JP3084815B2 - Data recording method and device - Google Patents

Abstract

PURPOSE:To monitor a real time data in recording a compression encoded data to an IC card and to efficiently check the recording contents in a short time. CONSTITUTION:When the compression encoded data of a fixed bit rate recorded on a magneto-optical disk 1 is reproduced and recorded to the IC card 2, the compression data recorded on the IC card 2 is read out, and bits reduced by an ATC encoder 63 and a remaining bit reducing circuit 84 are zero-packed, and the data is restored to its original bit length PCM data by an ATC decoder 73, and is reproduced at a real time rate, and then the recording monitor is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a data recording method and apparatus for recording compressed data obtained by bit-compressing a digital audio signal or the like, and more particularly to a method for recording data between a constant bit rate recording medium and a variable bit rate recording medium. The present invention relates to a data recording method and apparatus for transferring and recording data.

[0002]

2. Description of the Related Art The applicant of the present invention has previously disclosed a technique for compressing an input digital audio signal into bits and recording the digital audio signal in bursts using a predetermined data amount as a recording unit, for example, as disclosed in Japanese Patent Application No. 2-221364. , Japanese Patent Application No. 2-2136
No. 5, Japanese Patent Application No. 2-222821, Japanese Patent Application No. 2-2228
No. 23 has been proposed in the specification and drawings.

This technology uses a magneto-optical disk as a recording medium and records and reproduces AD (adaptive difference) PCM audio data defined in an audio data format of a so-called CD-I (CD-interactive) or CD-ROM XA. The ADPCM data is recorded in a burst on the magneto-optical disk using, for example, 32 sectors of ADPCM data and several sectors for linking for interleave processing as a recording unit.

Several modes can be selected for the ADPCM audio in the recording / reproducing apparatus using this magneto-optical disk. For example, a level A having a compression ratio twice as high as the normal CD reproducing time can be selected. , 4x level B,
An eight-fold level C is defined. That is, for example, in the case of the level B, the digital audio data is compressed to approximately 1/4, and the reproduction time (play time) of the disc recorded in this level B mode is a standard CD format (CD). -DA format). This is the standard 12c for smaller discs
Since the same recording and reproduction time as m can be obtained, the size of the apparatus can be reduced.

However, the rotation speed of the disk is a standard C
Since it is the same as D, for example, in the case of the level B, compressed data for a reproduction time four times as long as the predetermined time is obtained. For this reason, for example, the same compressed data is read out four times in units of time such as sectors or clusters, and only one of the compressed data is used for audio reproduction. Specifically, when scanning (tracking) a spiral recording track, 1
A track jump is performed to return to the original track position for each rotation, and the reproduction operation proceeds in such a form that the same track is repeatedly tracked four times. This means that normal compressed data need only be obtained at least once out of, for example, four times of redundant reading, and is resistant to errors due to disturbances and the like, and is particularly preferable when applied to portable small devices.

In the future, it is considered that a semiconductor memory is used as a recording medium. In order to further increase the compression efficiency, compression encoding using a variable bit rate such as so-called entropy encoding is used. Specifically, it is a method of recording and reproducing an audio signal using a so-called IC card.
The compressed data obtained by bit-compressing the compressed data at the same compression rate or at a higher compression rate is recorded and reproduced.

[0007] In such an IC card using a semiconductor memory, an increase in recording capacity and a reduction in price have been realized with the progress of semiconductor technology. The capacity is likely to be short and expensive. Therefore, it is sufficiently conceivable that the contents are transferred from another low-cost, large-capacity recording medium such as the above-mentioned rotating disk (magneto-optical disk, optical disk) or the like to an IC card or the like and frequently rewritten and used. Specifically, for example, of a plurality of songs recorded on the above-mentioned magneto-optical disk or the like, a desired song is dubbed to an IC card, and replaced with another song when it becomes unnecessary. In this way, by frequently rewriting the contents of the IC card,
Various songs can be enjoyed outdoors or the like with a small number of IC cards.

