JPH0430107B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a disc playback device applied to, for example, an optical playback digital audio disc, a so-called compact disc.

"Background Art and Problems Therewith" In a compact disc, an audio signal is converted into a digital signal having the data structure shown in FIGS. 1 and 2 and recorded thereon.

As shown in Figure 1, this digital signal is
One frame consists of 588 bits, and a frame synchronization pulse FS of a specific pattern is added to the beginning of each frame. A 3-bit DC component suppression bit RB is provided after the frame synchronization pulse FS, and after that, 0 to 32nd data bits DB each having 14 bits and a 3-bit DC component suppression bit RB are arranged alternately. It is set in. The 0th bit in the data bit DB is called a sub-coding signal or user's bit, and is used for disc playback control and the like. 1st to 12th, 17th to 28th data bit DB
is assigned to audio data and the remaining 13~
The 16th, 29th to 32nd data bits DB are assigned to parity data of the error correction code. Each data bit DB is converted into 8 bits by 8-14 conversion during recording.
This is bit data converted to 14 bits.

The 98 frames of the digital signal mentioned above are called one block, and various processes are performed in units of this one block.

FIG. 2 shows a state in which one block (98 frames) is sequentially arranged in parallel, with each data bit DB having 8 bits, excluding the DC component suppression bit. The sub-coding signals P to W of frames 0 and 1 are:
A sync pattern, which is a predetermined bit pattern, is formed. Furthermore, regarding the P channel and Q channel, a CRC code for error detection is inserted into 16 frames on the terminal side among the 98 frames.

The P channel is a flag indicating a pause and music, and has a low level for music, a high level for a pause, and a pulse of 2 Hz period in the lead-out section. Therefore, by detecting and counting the P channels, it becomes possible to select and reproduce designated music. The Q channel allows for more complex control of the same type,
For example, by importing Q channel information into a microcomputer installed in a disc playback device,
It is possible to perform random music selection, such as immediately switching to playing other music even when music is not being played.
The R channel to W channel other than these are used to display the lyricist, composer, explanation, poem, etc. of the song recorded on the disk, or to provide an audio explanation.

R channel ~W of this sub-coding signal
If a channel records an audio signal that plays back the main channel audio signal at the same time (for example, the audio of a parallel translation of foreign language lyrics), the main channel playback audio signal and the subchannel audio signal will be output at the same time during playback. , the user will hear both sounds, causing inconvenience.

OBJECT OF THE INVENTION The object of the present invention is to provide a disc playback device that allows the user to listen to the playback sound of the main channel and the playback sound of the subchannel without any trouble, and that is easy to operate for this purpose.

"Embodiment" An embodiment of the present invention will be described below with reference to FIGS. 3 and 4.

FIG. 3 shows a configuration for generating signals to be recorded on a compact disk and recording them on a master tape. In FIG. 3, 1 and 2 indicate input terminals to which two-channel audio signals such as stereo are supplied. The audio signals of each channel are supplied to sample and hold circuits 5 and 6 via low-pass filters 3 and 4, and
One sample is converted into 16 bits by D converters 7 and 8. This two-channel audio PCM signal is converted into a one-channel signal by a multiplexer 9 and supplied to an error correction encoder 10.

In the error correction encoder 10, the audio
The PCM signal is subjected to cross-interleaving processing to perform error-correctable encoding using a Reed-Solomon code. Cross-interleave processing rearranges the order of data so that each symbol is included in two different error correction code sequences. The output of this error correction encoder 10 is supplied to a multiplexer 11.

Further, an encoder 12 for the P channel and Q channel of the sub-coding signal and an encoder 13 for the R channel to W channel are provided, and their outputs are sent to a multiplexer 14.
are combined and supplied to the multiplexer 11. The output of the multiplexer 11 is supplied to a digital modulation circuit 15 and subjected to (8→14) conversion modulation. In this case, the frame sync from the synchronization signal generation circuit 16 is mixed and taken out to the output terminal 17. The encoder 12 for the P channel and the Q channel is configured to add a 16-bit CRC code, and the encoder 13 for the R channel to W channel performs error correction encoding using a Reed-Solomon code and interleaving.

In addition, sample hold circuits 5, 6, A/D converters 7, 8, multiplexers 9, 11, 14
For each circuit such as, timing generation circuit 18
A clock pulse formed by a timing signal is provided. 19 is an oscillator for generating a master clock.

FIG. 4 shows the configuration of a reproducing system for processing a reproduced signal from a compact disc, and an input terminal indicated by 20 is supplied with a signal optically reproduced from the compact disc.

