JP3136322B2 - Color video signal generation circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a color video signal generating circuit, and more particularly to an improvement in a burst signal generating means in a color video signal generating circuit capable of supporting both the NTSC type and the PAL type.

[0002]

2. Description of the Related Art A video tape recorder, a computer terminal device, a game machine, various video processing devices, and the like often have a built-in color video signal generation circuit, which generates a composite video signal, a so-called composite signal. Is done. Then, it is output to the monitor television and an image is displayed. In particular, in the case of a video tape recorder or a home game machine, most of them output a composite video signal on the assumption that a commercial receiver is used instead of a dedicated monitor.

[0003] However, the standard of the composite video signal is not unique, and there are a plurality of standards such as the NTSC system, the SECAM system, and the PAL system. However, if dedicated circuits or ICs are prepared for each of these standards, the production efficiency is poor. For this reason, a general-purpose color video signal generation circuit that can support a plurality of systems such as the NTSC / PAL system has been demanded and has been put to practical use. Here, the difference between the PAL system and the NTSC system is that there are differences in the number of scanning lines and the like, but, above all, Phase Alternation by Li
As the name of the method ne indicates, in the PAL method, the phase of the color subcarrier is inverted for each scanning line. Therefore, the phase of the burst signal, which is a reference signal for transmitting the phase of the color subcarrier to the receiver, is also inverted. In order to simplify the predicate, in this specification, a system in which the phase of the color subcarrier is inverted for each scanning line is abbreviated as a PAL system, and a system in which the phase is not reversed is abbreviated as an NTSC system. .

[0004] How this is realized will be specifically described below with reference to the drawings. FIG. 3 is a block diagram mainly showing a burst signal generating means in the conventional color video signal generating circuit. This color video signal generation circuit includes a television signal timing control processor 1 (hereinafter, referred to as a TV signal timing control processor).
MPU 1), a phase selection signal generation circuit 2, a burst phase signal generation circuit 3, and a burst signal generation circuit 4
And a composite video signal synthesizing circuit 5 for generating a composite video signal V which is a color video signal.

[0005] The MPU 1 includes a timing generator 1a and a P
An AL timing signal generating means 1b is provided to generate various timing signals and to control the entire color video signal generating circuit and the like, but the details are omitted except for the means and signals necessary for the description. Only the main parts are shown. Here, the timing generation means 1a is provided in the MPU 1 and generates timing signals such as a burst pulse BFP for generating a color video signal and a horizontal synchronization signal SYNC.

Further, PAL timing signal generating means 1
b is a special means in the timing generation means 1a in the MPU 1. This means receives an NTSC / PAL system selection signal Z for selecting one of the NTSC system and the PAL system from the outside via the MPU 1. When the NTSC / PAL system selection signal Z, which takes a static value, selects the PAL system, the phase of the color subcarrier of the first scanning line of the next frame is set to a predetermined value each time the frame is switched. PAL indicating the timing to set the phase of
A timing signal A is generated. NTSC / PAL
When the system selection signal Z does not select the PAL type system, the PAL timing signal A is generated as a fixed value.

The phase selection signal generating circuit 2 is constituted by using a toggle type flip-flop 2a, receives a horizontal synchronizing signal SYNC at a terminal T, and inverts the value of the flip-flop 2a at the end of the horizontal synchronizing signal SYNC. , PAL timing signal A is received by a reset terminal R,
The value of the flip-flop 2a is reset by the timing signal A. Then, the normal output and the inverted output of the flip-flop 2a are output to the burst phase signal generation circuit 3 as phase selection signals QP and * QP.

The burst phase signal generating circuit 3 has a 90 ° phase signal generating circuit 3a, and has a function corresponding to the color subcarrier.
A 0 ° phase signal is generated, and a 270 ° phase signal generating circuit 3b is provided to generate a 270 ° phase signal having a 180 ° phase shift from the 90 ° phase signal. Further, a gate circuit 3c is provided to select a 90 ° phase signal when receiving the phase selection signal * QP, and to select a 270 ° phase signal when receiving the phase selection signal QP. Output to the generation circuit 4. At this time, the burst phase signal P is directly applied to the color subcarrier, or
An in-phase signal from another circuit similar to the burst phase signal generation circuit 3 is used.

The burst signal generation circuit 4 receives the burst pulse BFP and the burst phase signal P, and outputs the burst phase signal P only while the burst pulse BFP exists, thereby generating the burst signal B. The composite video signal synthesizing circuit 5 includes a horizontal synchronizing signal SYNC and a burst signal B.
, A luminance signal Y, and a chroma signal C carrying color information, and combine these signals to generate a composite video signal V, a so-called composite signal, which is output to the outside as an output of a color video signal generation circuit. .