[0008]

By the way, for example, the music recorded on the magneto-optical disk is reproduced and the IC is read.
When dubbing to a card, the price per unit bit of an IC card is much higher than the price per unit bit of a magneto-optical disk. Therefore, when dubbing to the IC card, it is desirable to further compress the information in addition to the high-efficiency encoding on the magneto-optical disk.

However, the fact that the target data has been written to the IC card and then collectively confirming it by playing it back after recording has the advantages of prolonging the total time of copying (dubbing) and shortening the copying time. Reduce.

The present invention has been made in view of such circumstances, and has been developed to reduce the data recorded by being bit-compressed at a constant bit rate so that the compression rate does not fall below at least the compression rate of the one recording medium. , A data recording method and apparatus which enables a user to simultaneously confirm that written data is a desired one when writing to an IC card, a rotating disk or the like in a compressed state of a fixed or variable bit rate. The purpose is to provide.

According to the present invention, when inputting compressed digital data and recording the same on a recording medium, the compressed digital data is encoded with a variable bit rate by reducing the surplus bits. The above-mentioned problem is solved by extending and reproducing a predetermined continuous portion of the digital data recorded on the recording medium during the time required to record the converted digital data on the recording medium. . Here, the reproduction of the digital data encoded with the variable bit rate includes expanding the continuous portion at the head of the digital data recorded on the recording medium and reproducing it. During recording time of each of a plurality of different compressed digital data, a predetermined continuous portion of each compressed digital data is expanded and reproduced.

Here, the reproduction of the compressed digital data includes expanding and reproducing a continuous portion at the head of the compressed digital data.
During recording time of each of a plurality of different compressed digital data, a predetermined continuous portion of each compressed digital data is expanded and reproduced.

At this time, the compressed data is sent to the recording system without decompression processing, and the compression rate of the other recording medium does not fall below at least the compression rate of the one recording medium. Compressing and recording is desirable for reducing the hardware scale and increasing the compression ratio.

Here, not only the data which has been subjected to the bit compression processing at the constant bit rate but also the constant recording rate compressed data is bit-compressed into the other recording medium at a variable bit rate. Is preferably recorded. It is preferable that not only the variable bit rate compressed data but also data amount information for performing bit compression recording at a constant bit rate on the one recording medium is recorded on the other recording medium. Further, it is preferable to record on the other recording medium with a variable length code from which bits giving noises lower than the entropy coding and the masking threshold are removed to reduce the data amount.

[0015]

The compressed data recorded on one recording medium of the reproduction system is continuously reproduced, sent to the recording system, and recorded on the other recording medium. It is possible to confirm in a short time that there is no mistake and that the information is recorded correctly.

[0016]

FIG. 1 is a block circuit diagram showing a schematic configuration of a compressed data recording / reproducing apparatus to which an embodiment of a data recording method and apparatus according to the present invention is applied. The recording / reproducing apparatus shown in FIG. 1 is configured by assembling two units of a recording / reproducing unit of a magneto-optical disk 1 as one recording medium and a recording unit of an IC card 2 as another recording medium into one system. Have been. When recording the signal reproduced by the reproducing system on the magneto-optical disk recording / reproducing unit side with the IC card recording unit,
The read compressed data is read by the optical head 53, sent to the decoder 71, and subjected to EFM demodulation, deinterleave processing, error correction processing, and the like.
C (Adaptive Transform Coding) audio data is stored in the memory 8 of the IC card recording unit.
5 and a variable bit rate encoding process is performed on the memory 85 by a surplus bit reduction circuit 84.
It is recorded on the IC card 2 via the C card interface circuit 86. The compressed data reproduced in this way is, for example, an ATC decoder 7 that performs the reverse processing of the ATC.
3 is sent to the recording system in the compressed state before being subjected to the decompression process by the
Will be recorded. Here, various IC memories such as an IC memory cartridge and an IC memory pack may be used instead of the IC card.

By the way, during normal reproduction (for audio listening), a predetermined data amount unit (for example, 3
Compressed data is read out in (2 sectors + several sectors), expanded and converted into a continuous audio signal. At the time of the so-called dubbing, the compressed data on the medium is continuously read and sent to the recording system. Have recorded. Thereby, high-speed (short-time) dubbing according to the data compression ratio can be performed.