This reproduced signal is supplied via a waveform shaping circuit 21 to a digital demodulation circuit 22, a clock reproduction circuit 23, and a synchronization detection circuit 24. A bit clock synchronized with the reproduced data is extracted by a clock reproducing circuit 23 having a PLL configuration. Further, the synchronization detection circuit 24 is configured to detect frame sync and generate a timing signal synchronized with reproduction data, and supplies a predetermined timing signal to each circuit of the reproduction system.

Among the outputs of the digital demodulation circuit 22, main channel data undergoes error detection, error correction, and interpolation processing in an error correction circuit 25. Also, the sub-coding signal is sent to the decoder 3.
3, it undergoes error detection and error correction processing.

The output of the error correction circuit 25 is supplied to a demultiplexer 26 and divided into two channels. The reproduced digital audio signal of each channel is connected to the digital gain control circuits 27 and 28 and the D/
A converter 29, 30 and low pass filter 3
1 and 32, and the reproduced audio signals of each channel appear at output terminals 33 and 34.

Furthermore, data of the P channel and Q channel of the sub-coding signal obtained from the decoder 35 is supplied to a system controller 36 including a microcomputer, and is used for operations such as cueing and random music selection. The time code included in the Q channel is displayed on the display section 37.
is supplied and displayed.

Further, audio data such as translations and explanations included in the R channel to W channel from the decoder 35 is supplied to the D/A converter 39 via the digital gain control circuit 38. This D/
The output of the A converter 39 is passed through the low pass filter 40
It is taken out to the output terminal 41 via. A speaker is connected to this output terminal 41 via a low frequency amplifier (not shown).

As the digital gain control circuits 27, 28, and 38, a configuration in which data is immediately shifted to the upper or lower side by one bit, a configuration using a lookup table method using a ROM, etc. can be used. A control input section 42 is provided for generating control signals for the digital gain control circuits 27, 28, 38.

The control input unit 42 includes a sliding knob, and the gain of the digital gain control circuits 27 and 28 can be adjusted by the user changing the setting position of the knob.
G ₁ and the gain G ₂ of the digital gain control circuit 38 can be changed differentially.

In other words, with the knob set in the center position,
(G ₁ =G ₂ ), and the levels of the audio signals of the main channel and the sub channel become equal. When you move the knob from the center position to one side,
(G ₁ > G ₂ ), and the main channel audio signal level becomes larger than the sub channel audio signal level, and when you move it to the maximum position on one side, G ₁ becomes the maximum, and (G ₂ =0)
You can only hear the audio signal from the main channel. If you move the knob to the other side opposite to this, (G ₁ < G ₂ ), and if you move the knob further, G ₂ will be the maximum, (G ₁ = 0), and the audio signal of the subchannel will be can only be heard.

In addition to the gain control method described above, various gain control modes are possible. One of them is switching control that switches between two states: (G ₁ = maximum, G ₂ = 0) and (G ₁ = 0, G ₂ = maximum). This switching control may be performed according to a user's manual operation, but it may also be performed automatically based on control data that detects or indicates the presence of audio data in a subchannel. good. In this case, instead of setting the gain of the other to 0, the gain of the other may be set to a certain degree so that the reproduced sound of the other can be heard at a low volume.

"Application Example" The present invention can also be applied to a case where a subchannel includes display data together with audio data. Furthermore, the present invention is applicable not only to optical discs but also to capacitive discs.

"Effects of the Invention" According to the present invention, there is no need to separately adjust the volumes of the main channel playback sound and the subchannel playback sound, and both can be played back at the desired level relationship. . Moreover, this invention
Since gain control is performed at the digital data stage, it is possible to have a simple circuit configuration using logic circuits and ROM, and it can be mounted on the same board as other signal processing circuits.
It can be converted into an IC (LSI).

[Brief explanation of drawings]

1 and 2 are schematic diagrams used to explain the data structure of a compact disk to which the present invention can be applied, and FIG. 3 is a block diagram showing the configuration of a recording system according to an embodiment of the present invention. FIG. 4 is a block diagram showing the configuration of a reproduction system according to an embodiment of the present invention. 10...Error correction encoder, 12...Encoder regarding P channel and Q channel,
13... Encoder for the R channel to W channel, 20... Input terminal to which the playback signal of the compact disc is supplied, 25... Error correction circuit, 27, 28, 38... Digital gain control circuit, 42... Control input Department.

Claims (1)

[Claims] 1 In an apparatus for reproducing a disc on which a main channel containing a first digital audio signal and a subchannel containing control data and a second digital audio signal are recorded, a first decoder for reproducing data of the main channel; , a second channel for reproducing the data of the above subchannel.
a digital gain control circuit to which the first and second digital audio signals appearing at the outputs of the first and second decoders are supplied; What is claimed is: 1. A disc playback device comprising: gain control signal input means for setting the gain for each audio signal in a desired relationship.