JPH04156082A - Video scanning frequency conversion device and its control method - Google Patents

Abstract

PURPOSE:To simplify memory control by providing this image scanning frequency converter with an I/O switch for switching a memory block to which image data are to be read out synchronously with the blanking period of an output side vertically synchronizing signal. CONSTITUTION:This converter is provided wit the 1st and 2nd memory blocks 2, 3 for writing/reading out image data for one screen and the I/O switch 1 for switching an image data writing memory block synchronously with the blanking period of an input side vertically synchronizing signal and switching an image data reading memory block synchronously with the blanking period of an output side vertically synchronizing signal. Thereby, I/O control using two memory blocks divided in each image data for one screen and utilizing the blanking period of the vertically synchronizing signal can be attained differently from I/O control using memories divided in each image data of one scanning and utilizing the blanking period of a horizontal synchronizing signal. Consequently, I/O switching frequency can be reduced and memory control can be simplified.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a video scanning frequency conversion device that converts the video scanning frequency of an arbitrary video signal to another video scanning frequency.
In particular, the present invention relates to a video scanning frequency conversion device and its control method that can simplify the control of video memory in the video scanning frequency conversion device and stabilize frequency conversion.

(Prior Art) A conventional video scanning frequency conversion device will be explained with reference to FIG.

FIG. 3 is a block diagram of a memory and an input/output section of a conventional video scanning frequency conversion device.

A conventional video scanning frequency conversion device includes a memory controller 4 to which an input horizontal synchronizing signal S Hin and an output horizontal synchronizing signal S Hout are input, a serial input memory 5 on the input side, a serial output memory 7 on the output side, and It consisted of a video memory 8 consisting of a memory array 6 connecting a serial input memory 5 and a serial output memory 7.

The memory controller 4 receives an input horizontal synchronization signal S Hi
n, and based on the blanking period of this input-side horizontal synchronization signal S Hin, the transfer provides the timing to transfer the serial input data Din of the serial input memory 5 to the memory array 6 as parallel data Pin. Issues the command T, receives the output side horizontal synchronization signal S Hout, and transfers the parallel data P out of the memory array 6 to the serial output memory 7 based on the blanking period of the output side horizontal synchronization signal S Hout. A transfer command T is issued to give the timing for the transfer.

The transfer command T is given to the serial input memory 5, memory array 6, and serial output memory 7, respectively, and the transfer command T issued based on the blanking period of the input side horizontal synchronization signal S Hin is Each section can determine whether the transfer command T is issued based on the blanking period of the output side horizontal synchronization signal S Bout.

The serial input memory 5 in the video memory 8 stores serial input data Di for one horizontal scanning line of manually input video signals.
n is stored serially and transferred to the memory array 6 as parallel data Pin in response to a transfer command T from the memory controller 4.

That is, between the serial manual memory 5 and the memory array 6, the video data is converted from analog serial data to digital parallel data (A/D conversion).

Further, the memory array 6 in the video memory 8 stores the video data from the serial input memory 5 as parallel data Pin, and transfers the stored parallel data P out to the serial output memory 7 by a transfer command T from the memory controller 4. Transfer to. Here, the parallel data Pin and the parallel data P out are video data with the same content, but for convenience, they are distinguished by defining the data input to the memory array 6 as the parallel data Pin and the data output from the memory array 6 as the parallel data P out. It shall be.

The serial output memory 7 in the video memory 8 outputs the parallel data P out transferred from the memory array 6 as serial output data Do for 1942 horizontal scans of the video signal.
It outputs serially as ut. Between the memory array 6 and the serial output memory 7, the video data is converted (D/A) from digital parallel data to analog serial data.

Next, a frequency conversion control method in the conventional video scanning frequency conversion device will be described.

When the serial input data Din for one horizontal scanning line of the input video signal is input to the serial input memory 5 of the video memory 8, the memory controller 4 inputs the input horizontal synchronization signal 5Hin for one horizontal scanning line. A transfer command T is issued based on the ranking period, and the transfer command T is received by the serial input memory 5 and transferred and stored in the memory array 6 as parallel data Pin. As a result, the video data is A/D converted.

Next, the output side horizontal synchronization signal S is sent to the memory controller 4.
When Hout is input, the output side horizontal synchronization signal S
Transfer command T based on the blanking period of Hout
is issued, the memory array 6 receives the transfer command T, outputs the parallel data P out to the serial output memory 7, and serially outputs the serial output data D out for one horizontal scanning line of the video signal on the output side. It outputs serially from the output memory 7. As a result, the video data is D/A converted.

