JPH08147884A - Voice output circuit - Google Patents

Abstract

PURPOSE: To improve the SN ratio by switching the signal paths so that one stream is inputted to two D/A converters and the outputs of these coverters are merged to be amplified by a LPF amplifier. CONSTITUTION: The L- and R-channel outputs of the D/A converter 25 are supplied to a mixing circuit 33 through the LPF amplifiers 29, 30 and the L- and R channel outputs from the D/A converter 26 are supplied to the mixing circuit 33 through the LPF amplifiers 31, 32. By receiving voice switching signal E, the mixing circuit 33 mixes the voice signals inputted from the LPF amplifiers 29, 31 with the outputs of the LPF amplifiers 30, 32 for each channel and outputs the respective mixed signals to the L-channel output terminal, 34, and the R-channel output terminal 35.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio output circuit for simultaneously reproducing a plurality of audio digital data called an audio data stream.

[0002]

2. Description of the Related Art In recent years, it has been desired to reduce the cost of a digital video disc player for reproducing video information and audio information from a video disc on which information is digitally recorded.

A conventional digital video disc player optically reads information from a video disc on which video information and audio information are digitally recorded, separates the information into video information and audio information, and reproduces them separately.
It has an audio output circuit for reproducing the separated audio information.

This audio output circuit, as shown in FIG.
An audio data stream demodulation circuit 100 that reproduces a plurality of audio digital data, that is, audio data streams F and G simultaneously, and a CPU 101 that outputs an audio switching signal based on the data content identification data A from the audio data stream demodulation circuit 100. , A plurality of demodulated audio data streams F and G are provided respectively, and each stream is D / A converted into analog stereo audio (L and R channels) by a data clock H from the audio data stream demodulation circuit 100. D / A converter 102 to perform,
103, LPF amplifiers 104 and 105 for amplifying the L and R channel outputs from the D / A converter 102, and D
LPF amplifiers 106 and 107 that amplify the L and R channel outputs from the A / A converter 103, a mixing circuit 108 that synthesizes the outputs of the LPF amplifiers 104 to 107 at the input timing of the audio switching signal, and the mixing circuit 10.
8, a terminal 109 for outputting L channel main audio and a terminal 11 for outputting R channel main audio.
0, and a terminal 111 for outputting the L channel sub audio,
It is composed of a terminal 112 for outputting an R channel sub sound.

In such an audio output circuit, the CPU 101 discriminates the contents of the stream, the switching of the mixing circuit 108 is performed accordingly, and the outputs of the LPF amplifier 104 and the LPF amplifier 106, and the outputs of the LPF amplifier 105 and the LPF amplifier 107 are synthesized, respectively. Output it or output it as the main and sub outputs independently.
In this case, the D / A converters 102 and 103 are individually used for each stream.

By the way, in recent years, a digital video disc player having this kind of audio output circuit has been promoted to be low cost, that is, to use low cost parts.

At this cost reduction, the highly accurate D / A converters 102 and 103 cannot be used because they are expensive.

However, the D / A converter 102,
When low-cost parts are used for 103, they are inferior in terms of SN ratio, THD characteristics, etc., as compared with a high-grade machine. If the performance of the player itself is deteriorated by using low-cost parts, the original cost reduction is meaningless.

[0009]

As described above, in the conventional audio output circuit, since it is not possible to use a highly accurate D / A converter for cost reduction, the SN ratio and THD characteristics are different from those of a high-end model. There was a problem that it was inferior.

The present invention has been made in order to solve such a problem, and it is possible to realize a performance comparable to that of a high-class machine even when a popular low-cost D / A converter is used. The purpose is to provide an audio output circuit.

[0011]

In order to achieve the above-mentioned object, an audio output circuit according to claim 1 generates a plurality of digital data at the same time, and a plurality of D / Ds corresponding to the digital data are generated.
In a voice output circuit for converting into an analog signal by an A converter and outputting the analog signal, data demodulating means for generating the plurality of digital data and outputting identification information for identifying the contents of the digital data, and the data demodulating means. Data identifying means for identifying whether or not the digital data is predetermined data based on the identification information output from the means, and the data demodulating means when the data identifying means identifies the predetermined data. From one of the plurality of digital data simultaneously output from the plurality of D / A converters.

