JP3500854B2 - Sub-screen video signal vertical compression circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention operates at a different synchronization timing from the main screen when displaying a plurality of video signals having different synchronizations on a video display device. The present invention relates to a sub-screen video signal vertical compression circuit for vertically compressing a sub-screen to be compressed. In particular, the present invention relates to a sub-screen video signal vertical compression circuit for displaying one or a plurality of sub-screens which are different from the synchronization timing of the main screen at the same time on the same screen together with the main screen of the interlaced display. 2. Description of the Related Art In recent years, there has been an increasing need to simultaneously display a plurality of images and information. There is a need for a display device that supports such multimedia. FIG.
FIG. 6 shows an example of the display device, such as a case where the sub-screen 2 is displayed in the main screen 1 as shown in FIG.
As shown in (b), the sub-screens 4, 5,
6 may be displayed at the same time. At this time, the main screen is a screen that displays a video signal used as a synchronization signal of the screen to be displayed. As described above, when a plurality of video signals having different synchronization signal timings are simultaneously displayed on one video display device, the synthesizing technique becomes important. Since the main screen signal is synchronized with the video display device, video signal processing such as screen compression does not matter much in terms of timing. However, the sub-screen signal is not synchronized with the display device. Consideration is needed. The present invention relates to a sub-screen video signal vertical compression circuit for compressing the sub-screen video signal in the vertical direction by vertical interpolation, and presupposes that both the main screen signal and the sub-screen signal are interlaced signals. Hereinafter, a conventional sub-screen video signal vertical compression circuit will be described with reference to the drawings. FIG. 4 is a block diagram of a conventional sub-screen video signal vertical compression circuit, and FIG. 5 is an operation waveform diagram for explaining the operation of the conventional sub-screen video signal vertical compression circuit. The signals shown in FIGS. 4 and 5 correspond to each other. In FIG. 4, reference numeral 31 indicates a polarity, that is, whether the scanning is started from the first field (odd field) or the second field (even field) in the interlaced scanning based on the vertical pulse and the horizontal pulse. This is a field discrimination circuit that performs field discrimination to be performed. Reference numeral 32 denotes an offset generation circuit that generates an offset corresponding to a compression ratio in the first field and the second field. Reference numeral 33 denotes an interpolation circuit that performs interpolation and compression based on the compression ratio. The operation of the sub-picture video signal vertical compression circuit having the above configuration will be described below. First, a field discriminating circuit 31 discriminates from a vertical pulse and a horizontal pulse whether it is a first field or a second field and outputs it. Next, the offset generation circuit 32 sets the offset of the first field to 0, and obtains the offset of the second field according to the compression ratio of the sub-screen. In FIG. 5, the signal of 5 lines of the input sub-screen video signal is compressed into a signal of 4 lines in the sub-screen, so that the compression ratio is 4/5,
The half of the interlace is subtracted from 1/2 (ie, 5/8) of the reciprocal of the compression ratio, and 1/8 is the offset. Next, a pixel value between scanning lines is set by interpolation by an interpolation circuit 33, and a video signal compressed by thinning out the scanning lines is output. At this time, in the second field, the interpolation phase is temporally delayed by the offset and the pixel value is interpolated at the position. In the above-described conventional configuration, when a main screen and a sub-screen signal having different field polarities are simultaneously displayed, the phase of the signal of the second field of the compressed sub-screen is displayed. Is not displayed at a half of the phase of the first field, and the vertical scanning order of the sub-screen signal is reversed in the first field and the second field, thereby causing unnaturalness in the vertical image. was there. In view of the above problems, the present invention determines whether or not the main screen and the sub-screen have the same field polarity, and generates an offset between the first field and the second field according to the result. An object of the present invention is to provide a sub-screen video signal vertical compression circuit that corrects the phase of pixel value interpolation based on the correction and performs interpolation and compression, so that the sub-screen does not become unnatural even in vertical movement. In order to solve the above-mentioned problems, a sub-screen video signal vertical compression circuit according to claims 1 to 5 of the present invention uses a vertical pulse and a horizontal pulse of a main screen to generate a main screen. A main screen field discrimination circuit for generating a field discrimination signal for discriminating the polarity indicating whether the field scan starts from the first field or the second field, and a sub-screen for compressing and displaying the input screen