JPH0440073A - Sampling clock setting method for video interface device - Google Patents

Abstract

PURPOSE:To easily set a sampling clock by calculating the number of temporary dot clocks based on the number of continuous white character picture elements in the video signals of continuous white characters to be fetched, and correcting the temporary dot clocks based on the number of actually fetched continuous white character picture elements. CONSTITUTION:Based on the number of initial dot clocks coincident with the number of initial display effective picture elements, the initial sampling clock is generated, and the number of continuous white characters H for one line in the case of fetching the video signals of the continuous white characters H is calculated. Based on a number GO of the initial effective display picture elements and a number (n) of characters, a number HO of real picture elements in the continuous white characters H is calculated, and the number of continuous white character picture elements is calculated. Based on the number (n) of characters and the number of picture elements in the continuous white characters, the number of temporary dot clocks is calculated. Next, according to the temporary sampling clock coincident with the number of temporary dot clocks, the video signals of the continuous white characters H are fetched, and the number of temporary dot clocks is corrected by comparing the number of picture elements in the continuous white characters with the number HO of real picture elements. Thus, the sampling clock can be set with flexibility to the dot clock frequency of the video signal.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for setting the sampling clock of a video interface device to match a dot clock, and particularly to a method for setting the sampling clock of a video interface device automatically and accurately. The present invention relates to a sampling clock setting method for an ink face device.

[Prior Art] Generally, when making a color hard copy, it is necessary to write a video signal to a screen memory, but in order to accurately reproduce an image pattern on the screen memory, a sampling clock corresponding to a dot (pixel) is required. must be set accurately. For this reason, the frequency division ratio of a sampling clock generation circuit such as a PLL has conventionally been set by the CPU.

FIG. 3 is a block diagram schematically showing a general video interface device described in, for example, Japanese Patent Application No. 63-63428.

In the figure, (1) is a video signal input terminal into which video signal A from a host device (not shown) is input, (2) is an amplifier that amplifies video signal A, and (3) is an analog video signal input terminal. An AD converter for converting into a digital signal, and (4) a screen memory in which the digitally converted video signal A is stored.

(5) is a synchronization signal input terminal into which synchronization signal B from the host device is input, (6) is a sampling clock generation circuit that generates sampling clock C synchronized with synchronization signal B, and (7) is synchronization signal B and sampling A memory control circuit (9) is for controlling the screen memory (4) in synchronization with the clock C, and a display pixel number setting device (9) is for setting the number of effective display pixels per line of the screen memory (4).

(10) is a C that controls the entire video interface device.
It is a PU and generates a dot clock signal and a control signal E based on the setting value of the display pixel number setting device (9).

Next, a conventional sampling clock setting method using the video interface device of FIG. 3 will be described with reference to the flowchart of FIG. 4 showing the processing operation of the CPU (10).

First, the initial effective display pixel number GO is preset via the display pixel number setter (9).

The CPU (10) outputs a dot clock signal with the initial effective display pixel number Go as the initial dot clock number DO, and outputs an initial sampling clock C○ that matches the initial dot clock number Do to the sampling clock generation circuit (6). (Step S1).

In this state, the video signal AO of the white level where all the voltage levels of the R, G, and B signals are maximum is taken in, and the first number of effective display pixels G1 to be counted at this time is determined (step S2). The number of effective display pixels 01 is included in the screen signal F and is obtained from the screen memory (4).

Next, based on the initial number of effective display pixels Go and the first number of effective display pixels 01, a temporary number of dot clocks D' is calculated as D'=GO''/Gl . . . (Step S3).

However, since the provisional number of dot clocks D' includes errors caused by the AD converter (3), calculation errors, etc., the following correction steps are performed.

First, a temporary number of dot clocks D' is outputted as a dot clock signal, and a temporary sampling clock C' matching this number of dot clocks D' is generated (step S4).

Then, in this state, the second effective display pixel number G2 when the white level video signal A○ is actually taken in is determined (step S5), and this is compared with the initial effective display pixel number Go (
Step S6).

If GO≠G2, the magnitude relationship between the two is further determined (step S7); if Go>02, the temporary dot clock number D' is incremented (step S8), and the process returns to step S4, and Go< In the case of G2, the temporary number of dot clocks D' is decremented (step S9) and the process returns to step S4.

The above steps 84 to S9 are repeated until the initial number of effective display pixels GO and the second number of effective display pixels 02 match,
When they match (G O = G 2 ), the sampling clock C is generated using the temporary dot clock number D'' as the true dot clock number (step sio>).

The number of repetitions of this correction step is usually 1.2 times because only the error is removed.

