JPS6351435B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a digital video signal storage device that stores unit image information digitized corresponding to frames, fields, or the like.

When a video signal is digitized and stored, the video signal is written in frame units or field units and stored in frame memory or field memory, but the seam of the screen stored in each memory is vertical. It is set using the blanking period. During this vertical blanking period, a signal such as a color subcarrier burst signal is set, and a vertical synchronization signal for deflection control of the playback screen is also set. Therefore,
If the screen seam is set within this vertical blanking period as described above, discontinuity may occur in the timing or color subcarrier at the seam of each unit screen, and this may occur on the playback screen. There is a high possibility that it will have a direct impact on the

That is, as shown in A in FIG. 1, the video signal has a video period B set against a vertical blanking period A, and when this video signal is digitized and stored in a frame memory, the storage period is As shown in Figure B, the vertical blanking period A
The blanking period A includes the start and end points of storage. C in FIG. 1 shows the actual display period excluding the overscan portion appearing on the display screen of the cathode ray tube.

When writing and storing a digital video signal in a frame memory, the cycle time of the memory element is long due to the structure of the frame memory, so if multiple pixels are written and read in parallel, one frame period will be an integral multiple of the frame memory. It may not be familiar, and there may be a time jump of fractional minutes. Further, the color subcarriers may be inverted between frames, but unless a circuit is used to process this on the readout side, a phase jump will occur at the time of frame switching. This occurs when the relationship between the color subcarrier and the synchronization signal does not meet the standard of the regular NTSC video signal, for example on a home VCR.
The same holds true for the reproduced signal.

In other words, these causes the discontinuity in the timing and phase of the color carrier mentioned above, and such discontinuity occurs when the time from the vertical blanking period A to the display period shown by C in FIG. Since it is short, the effect will be visible on the display screen.

For example, if the timing jumps, the second
As shown in the figure, a curved vertical line pattern will now be displayed at the top of the screen. If the color subcarrier is discontinuous, this will appear as a change in hue at the top of the display screen.

This invention was made in view of the above points, and even when a video signal is digitized and stored in a memory in units of frames, for example, it is possible to effectively absorb time jumps, and furthermore, it is possible to effectively absorb the time jump. It is an object of the present invention to provide a digital video signal storage device that prevents carrier phase discontinuity from appearing on a display screen.

An embodiment of the present invention will be described below with reference to the drawings. FIG. 3 shows its configuration. A video input signal is supplied to a frame memory 11, digitized, and written in frame units. Further, this input video signal is supplied to a vertical synchronization separation circuit 12 to separate and extract a vertical synchronization signal and extract a frame pulse signal based on this synchronization signal. And this separation circuit 1
The monostable multivibrator 13 is driven by the frame pulse signal taken out from the frame pulse signal 2 to form a timing signal that is delayed until just before the vertical blanking period of the video signal. Based on the timing signal from the multivibrator 13, the storage period is set, and the vertical blanking period is set as shown in B in the figure for the video signal shown in A in FIG. The storage period starts immediately before the blanking period and ends immediately before the blanking period. In this case, the start and end points of this storage period are set by the monostable multivibrator 13 so that they are outside the display period shown in C in the figure and located immediately before the vertical blanking period.

That is, the write control circuit 14 controls the write command based on the above-mentioned timing signal of the monostable multivibrator 13, and the B in FIG.
The write storage period shown in FIG. 1 is set, and the frame memory 11 is write-controlled to write and store the digitized video signal.

That is, for the frame memory 11 in which the video signal is digitized and written, a storage period that starts and ends before the vertical blanking period A and outside the display period that is not displayed in the overscan of the television playback screen. is set.

Therefore, the time from the point of discontinuity in the timing or phase of the color subcarrier to the display period of the playback screen is set to be sufficiently long.For example, time jumps are caused by the scanning circuit on the television playback device side This can be absorbed by the response of the AFC circuit. In addition, the phase discontinuity of the color subcarrier is such that the actual display period begins after the transient response period of the color circuit has passed, and the above-mentioned image distortion and hue shift at the top of the playback screen can be reliably prevented. state.

FIG. 5 shows another embodiment of this invention,
In the synchronization separation circuit 15 to which the input video signal is supplied,
Extract the vertical synchronization signal V and horizontal synchronization signal H. Then, the counter 16 is cleared by this vertical synchronizing signal V, the counter 16 is set to count the horizontal synchronizing signal H, the counted value of the counter 16 is detected by the decoder 17, and the result is shown in 13 in FIG. Timing signals at the start and end points of the storage period are obtained. Other components that are the same as those in Figure 3 are as follows:
The same reference numerals are used to omit the explanation.

As described above, according to the present invention, it is possible to reliably prevent the influence on the reproduced image due to the discontinuity of the timing or color subcarrier that occurs at the next storage period in the digitalized stored video signal stored in the memory. The effects are extremely significant, as the structure of this type of video signal storage device can be simplified and its adaptability to various input signal conditions can be expanded.

In the embodiment, the unit image is described as a frame, but it may be a field unit, or even a plurality of frames. Furthermore, in the embodiment, the vertical synchronization signal is used to obtain the timing of the start and end points of the storage period, but it is not necessarily necessary to use the vertical synchronization signal, and signals from other signal generation means may also be used. , which can be implemented in the same manner as the above embodiment.

[Brief explanation of drawings]

FIG. 1 is a diagram illustrating the relationship between a video signal and a storage period in a conventional storage device, FIG. 2 is a diagram illustrating a reproduced image according to the storage period, and FIG. 3 is a storage according to an embodiment of the present invention. FIG. 4 is a diagram illustrating the storage period in the above embodiment, and FIG. 5 is a diagram illustrating another embodiment of the present invention. 11... Frame memory, 12, 15... Synchronous separation circuit, 13... Monostable multivibrator, 14...
Write control circuit.

Claims (1)

[Claims] 1 means for generating a timing signal just before the vertical blanking period and outside the playback display screen; means for digitizing the input video signal; and writing the digitized image information into an image memory based on the timing signal. and a means for entering the
Even if there is discontinuity in the timing or phase of the color carrier in the readout signal from the image memory,
A digital video signal storage device characterized in that by setting a sufficiently long time from the point of discontinuity to the display period of the playback screen, these can be absorbed by a response on the image playback device side.