Hereinafter, the specific configuration of FIG. 1 will be described in detail. In the magneto-optical disk recording / reproducing unit of the compressed data recording / reproducing apparatus shown in FIG. 1, a magneto-optical disk 1 driven by a spindle motor 51 is used as a recording medium. When recording data on the magneto-optical disk 1, for example, a so-called magnetic field modulation recording is performed by applying a modulation magnetic field corresponding to the recording data with the magnetic head 54 while irradiating the laser light with the optical head 53. The data is recorded along the recording track of. At the time of reproduction, a recording track of the magneto-optical disk 1 is traced by a laser beam by the optical head 53, and reproduction is performed magneto-optically.

The optical head 53 includes, for example, a laser light source such as a laser diode, a collimator lens, an objective lens,
The optical system includes optical components such as a polarizing beam splitter and a cylindrical lens, and a photodetector having a light receiving portion having a predetermined pattern. The optical head 53 is provided at a position facing the magnetic head 54 via the magneto-optical disk 1. When data is recorded on the magneto-optical disk 1, the magnetic head 54 is driven by a recording-system head drive circuit 66, which will be described later, to apply a modulation magnetic field in accordance with the recorded data. By irradiating the track with laser light, thermomagnetic recording is performed by a magnetic field modulation method. The optical head 53 detects reflected light of the laser beam applied to the target track, detects a focus error by, for example, a so-called astigmatism method, and detects a tracking error by, for example, a so-called push-pull method. When reproducing data from the magneto-optical disk 1, the optical head 53 detects the focus error and the tracking error, and at the same time, detects the difference in the polarization angle (Kerr rotation angle) of the reflected light of the laser light from the target track and reproduces the data. Generate a signal.

The output of the optical head 53 is supplied to an RF circuit 55. The RF circuit 55 extracts the focus error signal and the tracking error signal from the output of the optical head 53 and supplies the focus error signal and the tracking error signal to the servo control circuit 56.
Feed to 1.

The servo control circuit 56 comprises, for example, a focus servo control circuit, a tracking servo control circuit, a spindle motor servo control circuit, a thread servo control circuit and the like. The focus servo control circuit performs focus control of the optical system of the optical head 53 so that the focus error signal becomes zero. Further, the tracking servo control circuit performs tracking control of the optical system of the optical head 53 so that the tracking error signal becomes zero. Further, the spindle motor servo control circuit controls the spindle motor 51 so as to rotate the magneto-optical disk 1 at a predetermined rotation speed (for example, a constant linear speed). The thread servo control circuit moves the optical head 53 and the magnetic head 54 to target track positions of the magneto-optical disk 1 specified by the system controller 57.

The IC card detection circuit 52 is provided for the IC card 2
Is in the mounted state, and confirms by any means that recording or reproduction is possible, sends a signal to the servo control circuit 56, and controls the spindle motor control circuit to increase the rotation speed of the rotating disk. Let me
The data transfer rate is increased by controlling the thread servo control circuit to at least reduce the number of track jumps. As a specific example for confirming that the IC card 2 is in the mounted state and in a state where recording or reproduction is possible, a mechanical switch
Detecting the presence of the card 2 may be mentioned, and as another specific example, it is conceivable to check the presence by sending a signal from the IC card 2 when the IC card 2 is mounted.

The servo control circuit 56 for performing such various control operations sends information indicating the operation state of each unit controlled by the servo control circuit 56 to the system controller 57.

A key input operation unit 58 and a display unit 59 are connected to the system controller 57. The system controller 57 controls a recording system and a reproduction system in an operation mode specified by operation input information from the key input operation unit 58. Further, the system controller 7 controls the optical head 53 and the magnetic head 54 based on the address information in the unit of sector reproduced from the recording track of the magneto-optical disk 1 based on the header time and the Q data of the subcode.
Manages a recording position and a reproduction position on the recording track that are being traced. Further, the system controller 57
The bit compression mode information in the ATC encoder 63, which will be described later, which is switched and selected by the key input operation unit 58,
Based on the bit compression mode information in the reproduction data obtained from the F circuit 55 through a reproduction system described later, the bit compression mode is displayed on the display unit 59, and the data compression ratio in the bit compression mode and the recording track are recorded. Control is performed to display the reproduction time on the display unit 59 based on the above reproduction position information.

