referred to as an "overlay switch" because it combines the compressed auxiliary video signal with the main video signal (although it replaces one signal with another). The switching control signal for the multiplexer 15 may also be referred to as a "fast switching" or "FSW" control signal because the multiplexer 15 operates at that speed.

In particular, the multiplexer 15 starts at a predetermined horizontal scanning line corresponding to the upper edge of the auxiliary image and starts at the corresponding predetermined pixel at another predetermined scanning line corresponding to the lower edge of the auxiliary image and then at the right edge of the auxiliary image. During a predetermined portion of each horizontal scanning line in a predetermined portion of each field ending at another predetermined pixel corresponding to the position, it is operated to replace the main video signal with the auxiliary video signal. This operation is shown in FIG. The contents of the memory of the compression device 5 are read during the period in which the main video signal is replaced with the auxiliary video signal in response to the address signals.

The multiplexer 7 and associated "boundary" device 9 provide the boundaries of the secondary image. The boundary device 9 is a register for storing digital values corresponding to the contrast of the boundary in the case of the luminance signal component and the color level in the case of the color component. If only gray-scale boundaries are desired, the digital boundary values for the color components may correspond to blanking levels. The multiplexer 7 is operated in response to the switching control signal to separate the output signal of the compression device 5 from the D / A converter 11 and replace the output signal with a digital boundary value at the desired position of the boundary. . The multiplexer 7 operates to synthesize the compressed auxiliary video signal and the signal representing the boundary thereof. Thus, the multiplexer 7 is also referred to as a "border insert" switch, and its switching control signal is also referred to as a "BORDER INSERT" switching control signal.

In more detail with regard to the generation of the boundary, during the predetermined number of horizontal scan lines (e.g. three) on the upper edge of the auxiliary image, the boundary insertion multiplexer 7 is used to determine the width of the auxiliary image and For a predetermined portion of each scan line corresponding to the sum of the widths (e.g., three pixels), the boundary value provided by the boundary device 9 is coupled to the D / A converter 11. As a result, an upper boundary is formed. During each of the predetermined number of horizontal scan lines corresponding to the height of the auxiliary image, the boundary insertion multiplexer 7 performs a boundary value for a predetermined number (eg, three) pixels before the left edge and after the right edge of the auxiliary image. To the D / A converter 11. As a result, left and right boundaries are formed as shown in FIG. Finally, during a predetermined number of horizontal scan lines below the lower edge of the secondary image (eg, three), the boundary insertion multiplexer 7 is provided with the width of the secondary image and the width of the left and right boundaries (eg, three). A boundary value is coupled to the D / A converter 11 for a predetermined portion of each scan line corresponding to the sum of the pixels). As a result, the lower boundary is formed.

Note that the " overlay " multiplexer 15 actually synthesizes the sum of the compressed auxiliary video signal and the boundary signal with the main video signal. Referring to Fig. 4, while the auxiliary image is displayed, the period of the high logic level of the FSW control signal for the horizontal scan line actually corresponds exactly to the sum of the width of the auxiliary image and the width of the left and right sides of the boundary. therefore, The BORDER INSERT switching control signal is generated in association with the FSW control signal.

Hereinafter, an operation of the PIP processing unit for selectively reducing the size of the auxiliary image by cropping a predetermined portion of the auxiliary image will be described with reference to FIG. 3. 3 shows an auxiliary image of a predetermined size, such as 1/3 size, including, for example, a circle. When the size of the auxiliary image is reduced, for example from 1/3 size to 1/4 size, the auxiliary image is cropped by removing approximately 12.5% of the auxiliary image from both left, right, top and bottom. This means that although the secondary image is less visible, the objects (e.g., circles) contained within the secondary image are the same size and position in both the third and the secondary and quarter size secondary images. .