In this way, the input video signal is A/D-converted, stored as data, read out again, D/A-converted, and output as a video signal, which is continuously performed asynchronously, thereby converting the video scanning frequency. was going on.

FIG. 4 is a timing chart explaining the conventional video scanning frequency conversion, in which the input side horizontal synchronizing signal S! (This is a timing chart diagram of in and output side horizontal synchronization signal S Hout.

As shown in FIG. 4, since the scanning frequencies of the input side horizontal synchronization signal 5Hin and the output side horizontal synchronization signal S Hout are different, blanking periods of the horizontal synchronization signals may overlap as shown at point A in the figure. In this case, memory array 6
Since only one transfer command T can be issued at a time, it is necessary to transfer input data from the serial input memory 5 to the memory array 6 or transfer output data from the memory array 6 to the serial output memory 7. It was necessary to take steps to delay one or the other.

(Problems to be Solved by the Invention) However, the conventional video memory 8 described above requires complicated memory control as described above, and the short time video scanning frequency for each blanking period of the horizontal synchronization signal is If the video data transfer process between memories is delayed due to the conversion process, there is a problem in that the input/output timing is shifted, resulting in flickering of the output video signal.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a video scanning frequency conversion device and its control method that use a general-purpose memory instead of a special video memory and can simplify complicated memory control. With the goal.

(Means for Solving the Problems) The invention according to claim 1 for solving the problems of the conventional example has a first memory block and a second memory for writing and reading video data for one screen. the first block in synchronization with the blanking period of the input vertical synchronization signal.
The video data is written by switching between the memory block and the second memory block, and the first memory block and the second memory block are switched in synchronization with the blanking period of the vertical synchronization signal on the output side. The device is characterized in that it has an input/output switch that switches between the input and output switches to read out the video data.

The invention according to claim 2 for solving the problems of the conventional example is, in the video scanning frequency conversion device according to claim 1,
When the input/output switcher writes video data by switching between the first memory block and the second memory block in synchronization with the blanking period of the vertical synchronization signal on the input side, the video data is stored in the memory block to which writing is performed. When reading is being performed, no video data is written, and the input/output switch switches between the first memory block and the second memory block in synchronization with the blanking period of the vertical synchronization signal on the output side. If video data is being written in the memory block to be read, switch the input/output switch to the previous memory block and read the video data that was previously read. It is characterized by reading out again.

(Function) According to the invention described in claim 1, the first memory block and the second memory block for writing and reading video data for one screen, and the blanking period of the input side vertical synchronizing signal. Since the video scanning frequency conversion device has an input/output switch that switches the memory block to which video data is written in synchronization and switches the memory block to which video data is read in synchronization with the blanking period of the output side vertical synchronization signal, Unlike conventional memory input/output control in units of video data of one scan using the blanking period of the horizontal synchronization signal, two memory blocks of video data of one screen are controlled using the blanking period of the vertical synchronization signal. As a result, the input/output control that is used reduces the frequency of switching between memory inputs and simplifies memory control.

According to the invention set forth in claim 2, in the video scanning frequency conversion device set forth in the claim, when the memory block is switched by the input/output switch and video data is written, the memory block to be written is in the state where the video data is being read. When this is the case, no video data is written, and when the memory block is switched by the input/output switch and the video data is read out, if the memory block to be read is in the process of writing video data, the video data is not read out. The control method for the video scanning frequency conversion device is to switch the input/output switch and read out the previously read video data again. Since scanning frequency conversion processing can also be performed stably, disturbances and flickering in the output signal can be eliminated.

(Example) An example of the present invention will be described with reference to the drawings.

FIG. 1 is a configuration block diagram showing input and output of video data to and from memory blocks in a video scanning frequency conversion device according to an embodiment of the present invention.

The video scanning frequency conversion device of this embodiment uses two general-purpose memory blocks as a first memory block 2 and a second memory block 3, and inputs data to the first memory block 2 and second memory block 3. Input/output for writing video data Vin, reading output video data Vout from the first memory block 2 and second memory block 3, and controlling switching of video data output to two memory blocks. It consists of a switch 1.

The input/output switch 1 converts the input video data Din into analog/
Digital conversion (A/D conversion) and input side vertical synchronization signal S
Based on the blanking period of Vin, one screen worth of human video data Vin is transferred to either the first memory block 2 or the second memory block 3, and is also transferred to the first memory block 2 or the second memory block. 3, one screen worth of video data is read out, digital/analog conversion (D/A conversion) is performed, and one screen worth of output video data Vo is read out based on the blanking period of the output synchronization signal S Vout.
ut to a display unit (not shown) such as a CRT.