This reproduction time display is based on address information (absolute time information) in sector units reproduced from a recording track of the magneto-optical disk 1 by a so-called header time or so-called subcode Q data, etc. The actual time information is obtained by multiplying the reciprocal of the compression ratio (for example, 4 in the case of 、 compression), and this is displayed on the display unit 9. At the time of recording, if absolute time information is recorded in advance on a recording track of a magneto-optical disk or the like (preformatted), the preformatted absolute time information is read and the data compression ratio is adjusted. By multiplying the reciprocal, the current position can be displayed by the actual recording time.

Next, in the recording system of the recording / reproducing apparatus of the disc recording / reproducing apparatus, the analog audio input signal A _IN from the input terminal 60 is applied to the A through the low-pass filter 61.
The A / D converter 62 quantizes the analog audio input signal A _IN . A /
The digital audio signal obtained from the D converter 62 is supplied to the ATC encoder 63. The digital audio input signal D _IN from the input terminal 67 is supplied to the ATC encoder 63 via the digital input interface circuit 68. The ATC encoder 63 is
The digital audio PCM data of a predetermined transfer rate obtained by quantizing the input signal A _IN by the A / D converter 62 is subjected to bit compression (data compression) processing corresponding to various modes in the CD-I system described above. ,
The operation mode is designated by the system controller 57. For example, in the predetermined mode, the sampling frequency is 44.1 kHz and the average number of bits per sample is 4 bits of compressed data.
Consider the mode supplied to 4. The data transfer rate in this predetermined mode is 1/4 (18.7) of the data transfer rate (75 sectors / second) of the standard CD-DA format.
5 sectors / second).

Here, in the embodiment of FIG. 1, the sampling frequency of the A / D converter 62 is, for example, the standard C
4 which is the sampling frequency of the D-DA format
It is fixed at 4.1 kHz, and it is assumed that the ATC encoder 13 performs bit compression processing from 16 bits to 4 bits after performing a sampling rate conversion according to the compression mode, for example. doing.
As another configuration example, the sampling frequency of the A / D converter 62 may be switched and controlled in accordance with the compression mode. In this case, the switched A / D converter is controlled.
The cutoff frequency of the low-pass filter 61 is also switched according to the sampling frequency of the converter 62. That is, the sampling frequency of the A / D converter 62 and the cutoff frequency of the low-pass filter 61 may be simultaneously switched in accordance with the compression mode. Also, even if the sampling frequency does not change depending on the mode,
In a mode in which the number of bits used is small, the restriction on the frequency band may be increased.

Next, writing and reading of data in the memory 64 are controlled by the system controller 57.
ATC data supplied from the ATC encoder 63 is temporarily stored, and is used as a buffer memory for recording on a disk as needed. That is, for example, in the above-described predetermined mode, the compressed audio data supplied from the ATC encoder 63 has a data transfer rate of 1/4 of the data transfer rate (75 sectors / second) of the standard CD-DA format, that is, 1
This is reduced to 8.75 sectors / second, and the compressed data is continuously written to the memory 64. The compressed data (ATC data) is one for every four sectors as described above.
Sector recording is sufficient, but such recording at every fourth sector is practically impossible. Therefore, continuous recording of sectors as described later is performed. In this recording, a data transfer rate (7), which is the same as the standard CD-DA format, is used as a recording unit in a cluster consisting of a predetermined plurality of sectors (for example, 32 sectors + several sectors) through a pause period.
(5 sectors / sec). That is, in the memory 64, 1 is set according to the bit compression rate.
The ATC audio data of the predetermined mode written continuously at a low transfer rate of 8.75 (= 75/4) sectors / second is read as recording data in a burst at the transfer rate of 75 sectors / second. The overall data transfer speed of the read and recorded data, including the recording pause period, is as low as 18.75 sectors / sec. The instantaneous data transfer rate in the above is the standard 75 sectors / second. Therefore, when the disk rotation speed is the same speed (constant linear speed) as the standard CD-DA format, the same recording density and storage pattern as in the CD-DA format are recorded.