In the color video signal generation circuit having such a configuration, if the value of the NTSC / PAL system selection signal Z is set at the time of assembling or adjusting a device incorporating the circuit, the PAL type system is selected. A burst signal having an appropriate phase can be generated regardless of whether or not another method is selected, so that a composite video signal V conforming to the standard can be output for any method. . This will be described below separately for a case where the PAL type system is selected and a case where another system is selected.

First, when a system other than the PAL system, for example, the NTSC system, is selected, the PAL timing signal A is fixedly output.
a is always reset. As a result, the phase selection signal * Q
Since P is output and only the 90 ° phase signal is continuously selected as the burst phase signal, the phase of the burst signal is always fixed. This is in accordance with the NTSC standard.

Next, when the PAL type is selected, there is no PAL timing signal A in one frame, so that the flip-flop 2a is inverted every time the horizontal synchronizing signal SYNC is received. Therefore, the phase selection signals QP,
* QP is output alternately and 90 as burst phase signal
Since the phase signal and the 270 phase signal are alternately selected, the phase of the burst signal B is inverted for each scanning line. This is in accordance with the PAL standard.

[0013]

However, according to the standard,
The horizontal synchronization signal SYNC includes not only timing pulses for horizontal synchronization but also so-called equivalent pulses for vertical synchronization. Because of this relationship, the horizontal synchronizing signal SY
If the number of NCs is an odd number for one frame, if no care is taken, the burst signal of the next frame will be out of phase and will not conform to the standard. In order to prevent this, conventionally, a PAL timing signal generating means is provided, and this means generates the PAL timing signal A every time a frame is switched. Then, the flip-flop 2a is reset by the timing signal A, and the phase selection signal * QP is output. Therefore, every time the frame is switched, the burst phase signal of the first scan line of the next frame and the color subcarrier are switched. The phase is set to the phase of the 90 ° phase signal.

In the conventional circuit, the composite video signal V conforming to the PAL standard is generated in this manner. Therefore, the PAL timing signal A has a great adverse effect on the color subcarrier of the composite video signal V, which is the final output, if the period and the relationship with other timing signals are slightly deviated, and the PAL timing signal A has an adverse effect on the receiver side. Will not be colored on the displayed video. Therefore, the burden on the television signal timing control processor (MPU1) responsible for the generation is extremely large.

However, the MPU 1 is an alternative to a conventional television signal timing control circuit or the like due to restrictions on cost and the like, but for the same reason, an expensive processor cannot be used even if the processing capacity is large. . on the other hand,
Recent demands for higher functionality have only increased the load on the MPU 1, and it has become impossible to meet new demands with many timing signal generating means having strict processing conditions. SUMMARY OF THE INVENTION An object of the present invention is to solve such a problem of the prior art, and to realize a color video signal generation circuit which can balance loads between circuit elements and withstand function expansion.

[0016]

To achieve the above object, a color video signal generating circuit according to the present invention comprises a timing generating means, a phase selection signal generating circuit, a burst phase signal generating circuit, and a burst signal generating circuit. And a circuit. The timing generating means generates a timing signal such as a burst pulse for generating a color video signal and a horizontal synchronizing signal.

A first flip-flop reset by a signal obtained by delaying the horizontal synchronizing signal so as not to overlap with the burst pulse and set at a start end of the burst pulse;
NTS to select one of PAL type and PAL type
When the C / PAL system selection signal does not select the PAL type system, the signal is reset. When the NTSC / PAL system selection signal selects the PAL type system, the horizontal synchronization is performed when the first flip-flop is set. A second flip-flop that inverts at the start of the signal, and outputs the output of the second flip-flop to the burst phase signal generation circuit as the phase selection signal.

The burst phase signal generation circuit generates a first phase signal corresponding to the chrominance subcarrier, and generates a second phase signal 180 degrees out of phase with respect to the first phase signal.
Either the first phase signal or the second phase signal is selected according to the phase selection signal and output as a burst phase signal. A burst signal generation circuit receives the burst pulse and the burst phase signal, and outputs the burst phase signal as a burst signal only while the burst pulse exists.

[0019]

In the color video signal generating circuit of the present invention having such a configuration, the phase selection signal generating circuit receives only the burst pulse and the horizontal synchronizing signal as the timing signals, and receives the first and the first signals from these signals. An appropriate phase selection signal is selected by the second flip-flop and output to the burst phase signal generation circuit. In other words, in detail, NTS
When the C / PAL system selection signal does not select the PAL type system, the second flip-flop is always reset, and the phase selection signal is not always output or the inverted phase selection signal is always output. The appropriate first phase signal selected by the burst phase signal generation circuit according to the phase selection signal is always selected as the burst phase signal.

