JPH1098659A - Sound switching circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To execute a compulsory mono mide while stereo broadcast is on by providing a selection signal generation part generating a selection signal from a prescribed indication signal and a compulsory mono signal and a sound switch part which selectively outputs the sound signal with the selection signal as a control signal and executing stereo display at a compulsory mono mode during the reception of stereo broadcast. SOLUTION: In a sound switch circuit, a sound multiplex decoder part 1 outputs plural indication signals showing a sound mode, outputs the corresponding sound signal and always outputs 'left sound+right sound' to a mono output terminal. A microcomputer part 2 receives indication input, outputs the compulsory mono signal, receives a 'stereo' indication signal, a 'main sound' indication signal and an 'auxiliary sound' indication signal from the decoder 1 and executes stereo display on a display part 3. The selection signal generation part 4 generates the selection signal from the 'main sound' indication signal, the 'auxiliary sound' indication signal and the compulsory mono signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an audio switching circuit for switching an output audio signal of an audio multiplex decoder.

[0002]

2. Description of the Related Art Conventionally, PDP (plasma display panel)
When a forced monaural (mono) is selected, an instruction signal indicating that the output audio is mono is given priority even if a stereo broadcast is currently received. Is output. When this kind of audio multiplex decoder is used, for example, when a television channel is changed, or when a PD mounted on an automobile is used.
When watching P-TV while driving, the electric field strength varies depending on the received electric field strength for each channel or the terrain during driving, and the electric field strength is higher than the required electric field strength for stereo reception. Shortages can occur.
In general, the required electric field strength for mono reception is smaller than the required electric field strength for stereo reception. At that time, the required electric field strength can be reduced by selecting the forced mono. , So that less voice can be obtained.

FIG. 4 is a diagram showing an embodiment of a main part of a conventional audio switching circuit. For example, an audio selection instruction input from a remote controller or the like is supplied to the audio multiplex decoder unit 1 via the microcomputer unit 2 as a selection signal. The audio multiplex decoder 1 switches the audio output based on this selection signal and outputs a corresponding instruction signal indicating the audio output state.
For example, when the audio selection instruction is forcible mono, the audio multiplex decoder unit 1 sets the audio output to mono (MONO) and turns off the stereo instruction signal indicating the audio output state. The microcomputer unit 2 displays a mono display on the display unit 3 indicating that the compulsory product is being implemented,
For example, it is displayed on the screen.

In the audio switching circuit shown in FIG. 4, when forced mono is implemented, there is a problem that it is not possible to know whether the current broadcast is a stereo broadcast or a mono broadcast because the stereo instruction signal is off. For example, when the forced mono channel is switched to another channel, there is a case where the shortage of the received electric field strength can be solved. However, even in that case, since the stereo instruction signal remains off, there is no clue as to whether the broadcast of the new reception channel is stereo or mono.

[0005] For example, when bilingual broadcasting is received by switching channels during execution of forced mono, the mono audio output of "main audio + sub audio" is a mixture of Japanese and English, for example. There was a problem that noise was output.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an audio switching circuit capable of executing a forced mono while displaying a stereo broadcast.

[0007]

In order to achieve the above object, a plurality of instruction signals indicating a voice mode are output, a corresponding voice signal is output, and "left voice + right voice" is always output to a mono output. A selection signal generation unit that generates a selection signal from a predetermined instruction signal and a forced mono signal in an audio switching circuit of an audio multiplex decoder, and an audio switching unit that selectively outputs an audio signal using the selection signal as a control signal, Added stereo display in forced mono mode while receiving stereo broadcast.

[0008] The predetermined instruction signals are a "main sound" instruction signal and a "sub sound" instruction signal.

The selection signal generator turns on the selection signal only when both the "main audio" instruction signal and the "sub audio" instruction signal are turned off and the forced mono signal is turned on.