The first memory block 2 and the second memory block 3 are
When analog data of input video data Vin for one screen is digitally converted and provided as digital data by the operation of the input/output switch 1, the video data of the digital data is written, and the input/output switch 1 1 reads digital video data from the first memory block 2 or the second memory block 3 to the input/output switch 1.

In addition, the input/output switch 1 has an input vertical synchronizing signal S Vi
In synchronization with the n blanking period, the memory block to which one screen worth of input video data Vin is written is switched, and the output side vertical synchronization signal S Vo
In synchronization with the blanking period of ut, the memory block from which one screen worth of output video data Vout is read is switched.

However, even if you try to write the input video data Vin to the memory block by switching the input/output switch 1, if the output video data V out is being read from the memory block, the input video data Vin cannot be written. Furthermore, even if an attempt is made to read the output video data V out from the memory block by switching the input/output switch 1, the input video data Vin will not be written to the memory block. If the output video data Vout is in the middle, the output video data Vout cannot be read out, and the output video data Vout stored in another memory block and read out before the switching operation is performed is read out again. It is controlled by an output switch 1.

Next, a method of controlling the video scanning frequency conversion device of this embodiment will be explained using FIG. 2.

Figure 2 shows input and output video data V ln, V o
4 is a timing chart showing the relationship between ut and read (R)/write (W) in the first memory block 2 and the second memory block 3. FIG.

In FIG. 2, Vfn is one screen worth of input video data.
V out is the video period of one screen of output video data (several meters
~number+m5ec), and in the first and second memory blocks 2.3, R indicates the read state for one screen, and W indicates the write state for one screen. Although the input video data Vin is discontinuous, it is written to the first or second memory block one screen at a time, and the output video data V ou
t is a first or second memory block that continuously reads out the latest video data in units of one screen.

The numbers in the data are written to clarify which video data is being input and output.The numbers in circles indicate video data that was not written to the memory block, and the diagonally shaded data areas represents the input/output of video data in the second memory block 3.

When input video data Din is input to the input/output switch 1 of the video scanning frequency conversion device of this embodiment, the serial input video data is A/D converted into parallel data at the timing of the input side dot clock CKin. In this practical example, vl is written into the first memory block 2 as input video data V1n for one screen in synchronization with the blanking period of the input side vertical synchronization signal S Vin.

Next, when writing of the input video data Vl to the first memory block 2 is completed, the input end vertical synchronization signal S Vin
The input/output switch 1 switches to the second memory block 3 in synchronization with the blanking period, but since the output video data vO is being read out in the second memory block 3, the input Video data v2 is not written to the memory block. In the case of the input video data V3, the input video data v3 is written to the second memory block 3 since no video data is read out from the second memory block 3.

In this way, the input video data Vin can be changed by switching the input/output switch 1 if the memory block to which the input/output switch 1 is to be written is reading the output video data V out.
It can be written only if it cannot be written to and is not being read.

In addition, the input/output switch 1 has a dot clock CK on the output side.
out is given, and this dot clock CKou
The video data written in the memory block at the timing t is D/A converted from parallel to serial, and the output video data V out for one screen is output at the timing of the output side vertical synchronization signal s VOt + t. .

In this embodiment, as shown in FIG. 2, the output video data vo is read from the second memory block 3, and the input/output switch 1 is read out in synchronization with the blanking period of the output side vertical synchronization signal S Vout. switches to the first memory block 2 and tries to read the video data written in the first memory block 2, but since the input video signal Vln is being written in the first memory block, Since the video data cannot be read from the first memory block 2, the output video data vO is read from the memory block 3 of node 2 again and output.

When the reading of the second output video data vo is completed, the input/output switch 1 switches to the first memory block 2 in synchronization with the blanking period of the output side vertical synchronization signal S Vout, and the input/output switch 1 switches to the first memory block 2. The video data Vl written in block 2 is serially D/A converted by the dot clock CKout, and the output side vertical synchronization signal Sv
At the out timing, one screen worth of output video data Vl is output.

In this way, the output video data Vout is continuously output even if video data with the same content is read out successively.

According to the video scanning frequency conversion device of this embodiment, the first memory block 2 and the second memory block 3 perform writing and reading of video data for one screen, and the blanking of the input side vertical synchronization signal S Vin. The input video data Vin is written by switching between the first memory block 2 and the second memory block 3 in synchronization with the period, and the output side vertical synchronization signal SV is generated.