When the NTSC / PAL system selection signal is P
When the AL type is selected, the first flip-flop is set, that is, when a burst pulse indicating the existence of a valid scanning line is received, and a signal obtained by delaying the horizontal synchronizing signal is used. Since the first flip-flop is reset, the second flip-flop is inverted at the start end of the horizontal synchronization signal indicating the start of the next scan line only when receiving a burst pulse indicating the existence of a valid scan line. Therefore, appropriate phase inversion in accordance with the PAL system can be performed without being affected by undesired effects such as an equivalent pulse inserted between frames.

Therefore, even when the PAL type system is selected, the phase selection signal generation circuit does not need the PAL timing signal, so that the PAL timing generation means conventionally provided in the television signal timing control processor becomes unnecessary. Become. As a result, with a slight circuit change,
Since the burden on the television signal timing control processor is reduced and the processing capacity has a margin, the color video signal generation circuit having the configuration of the present invention can withstand functional expansion such as enhancement of functions and addition of functions.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a color video signal generation circuit having the configuration of the present invention will be described below. FIG. 1 is a block diagram showing a configuration centered on a circuit for generating a burst signal in this embodiment, and corresponds to FIG. 3 of the conventional example. The color video signal generation circuit includes a television signal timing control processor 10 (hereinafter, referred to as MPU 10), a phase selection signal generation circuit 20, a burst phase signal generation circuit 3, a burst signal generation circuit 4, a composite video signal synthesis And a circuit 5 for generating and outputting a composite video signal V which is a color video signal.

The same components as those of the conventional example are denoted by the same reference numerals, and description thereof is omitted. MPU10
Is responsible for the control of the entire color video signal generation circuit and the like, and is provided with a timing generation means 10a.
The timing signal generator 1b is removed. That is, the timing generator 10a generates timing signals such as the burst pulse BFP and the horizontal synchronization signal SYNC for generating a color video signal, but does not generate the PAL timing signal A.

The phase selection signal generation circuit 20 includes a delay circuit 2
0a, a flip-flop 20b (first flip-flop), and a flip-flop 20c (second flip-flop), and receives the burst pulse BFP and the horizontal synchronization signal SYNC to generate phase selection signals QP and * QP. . The flip-flop 20b outputs the burst pulse B
The horizontal synchronizing signal SYNC is reset by the signal DR delayed by the delay circuit 20a so as not to overlap with the FP, and is set at the start end of the burst pulse BFP.

The flip-flop 20c is, for example, a JK flip-flop, and receives a signal S at its J and K inputs.
The horizontal synchronization signal SYNC is received at the clock input T,
The C / PAL system selection signal Z is received at a reset input R. Note that the NTSC / PAL system selection signal Z is
As described above, this is a signal for selecting one of the NTSC type system and the PAL type system. The signal may be provided from the outside or may be generated by the MPU 10. In order to clearly show that the setting signal is a static value setting signal, this example employs a circuit configuration in which the setting signal is generated using a switch.

In the color video signal generation circuit having such a configuration, if the value of the NTSC / PAL system selection signal Z is set at the time of assembling or adjusting a device incorporating the circuit, the PAL type system is selected. The burst signal B and the chrominance subcarrier having the appropriate phase can be generated regardless of whether or not another method is selected, so that the composite video signal V conforming to the standard can be generated for any method. Can be output. This will be specifically described below for the case where the PAL system is selected and the case where another system is selected.

First, when the NTSC / PAL type selection signal Z does not select the PAL type, the NTSC / PAL type
/ PAL system selection signal Z causes flip-flop 20c
Are always reset, the phase selection signal * QP is output, and only the 90 ° phase signal is continuously selected as the burst phase signal P, so that the phases of the burst signal B and the color subcarrier are always fixed. Therefore, the composite video signal V conforming to the standard such as the NTSC system is generated in exactly the same manner as in the related art.

Next, the operation when the PAL type system is selected will be described in detail with reference to the waveform example of FIG. Note that, for convenience of description, the reference numerals for the respective signals in FIG. 1 and the reference numerals for the waveform examples of the signals are denoted by the same reference numerals. The waveform V of the composite video signal is, for example, as shown in FIG.
Horizontal sync signal waveform SYNC and burst signal waveform B
And the waveform Y of the luminance signal and the waveform C of the chroma signal modulated by the chrominance subcarrier are generated by being synthesized by the composite video signal synthesizing circuit 5.

