JPH0690774B2 - Digital disc player - Google Patents

Description

Description: “Industrial field of use” The present invention relates to a reproducing apparatus for a digital disc in which digital data consisting of audio data and video data is recorded.

"Background Art and Its Problems" In a reproducing device using an optical digital audio disc (called a compact disc), by recording sound information and image information on the compact disc, both It is possible to realize a complete collection of art by information, travel guides, picture books, educational systems, etc. In this case, the amount of audio data that can be transmitted is reduced because the still image data is recorded.

One of them is one sample of the current compact disk
While the number of bits is 16 bits, the number of bits per sample is 8 bits, that is, the dynamic range is reduced. For example, in the case of 16 bits, a dynamic range of 96 dB can be obtained, whereas in the case of 8 bits, only a dynamic range of 48 dB can be obtained. However, the problem is that D-PCM
By using this method or the analog companding method, it is possible to obtain a value close to the initial dynamic range, such as 60 dB or 78 dB.

Another problem is the reduction of the transmission band due to the lack of sampling data that can be transmitted. The current compact disk has a transmission band of 20 kHz. However, if the sampling data is insufficient for recording still image data, the transmission band will be about 10 kHz. Even in this case, there is no great inconvenience in reproducing sound, but when reproducing music, a transmission band of about 15 kHz is desirable.

[Object of the Invention] The present invention is intended to solve the problem of the reduction of the transmission band due to the lack of the number of samples of audio data when reproducing a digital disc on which both audio data and video data are recorded. Is.

[Summary of the Invention] In the present invention, control data indicating the linear velocity of a digital disc at the time of reproduction is recorded. With this control data, the digital disc is rotated at a constant linear velocity at the time of reproduction, and The clock signal of the frequency corresponding to the transmission rate is supplied to the reproducing circuit, the reproduced audio data from the reproducing circuit is D / A converted, and the pass band of the low-pass filter to which the reproduced analog audio signal is supplied is the band of the reproduced analog audio signal. It is adapted to.

[Embodiment] An embodiment of the present invention is one in which the present invention is applied to a digital disc reproducing apparatus using a compact disc.

The data structure of the signal recorded on the compact disk will be described with reference to FIGS. 1 and 2.

FIG. 1 shows a data stream recorded on a compact disc. The 588 bits of the recording data are set as one frame, and the frame synchronization pulse FS of a specific bit pattern is added to the beginning of each frame. After the frame synchronization pulse FS, a 3-bit DC suppression bit RB is provided, and thereafter, each 14-bit data bit 0 to 32 data bit DB and a 3-bit DC suppression bit RB alternate. It is provided in. This data bit DB
The 0th one among them is called a sub-coding signal or user's bit, and is used for reproduction control of a disk and display of related information. 1 to 1
The 2,17th to 28th data bit DBs are assigned to the main channel audio data, and the remaining 13th to 16th, 29th to 32nd data bit DBs are assigned to the parity data of the main channel error correction code. Each data bit DB contains 8 bit data when recorded by 8-14 conversion.
It was converted to 14 bits.

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

Fig. 2 shows each data bit DB except the DC suppression bit.
8 bits, one block (98 frames) is arranged in parallel in order. The sub-coding signals P to W of the 0 and 1 frames form a sync pattern which is a predetermined bit pattern. Regarding the Q channel, the CRC code for error detection is inserted in 16 frames on the terminating side of the 98 frames.

The P-channel is a flag that indicates a pose and music. The P-channel is a low level for music, a high level for pause, and a pulse of 2 Hz cycle in the lead-out section. Therefore,
By detecting and counting this P-channel, it becomes possible to select and play the specified music. The Q-channel can perform the same kind of control in a more complicated manner. For example, the information of the Q-channel is loaded into the microcomputer provided in the disc playback device, and immediately after the music is played, another music is played. It is possible to select a random song. Other than this, R-channel to W-channel display the songwriter, composer, commentary, poem, etc. of the song recorded on the disc.
Used for audio commentary.

In one embodiment of the present invention, digital data other than a stereo music signal is recorded in the same form as the data stream shown in FIG. 1 of a compact disc. This digital data is subjected to error correction coding and channel modulation (EFM modulation) in the same system as that for stereo music signals, and is recorded with a sub-coding signal consisting of P to W channels added. The digital data constitutes one block with the data of one frame length (16 × 6 × 2 = 192 bits).

FIG. 3, FIG. 4, FIG. 5, and FIG. 6 respectively show the constitution of one block of this digital data. In this example, three modes are used as digital data. First
The mode of consists of only color still image data. The second mode is composed of color still image data and 2-channel audio data. The third mode is composed of color still image data and audio data of 3 channels. The fourth mode is composed of color still image data and audio data of 5 channels.

FIG. 3 shows the data structure of one block in the first mode. The data is in units of 8 bits, and there are (12 × 2 = 24) data in one block. In FIG. 3, the four pieces of data at the ends are control data and address data. The control data consists of a 3-bit mode, a 3-bit item and a 6-bit instruction. The mode distinguishes the graphic mode, the still image mode, etc., and the item is for designating a more detailed mode in this mode. This embodiment is a still image mode, and the first to fourth modes described above are distinguished by items. Instructions are commands in each mode. The address data is composed of 10-bit rows and columns indicating the vertical and horizontal addresses of the display area.