The cropping is achieved by controlling the overlay multiplexer 15 to remove additional scan lines and additional pixels per scan line from the compressed auxiliary signal. The compressed auxiliary signal is continuously generated in the 1/3 magnitude mode state without being changed. In another aspect, as shown in FIG. 4, the multiplexer 15 changes the duration of the high logic level of the FSW control signal so that the multiplexer 15 extends to a time interval corresponding to the area of the secondary image to be cropped so that the compressed secondary video signal is main. The time to be coupled to the display device 17 instead of the video signal is reduced. In addition, as shown in FIG. 4, there is a corresponding change in the BORDER INSERT switching control signal so that the boundary is inserted at the correct position with respect to the cropped auxiliary image.

As such, in the above exemplary embodiment, the use of the cropping method for reducing the size of the auxiliary image only requires changing two signals, and does not need to change other signals. Moreover, in the PIP processing section which does not provide a boundary, the cropping method only needs to change the FSW control signal which is only one signal. This method of operation does not need to be complicated or expanded because there is very little change in the system to achieve size reduction.

Figure 5 shows the FSW and BORDER INSERT to crop the secondary image. A circuit for changing the switching control signal is shown. Basically, the contents of the registers that determine the positions of the left, right, top, and bottom edges of the auxiliary image are selectively changed in response to a user initiated crop (CROP) signal. In particular, a digital word comprising, for example, 8 bits representing the positions of the left, right, top, and bottom edges relative to the sizes of the two secondary images, for example 1/3 and 1/4, is a digital digital multiplexer (21-21). 1, 21-3, 21-5 and 21-7). For example, in Fig. 5, "HP" represents the left edge position of the non-cropped 1/3 sized secondary image, and "VP" represents the upper edge position of the non-cropped 1/3 sized secondary image. The multiplexers 21-1 and 21-3 select digital values for left and right edge positions, respectively, and the multiplexers 21-5 and 21-7 select digital values for upper and lower edge positions, respectively. The outputs of the multiplexers 21-1, 21-3, 21-5 and 21-7 are coupled to their respective registers 21-9, 21-11, 21-13 and 21-15. Since the contents of the registers 21-9 and 21-11 represent the left and right edge positions of the auxiliary image, they are also related to the left and right boundaries. Since the contents of the registers 21-13 and 21-15 represent the upper and lower edge positions of the auxiliary image, they are also related to the upper and lower boundaries. The switching control signal generating device compares the pixel and scan line counters corresponding to the vertical (V) and horizontal (H) synchronization components of the main video signal and the clock signal, and compares the contents of the registers 21-9 and 21-11 with the pixel count. And the comparators for generating the FSW control signal by comparing the contents of the registers 21-13 and 21-15 with the scan line count. BORDER INSERT The switching control signal is also generated in a similar way.

In operation, when a non-cropped third sized auxiliary image is desired, the crop (CROP) control signals have a low logic level and a digital representation of the left, right, top, and bottom edge positions for the uncropped image. The value is selected and coupled to the respective registers 21-9, 21-11, 21-13 and 21-15. If you want a cropped quarter-size secondary image, the crop (CROP) control signals have a high logic level, and digital values representing the left, right, top, and bottom edge positions for the cropped image are selected, respectively. Are coupled to the registers 21-9, 21-11, 21-13 and 21-15.

Although the present invention has been described with reference to specific embodiments, modifications may be made by those skilled in the art. For example, it is not necessary to change all four edge positions to reduce the size of the auxiliary image. This is in some ways less desirable than the methods disclosed in detail. If only one edge position is changed, the aspect ratio will also be changed. If only two orthogonal edge positions change, the center of the secondary image will change. In addition, the topology may change. For example, the analog level corresponding to the boundary may be inserted after the compressed auxiliary video signal is converted into analog form. These and other variations can be considered within the scope of the invention as defined by the following claims.