sub-screen video signal at a predetermined compression ratio A sub-screen field discriminating circuit for generating a field discriminating signal for judging the field scanning start polarity of the sub-screen from the vertical pulse and the horizontal pulse of the sub-screen; An offset generating circuit for generating an offset corresponding to the compression ratio in the first field and the second field, and the offset and the compression ratio And an output circuit for inputting an input sub-screen video signal and vertically compressing and outputting the input sub-screen video signal by shifting the field scanning start timing of the sub-screen by an amount corresponding to the offset. A vertical compression circuit for a sub-screen video signal according to a sixth aspect of the present invention includes a main-screen field discrimination circuit for generating a main-screen field discrimination signal from a main screen vertical pulse and a horizontal pulse, and a sub-screen vertical pulse. A sub-screen field discriminating circuit for generating a sub-screen field discriminating signal from the horizontal pulse, a main screen field discriminating signal, a sub-screen field discriminating signal, and a compression ratio. 5. An offset generating circuit according to claim 4, which generates a corresponding offset, and inputs a main screen field discriminating signal, a sub-screen field discriminating signal, and a compression ratio, and performs an offset according to the compression ratio in the first field and the second field of the sub-screen. And an output signal of the offset generating circuit according to claim 4 for generating the offset signal. 5. The output signal of the offset generating circuit according to claim 4, wherein the output signal of the offset generating circuit, the main screen field frequency and the sub-screen field frequency are inputted, and the difference between the main screen field frequency and the sub-screen field frequency is detected. Item 5. A frequency difference detection circuit for selecting and outputting one of the output signals of the offset generation circuit according to Item 5, an output signal of the frequency difference detection circuit, a compression ratio, and an input sub-screen video signal are input, and the input sub-screen video signal is input. And an interpolation circuit for interpolating and outputting. According to the present invention, an appropriate offset is generated between a first field and a second field according to whether or not the main screen and the sub-screen have the same field polarity. To prevent reversal of the vertical scanning order in the first field and the second field of the sub-screen signal after synthesis with the main screen, and to display a sub-screen image in which the sub-screen does not become unnatural even in the vertical direction. Obtainable. Further, the present invention improves the generation of a more preferable offset by switching between the two offset circuits using the main screen field frequency and the sub-screen field frequency. (Embodiment 1) Hereinafter, a sub-screen video signal vertical compression circuit according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing one embodiment of claims 1 to 5 of the present invention, and FIG. 2 is a block diagram of a sub-screen video signal vertical compression circuit showing one embodiment of claim 6 of the present invention. FIG. 3 is an operation waveform diagram for explaining the operation of the sub-screen video signal vertical compression circuit according to a sixth embodiment of the present invention. The signals shown in FIGS. 1 to 3 correspond to each other. In FIG. 1, reference numeral 11 denotes a main screen field discrimination circuit for discriminating the field polarity of the main screen from the vertical pulse and the horizontal pulse of the video signal having the video information of the main screen. Reference numeral 12 denotes a sub-screen field discrimination circuit for discriminating the field polarity of the sub-screen from the vertical pulse and the horizontal pulse of the input sub-screen video signal having the video information of the sub-screen. Reference numeral 13 denotes an offset generation circuit that generates an offset corresponding to a compression ratio in the first field and the second field of the sub-screen. An interpolation circuit 14 interpolates and outputs the input sub-screen video signal based on the offset and the compression ratio. The operation of the vertical compression circuit for sub-picture video signals configured as described above will be described below. First, the main screen field discriminating circuit 11 discriminates from the vertical pulse and the horizontal pulse of the main screen whether it is the first field or the second field and outputs it. Next, the sub-screen field discriminating circuit 12 discriminates from the vertical pulse and the horizontal pulse of the sub-screen whether it is the first field or the second field and outputs it. Next, an offset is obtained by the offset generation circuit 13. First, when the main screen and the sub-screen have the same field polarity, the offset of the first field is set to 0, and the offset of the second field is obtained according to the compression ratio. In FIG. 3, since the signal of 5 lines of the input sub-screen video signal is compressed into a signal of 4 lines on the sub-screen, the compression ratio is 4/5, and か ら is subtracted from 逆 of the reciprocal of the compression ratio. 1/8 is the offset. When the main screen and the sub-screen have different field polarities, the offset of the first field is 1 which is the reciprocal of the compression ratio.
