JPH0793901A - Cd-rom apparatus - Google Patents

Abstract

PURPOSE:To read computer data carrying out a CDPCM reprodution as for a DC-ROM having a mixture of CDPCM data and data for computer. CONSTITUTION:In a CD-ROM apparatus capable of reading data faster than a standard speed, a means is provided to send a specified amount of data necessary for CDPCM reproduction out of the data already read out to a CDPCM reproduction means and the rest thereof to a host computer. For example, 2352 bytes necessary for the CDPCM reproduction are used out of 4096 tytes read out for 1/75sec. at a dual speed access for reproduction with sounds and the remaining 1744 bytes are sent to the host computer through an SCSI bus.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a CD-ROM device for reading data at a speed faster than the standard.

[0002]

2. Description of the Related Art An optical compact disc (CD) was developed as a medium capable of digitally recording and reproducing voice, and has become popular as a CD audio disc capable of reproducing faithful sound and continuously reproducing for a long time. Furthermore, attention is paid to large capacity and high-speed access performance, and its use as a recording medium is advancing.

The data structure of a CD audio disc will be described. L / R audio signal is PCM modulated and 1
Obtain digital data of 6 bits × 2 channels. 24 bytes of digital data in 6 sample sections are in 1 frame units. For the purpose of suppressing errors, when data is converted in units of L / R 12 bytes, an error correction code is entered and interleaved, 8 bits × 12 data and 8 bits × 4 parity are respectively obtained. A 1-byte subcode is added to 1 frame, and a digital signal obtained by modulation is recorded on a CD.

98 frames form one subcode block. The first 2 bytes are the subcode header,
The remaining 96 bytes are the subcode 8 channels. Of the subcode, 24 bytes are used for read control,
Address information for searching, such as the type of user data, absolute time, and subcode frame number, is recorded. 1
The data attached to one subcode block is 2352.
Equivalent to the amount of information in bytes.

The CD audio disc reproducing apparatus is provided with a program function using sub-codes, such as a cue of a music piece and setting of a reproduction order, as means for performing digital signal processing. Using the index on the innermost circumference of the disc as a clue,
The sub-code is searched for and demodulated, and the target block is searched by the absolute time of the sub-code. The read digital signal is demodulated, error correction is performed by deinterleaving and error correction code, and digital signal processing is performed to obtain digital data. Digital data is processed by D / A converter,
It is output as an audio signal.

A typical example of using an optical compact disc as a computer recording medium is a CD-ROM whose physical format is a unified standard. CD-R
The OM physical format standard is shown in FIG. As the physical format, three kinds of modes of mode 0, mode 1 and mode 2 are defined. One sector of CD-ROM is
It is composed of data of 2352 bytes which is equal to a subcode block of a CD audio disc, and a 12-byte block sync signal (sync) is placed at the head of each block for separating the blocks.

After the block synchronization signal, 4 bytes of header are arranged, which consists of 3 bytes of block address and 1 byte indicating the data recording mode. In mode 0 and mode 2, the remaining 2336 bytes are the data area. In mode 0, this data is all 0s.

Mode 1 is used for computer data that requires more accurate error correction. Program data, image data having a high compression rate, and the like cannot operate normally even with a 1-bit error. Unlike such image data or acoustic data that can be interpolated, such data is not allowed to have errors.

In order to improve the reliability of the data of the CD-ROM, an auxiliary data area is set in the data structure of 2336 bytes, and 2048 bytes of user data and 28
Divided into 8 bytes. The setting of auxiliary data is defined by setting the data recording mode to mode 1. 288 bytes of auxiliary data are 4 bytes for error detection,
The error correction is 276 bytes including 8 bytes of space, 172 bytes of P parity and 104 bytes of Q parity.

Mode 2 has a data structure in which 2336 bytes are all user data, and image / sound data and the like that can be error-corrected by interpolation processing can be recorded. However, in general, define the structure in the user data of mode 2,
The physical format is expanded and the data structure of mode 2 is used when performing time division processing of various data.

The program data and the like have a large number of consecutive redundant codes of the same code, and read errors are likely to occur. Therefore, in the block of 2352 bytes in which the sync data, the header data, and the auxiliary data data are added to the user data, the scrambling process is performed while leaving the sync data to eliminate the redundant code.

After the scramble process, like the CD audio disc, an error correction code is inserted and interleaved, a subcode is added, and a digital signal obtained by modulation is recorded in a CD-ROM.

The subcode corresponds to the structure of the CD audio disc, and one having a size of 8 channels × 12 bytes is added to one block. Of these, two channels are used for read control, and address information for searching, such as the type of user data, absolute time, and subcode frame number, is recorded.

The CD-ROM player is a computer,
An image display means such as a CRT or a printer, a data input means such as a keyboard, and a CD-ROM reading means are combined. In response to the address designation by the computer, the CD-ROM reading means performs digital signal processing in exactly the same manner as the reproduction of a CD audio disc.