The ATC audio data, ie, recorded data, read from the memory 64 in a burst at the (instantaneous) transfer rate of 75 sectors / second is transferred to the encoder 65.
Supplied to Here, from the memory 64 to the encoder 65
In the data sequence supplied to the cluster, the unit continuously recorded in one recording is a cluster including a plurality of sectors (for example, 32 sectors) and several sectors for cluster connection arranged before and after the cluster. The cluster connection sector is set to be longer than the interleave length in the encoder 65, so that even if interleaved, data in other clusters is not affected.

The encoder 65 operates on the recording data supplied in bursts from the memory 64 as described above.
Encoding processing (parity addition and interleaving processing) for error correction, EFM encoding processing, and the like are performed. The recording data that has been subjected to the encoding process by the encoder 65 is supplied to the magnetic head drive circuit 66. The magnetic head drive circuit 66 is connected to the magnetic head 54 and drives the magnetic head 54 so as to apply a modulation magnetic field according to the recording data to the magneto-optical disk 1.

The system controller 57 controls the memory 64 as described above,
By this memory control, the recording position is controlled so that the recording data read out from the memory 64 in a burst manner is continuously recorded on the recording track of the magneto-optical disk 2.
The recording position is controlled by controlling the recording position of the recording data read in a burst from the memory 64 by the system controller 57 and transmitting a control signal designating the recording position on the recording track of the magneto-optical disk 1 to a servo control circuit. 56.

Next, a reproducing system of the magneto-optical disk recording / reproducing unit will be described. This reproducing system is for reproducing the recorded data continuously recorded on the recording tracks of the magneto-optical disk 1 by the recording system described above.
A decoder 71 is provided, in which a reproduction output obtained by tracing a recording track of the magneto-optical disk 1 with a laser beam by the optical head 53 is binarized by the RF circuit 55 and supplied.

The decoder 71 corresponds to the encoder 65 in the above-mentioned recording system, and performs the above-described decoding processing for error correction and EFM decoding on the reproduced output binarized by the RF circuit 55. ATC audio data of the above-mentioned predetermined mode is performed by performing processing such as processing.
Reproduction is performed at a transfer rate of 75 sectors / sec, which is faster than the normal transfer rate in the predetermined mode. The reproduction data obtained by the decoder 71 is supplied to the memory 72.

In the memory 72, data writing and reading are controlled by the system controller 57, and reproduced data supplied from the decoder 71 at a transfer rate of 75 sectors / second is written in burst at the transfer rate of 75 sectors / second. It is. The memory 72 stores the reproduced data written in a burst at the transfer rate of 75 sectors / sec.
It is read continuously at a transfer rate of seconds.

The system controller 57 writes the reproduced data to the memory 72 at a transfer rate of 75 sectors / sec.
Memory control is performed such that data is read continuously at a transfer rate of 5 sectors / second. Further, the system controller 57 performs the above-described memory control for the memory 72, and reproduces the reproduction data written in a burst from the memory 72 by the memory control from the recording track of the magneto-optical disk 1 continuously. Control the playback position. This playback position control is performed by the system controller 5.
7 controls the reproduction position of the reproduction data read out from the memory 72 in a burst manner, and supplies a servo control circuit 56 with a control signal designating the reproduction position on the recording track of the magneto-optical disk 1.

The ATC audio data in the predetermined mode as the reproduction data continuously read from the memory 72 at a transfer rate of 18.75 sectors / sec is supplied to the ATC decoder 73. The ATC decoder 73 corresponds to the ATC encoder 63 of the recording system. When the operation mode is specified by the system controller 57, the ATC decoder 73 expands the 4-bit ATC data by four times (bit expansion). Play 16-bit digital audio data. The digital audio data from the ATC decoder 73 is supplied to a D / A converter 74.