Claims (8)

Means for providing a main video signal MAIN corresponding to the main image; Means for providing an auxiliary video signal (AUXILIARY); Means (5) for compressing the auxiliary video signal at a predetermined compression ratio to generate a compressed auxiliary video signal corresponding to the auxiliary image of the first size; Means (15) for synthesizing the main video signal and the compressed sub video signal to generate a synthesized PIP-video signal corresponding to an image obtained by combining the main image and the sub image; Means (17) for coupling the synthesized video signal to a display device; In response to a command signal initiated by the user. In order to selectively change the size of the auxiliary image from the screen of the first size to a screen of a predetermined second size smaller by a predetermined amount, without changing the compression ratio and aspect ratio of the compressed auxiliary video signal, Means 21 for selectively cropping the amount of the secondary image by cropping a predetermined amount of the image Device for changing the size of the secondary image, including 2. The cropping apparatus according to claim 1, wherein the cropping means, in response to a command signal initiated by a user, adds a predetermined number of scan lines from a predetermined number of scan lines of the compressed auxiliary video signal and one scan line of the compressed auxiliary video signal. An apparatus for changing the size of an auxiliary image which is a means for selectively removing a predetermined number of additional pixels per scan line from a predetermined number of pixels, The apparatus of claim 2, wherein the synthesizing means includes a switching device for selecting one of the main video signal and the compressed auxiliary video signal in response to a switching control signal. And said selectively removing means comprises means for generating said switching control signal to remove said predetermined number of scan lines and said predetermined number of pixels per scan line. The switching control signal generating means of claim 3, Means for storing a vertical edge position of the secondary image; Means for storing a horizontal edge position of the auxiliary image; A stage for generating the switching control signal in response to contents of the vertical and horizontal edge position storing means; Means for selectively loading one of a first predetermined vertical edge position value and a second predetermined vertical edge position value into the vertical edge position storing means; Means for selectively loading one of a first predetermined horizontal edge position value and a second predetermined horizontal edge position value into the horizontal edge position storing means, Wherein the first vertical and horizontal edge position values correspond to the first size of the secondary image, and the second vertical and horizontal edge position values correspond to the second size of the secondary image. Resizing device. The switching control signal generating means of claim 3, Means for storing a left edge position of the auxiliary image; Means for storing a right edge position of the auxiliary image; Means for storing an upper edge position of the secondary image; Means for storing a lower edge position of the secondary image; Means for generating said switching control signal in response to contents of said left, right, upper and lower edge position storing means; Means for selectively loading one of a first predetermined left edge position value and a second predetermined left edge position value into the left edge position storing means; Means for selectively loading one of a first predetermined right edge position value and a second predetermined right edge position value into the right edge position storing means; Means for selectively loading one of a first predetermined upper edge position value and a second predetermined upper edge position value into the upper edge position storing means; Means for selectively loading one of a first predetermined lower edge position value and a second predetermined lower edge position value into the lower edge position storing means, The first left, right, upper and lower edge position values correspond to the first size of the secondary image, and the second left, right, upper and lower edge position values are the second size of the secondary image And a device for changing the size of the secondary image. 3. The compressed secondary video as claimed in claim 2, further comprising means for generating a boundary signal corresponding to a boundary surrounding the secondary image and a further synthesized video signal corresponding to the secondary image surrounded by the boundary. And further synthesizing means for synthesizing the signal and the boundary signal, wherein the sub-image is modified to synthesize the main video signal and the further synthesized video signal to generate the synthesized video signal. Device. 7. The apparatus according to claim 6, wherein said combining means comprises a switching device for selecting one of said main video signal and said further synthesized video signal in response to a switching control signal, And said selectively removing means includes means for generating said switching control signal to remove said predetermined scan line of said additional portion and said predetermined pixel of said additional line per scan line. The method of claim 6 or 7, wherein said further synthesizing means is: An additional switching device for selecting one of the boundary signal and the compressed auxiliary video signal in response to an additional switching control signal; Means for inducing said further switching control signal in response to said switching jag signal.