Subtract 1/2 from / 2. The offset of the second field is -1. Next, since it is necessary to arrange pixels in a portion where no scanning line exists due to thinning-out by compression in the interpolation circuit 14 or the like, by arranging pixels between scanning lines by interpolation, Compresses and outputs the sub-screen video signal. At this time, the interpolation phase is delayed by the offset in each of the first field and the second field. In some cases, depending on the method of thinning out, it is possible to perform compression using pixels having scanning lines, and in this case, naturally, the interpolation operation is not performed and the compression by simply thinning out the scanning lines is performed. Is That is, in FIG. 3, "when the offset circuit of claim 4 is used" corresponds to this case. When the field polarity of the main screen and the sub-screen is the same, the offset of the first field is 0. Is that the interpolation phase of the input sub-screen video signal and the output sub-screen video signal (when the main and sub-field polarities are the same) are in phase, and the offset of the second field is 1/8, so that the input sub-screen video signal of the second field is It can be seen that the phase of the output sub-screen video signal is delayed by 1/8 (when the main and sub-field polarities are the same). When the main screen and the sub-screen have different field polarities, the offset is 1 in the first field.
Similarly, the output sub-screen video signal is 1/8 (when the main and sub-field polarities are different) with respect to the input sub-screen video signal.
Only the phase is delayed and the offset is -1 in the second field. Therefore, the output sub-screen video signal is advanced by 1 (when the main and sub-field polarities are different) with respect to the input sub-screen video signal in the second field. You know that you are. As described above, by switching the offsets generated in the first field and the second field in accordance with whether the main and sub field polarities are the same or different, the first and second sub screen signals of the main screen and the synthesized sub screen signal are switched. The reverse of the scanning order in the vertical direction between the field and the second field can be prevented, and a sub-screen image can be obtained in which the sub-screen is natural even in the vertical direction. In addition, there is an advantage that the image quality of the sub-screen after the interpolation compression can be maintained in the vertical direction because the way of giving the offset of the first field and that of the second field are merely interchanged when the main and sub-field polarities are different from each other. . (Embodiment 2) However, there is a disadvantage that the phase of the sub-picture after interpolation compression is shifted by 0.5 lines in the vertical direction when the main and sub-field polarities are the same and different. According to a fifth aspect, when the field polarity of the main screen and the sub-screen is the same, the offset of the first field is set to 0 and the offset of the second field is １ ／ of the reciprocal of the compression ratio. Is subtracted from １ ／. On the other hand, when the field polarities of the main screen and the sub-screen are different, the offset of the first field is 1/2 of the reciprocal of the compression ratio, and the offset of the second field is -1/2. The phase of the sub-picture after the interpolation compression in the vertical direction can be made the same when the polarity is the same or different. That is, the case where the offset circuit of claim 5 is used in FIG. 3 corresponds to this case. When the main screen and the sub-screen have the same field polarity, the offset of the first field is the same as in the case of claim 2. Is 0, the interpolation phase of the input sub-screen video signal and the output sub-screen video signal (when the main and sub-field polarities are the same) in the first field are the same, and the offset of the second field is 1/8. It can be seen that the phase is delayed by ８ of the output sub-screen video signal (when the main and sub-field polarities are the same) with respect to the input sub-screen video signal. When the main screen and the sub-screen have different field polarities, the offset is 5 in the first field.
