JPS61181293A - Two-scope television receiver - Google Patents

Abstract

PURPOSE:To correct a time difference between signals produced by a signal separation filter by giving a time difference to sampling clocks for a luminance signal and a color difference signal to sample both the signals. CONSTITUTION:A video signal fed to an input terminal 1 is fed to and demodulation circuit 4 and also to a filter 3, where only a chrominance carrier signal is extracted and fed to the demodulation circuit 4. The filter 3 causes a delay in the chrominance carrier signal and there is a time difference that a luminance signal Y is outputted a slightly earlier between the luminance signal and color difference signals (R-Y), (B-Y). Then a time difference is given to sampling clocks fed to an A/D converter 5a and A/D converters 5b, 5c and the sampling clock given to the latter is retarded slightly. Thus, data read from 1H memories 6a, 6b, 6c are subjected to correction for the delay in the color difference signals.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention reduces a second image such as an image of another channel, an image of a VTR, an image of a video camera, etc. to a part of the original image of a television receiver. This invention relates to a two-screen television receiver that displays images simultaneously.

Prior Art Figure 3 briefly shows the main parts of the display data creation circuit for the sub-screen of the two-screen display circuit of a conventional two-screen television receiver. Video signal demodulation circuit 4
demodulates into a luminance signal and color difference signal. At this time, as a known technique, the luminance signal and the carrier chrominance signal are separated by a filter 3 using a peaking coil by utilizing the difference in frequency bands between the luminance signal and the carrier chrominance signal, and the signal is added to the demodulation circuit 40 on the chrominance signal processing side. As a measure against the time delay caused by the filter 3, a signal obtained by delaying the video signal input by the delay circuit 2 is added to the input side of the demodulation circuit 4.

The luminance signal and color difference signal output obtained from the demodulation circuit 4 are applied as time-adjusted signals to the A/D converters 6a to 6C, and converted into digital data by the sampling clocks Φ and 2 of the timing chart shown in FIG. be done. The gate 9 and the frequency dividing circuit 12 are gate circuits that generate sampling clocks for the luminance signal and color difference signal.

Problems to be Solved by the Invention However, in conventional circuits like this, the delay circuit 2 is composed of a resistor and a capacitor with a coil as the basic element, so the delay time changes due to temperature changes and aging. Furthermore, since correction is performed on the analog part of the signal, the circuit configuration is not suitable for IC implementation.

Means for Solving the Problems In the two-screen television receiver of the present invention, the time difference between the luminance signal and the color difference signal at the time of input to the A/D converter is determined by adjusting the time difference between the luminance signal sampling and the color difference signal sampling. This is corrected by delaying the signal by an appropriate amount of time, temporarily storing the luminance signal and color difference signal for one horizontal scanning period, and reading them out at the same time when they are read from the temporary storage.

According to the dual-screen television receiver of the present invention, time difference is achieved by sampling each signal with a time difference in the sampling clock applied to the A/D converter for A/Ding the luminance signal and color difference signal. After correcting the delay, each sampled signal is temporarily stored, and when reading the temporarily stored data, each data is read out simultaneously.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIGS. 1 and 2. FIG. 1 is a block diagram of a sub-screen display data creation part of a two-screen television receiver according to an embodiment of the present invention, and FIG. 2 is a timing chart of each part in FIG. 1. In this embodiment, four luminance signals are used during one pixel of color difference signals.
An example of sampling pixels is shown below.

The video signal applied to the video signal input terminal 1 is sent to the demodulation circuit 4.
As inputs, one inputs the video signal as it is, and the other inputs a signal obtained by extracting only the carrier color signal by the filter 3. This filter 3 causes a signal delay on the carrier color signal side, and the demodulation circuit 4 separates and demodulates the luminance signal (Y).
There is a time difference between the luminance signal and the color difference signals (R-Y) and (B-Y) in that the luminance signal is output slightly earlier.