[0010] When one of the "main sound" instruction signal and the "sub sound" instruction signal is turned on, the selection signal generating unit is turned on.
Turn off the selection signal.

Further, the audio switching unit selects "mono output" or "left audio output and right audio output" in accordance with the selection signal.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS With the above configuration, FIG.
With reference to (1) "main sound" instruction signal and "secondary sound"
When the instruction signal is turned off and the compulsory mono signal is turned on, the selection signal is turned on, and the audio switching unit is controlled to select “mono output”. (2) When any one of the "main audio" instruction signal and the "sub audio" instruction signal is on, the selection signal is turned off regardless of the compulsory mono signal, and the audio switching unit performs "left audio output and right audio output". Control to select.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an audio switching circuit according to the present invention will be described.
This will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing an embodiment of a voice switching circuit according to the present invention. Reference numeral 1 denotes an audio multiplex decoder which outputs a plurality of instruction signals indicating an audio mode, outputs a corresponding audio signal, and always outputs "left audio + right audio" to a mono output terminal. Numeral 2 receives an instruction input from a remote controller (not shown) or the like, outputs a forced mono signal, and outputs a “stereo” instruction signal, a “main audio” instruction signal, and a “sub audio” instruction signal from the audio multiplex decoder unit 1. This is a microcomputer unit that receives the information and performs stereo display on the display unit 3. Reference numeral 3 denotes a display unit for displaying, for example, on-screen stereo or bilingual language. Reference numeral 4 denotes a selection signal generation unit that generates a selection signal from a “main audio” instruction signal, a “sub audio” instruction signal, and a forced mono signal. 5
Is an audio switching unit for selecting and outputting an audio signal using the selection signal as a control signal.

The overall operation of the audio switching circuit according to the present invention will be described with reference to FIG. First, when the currently received broadcast is a stereo broadcast, the audio multiplex decoder 1
Sets the “stereo” instruction signal to logic “1” and “main sound”
The instruction signal is set to logic “0”, and the “sub-audio” instruction signal is set to logic “0”. The microcomputer part 2 is "stereo"
Since the instruction signal is logic "1", stereo display is performed.
In this state, the compulsory item is executed. In other words, the microcomputer unit 2 outputs the forced mono signal of logic “1” to the selection signal generation unit 4.
To supply. The selection signal generation unit 4 outputs a selection signal of logic “1” to the audio switching unit 5. The audio switching unit 5 selects a mono terminal of the audio multiplex decoder unit 1 and outputs mono audio. The difference from the conventional one is that the forced mono signal is not supplied to the audio multiplex decoder unit 1, but is supplied to the audio switching unit 5 via the externally provided selection signal generation unit 4 to execute the forced mono signal. is there. Next, for example, the channel is changed. The audio multiplex decoder 1 supplies an instruction signal indicating the state of the receiving channel, “stereo”, “bilingual”, etc., to the microcomputer 2, and performs an appropriate display via the microcomputer 2. In this case, the “mono” display is confirmed and the forced mono is stopped.

The operation of the audio switching circuit according to the present invention for generating a selection signal will be described with reference to FIG. FIG. 3 is a truth table showing an operation of generating a selection signal in the selection signal generation unit of the audio switching circuit according to the present invention. According to the truth table, (1) both the “main sound” instruction signal and the “sub sound” instruction signal are turned off and the selection signal is turned on when the forced mono signal is turned on. (2) When any one of the “main audio” instruction signal and the “sub audio” instruction signal is on, the selection signal is turned off regardless of the forced mono signal. Therefore, the instruction signal shown in FIG. That is, by turning on the selection signal, the audio switching unit 5 selects the mono terminal of the audio multiplex decoder unit 1 and outputs mono audio.
When the selection signal is turned off, the voice switching unit 5 selects "left voice output, right voice output" and outputs bilingual voice.
The above ON corresponds to a logical value “1”, and the OFF corresponds to a logical value “0”.