According to a second aspect of the present invention, in the voice output circuit, a plurality of voice digital data are simultaneously generated, and a plurality of D / A converters corresponding to the voice output data are respectively converted into analog signals and output. Data demodulation means for generating audio digital data and outputting identification information for identifying the content of the audio digital data, and the audio digital data is predetermined data based on the identification information output from the data demodulation means. One of the plurality of audio digital data which are simultaneously output from the data demodulating means when the data identifying means identifies whether or not the audio data is predetermined audio data by the data identifying means. Switching means for switching the data path so as to output the data to the plurality of D / A converters;
Second switching means for switching the signal path so as to merge the two stereo audio signals converted into analog by the D / A converters by the data supply from the switching means and the second switching means. And a signal synthesizing means for outputting a stereo audio signal.

According to a third aspect of the present invention, there is provided an audio output circuit according to the first aspect.
The audio output circuit according to any one of 1 to 2 is characterized in that the predetermined data is background sound + dialog.

[0014]

According to the present invention, the data identifying means identifies whether or not the audio data is predetermined data. As a result of this identification, if it is predetermined data, one audio data is input to the two D / A converters.

That is, in the case of an audio data stream such as background sound + dialog, the audio information can be sufficiently reproduced with a single stream, so that it is not necessary to combine the two streams.

Therefore, in this case, one stream is input to the two D / A converters, the outputs of the respective D / A converters are combined, and the first and second switching means are arranged so as to be amplified by the LPF amplifier. The signal path is switched by.

As a result, one stream is converted into two D
The D / A conversion can be performed by the / A converter, and the SN ratio can be improved by about 3 dB as compared with the case of performing the conversion alone.

[0018]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a diagram showing a configuration of a video disc player of an embodiment according to the present invention, and FIG. 2 is a diagram showing an audio data demodulation unit which is an audio output circuit of the video disc player of FIG. .

In FIG. 1, reference numeral 1 denotes a disk, in which video data and audio data are digitally multiplexed and recorded on a spiral track. Reference numeral 2 denotes a disc rotating unit that rotates the disc 1. An optical reading unit 3 optically reads video data and audio data from the disc 1. A data demodulation unit 4 demodulates the data modulated at the time of disk recording, performs error detection, correction, correction, and the like, and generates a reproduction synchronization signal for reproducing the data block by block. A video / audio data separation unit 5 separates the multiplexed video data and audio data. A video data demodulation unit 6 demodulates the separated video data into an analog signal and outputs a delay amount setting signal for setting the delay amount of the audio output to the video. 7 is a voice channel data selection unit,
Arbitrary channel data is selectively reproduced from a plurality of audio channels. An audio data delay control unit 8 delays audio data in order to match the timing of audio output with respect to video output. A voice data demodulation unit 9 demodulates the separated voice data into an analog signal. A system control unit 10 controls the operation of each of the above units.

As shown in FIG. 2, the audio data demodulation section 9 identifies the stream content based on the input stream content identification data A, and outputs the DAC switching signals B, C, D and the audio switching signal E. CPU 22 for output, demodulated individual audio data streams (digital data) F, G
And a switch SW23, 24 for switching the path of the two digital data F, G by the input of the audio data stream demodulation circuit 21, which outputs the data clock H, and the DAC switch signals B, C. Analog stereo audio signals from the D / A converters 25 and 26 and the D / A converters 25 and 26 that perform D / A conversion on the digital data F and G input through the switched paths at the input timing of the data clock H. SW that switches the path of the input signal by inputting the DAC switching signal D
27, 28 and a plurality of LPF amplifiers 29 for amplifying the stereo audio signals switched by the respective switching SWs 27, 28.
32, a mixing circuit 33 that mixes and outputs each stereo audio signal amplified by each LPF amplifier 29 to 32 at the input timing of the audio switching signal E, and outputs the L channel main audio output signal from the mixing circuit 33 to the outside. Terminal 34 for outputting the R channel main audio output signal to the outside, terminal 35 for outputting the L channel sub audio output signal to the outside, R
It is composed of a terminal 37 for outputting the channel sub audio output signal to the outside.

From the audio data stream demodulation circuit 21, the demodulated digital data F is input to one input terminal 23a of the switching SW 23 and one non-selection terminal 24 of the switching SW 24.
It is output to b and. The demodulated digital data G is switched S
The other non-selection terminal 23b of W23 and the switching SW 24
Is output to the other input terminal 24a.