In the first mode, the other 20 data of 1 block are used as still image data. In this example, the luminance data Y and 2
Image data obtained by component coding including one color difference data V and U is used. The ratio of the color difference data of one sample to the luminance data of three samples is set. In the first mode, 12 samples of luminance data Y ₁₁ , Y
₁₂ 、 Y ₁₃ …… Y ₄₂ , Y ₄₃ and color difference data V _{1 to} V for 4 samples each
₄ , U _{1 to} U ₄ are inserted in one block.

As an example, the number of vertical pixels required to display one still image is 576, and the number of horizontal pixels is 612,
The total number of pixels is (576 × 612 = 352512). Since the compact disk reproduces 7350 frames of data per second, it can be used to reproduce the data of one still image. Requires.

In the second mode, as shown in FIG. 4, the same control data and address data as described above are inserted in one block, and color still image data for two pixels and an audio channel for two channels A and B are inserted. Data and are inserted. For audio data, 5 samples are inserted in one channel with 8 bits as one sample. Since the current compact disk has a sampling frequency of 44.1 kHz and 6 samples are inserted in one frame, the reduction ratio of the number of samples is Becomes If the transmission band is (1 / 2.2) of the sampling frequency, the transmission band of the audio signal in the second mode is Becomes Also, the time to play the data of one still image is twice as long as that in the first mode, and the number of images that can be recorded on one compact disk is Becomes

In the third mode, as shown in FIG. 5, the same control data and address data as described above are inserted, and color still image data for 2 pixels and audio data for a total of 3 channels of A, B, C are included. And are inserted. Audio data is inserted in one block at a rate of 3 samples per channel. The reproduction time of the data of one still image is the same as that in the second mode. Also, in the third mode, one data in one block becomes redundant.

In the fourth mode, as shown in FIG. 6, the same control data and address data as described above are inserted, and color still image data for one pixel and A, B, C, D, E total 5
The audio data of the channel is inserted. Audio data is inserted in one block at a rate of 3 samples per channel.

In the third mode and the fourth mode, the number of samples of one channel is reduced to half of the current compact disc, so that the transmission band of the audio signal is reduced to 10.02 kHz. Therefore, the sampling frequency of the audio data in the third mode and the fourth mode is 1.5 times. Therefore, the transmission band of audio data is Can be expanded. Also, set the sampling frequency to 1.
In order to increase the speed to 5 times, the linear velocity of the compact disk during playback is also set to 1.5 times. Since the current compact disk is rotated at a constant linear velocity of 1.25 m / sec, the linear velocity is set to 1.875 m / sec in the third mode and the fourth mode.

Thus, if the linear velocity during reproduction is set to 1.5 times, the reproduction time of the data of one still image is shortened to 5.33 sec (third mode) and 10.66 sec (fourth mode). The number of still images that can be recorded on one compact disk does not decrease. The playback time is 40 minutes shorter than the current compact disk (60 minutes), but in practice,
It doesn't matter.

Further, in order to make the transmission band of audio data equal to that of the current compact disk (20 kHz), a linear velocity of 1.2 times in the second mode and a linear velocity of twice in the third mode are required.

In order to identify the above difference in linear velocity during playback,
Record the control data on the compact disk.

The compact disc has a TOC (Tab
data is recorded, the identification data is inserted in the control bit of this part or the control bit of the sub-coding signal (Q channel). The control bit is 4 bits, and is defined as follows in the current compact disk.

0000: Audio data of 2 channels with no pre-enfasis 1000: Audio data of 4 channels without pre-emphasis 0001: Audio data of 2 channels with pre-emphasis 1001: Audio data of 4 channels with pre-emphasis Therefore, the following is added as the meaning of the control bit.

0010: Same speed reproduction 0100: 2x speed reproduction 0110: 1.2x speed reproduction This is for expanding the audio data transmission band to 20 kHz. Also, with this control bit, it is possible to distinguish between a compact disc in which a stereo audio signal of 2 channels is recorded and a compact disc in which digital data including image data is recorded, as in the conventional case.

The configuration of an embodiment of the present invention will be described with reference to FIG. In FIG. 7, 1 indicates a compact disk, and 2 indicates a motor for rotating the compact disk 1. The signal reproduced from the compact disk 1 by an optical pickup (not shown) is supplied to the reproduction processing circuit 4 and the synchronization detection circuit 5.

The reproduction processing circuit 4 includes an RF amplifier, a bit clock reproduction circuit,
It includes an EMF demodulation circuit and error correction circuit, and the reproduced data can be obtained at the output. In addition, the synchronization detection circuit 5
Detects the frame sync pulse. The reproduction data from the reproduction processing circuit 4 is supplied to the data separation circuit 6 and the control data reproduction circuit 7. This control data reproducing circuit 7 is a control data (mode and item) added to the data designating the linear velocity of the compact disk at the time of reproduction and the digital data.
To generate a predetermined switching signal.