Therefore, the sampling clock (■) of the luminance signal is obtained by adding the basic clock (■) to the gate circuit 9, and inputting the control signal (■) which becomes high level only during the second horizontal scanning period and the control signal (■) which permits sampling to other inputs of the gate circuit 9. Create by adding to. On the other hand, as the sampling clock for the color difference signal, a clock obtained by dividing the luminance signal sampling clock Φ by 4 through the frequency dividing circuit 12 is added to the shift circuit 13 to obtain the clocks ■ and ■ (in this example, a four-stage shift circuit shown), the clock selected by the switching means 14 is used.

The luminance signal data sampled by the sampling clock ■ is obtained through an inverter 7 and a control signal obtained by inverting the basic clock and a control signal ■ which is at a high level only during the first horizontal scanning period, and a sampling permission control signal ■ through a gate circuit 8. 1H for one horizontal scanning line in the second horizontal scanning period by the write/read clock
The data are sequentially written into the memory 6a. Similarly, the color difference signal data sampled by the selected clock of the sampling clocks tO+■ is set to the writing/reading clock delayed by one clock from the sampling clock by the switching means 14 during the second horizontal scanning period. ,
(1) or (2)) are sequentially written into the 1H memories 6b and ec.

In this example, one unit of video signal sampling is one pixel of the color difference signal (one sampling) for four pixels of the luminance signal (four samplings), so the first
A clock delayed by t time from the luminance signal sampling clock is used as the color difference signal sampling clock. Furthermore, since the number of samples per unit is four times that of the luminance signal than the color difference signal, the capacity of the 1H memory 6a for luminance signal data is equal to the capacity of the 1H memory 6b for color difference signal data.

Four times more is required than 6C.

The data temporarily stored in the 1H memories 6a, eb, and 6c are read out simultaneously during the third horizontal scanning period. The read clock for the luminance signal data is the same as the write clock ■, but the read clock for the color difference signal data is high only during the third horizontal scanning period of the basic clock that generates the luminance signal data read clock ■. A clock (2) is used, which is obtained by dividing a clock obtained by passing a control signal (◎) varying in level and a sampling permission control signal (2) through a gate circuit (10) into four by a frequency dividing circuit (11). As a result, the color difference signal data is also read out at the same time as the first luminance signal data of one unit is read out.Thus, the color difference signal that is delayed by time t from the luminance signal at the time of signal demodulation is transferred to the data from the temporary storage means. At the time of reading, the delay is corrected so that they are read out simultaneously.

Effects of the Invention As described above, according to the two-screen television receiver of the present invention, the time of the sampling clock for sampling the luminance signal and the color difference signal is shifted, the sampling data is temporarily stored for one horizontal scanning period, and the sampling data is stored temporarily for one horizontal scanning period. By reading out the temporarily stored data at the same time, it is possible to correct the time difference between signals caused by the signal separation filter. Furthermore, the delay correction time can be finely adjusted by the switching means. Unfortunately, this method allows for delay correction in the digital signal range compared to conventional methods that delay in the analog signal range, making it possible to reduce color shifts caused by temperature changes and aging, and is also suitable for IC implementation. This method is extremely advantageous in practical terms.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of the main parts of a two-screen television receiver according to an embodiment of the present invention, Fig. 2 is a timing chart of each part explaining its operation, and Fig. 3 is a diagram of a conventional two-screen television receiver. FIG. 2 is a block diagram of main parts. 2... Delay circuit, 3... Luminance/color difference separation filter, 4... Demodulation circuit, 5...
A/D converter, 6...Temporary memory memo IJ, 7,
8,9,10. , -15...gate circuit, 11
．． 12... Frequency divider circuit, 13... Shift register, 14... Changeover switch.

Claims (1)

[Claims] means for sampling the color difference signal with a fixed time delay with respect to the sampling of the brightness signal when converting the brightness signal and color difference signal of the television signal into digital signals, means for making the sampling delay time variable; means for performing the sampling in a second horizontal scanning period of the three horizontal scanning periods and temporarily storing the sampled luminance signal and color difference signal for one horizontal scanning period; A two-screen television receiver comprising: means for correcting the fixed time delay by reading data from the means.