Then, the output on the selected side is input to the D / A converter 25 from the output terminal 23c of the switching SW 23. Also, from the output terminal 24c of the switch SW24,
The output on the selected side is input to the D / A converter 26. The data clock H is input to the D / A converters 25 and 26, respectively. The L and R channel outputs of the D / A converter 25 are LPF amplifiers 29 and 30, and a switching SW 27.
It is output to one of the non-selection terminals 27b. The L / R channel output of the D / A converter 26 is switched SW27, 28
Input to the selection terminals 27a and 28a. Switch SW2
LPF is connected to the other non-selection terminals 27b and 28b of 7 and 28.
The amplifiers 31 and 32 are connected to each other. The amplified L and R channel outputs from the LPF amplifiers 31 and 32 are output to the mixing circuit 33. The DAC switching signal B from the CPU 22 is output to the control terminal of the switching SW 23, the DAC switching signal C is output to the control terminal of the switching SW 24, and the DAC switching signal D is output to the control terminals of the switching SW 27, 28. The audio switching signal E is output to the mixing circuit 33.

The operation of this video disc player will be described below.

In this video disc player, when the disc 1 is rotated by the disc rotating portion 2 and the video data and the audio data are read from the disc 1 by the optical reading portion 3, each data is transferred to the data demodulating portion 4. .

The data demodulation section 4 demodulates the data modulated at the time of recording on the disc, and performs error detection, correction, correction and the like. Here, a reproduction synchronization signal for reproducing the data for each block is further generated. Then, the video / audio data separation unit 5 separates the multiplexed video data and audio data from the demodulated data. Of the separated video data and audio data, the video data is demodulated into an analog signal by the video data demodulation unit 6 and the delay amount of the audio output with respect to the video is set, and the delay amount setting signal is the audio data delay control. It is sent to the section 8. The separated audio data is sent to the audio channel data selection unit 7, and the audio channel data selection unit 7 selects from among the plural audio channels,
Any channel data is selectively reproduced. The channel data reproduced here is the audio data delay control unit 8
Is supplied to. The audio data delay control unit 8 delays the audio data so as to match the timing of the audio output with the video output, and outputs the delayed audio data to the audio data demodulation unit 9.

The operation of the audio data demodulation unit 9 will be described below with reference to the flowchart of FIG. In the audio data demodulation unit 9, as shown in FIG. 3, when the audio data stream demodulation circuit 21 demodulates the stream content identification data A (step 301), the data A is transferred to the CPU 22, and the CPU 22 contents the stream. Is identified as background sound + dialog (step 302)
).

As a result of the identification, if the contents of the stream are background sound + dialog (Yes in step 302), it is not necessary to reproduce the demodulated digital data F and G individually, and it is possible to reproduce sufficient information in either one. means.

Therefore, in this case, the CPU 22 causes the changeover switch 23 to demodulate digital data (stream) F.
Is selected (step 303), the demodulation digital data F is selected by the changeover switch 24 (step 304), and the LPF amplifier 29 is selected by the changeover switch 27 (step 305).
), And the LPF amplifier 30 is selected by the changeover switch 28 (step 306).

That is, the CPU 22 outputs (controls) the DAC switching signals B, C and D so that the D / A converters 25 and 26 are connected in parallel, and the changeover switch 2
Switch 3, 24, 27, 28.

One of the demodulated digital data E is supplied to the D / A converters 25 and 26 by switching the respective changeover switches in this manner. The L / R channel outputs of the D / A converters 25 and 26 are both LPF.
It is supplied to the mixing circuit 33 through the amplifiers 29 and 30.

The mixing circuit 33 receives the audio switching signal E from the CPU 22 and outputs the respective L and R channel outputs inputted from the LPF amplifiers 29 and 30 to the L channel output terminal 34 and the R channel output terminal 35, respectively. (Step 307). On the other hand, if the identification result indicates that the content of the stream is only the background sound or only the dialogue (No in step 302), sufficient information cannot be reproduced by each of them. That is, two audio data streams must be independently D / A converted and then both must be combined.

Therefore, in this case, the CPU 22 first selects the demodulated digital data F by the changeover switch 23 (step 308), selects the demodulated digital data G by the changeover switch 24 (step 309), and the changeover switch 27.
The LPF amplifier 31 is selected by (step 310), and the LPF amplifier 32 is selected by the changeover switch 28 (step 311).

