JP2569735B2 - Standard method conversion method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a standard method conversion method for color television.

[Summary of the Invention]

The present invention is based on the 625-line PAL or SECAM method.
In the standard system conversion method to the 25-line NTSC system, one line of the luminance signal is thinned out every predetermined number of lines, and two consecutive color signals are thinned out every two times the predetermined number of lines, so that before and after thinning out. , The regularity of the transmission of the color signal to the line is maintained.

[Conventional technology]

As is well known, there are three standard systems for color television, NTSC, PAL and SECAM.

In the NTSC system and the PAL system, a color subcarrier is quadrature-modulated with a pair of color signals and transmitted together with a color synchronization signal (color burst). In the PAL system, since the polarity of one of the RY of the color signals is inverted for each line and transmitted, the third
As shown in the figure, the phase of the color burst is +
The angle is switched between 135 ° and −135 ° and used for polarity inversion discrimination.

In the SECAM system, a pair of color signals is switched line-sequentially,
The color subcarrier is frequency modulated (FM) and transmitted. For this reason, the color order determination signal is inserted in the vertical blanking period.

The scanning method is NTSC and PAL in some areas.
The system adopts 525 lines and 525/60 system of 60 fields / second. The SECAM system and most PAL systems have the number of lines.
The 625/50 field / second 626/50 system is used.

When performing system conversion between these two scanning systems, correction of the scanning line length, conversion of the number of lines, and conversion of the number of fields are required, and a field memory is used.

[Problems to be solved by the invention]

In the conversion from the 625/50 system to the 525/60 system, for simplicity, if the ratio of the number of effective lines in both scanning systems is 6: 5, then 6
The line number conversion is temporarily achieved by thinning out one line for each line.

However, in the conversion from the PAL system or SECAM system based on the 625/50 system to the NTSC system based on the 525/60 system, as described above, when one line is simply thinned out every six lines, the above-described pair of one line is used. The regularity of the color signal transmission to the line, such as the inversion of the polarity of one of the color signals RY for each line, and the line-sequential transmission of a pair of color signals RY and BY is impaired. As described, a problem occurs in that the quality of the reproduced image is degraded.

As described above, in the PAL system, the polarity of the RY signal is inverted for each line, so that the carrier color signals of the n-th line and the (n + 1) -th line are symmetric with respect to the BY axis, and as shown in FIG. Expressed as vectors P _n and P _{n + 1} .

If there is a phase shift of δ in the transmission system due to the jitter of the VTR or the like, the vectors P _n and P _{n + 1} rotate in the same direction (for example, counterclockwise) to become Q _n and Q _{n + 1} , respectively. .
On the demodulation side, as shown in FIG. 4, a comb filter (10) composed of a 1H delay line (11) and a subtractor (12) is used, and R
Align the polarity of the -Y signal, a vector from the vector Q _{n + 1}
to obtain a _{n + 1,} the vector _{n + 1} by combining the vector Q _n, had gained Vector P _n in phase.

That is, in the PAL system, the hue error caused by the transmission system is canceled between two adjacent lines.

However, as shown in the left column of FIG. 5, from the polarity of the RY signal and the color signal of the PAL method inverting for each line,
When one line, for example, the sixth line is thinned out for every six lines and the line number is converted, in the converted color signal, for example, the fifth and seventh odd lines are adjacent to each other as shown in the right column of FIG. Therefore, during this time, the hue error caused by the transmission system as described above cannot be canceled,
After the conversion, a hue error appears at a rate of one line out of five lines, resulting in color unevenness in a reproduced image.

5 and the RY signal and the B signal, respectively.
If the -Y signal is substituted, in the SECAM line number conversion, it is easily understood that the color order is out of order every five lines and a correct color image is not reproduced after the conversion.

In view of such a point, an object of the present invention is to perform a process before and after thinning,
It is an object of the present invention to provide a standard method conversion method in which the transmission of color signals to lines is maintained.

[Means for solving the problem]

The present invention provides a first standard PAL or SECAM color video signal that has a first number of lines 625 and that alternately switches the transmission characteristics of a pair of color signals line by line. In a standard format conversion method for converting into a second standard format NTSC color video signal having a small number of second lines 525 and having a fixed transmission characteristic of a pair of color signals, a luminance signal of a first standard format Is thinned out for every predetermined number of lines, and two consecutive color signals of the first standard type are thinned out every two times a predetermined number of lines.