Since the obtained digital data is scrambled, the sync in the data block is detected to descramble the data, the header address is detected, and then the target block is accessed. After the error detection and correction using the auxiliary data is performed according to the data structure mode in the header, the user data is read into the computer. The reliability of data is enhanced by such a two-step error correction function.

The CD-ROM is common with the CD audio disc in digital signal processing. Originally CD-
Since the ROM is derived from the CD audio disc, most CD-ROM reading means are
It also serves as a playback device for audio discs.

The CD-ROM reproducing device is utilized as a multimedia, and image data as well as program data,
We handle acoustic data. The data transfer rate of the CD-ROM reading means is based on 1/75 second per block. By matching the data transfer rate to that of a CD audio disk and setting 1/75 second as a reference, it is used as a shared machine.

As the image display means such as a CRT, the NTSC system in which the horizontal synchronization and the vertical synchronization are about 16 kHz and about 60 Hz, respectively, is widespread. When displaying a moving image using a multimedia composed of a CD-ROM and a computer, the CPU prepares each screen data by processing the image data in the vertical blanking period every 1/60 seconds. Since the CD-ROM reading means transfers data every 1/75 second, the image data is temporarily held in a dedicated secondary buffer and is read from the buffer at a rate equal to the vertical synchronizing signal to achieve synchronization. ing.

In both the CD audio disc and the CD-ROM, the subcode has a space of 6 channels × 12 bytes. By inserting character data or image data here, a screen display function is added or supplemented. Even a CD audio disc can be displayed on the screen by providing a circuit for converting data into characters and images, a CRT, etc. in the reproducing device.

[0020]

In a CD-ROM, data is collectively stored in a certain fixed unit. This is called a block, and reading is performed in block units. The block length is set to 1/75 second, which is the same as the length of the CD subcode. The total amount of data that can be described in a block is 2
It is 352 bytes. 2 in 1/75 seconds for mode 1
048 bytes can be read for data.
For example, in a CD-ROM device with double speed function,
That is, 4096 bytes can be read for pure data.

Since the access speed of the CD-ROM is originally defined for music, a higher reading speed is possible for a computer. At present, a double speed CD-ROM device which reads at a double speed is often used as a recording device of a computer. In this case, the computer is a CD-
I am receiving data from the ROM device at double speed,
It's just getting the data in early.

The present invention relates to a CD-ROM in which CDPCM data and computer data are mixed,
An object is a device for reading computer data while performing M reproduction.

[0023]

The device of the present invention is a CD-ROM device for reading data faster than the standard speed. In the CD-ROM device, a predetermined amount of data of the read data necessary for CDPCM reproduction is read by the CDPCM reproduction means. Means to send to,
And a CD-ROM device with means for sending the rest of the data to the host computer.

For example, of the 4096 bytes read in 1/75 second during double speed access, 2352 bytes required for CDPCM reproduction are used for sound reproduction, and the remaining 1744 bytes are sent to the host computer through the SCSI bus. Is.

FIG. 2 is a conceptual diagram thereof, but according to this apparatus, the data for program processing can be read at the same time while reproducing the CDPCM sound.

[0026]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described by taking an apparatus including a double speed CD-ROM apparatus shown in FIG. 3 as an example.

(1) The host machine () is PLAY & R
Issue an EAD instruction. (2). This command is received by the SCSI controller () via the SCSI bus, and the CD CPU () judges and operates the CDROM drive () to read the data into the CD internal buffer RAM (). (3). 307200 / s (= 2048 × 2 in the buffer)
X75) bytes are sent, of which 17640
0 (= 2352 × 75) bytes are output as audio data through the CDPCMDA conversion device (). (4). The remaining 130800 (= 1744 x 75) is S
Host machine () through CSI controller ()
Read in.

Since the amount of data consumed as audio is 176400 bytes per second, the faster the reading speed, the more data the host machine can receive. In this embodiment, the buffer inside the CD is divided into two, one for audio and the other for host machine data.

[0029]

By using the apparatus of the present invention, sound reproduction and program processing data reading can be performed in parallel. Further, since the amount of data required for reproducing sound is fixed, there is an advantage that the faster the CR-ROM is read, the more amount of data is required for program processing.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a data format structure of a CD-ROM.

FIG. 2 is a conceptual diagram of audio reproduction and data reading to a host machine in the device of the present invention.

FIG. 3 is a block diagram of a CD-ROM device of the present invention.

Claims (1)

[Claims] 1. A CD-ROM device for reading data faster than a standard speed, wherein a predetermined amount of data required for CDPCM reproduction of the read data is stored in the CDPCM device.
A CD-ROM device comprising means for sending to a reproducing means, and means for sending the remaining data of the read data to a host computer.