In this way, by capturing the experimental white level video signal AO several times, an accurate sampling clock C is automatically set based on the error-free dot clock signal. Regardless of the dot clock frequency, the video signal A can be reliably captured and stored in the screen memory (4). Therefore, a sampling clock setting method having flexibility with respect to the dot clock frequency of the video signal A is realized.

[Problem to be Solved by the Invention] As described above, in the conventional sampling clock setting method of a video interface device, in step S2, R
It is necessary to input the video signal AO at the white level where the voltage levels of all the signals, G signal, and B signal are maximum.
It is not common for a host device to output a video signal AO with a white level equal to the number of effective display pixels, and there is a problem in that the user is often unable to set the sampling clock because the user does not know how to operate it.

This invention was made to solve the above-mentioned problems, and provides a sampling clock setting method for a video interface device in which the sampling clock can be easily set by outputting general continuous white characters. The purpose is to obtain.

[Means for Solving the Problems] A sampling clock setting method for a video interface device according to the present invention includes a first step of generating an initial sampling clock based on an initial number of dot clocks that matches an initial number of effective display pixels; a second step of calculating the number of continuous white characters in one line when a video signal of continuous white characters is captured by an initial sampling clock;
A third step of calculating the actual number of pixels of continuous white characters based on the initial number of effective display pixels and the number of characters, and a step of calculating the first number of pixels of continuous white characters when the video signal of continuous white characters is taken in by the initial sampling clock. 4 steps, a fifth step of calculating a temporary number of dot clocks based on the number of characters and the number of pixels of the first continuous white character, and a step of calculating a video signal of continuous white characters using a temporary sampling clock that matches the temporary number of dot clocks. The second continuous white character pixel number when inserted is compared with the actual pixel number to correct the provisional dot clock number.

[Operation] In the present invention, a temporary number of dot clocks is calculated based on the first number of continuous white character pixels of a video signal of continuous white characters captured by a sampling clock that matches the initial number of effective display pixels, and The temporary number of dot clocks is automatically corrected based on the number of second consecutive white character pixels actually captured by the temporary number of dot clocks.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. 1st
The figure is a flowchart showing the processing operation of the CPU according to an embodiment of the present invention.
is the same step as described above.

FIG. 2 is an explanatory diagram showing the number of pixels for one line of continuous white characters, where H is an example of continuous white characters and G is an example of continuous white characters.

is the number of initial effective display pixels corresponding to the number of pixels for one line, xl
is the number of pixels corresponding to the left margin, x2 is the number of pixels corresponding to the right margin, xo is the number of pixels corresponding to the pitch of continuous white characters H, n is the number of continuous white characters H, H○ is the first character This is the number of pixels from the left side of the character to the left side of the final character.

The video interface device to which the present invention is applied is as shown in FIG. 3, and it is only necessary that a part of the program in the CPU (10) be changed.

Further, the basic operation is the same as the conventional one except that the CPU (10) is equipped with a function to measure the number of consecutive white characters, and therefore will not be particularly explained here.

Next, an embodiment of the present invention will be described with reference to FIGS. 1 to 3.

First, as shown in FIG. 2, one stack of arbitrary characters H is made into a continuous white character, and arranged on the left and right by one line across the screen at regular intervals. Here, when the interval between each letter H is X, dots, the number of characters is n, and the initial number of effective display pixels is Go, G OX e ・n = X + 10X 2 < n
- Arrange the number of characters n that satisfies ■■.

Next, in the same way as described above, the initial effective display pixel number GO is preset via the display pixel number setter (9), and the CPU (1
0), the initial sampling clock CO is generated from the sampling clock generation circuit (6) with the initial effective display pixel number Go as the initial dot clock number Do (step S1).

In this state, a video signal AH of continuous white characters consisting of R, G, and B signals is taken in, and the number n of characters for one line counted at this time is determined (step 512).

This number of characters n is measured based on the screen signal F from the screen memory (4).

Also, with xo as the quotient of the division formula G O/n, the actual number of pixels HO from the first character to the last character of continuous white characters is expressed as HO=
(n 1 )x o + 1 −■ (step 513).

That is, from GO=xo·n+Go−xa·n, Go/n=X0+(Go−Xs′ n)/n. Here, from the equation (2), (Go-xo-n)/n<1, and since Xo is a natural number, xo can be uniquely determined. Also, if the number of continuous white character pixels is defined as the number of pixels from the first character to the beginning of the last character, the actual number of pixels HO is 0.
It is expressed as the formula.