That is, the CPU 22 controls the DAC switching signals B, C and D, and switches the changeover switches 23, 24, 27 and 28 so as to independently D / A convert the two audio data streams.

By switching the changeover switches in this manner, the demodulated digital data F and G are independently supplied to the D / A converters 25 and 26. The outputs of the L and R channels from the D / A converter 25 are both supplied to the mixing circuit 33 through the LPF amplifiers 29 and 30. The L and R channel outputs from the D / A converter 26 are supplied to the mixing circuit 33 through the LPF amplifiers 31 and 32.

The mixing circuit 33 receives the voice switching signal E from the CPU 22, and mixes the outputs of the LPF amplifiers 30 and 32 with the voice signals input from the LPF amplifiers 29 and 31 for each channel (step 312). ,
The respective mixed signals are output to the L channel output terminal 34 and the R channel output terminal 35 (step
313).

As described above, according to the audio output circuit of this embodiment, the CPU 22 discriminates the contents of the stream and uses the two D / A converters 25 and 26 individually or in parallel according to the contents of the stream. Or to use.

As a result, since a plurality of D / A converters 25 and 26 are used in parallel only in the case of an audio stream composed of, for example, a scene sound + dialog, the SN ratio is improved by about 3 dB as compared with the individual use. Can be made. Since it is a well-known fact that the S / N ratio can be improved by connecting the D / A converters 25 and 26 in parallel, it will not be described here.

[0039]

As described above, according to the present invention, it is necessary to combine two streams, since a single stream can sufficiently reproduce voice information as long as it is a voice data stream such as background sound + dialog. There is no. Therefore, in this case, the signal path is switched so that one stream is input to the two D / A converters, the outputs of the respective D / A converters are merged and amplified by the LPF amplifier.

As a result, one stream becomes two D
The D / A conversion can be performed by the / A converter, and the SN ratio can be improved by about 3 dB as compared with the case of performing the conversion alone.

As a result, high precision D is achieved for cost reduction.
Even if the A / A converter cannot be adopted, the performance similar to that of a high-end model can be realized.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of a video disc player according to an embodiment of the present invention.

FIG. 2 is a diagram showing a configuration of an audio data demodulation unit of the video disc player of FIG.

FIG. 3 is a flowchart showing the operation of this video disc player.

FIG. 4 is a diagram showing a configuration of an audio output circuit (audio data demodulation unit) of a conventional video disc player.

[Explanation of symbols]

21 ... Audio data stream demodulation circuit, 22 ... CPU,
23, 24, 27, 28 ... Changeover switches, 29 to 32 ...
LPF amplifier, 25, 26 ... D / A converter, 12,
33 ... Mixing switching circuit, 34 ... L channel main output terminal, 35 ... R channel main output terminal, 36 ...
L channel sub output terminal, 37 ... R channel sub output terminal, 107 ... Data clock, A ... Stream content identification data, B, C, D ... DAC switching signal, E ... Audio output switching signal, F, G ... Demodulated digital data (Audio stream).

Claims (3)

[Claims] 1. An audio output circuit for simultaneously generating a plurality of digital data, converting the analog signals by a plurality of D / A converters corresponding to the digital data, and outputting the analog signals. Data demodulation means for outputting identification information for identifying the content of the data, and data identification means for identifying whether or not the digital data is predetermined data based on the identification information output from the data demodulation means When the data identification means identifies the predetermined data, one of the plurality of digital data simultaneously output from the data demodulation means is used as the plurality of D / D data.
An audio output circuit comprising means for outputting through an A converter. 2. An audio output circuit which simultaneously generates a plurality of audio digital data, converts the analog digital signals by a plurality of D / A converters corresponding to the audio digital data, and outputs the analog signals. Data demodulation means for outputting identification information for identifying the contents of the audio digital data, and whether or not the audio digital data is predetermined data based on the identification information output from the data demodulation means When the data identification means and the data identification means identify the predetermined audio data, one of the plurality of audio digital data output simultaneously from the data demodulation means is converted into the plurality of D / A conversions. Switching means for switching the data path so as to output the data to the output device, and each D by the data supply from the first switching means.
Second switching means for switching the signal path so as to combine the two stereo audio signals converted into analog by the A / A converter, and signal synthesizing means for outputting the stereo audio signals combined by the second switching means. An audio output circuit comprising: 3. The audio output circuit according to claim 1, wherein the predetermined data is background sound + dialog.