/ 8, the interpolation phase of the output sub-screen video signal (when the main and sub-field polarities are different) with respect to the input sub-screen video signal is 5
/ 8 and the offset in the second field is -1/2. Therefore, the phase of the input sub-screen video signal of the second field is advanced by 1/2 of the output sub-screen video signal (when the main and sub-field polarities are different). You know that you are. (Embodiment 3) However, the way of giving an offset differs when the main and sub field polarities are the same and different, so that the image quality of the sub-picture after interpolation compression in the vertical direction is different. According to a sixth aspect of the present invention, the offset generating circuits of the fourth and fifth aspects are switched according to the difference between the main screen field frequency and the sub-screen field frequency. When the frequency difference is small, the switching between the main and sub field polarities does not occur frequently.
It is acceptable that the phase of the sub-screen after interpolation compression is shifted by 0.5 line in the vertical direction when the main and sub-field polarities are the same and different, and the image quality is prioritized, and the offset generating circuit according to claim 4 is selected. The interpolation compression is performed using the output signal of the offset generation circuit according to claim 4 as an offset. When the frequency difference is large, the polarity of the main and sub-fields is frequently changed, and it is not preferable that the sub-screen phase is shifted by 0.5 line. The phases of the sub-pictures after the interpolation compression are made the same. As described above, according to the present invention, the offset between the first field and the second field is switched depending on whether the field polarity of the main screen and the sub-screen is the same or different, and the main screen and the sub-screen are further switched. Due to the relationship of the field frequency of
By selecting a circuit that generates an appropriate offset from the two offset generation circuits and performing interpolation compression, it is possible to obtain a sub-screen image in which the vertical motion of a moving image is natural.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a sub-screen video signal vertical compression circuit showing one embodiment of claims 1 to 5 of the present invention. FIG. 2 is a block diagram of one embodiment of claim 6 of the present invention. FIG. 3 is a block diagram of a sub-screen video signal vertical compression circuit shown in FIG. 3; FIG. 4 is an operation waveform diagram for explaining the operation of the sub-screen video signal vertical compression circuit; FIG. FIG. 6A is a diagram showing a first example in which a plurality of video signals having different synchronization signal timings are displayed on one video display device. FIG. 6B is a timing chart of the synchronization signals. FIG. 2 is a diagram showing a second example in which a plurality of different video signals are displayed on one video display device. DESCRIPTION OF SYMBOLS 1, 3 Main screens 2, 4, 5, 6 Sub-screen 11 Main-screen field discriminating circuit 12 Sub-screen field The discrimination circuit 13 and the offset generation circuit 13a. Offset generation circuit 14 interpolation circuit 15 frequency difference detection circuit offset generating circuit 13b claim 5

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-55-153484 (JP, A) JP-A-64-51774 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 5/38-5/46

Claims (1)

(57) [Claims] [Claim 1] Determine the field polarity of the video signal of the main screen.
Separate main screen field discrimination circuit, and
A sub-screen that is reduced and displayed together with the video signal of the main screen
Sub-screen field to determine the field polarity of the video signal
From the main screen field discriminating circuit.
Signal and the signal from the sub-screen field discriminating circuit and the pressure
From the reduction ratio, the first field of the video signal of the sub-screen and the
Generates an offset corresponding to the compression ratio in the second field
An offset generating circuit that performs
An interpolation circuit for compressing the video signal of the screen,
The interpolation circuit is configured to input the input from the offset generation circuit.
The scan start timing is delayed by the
Outputting a video signal of a reduced sub-screen.
Sub-picture video signal vertical compression circuit that.