Next, the first continuous white character pixel count H1 from the first character to the last character is calculated by counting the screen signal F (step 514), and the initial effective display pixel number Go, the actual pixel number HO, and the first continuous white Based on the number of character pixels H1, the temporary number of dot clocks D' is calculated as D'=GO-HO/Gl ・(
Calculate by D (step S15>).

However, since the provisional dot crotter number D' includes the above-mentioned error, the following correction steps are performed.

First, a temporary sampling clock C' is generated using the temporary dot clock number D' as a dot clock signal (
Step S4), when the video signal AH of continuous white characters is actually taken in this state, the second continuous white character pixel number H2 is determined (step 516).

Then, the second continuous white character pixel number H2 is compared with the actual pixel number HO (step 517), and if it is not )10#82, the magnitude relationship between the two is further determined (step 518).
If HO>H2, the temporary dot clock number D' is incremented (step S8) and the process returns to step S4.
If O<H2, the temporary number of dot clocks D' is decremented (step S9) and the process returns to step S4.

The above correction steps S4, S18 to S18, S8 and S
Step 9 is repeated until the actual pixel number HO and the second consecutive white character pixel number H2 match, and at the point when they match (HO=H2), the sampling clock is set using the temporary dot clock number p' as the true dot clock number. C is generated (step 5IO).

The number of repetitions of this correction step is usually 1.2 times since only the error is removed.

In this way, by capturing the experimental video signal A○ of continuous white characters several times, an accurate sampling clock C is automatically set based on the error-free dot clock signal. Regardless of the dot clock frequency of signal A, video signal A can be reliably captured and stored in the screen memory (4). Therefore, a sampling clock setting method having flexibility with respect to the dot clock frequency of the video signal A is realized.

In addition, it saves the effort of observing the video signal A using a synchroscope and reading through document manuals.
A simple configuration and inexpensive sampling clock setting method is realized.

[Effects of the Invention] As described above, according to the present invention, the first step is to generate an initial sampling clock based on the initial number of dot clocks that matches the initial number of effective display pixels, and the first step is to generate a video of continuous white characters using the initial sampling clock. A second step of calculating the number of continuous white characters for one line when the signal is acquired, a third step of calculating the actual number of continuous white characters based on the initial number of effective display pixels and the number of characters, and an initial sampling clock. A fourth step calculates the number of pixels of the first continuous white character when a video signal of continuous white characters is taken in by 5 steps and by comparing the number of pixels of the second continuous white character when the video signal of continuous white characters is captured using a temporary sampling clock that matches the number of temporary dot clocks with the actual number of pixels, the number of pixels of the temporary dot clock is determined. The dot clock number is calculated and automatically corrected based on the number of pixels of continuous white characters that are actually captured, so that it is possible to output general continuous white characters. This has the effect of providing a sampling clock setting method for a video interface device that allows the sampling clock to be easily set.

[Brief explanation of the drawing]

FIG. 1 is a flow chart diagram showing an embodiment of the present invention;
FIG. 2 is an explanatory diagram showing continuous white characters and their number of pixels in an embodiment of the present invention, FIG. 3 is a block diagram showing a general video interface device, and FIG. 4 is a diagram showing a conventional video ink face device. FIG. 3 is a flowchart diagram showing a sampling clock setting method. (4)...Screen memory (6)...Sampling clock generation circuit (9)...
・Display pixel number setting device (10)...CPU A...Video signal AH...Video signal with continuous white characters C...Sampling clock CO...Initial sampling clock C'...Temporary sampling Clock D...Dot clock signal DO...Initial dot clock number D'...Temporary dot clock number Go...Initial effective display pixel number n...Character count HO...Actual pixel number H1.
...First continuous white character pixel number H2...Second continuous white character pixel number Sl...First step S12...Second step S13...Third step S14...Fourth step S15... ...Fifth step S4. S16-S18. S8, S9...Correction steps In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] A sampling clock setting method for a video interface device that generates a sampling clock that matches the number of dot clocks and captures a video signal, comprising: a first step of generating a sampling clock; a second step of determining the number of continuous white characters in one line when a video signal of continuous white characters is captured by the initial sampling clock; and a second step of determining the number of continuous white characters in one line; a third step of determining the actual number of pixels of the continuous white character based on the number of characters; and a step of determining the number of pixels of the first continuous white character when the video signal of the continuous white character is taken in using the initial sampling clock. a fifth step of calculating a temporary number of dot clocks based on the number of characters and the first number of continuous white character pixels; A video interface comprising: a correction step of correcting the provisional number of dot clocks by comparing the number of pixels of a second continuous white character when the video signal is taken in with the number of actual pixels; How to set the sampling clock of the device.