JP3363617B2 - Digital mixing circuit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital mixing circuit for digitally mixing moving picture and graphic data read from a laser disk. 2. Description of the Related Art A moving image is recorded on a laser disk together with sound. In the LD-G, graphic data as subcodes and video data representing the moving image and the graphic data are further recorded. Transparency data indicating the mixing ratio is recorded. In a conventional digital mixing circuit, digital video data representing a moving image is multiplied by transparency data K, while graphic data is multiplied by (1-K), and the result of the multiplication is added. Had gone. [0004] In order to realize the conventional mixing method, a multiplier is required for each of digital video data and graphic data, and one adder is required. Was needed. When such a mixing circuit is formed into an LSI, the adder and the subtractor are not so problematic because the circuit scale is small. However, since the multiplier occupies a large area, the circuit scale of the entire LSI increases. There were drawbacks. According to the present invention, there is provided a subtracter for performing a subtraction process between digital video data and graphic data, and subtracting the transparency data defining a mixing ratio between the video data and the graphic data. A digital mixing circuit is constituted by a multiplier for multiplying the result and an adder for adding the graphic data to the multiplication result of the multiplier to solve the above problem. In addition, the present invention is also directed to an input of the output of the adder and the digital video data, selecting the digital video data only when the transparency data has a specific value, and selecting the digital video data when the transparency data is not a specific value. A selector for selecting the output of the container is further provided. According to the present invention, the digital video data and the graphic data are subtracted first, the result of the subtraction is multiplied by the transparency data, and the graphic data is added to the result of the multiplication. Therefore, digital mixing can be achieved by using only one multiplier. Further, the selector for inputting the output of the adder and the digital video data selects the digital video data only when the transparency data is a specific value, and selects the output of the adder when the transparency data is not the specific value. So the transparency data is all 1
In this case, only pure video data that does not mix graphic data at all is reliably output. FIG. 1 is a block diagram showing the configuration of an embodiment of the present invention. Reference numeral 1 denotes an input terminal for inputting 8-bit digital video data LD representing a moving image read from a laser disk; 2 is an input terminal for inputting a subcode read from the laser disk, 3 is a subcode decoder for decoding the input subcode and extracting 12-bit graphic data and 6-bit transparency data K, 4 is a decode An RGB encoder for encoding the 12-bit graphic data composed of RGB components into 8-bit graphic data G composed of a luminance signal and a chroma signal. Reference numeral 6 denotes an 8-bit digital video data LD and an RGB encoder which are input to an input terminal 1 Subtraction with 8-bit graphic data G from A subtractor 7 for multiplying the subtraction result by the transparency data K; an adder 8 for adding the multiplication result from the multiplier 7 to the graphic data G from the RGB encoder; , And the digital video data LD input to the input terminal 1, and a selector 10 for selectively outputting either one of them. The selector 10 DA-converts the output of the selector 9 and converts the converted analog signal to a composite video signal. Is a DA converter that sends out to the output signal 11. Hereinafter, the operation of the present embodiment will be described in detail.
First, the sub-code input to the input terminal 2 is decoded by the sub-code decoder 3, and graphic data and transparency data K are extracted. The graphic data is encoded into 8-bit graphic data G by the RGB encoder 4, and the graphic data G is supplied to one input of a subtractor 6. The digital video signal LD input to the input terminal 1 is supplied to the other input of the subtractor 6, so that
In the subtracter 6, a subtraction process of (LD-G) is performed. Next, the result of the subtraction is input to the multiplier 7, where the result is multiplied by the transparency data K from the subcode decoder 3. Therefore, K · (LD-G) is obtained as the multiplication result. Furthermore, since the graphic data from the RGB encoder 4 is added to the multiplication result by the adder 8, the addition result of K · (LD−G) + G is supplied to one input terminal of the selector 9. The Rukoto. The other input terminal of the selector 9 is directly supplied with the digital video data LD inputted to the input terminal 1, and the selector 9 has the transparency data of all 1, ie, the graphic data is added to the video data. The video data LD is selected when the data indicates that no mixing is performed, and the addition result is selected when the data is not all 1s. Therefore, when the transparency data is all 1, an analog signal obtained by DA-converting the video data LD itself is transmitted to the output terminal 11, and when the transparency data is other than all 1, the addition result K is output.
-An analog signal obtained by DA-converting (LD-G) + G is transmitted. Here, the addition result K · (LD−G) + G
Is equal to the data obtained by adding K · LD and (1−K) · G, so that an output in which the video data LD and the graphic data G are mixed according to the transparency data K is obtained. Incidentally, the transparency data K is, specifically, 6-bit data, where the first bit is 0.5, the second bit is 0.25, and the third bit is
Since each bit is weighted such that the bit is 0.125, the actual output output from the adder 8 is not the LD itself even if all 6 bits become "1", It will include data G. However, in this embodiment, as described above, when the transparency data K is all 1, the video data LD is directly selected by the selector 9, so that the video data LD containing no graphic data is reliably output. Will be done. According to the present invention, digital video data and graphic data can be mixed by using only one multiplier, so that the circuit scale can be reduced when implementing an LSI. Become like Also, when the transparency data is a specific value, the video data itself can be output instead of the operation result.
Be able to provide high quality videos.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of an embodiment of the present invention. [Description of Signs] 1, 2 input terminals 3 sub-code decoder 6 subtractor 7 multiplier 8 adder 9 selector 10 DA converter 11 output terminal

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Claims (1)

(57) [Claim 1] A subtracter for performing a subtraction process between digital video data and graphic data, and transparency data defining a mixing ratio between the video data and the graphic data as the subtraction result. A multiplier for multiplying, an adder for adding the graphic data to the multiplication result of the multiplier, an output of the adder and the digital video data being input, and the transparency data being digital data
Do not mix graphic data with video data
The digital video data is selected only when the data indicates the digital video data.
A digital mixing circuit further comprising a selector for selecting the output of the adder when the data does not indicate that the data is not mixed.