When the PAL type system is selected, it is necessary to further invert the phases of the burst signal B and the color subcarrier every scanning line. FIG.
In other words, the phases of Ba and Bb of the waveform B are different. The phase selection signal generation circuit 20 has the above-described configuration, so that when the burst signal BFP (see the waveform BFP) is received, the flip-flop 20b is set and the signal S is output (see the waveform S). In addition, when the PAL type system is selected, the flip-flop 20c
Since the reset by the C / PAL system selection signal Z is not received, when the signal S is input, the horizontal synchronizing signal SYN
When C is received, the value is inverted at the start end (waveform QP, *
QP).

Thus, the phase selection signals QP, * Q
When the output of P is switched for each scanning line, the burst phase signal generating circuit 3 receiving the phase selection signals QP and * QP converts the burst phase signal P into a 90 ° phase signal and a 270 ° phase signal in the same manner as in the prior art. To switch. Here, since the horizontal synchronization signal SYNC is a signal indicating the start of a scanning line, the phase of the burst signal B generated from the burst phase signal P is inverted for each scanning line together with the color subcarrier. Further, after the signal S is referenced and used by the flip-flop 20c, the flip-flop 20b is reset by the delayed signal DR (see the waveform DR) of the horizontal synchronization signal SYNC. Then, it is set after the input of the next burst signal BFP, and the above operation is repeated for each scanning line.

Here, the burst signal BFP corresponds to the scanning line 1
Since one is produced for each frame, it is not sent to the phase selection signal generation circuit 20 between frames. Therefore, there is no signal S during that time because the flip-flop 20b is not set. Therefore, even if there is an equivalent pulse, that is, an extra horizontal synchronization pulse SYNC for vertical synchronization, the output state of the phase selection signals QP and * QP output from the flip-flop 20c does not change. As a result, since it is not affected by the equivalent pulse, when the PAL type system is selected, it operates according to the standard such as the PAL system. As described above, even when the PAL type system is selected or another system is selected, it is possible to generate a burst signal and a composite video signal according to the respective standards. In the above description, for the sake of simplicity, the phase signal for the chrominance subcarrier is limited to two types, that is, a 90 ° phase signal and a 270 ° phase signal. ° Phase signals are also used. However, since this 0 ° phase signal is used as in the prior art, it is not essential for the description of the present invention. Therefore, the explanation was omitted.

[0032]

As is apparent from the above description, by employing the structure of the present invention, it is possible to generate a composite video signal without using a PAL timing signal.
On the other hand, as described above, generating the PAL timing signal is an extremely heavy burden on the television signal timing control processor. Therefore, in the color video signal generation circuit having the configuration of the present invention, the load on the control processor side is reduced by eliminating the need for the PAL timing signal generation means while supporting a plurality of systems. Thus, there is an effect that the load can be balanced and the system can be prepared for further function expansion.

[Brief description of the drawings]

FIG. 1 is a block diagram mainly showing a burst signal generating means of a color video signal generating circuit having a configuration of the present invention.

FIG. 2 is a waveform example for explaining the operation of the color video signal generation circuit having the configuration of the present invention.

FIG. 3 is a block diagram mainly showing a burst signal generation unit in a conventional color video signal generation circuit.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... TV signal timing control processor (MPU1) 2 ... Phase selection signal generation circuit 3 ... Burst phase signal generation circuit 4 ... Burst signal generation circuit 5 ... Composite video signal synthesis circuit 10 ... TV signal timing control processor (MPU1)
0) 20 ... phase selection signal generation circuit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 9/455 H04N 9/64 H04N 11/06-11/18

Claims (1)

(57) [Claims] A first phase signal corresponding to the chrominance subcarrier, a second phase signal shifted by 180 degrees from the first phase signal, and a first phase signal and a second phase signal; And a burst phase signal generating circuit for selecting one of the two phase signals according to the phase selection signal and outputting the selected signal as a burst phase signal, and a pulse indicating the position of the chrominance subcarrier to be inserted after the horizontal synchronization signal. And a burst signal generating circuit for receiving the burst pulse and the burst phase signal, and outputting the burst phase signal as a burst signal only while the burst pulse is present, comprising one of an NTSC type system and a PAL type system. A color video signal generating circuit for generating a color video signal in response to an external NTSC / PAL system selection signal; A phase selection signal generation circuit for receiving a signal, wherein the phase selection signal generation circuit is reset by a delayed signal of the horizontal synchronization signal so as not to overlap with the burst pulse, and is set at a start end of the burst pulse. 1 flip-flop and the first flip-flop are set when the NTSC / PAL system selection signal does not select the PAL system, and the first flip-flop is set when the NTSC / PAL system selection signal selects the PAL system. And a second flip-flop that inverts at the start end of the horizontal synchronizing signal, and outputs the output of the second flip-flop to the burst phase signal generation circuit as the phase selection signal. Color video signal generation circuit.