JP3164118B2 - 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 may be used as it is for the chrominance subcarrier, but usually a signal of the same phase from another circuit having almost the same configuration as the burst phase signal generating 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.

The phase selection signal generating circuit is an NTSC / P which selects one of the NTSC type system and the PAL type system.
A flip-flop which is reset when the AL system selection signal does not select the PAL type system, and which is inverted at the end of the burst pulse when the NTSC / PAL system selection signal selects the PAL type system;
When the C / PAL system selection signal does not select the PAL type system, the output of the flip-flop is output as it is, and when the NTSC / PAL system selection signal selects the PAL type system, the output of the flip-flop is inverted. And a gate circuit that outputs an output of the gate circuit as the phase selection signal to the burst phase signal generation circuit.

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.

In order to achieve the above object, a color video signal generating circuit having another configuration according to the present invention comprises the above-described timing generating means, a phase selection signal generating circuit, a burst phase signal generating circuit, and a burst signal generating circuit. And a signal generation circuit. The phase selection signal generation circuit receives the burst pulse and is reset when the NTSC / PAL system selection signal does not select the PAL type system, and is reset when the NTSC / PAL system selection signal selects the PAL type system. A flip-flop that inverts at an end of the burst pulse, and outputs an output of the flip-flop to the burst phase signal generation circuit.

The burst phase signal generation circuit includes the NTS
Upon receiving the C / PAL system selection signal, the NTSC / PAL
When the system selection signal does not select the PAL type system, the value received from the flip-flop is used as the value of the phase selection signal as it is, and when the NTSC / PAL system selection signal selects the PAL type system, A value obtained by inverting the value received from the flip-flop as the value of the selection signal , or a signal obtained by exchanging the normal output and the inverted output of the flip-flop is used as the selection signal, One of the first phase signal and the second phase signal is selected according to the value and is output as a burst phase signal.

[0021]

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 as the timing signal, and the flip-flop and the gate circuit use the signal to output the burst signal. An appropriate phase selection signal is selected and output to the burst phase signal generation circuit. In other words, specifically, when the NTSC / PAL system selection signal does not select the PAL system, the flip-flop is always reset and its value becomes the phase selection signal as it is, so that the phase selection signal is not always output or Since 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 flip-flop is inverted only immediately after receiving a burst pulse indicating the existence of a valid scanning line. Since the horizontal synchronizing signal is not used in this manner, the phase of the burst signal can be inverted without being affected undesirably by an equivalent pulse inserted between frames. However, this alone
Since the phase is switched in the middle of the scanning line, the switching of the phase of the burst signal is delayed from the original timing, so that the phase is opposite to the phase of the color subcarrier. To correct this, the gate circuit
The output of the flip-flop is inverted and output. Thus, an appropriate burst signal phase in accordance with the PAL system is selected. By using the inverted signal, the burst signal
Switching the phase of the burst signal before the next frame
Can occur at the timing of occurrence.

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.

According to another aspect of the present invention, there is provided a color video signal generating circuit which includes a gate circuit included in a phase selection signal generating circuit in the above-described configuration, and which is shifted from the phase selection signal generating circuit to the burst phase signal generating circuit. The operation is exactly the same as that described above, except that the arrangement is simply changed and the apparent difference due to the block division.

[0025]

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 generating circuit 20 is composed of a flip-flop 20a and a gate circuit 20b, receives the burst pulse BFP, and receives the phase selection signals QP, * QP
Occurs. Toggle type flip-flop 20a
Receives the burst pulse BFP at the toggle input T, and
An SC / PAL system selection signal Z is received at a reset input R.

When the NTSC / PAL mode selection signal does not select the PAL mode, the gate circuit 20b outputs
The output of the flip-flop 20a is output as it is, and NT
When the SC / PAL system selection signal selects the PAL system, the output of the flip-flop 20a is inverted and output. The NTSC / PAL system selection signal Z is a signal for selecting one of the NTSC system and the PAL system as described above, and may be externally supplied or generated by the MPU 10. However, in order to clearly show that the signal is not a timing signal but a static value setting signal, this example employs a circuit configuration in which the 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 system selection signal Z does not select the PAL system,
/ PAL system selection signal Z causes flip-flop 20a
Is always reset, the phase selection signal * QP is output from the gate circuit 20b, 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 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. In the phase selection signal generation circuit 20, when the PAL type is selected, the flip-flop 20a does not receive the reset by the NTSC / PAL type selection signal Z, and therefore receives the burst signal BFP (see waveform BFP). At the end, flip-flop 20a is inverted. Therefore, the phase selection signals QP and * QP are also inverted (see waveforms QP and * QP). Burst signal BF of FIG.
Relationship between P, waveform * QP, and waveform Ba of berth signal B
Or the burst signal BFP, the waveform QP, and the wave of the burst signal B
As can be seen from the relationship with the type Bb,
By using the inverted signal that is inverted at
Switching the phase of the burst signal before the next frame
It can be an occurrence timing.