The D / A converter 74 includes an ATC decoder 73
Is converted into an analog signal to form an analog audio output signal A _OUT . The analog audio signal A _OUT obtained by the D / A converter 74 is output from an output terminal 76 via a low-pass filter 75.

Next, the analog audio input signal A _IN from the input terminal 60 is supplied to an A / D converter 62 via a low-pass filter 61 and quantized.
The digital audio signal obtained by being encoded by the C encoder 63 can be further compressed (bit-compressed) and recorded on the IC card 2. Hereinafter, this IC card recording system will be described.

That is, ATC audio data obtained by compression processing by the ATC encoder 63 is, for example, R
The signal is sent to a surplus bit reduction circuit 84, which is a kind of a variable bit rate encoder, via the AM 85. In the surplus bit reduction circuit 84, the number of bits giving noise below the masking threshold is reduced. Is performed. This process is executed while reading and writing data from and to the memory 85. The variable bit rate compression encoded data from the surplus bit reduction circuit 84 is transmitted to the IC card interface circuit 86 via the IC card interface circuit 86.
Recorded on card 2. Before recording on the IC card 2, variable-length coding using so-called entropy coding or removal of stereo correlation may be performed.

Here, the compressed data (ATC) from the decoder 71 of the reproducing system of the magneto-optical disk recording / reproducing unit is used.
) Is sent to the memory 85 of the IC card recording unit without being expanded. This data transfer is performed by the system controller 57 controlling the memory 85 and the like during so-called high-speed dubbing. The compressed data from the memory 72 may be sent to the memory 85.

Next, a so-called high-speed digital dubbing operation will be described. First, at the time of so-called high-speed digital dubbing, the system controller 7 performs a predetermined high-speed dubbing control processing operation by operating a dubbing operation key or the like of the key input operation unit 8. In particular,
The compressed data from the decoder 71 is sent as it is to the memory 85 of the IC card recording system, and the remainder bit reduction circuit 84
, And is recorded on the IC card 2 via the IC card interface circuit 86. If, for example, the ATC data of the predetermined mode is recorded on the magneto-optical disk 1, the decoder 7
From 1 the quadrupled compressed data is read continuously.

Therefore, at the time of the high-speed dubbing, the time from the magneto-optical disk 1 is quadrupled in real time (in the case of the predetermined mode).
Is obtained continuously, and this data is subjected to variable-length coding as it is and the IC card 2
, Four times faster dubbing can be realized.
Note that different compression modes have different dubbing speed magnifications. Also, dubbing may be performed at a high speed equal to or higher than the compression ratio. In this case, the magneto-optical disk 1 may be driven to rotate at a high speed several times higher than the steady speed.

By the way, the magneto-optical disk 1 has the structure shown in FIG.
As shown in FIG. 7, data compressed at a constant bit rate is recorded, and at the same time, the data amount obtained when the data is bit-compressed and encoded by the variable bit rate encoder 3 (that is, the data amount in the IC card 2). Information of the data recording capacity required for recording) is recorded. By doing so, for example, of the songs recorded on the magneto-optical disk 1, the number of songs or combination of songs that can be recorded on the IC card 2 can be immediately known by reading the data amount information. .

Conversely, in the IC card 2, not only the data compressed and coded at the variable bit rate but also
By recording the data amount information of the data that has been bit-compressed and encoded at a constant bit rate, it is possible to quickly know the data amount when data such as music is transmitted from the IC card 2 to the magneto-optical disk 1 and recorded. it can.

FIG. 3 shows a front external view of the compressed data recording / reproducing apparatus 5 having the structure shown in FIG. 1, in which a magneto-optical disk insertion section 6 and an IC card insertion slot 7 are provided.

Next, with respect to the ATC encoder and decoder unit shown in FIG. 1, an input digital signal such as an audio PCM signal is converted into band division coding (SBC), adaptive conversion coding (ATC), and adaptive bit allocation (APC-AB). ) Will be described with reference to FIG. 4 and subsequent figures.