The data separation circuit 6 separates the digital data, and the separated digital data is supplied to the data distribution circuit 8 and divided into video data and audio data. The video data and the audio data from the data distribution circuit 8 are supplied to the image reproduction circuit 9 and the audio reproduction circuit 10, respectively. The image reproduction circuit 9 includes a frame memory for storing video data, a D / A conversion circuit, and the like, and an analog color video signal appearing at its output is taken out to the output terminal 13 via the low-pass filter 11. The audio reproduction circuit 10 includes a memory, a D / A conversion circuit, and the like, and an analog audio signal appearing at its output is taken out to the output terminal 14 via the low-pass filter 12. Although not shown, an image reproducing device and an audio reproducing device are connected to the output terminals 13 and 14, respectively. The low-pass filter 12 is configured so that its pass band can be switched to a plurality of pass bands.

Further, there is provided a clock generation circuit 15 which generates a clock pulse used for data processing of each circuit of the reproduction system described above. Further, a servo circuit 3 is provided in association with a motor 2 for rotating the compact disc 1. The servo circuit 3 has a frequency multiplier 16 in which the output signal of the synchronization detection circuit 5 is M times larger. And the frequency dividing circuit 17 are supplied.

The control data reproducing circuit 7 includes a low pass filter 12
And the frequency of the clock pulse generated by the clock generation circuit 15. Of the frequency multiplier 16, a switching signal for setting the coefficient M of the frequency multiplier 16, and a switching signal for setting the coefficient N of the frequency dividing circuit 17. When the control data included in the reproduction data indicates the same speed reproduction, (M
= N = 1). As a result, the clock generation circuit
A clock pulse having a frequency is generated from 15, the band of the low-pass filter 12 is set to 20 kHz, and the servo circuit 3 is supplied with the signal of the frame frequency from the synchronization detection circuit 5. A typical example of the same speed reproduction is when reproducing a compact disc on which a current stereo music signal is recorded.

Further, when the control data indicates reproduction at 1.2 times speed, (M = 5, N = 6) is set. At this time, a clock pulse with a frequency of 1.2 is generated from the clock generation circuit 15, and the frequency of the signal supplied to the servo circuit 3 is changed. Fall to. The servo circuit 3 makes the frequency of the signal supplied from the frequency dividing circuit 17 equal to the frame frequency,
Since the rotational speed of the motor 2 is controlled, the linear velocity of the compact disk is 1.2 times. The pass band of the low pass filter 12 differs depending on which of the plurality of modes the digital data to be reproduced is. In the case of digital data in the second mode, low pass filter 12
Is set to 20 kHz, and in the case of digital data of the third and fourth modes, the pass band is set to 12 kHz.

Further, even when the control data indicates reproduction at 1.5x speed or 2x speed, the compact disk 1 rotates at the specified linear velocity in the same manner as described above, and the frequency of the clock pulse and the pass band of the low pass filter 12 are reproduced data. It will be changed to one that conforms to.

“Application Example” The present invention is not limited to the optical type, and can be applied to a digital disc that records a digital signal as a change in electrostatic capacitance, and has similar operational effects.

Further, the block structure of digital data may be set in units of 2 frames instead of in units of 1 frame.

[Advantages of the Invention] According to the present invention, when recording both video data and audio data on a digital disk, it is possible to prevent the audio signal band from being reduced due to the decrease in the number of audio data samples. . According to the present invention, the number of audio channels can be changed to multiple channels, and audio information in Japanese and multiple foreign languages can be recorded. For example, audio commentary associated with images for travel guidance can be in multiple foreign languages.

[Brief description of drawings]

1 and 2 are schematic diagrams showing the data structure of a compact disk to which the present invention is applied, and FIGS. 3, 4, 5, and 6 are digital data in an embodiment of the present invention. FIG. 7 is a block diagram showing the construction of one block of FIG. 7, and is a block diagram of an embodiment of the present invention. 1 ... Compact disk, 3 ... Servo circuit, 5 ... Sync detection circuit, 6 ... Data separation circuit, 7 ... Control data reproduction circuit, 11,12 ... Low pass filter, 15 ... Clock generation circuit.

Claims (1)

[Claims] 1. A data block is formed of a predetermined number of samples of data, digital data including audio data and video data is recorded in the data block, and the number of data samples in a channel of the audio data is changed. A reproducing apparatus for a digital disc on which control data indicating a set reproduction linear velocity which is supposed to be higher than that at the time of recording is recorded, and is represented by the control data indicated by the control data reproduced from the digital disc. Disc rotation speed control means for rotating the digital disc at the reproduction linear velocity, and the number of samples of digital audio data reproduced at the reproduction linear velocity, which is generated based on the reproduced control data. Frequency Clock signal and the reproduced digital audio data are supplied, and audio reproduction means including a memory and a D / A conversion circuit and an analog audio signal from the audio reproduction means are supplied and the reproduced control data is reproduced. And a low-pass filter whose pass band is adapted to the band of the analog audio signal.