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. Further, since the output of the flip-flop 20a is inverted by the gate circuit 20b to be the phase selection signals QP and * QP, a new problem caused by the phase switching in the middle of the scanning line is overcome. Specifically, flip-flop 2
0a is switched before the burst signal B by the horizontal synchronization signal SYNC, whereas the burst pulse B
The phase selection signal Q which depends on the timing difference to be switched after the burst signal B by the end of the FP
The difference between the values of P and * QP has been eliminated.

Here, since the burst pulse BFP is a signal indicating the presence of an effective scanning line, the phase of the burst signal B generated from the burst phase signal P is exactly the same as that of the circuit having the conventional configuration. , For each scanning line. Moreover, since one burst pulse BFP is generated for one scanning line, it is not sent to the phase selection signal generation circuit 20 between frames. Therefore, in the meantime, the flip-flop 20
Since a is not inverted, the output states of the phase selection signals QP and * QP, which are the outputs of the flip-flop 20c, do not change.

As described above, since the burst signal B can be generated without using the horizontal synchronization pulse SYNC, there is no influence from an equivalent pulse included in the horizontal synchronization pulse SYNC, that is, an extra pulse for vertical synchronization. Therefore, when the PAL type system is selected, PA
It operates according to the standard such as the L system. As a result, both when the PAL system is selected and when another system is selected, it is possible to generate a burst signal and a composite video signal according to the respective standards.

The chrominance sub-carrier is converted into phase signal generation circuits 3a and 3b in the burst phase signal generation circuit 3 as in the conventional circuit.
In the case where the signal is generated by a separate circuit, the above-mentioned correspondence is sufficient. However, when the color subcarrier is also generated by using the burst phase signal P together with the phase signal generating circuits 3a and 3b, the burst phase Since the signal P is switched in the middle of the scanning line and immediately before the color subcarrier is required, a phase signal having a phase opposite to that of the burst phase signal P is used as the color subcarrier.

The gate circuit 20b is connected to the gate circuit 3c.
Inclusion in the burst phase signal generation circuit 3 is merely a difference in recognition of a block division, and is substantially the same. Further, for example, a change in the positive logic and the negative logic, a change in the number of gate elements corresponding to the change, a change between inverted signals, and the like, for example, a change between a 90 ° phase signal and a 270 ° phase signal, and a phase selection signal QP and a phase selection signal * Replacement with QP and corresponding gate circuit 20
The change in the number of gate elements in b and 3c is merely a design change, and is substantially the same. In the above description, the phase signal for the chrominance subcarrier is set to 90 ° for simplicity.
Although the description is limited to two types of phase signals and 270 ° phase signals, a 0 ° phase signal is further used in an actual circuit. 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.

[0038]

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

Continuation of the front page (56) References JP-A-58-43690 (JP, A) JP-A-1-137683 (JP, A) JP-A-58-213594 (JP, A) JP-A-5-137149 (JP, A) , A) Fully open sho 60-82888 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) H04N 9/455 H04N 9/64 H04N 11/06-11/18

Claims (2)

(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 generating circuit for generating a phase selection signal, the phase selection signal generation circuit, the NTSC / PAL mode selection signal is reset when said NTSC / PAL mode selection signal has not selected the PAL type system is PAL
A flip-flop that inverts at the end of the burst pulse when the type system is selected;
When the AL system selection signal does not select the PAL type system, the output of the flip-flop is output as it is, and when the NTSC / PAL system selection signal selects the PAL type system, the output of the flip-flop is inverted and output. A color video signal generation circuit, comprising: a gate circuit that outputs an output of the gate circuit to the burst phase signal generation circuit as the phase selection signal. 2. A first phase signal corresponding to a chrominance sub-carrier is generated, a second phase signal having a phase difference of 180 degrees with respect to the first phase signal is generated, and the first phase signal and the second phase signal are generated. 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 format selection signal; The NTSC / PA is reset when but not selected PAL type system
A flip-flop that inverts at the end of the burst pulse when the L-system selection signal selects the PAL-type system; and a phase selection signal generation circuit that outputs the output of the flip-flop to the burst phase signal generation circuit. The burst phase signal generation circuit includes the NTSC / PA
When the L system selection signal is received and the NTSC / PAL system selection signal does not select the PAL type system, the value received from the flip-flop is used as the value of the phase selection signal, and the NTSC / PAL system selection signal is used. Is P
When the AL type is selected, the inverted value of the value received from the flip-flop is referred to as the value of the selection signal.
And, or, the signal interchanging the normal output or reversed output of the flip-flop and said selection signal, either the first phase signal and second phase signal depending on the value of the phase selection signal And outputting as a burst phase signal.