The video scanning frequency conversion device has an input/output switch 1 that switches between the first memory block 2 and the second memory block 3 in synchronization with the blanking period of ut to read out the output video data Vout. Since the input/output control uses two first and second memory blocks for each screen of video data using the blanking period of the vertical synchronizing signal, the blanking period of the conventional horizontal synchronizing signal is used. Unlike conventional frequency conversion, the relatively long blanking period of the vertical synchronization signal is used, making switching easier and reducing the frequency of memory input/output switching.
This has the effect of simplifying memory control.

Further, according to the control method of the video scanning frequency conversion device of this embodiment, when the input/output switch 1 switches the memory block and input video data Vin is written,
The memory block to be written is the output video data Vout
When the input video data Vin is being read, the input video data Vin is not written, and when the memory block is switched by the input/output switch 1 and the output video data V out is read, the read memory block is changed to the input video data V.
When in is being written, output video data V out
is not read out, but the input/output switch 1 is switched to read out the previously read output video data V out again, so even if 1.2 screens are missing in a row during writing, the readout Output video data Vo
ut is now output continuously, and when converting video signals output from computer terminals such as workstations, the purpose is not to convert moving images such as TV broadcasts, so disturbances and flickering are avoided. This has the advantage that the video scanning frequency conversion process can also be performed stably.

(Effects of the Invention) According to the invention described in claim 1, the first memory block and the second memory block for writing and reading video data for one screen, and the blanking period of the input side vertical synchronization signal. This video scanning frequency conversion device has an input/output switch that switches the memory block to which video data is written in synchronization with the blanking period of the output side vertical synchronization signal, and switches the memory block to which video data is read out in synchronization with the blanking period of the output side vertical synchronization signal. , unlike the conventional memory input/output control in units of video data for one scan using the blanking period of the horizontal synchronization signal, two memory blocks are controlled in units of video data for one screen using the blanking period of the vertical synchronization signal. This has the effect of simplifying memory control by reducing the frequency of memory input/output switching.

According to the invention set forth in claim 2, in the video scanning frequency conversion device set forth in claim 1, when the memory block is switched by the input/output switch and video data is written, the memory block to be written is the one from which the video data is read. When the memory block is in the middle, no video data is written, and when the memory block is switched by the input/output switch and the video data is read out, the video data is read out when the memory block to be read is in the middle of writing video data. The control method for the video scanning frequency conversion device is to switch the input/output switch and read out the previously read video data again, so the read video data is output continuously. Since the video scanning frequency conversion process can also be performed stably, it has the effect of eliminating disturbances and flickering in the output signal.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the configuration of a video scanning frequency conversion device showing an embodiment of the present invention, FIG. 2 is a timing chart for explaining the input/output operation of the memory of this embodiment, and FIG.
The figure shows a block diagram of a conventional video scanning frequency conversion device.
FIG. 4 is a timing chart diagram illustrating conventional video scanning frequency conversion. 1... Input/output switch 2... First memory block 3... Second memory block 4... Memory controller 5... Serial Input memory 6...Memory array 7...Serial output memory 8...Video memory Vin...Input video data V for one screen
out...Output video data for one screen S Vf
n...Input side vertical synchronization signal S ■out...
... Output side vertical synchronization signal S Hin ... ... Input side horizontal synchronization signal S Hout ... ... Output side horizontal synchronization signal Din ... ... Serial input data D
out... Serial output data Pin...
...Parallel data (input data) P out
...Parallel data (output data) CKin・
...Input side dot clock CKout...
・Output side dot clock j″−−−− Agent Patent attorney Nobuhiro Funatsu, j L-2

Claims (2)

[Claims] (1) A first memory block and a second memory block that write and read video data for one screen, and the first memory block and the second memory block that write and read video data for one screen, and writing the video data by switching between two memory blocks, and reading the video data by switching between the first memory block and the second memory block in synchronization with a blanking period of a vertical synchronization signal on the output side; What is claimed is: 1. A video scanning frequency conversion device comprising an input/output switch that performs the following steps. (2) In the video scanning frequency conversion device according to item 1,
When the input/output switcher writes video data by switching between the first memory block and the second memory block in synchronization with the blanking period of the vertical synchronization signal on the input side, the video data does not change in the memory block to which writing is performed. When data is being read, video data is not written, and the input/output switch switches between the first memory block and the second memory in synchronization with the blanking period of the vertical synchronization signal on the output side. When reading video data by switching between blocks, if video data is being written in the memory block to be read, switch the input/output switch to the previous memory block to display the previously read data. A control method for a video scanning frequency conversion device characterized by reading data again.