[Action]

According to such a configuration, the regularity of the transmission of the color signal of the first standard system to the line before and after the thinning is maintained.

〔Example〕

Hereinafter, an embodiment of the standard system conversion method according to the present invention will be described with reference to FIGS.

FIG. 1 is a conceptual diagram of the operation of one embodiment of the present invention, and FIG. 2 shows the configuration of a standard system conversion method according to the present invention.

In FIG. 2, (20) is a field memory,
(30) and (40) show the write system and read system of the memory (20) as a whole.

A 625-line PAL analog color video signal is supplied from an input terminal (31) to an A / D converter (32), and a digitized luminance signal Y is supplied to a signal processing circuit (33). of the carrier chrominance signal C _C is supplied to the decoding circuit (34) of the PAL system, the decoded chrominance signal C _B, that is, a pair of baseband color difference signals R-Y and B-Y signal processing circuit (33) Supplied. The output of the control circuit (35) is supplied to the memory (20) and a signal processing circuit (33), the luminance signal Y and chrominance signal C _B is sequentially written into the memory (20).

In a memory (20) and reading circuitry (40) signal processing circuit (41), the output is supplied to the control circuit (42), out of the memory (20) to read the luminance signal Y and color signal C _B And
The signal is supplied to the signal processing circuit (41). The control circuit (42) is supplied with the PAL vertical drive signal VD from the control circuit (35). With digital luminance signal Y that is output from the signal processing circuit (41) is directly supplied to the D-A converter (43), a digital color signal C _B outputted from the processing circuit (41)
Via a burst Sugekae circuit (44), it is supplied to the encoding circuit (45) of the NTSC system, the coming digital carrier color signal C _C is supplied to the D-A converter (43). From the DA converter (43), an analog color video signal of the NTSC system is led to an output terminal (46).

The thinning-out operation of the present embodiment using the system converter having such a configuration is as follows.

In the field memory (20), PAL color video signals of 625 lines are sequentially written as shown in the column in FIG. The number attached to each line indicates the vertical address on the memory (20).

The luminance signal is read out by thinning out one line every six lines, as shown in the left column of FIG.

As shown in the right column of FIG.
Two adjacent lines, for example, the sixth and seventh lines are thinned out and read. As a result, in the converted color signal, the odd-numbered and even-numbered two lines are always adjacent to each other, for example, the fifth and eighth lines. Cancellation is made between the lines, and the color unevenness of the reproduced image is removed.

Note that in the case of a color signal, an even number of lines such as 4, 6, 8,... May be thinned out, but it is preferable to thin out two adjacent lines in consideration of reproduction image quality.

Further, in order to suppress the vertical shift between the luminance signal and the chrominance signal, it is preferable that the addresses of the two signals on the memory (20) are not separated from each other.

In the above embodiment, the thinning is performed when the digital video signal is read from the field memory. However, when writing to the memory, a plurality of lines may be written to the same address.

As described above, the present invention has been described for the case of converting the PAL system of 625 lines to the NTSC system of 525 lines, but if the present invention is applied to the case of converting the SECAM system to the NTSC system,
It is possible to eliminate the above-described color order disorder.

〔The invention's effect〕

As described in detail above, according to the present invention, 625 line PAL
When converting from the SECAM system or the SECAM system to the 525-line NTSC system, one line of the luminance signal is thinned out every predetermined number of lines.
Since the color signals of two consecutive lines are thinned every two times the predetermined number of lines, a standard system conversion method that can maintain the regularity of the color signal transmission to the lines before and after the thinning is obtained.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram for explaining the operation of one embodiment of the present invention, FIG. 2 is a block diagram showing a configuration example of a standard system conversion apparatus according to one embodiment of the present invention, and FIGS. FIG. 5 is a vector diagram of a color signal of a PAL system and a block diagram of a comb filter for explaining the present invention, and FIG. 5 is a conceptual diagram for explaining the operation of a conventional standard system conversion method. (20) is a field memory, (30) is a writing system, and (40) is a reading system.

Claims (1)

(57) [Claims] A color video signal of a first standard system having a first number of lines and having a transmission characteristic of a pair of color signals alternately switched line by line is provided in a first video signal having a number smaller than the first number of lines. A standard system conversion method for converting a pair of color signals into a second standard system color video signal having a fixed transmission characteristic, the method comprising: 1 for every number of lines
A standard system conversion method, characterized in that, in addition to line thinning, two lines of color signals of the first standard system are thinned continuously for every twice the predetermined number of lines.