FIG. 2 is a circuit diagram showing an embodiment of a selection signal generator of the audio switching circuit according to the present invention. The selection signal generation unit 4 includes a three-input AND gate, a first inverter connected to a first input terminal, and a second inverter connected to a second input terminal. A "main audio" instruction signal (A) is supplied to the first inverter, a "sub audio" instruction signal (B) is supplied to the second inverter, and a forced mono signal (C) is supplied to a third input terminal. , The selected output (X) satisfies the following logical expression. X = inverted “main audio” (A) × inverted “sub audio” (B) × forced mono signal (C) The selection signal generation unit having the above configuration performs “main audio” (A) and “sub audio” (B) 3 are both 0, the selected output (X) is 1 when the forced mono signal (C) is 1, and the selected output (X) is 0 in other combinations of inputs. In other words, in FIG. Perform an operation that satisfies the truth table. Further, the selection signal generation section 4 may be configured by a ROM storing a lookup table containing the truth table of FIG. 3 so that a combination of inputs is used as an address and a required selection signal is read. good.

[0017]

As described above, the present invention provides an audio switching circuit capable of executing forced mono while displaying a stereo broadcast. Therefore, when the forced monaural (mono) is selected in the television receiver using the PDP (plasma display panel) or the like, the stereo display can be kept as it is. For example, when the television channel is changed, the stereo display is confirmed. You can release the compulsory thing. Also, when viewing a PDP television mounted on a car while traveling, there is an advantage that the stereo display can be similarly confirmed and the forced mono can be released. In addition, when the channel is switched during the execution of the compulsory item and the bilingual broadcast is received, the compulsory item is automatically released and the “main sound” and the “sub sound” are, for example,
Japanese and English are possible.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of a voice switching circuit according to the present invention.

FIG. 2 is a circuit diagram showing an embodiment of a selection signal generation unit of the audio switching circuit according to the present invention.

FIG. 3 is a truth table illustrating an operation of generating a selection signal of a selection signal generation unit of the audio switching circuit according to the present invention.

FIG. 4 is a diagram showing an embodiment of a main part of a conventional audio switching circuit.

[Explanation of symbols]

 Reference Signs List 1 audio multiplex decoder 2 microcomputer unit 3 display unit 4 selection signal generation unit 5 audio switching unit

Claims (7)

[Claims] An audio switching circuit of an audio multiplex decoder which outputs a plurality of instruction signals indicating an audio mode, outputs a corresponding audio signal, and always outputs "left audio + right audio" to a mono output. A selection signal generation unit that generates a selection signal from a signal and a forced mono signal, and an audio switching unit that selectively outputs an audio signal using the selection signal as a control signal are provided, and stereo display is performed in forced mono mode during stereo broadcast reception. An audio switching circuit to perform. 2. The audio switching circuit according to claim 1, wherein the predetermined instruction signals are a “main audio” instruction signal and a “sub audio” instruction signal. 3. The selection signal generator according to claim 2, wherein the selection signal generator turns on the selection signal only when both the “main audio” instruction signal and the “sub audio” instruction signal are turned off and the forced mono signal is turned on. Voice switching circuit. 4. The audio switching circuit according to claim 2, wherein the selection signal generator turns off the selection signal when any one of the “main audio” instruction signal and the “sub audio” instruction signal is on. 5. The selection signal generating section includes a three-input AND gate, a first inverter connected to a first input terminal, and a second inverter connected to a second input terminal. 3. The apparatus according to claim 2, wherein a "main audio" instruction signal is supplied to one inverter, a "sub audio" instruction signal is supplied to the second inverter, and a forced mono signal is supplied to a third input terminal. Voice switching circuit. 6. The audio switching circuit according to claim 2, wherein said selection signal generator is constituted by a ROM storing a look-up table. 7. The audio switching circuit according to claim 1, wherein the audio switching unit selects “mono output” or “left audio output and right audio output” according to a selection signal.