In the specific high-efficiency coding apparatus shown in FIG. 4, the input digital signal is divided into a plurality of frequency bands by a filter or the like, and the higher the frequency band, the wider the bandwidth is selected. Conversion is performed, and the obtained spectrum data on the frequency axis is adaptively bit-allocated for each so-called critical bandwidth (critical band) in consideration of human auditory characteristics described later and encoded.
Of course, a band division width by a filter or the like may be an equal division width. Further, in the embodiment of the present invention, before the orthogonal transformation, the block size (block length) is adaptively changed according to the input signal, and the floating process is performed in units of the block.

That is, in FIG. 4, an audio PCM signal of, for example, 0 to 20 kHz is supplied to the input terminal 10. This input signal is divided into a band of 0 to 10 kHz and a band of 10 to 20 kHz by a band division filter 11 such as a so-called QMF filter, and a signal of the band 0 to 10 kHz is similarly divided by a band division filter 12 such as a so-called QMF filter. It is divided into a 5 kHz band and a 5 kHz to 10 kHz band. 10k from band division filter 11
The signal in the band of ~ 20 kHz is an MD which is an example of an orthogonal transformation circuit.
The signal is sent to a CT (Modified Discrete Cosine Transform) circuit 13 and is divided into a band division filter 1
5 to 10 kHz band signal from the MDCT circuit 14
, And the signals in the band of 0 to 5 kHz from the band division filter 12 are sent to the MDCT circuit 15 to be subjected to MDCT processing.

For the above MDCT, for example, ICASSP,
1987, Subband / Transform CodingUsing Filter Bank De
signs Based on Time Domain Aliasing Cancellation,
JPPrincen, ABBradley, Modified DCT, Univ. Of S
urrey, Royal Melbourne Inst. of Tech.

Here, each of the MDCT circuits 13, 14, 15
FIG. 5 shows a specific example of a standard input signal for a block for each band to be supplied to. In the specific example of FIG. 5, the frequency band is widened and the time resolution is increased (the block length is shortened) toward the higher frequency side. That is,
1 block B for low-frequency 0-5 kHz band signal
Let L _L be 1024 samples, for example, and
For a signal in the 10 kHz band, the length T _{BL above}
Are divided into blocks BL _M1 and BL _M2 each having a half length T _BL / 2 of the block BL _L of the high frequency side 10k to
For a signal in the 20 kHz band, a block BL having a length T _BL / 4 of each of the above-mentioned low-side blocks BL _L is １ ／.
It is blocked by _H1 , BL _H2 , BL _H3 and BL _H4 .
When considering a band of 0 to 22 kHz as an input signal, the low band is 0 to 5.5 kHz and the middle band is 5.5 to 11 kHz.
kHz and the high frequency range is 11 to 22 kHz.

Referring again to FIG. 4, each MDCT circuit 13,
The spectrum data or MDCT coefficient data on the frequency axis obtained by the MDCT processing at 14 and 15 are collected for each so-called critical band (critical band) and sent to the adaptive bit allocation coding circuit 18. The critical band is a frequency band divided in consideration of human auditory characteristics, and a band of a pure tone when the pure tone is masked by a narrow band noise near the frequency of the pure tone. That is. The bandwidth of this critical band increases as the frequency increases, and the entire frequency band of 0 to 20 kHz is divided into, for example, 25 critical bands.

The allowable noise calculation circuit 20 calculates the allowable noise amount for each critical band in consideration of the so-called masking effect and the like based on the spectrum data divided for each critical band. The number of bits allocated to each critical band is determined based on the energy or peak value of the spectrum data, and the spectrum data (or MDCT coefficient) is calculated according to the number of bits allocated to each critical band by the adaptive bit allocation coding circuit 18. Data) is requantized. The data thus encoded is taken out via the output terminal 19.

FIG. 6 is a block circuit diagram showing a schematic configuration of a specific example of the permissible noise calculation circuit 20. In FIG. 6, spectrum data on the frequency axis is supplied to the input terminal 21 from each of the MDCT circuits 13, 14, and 15.

The input data on the frequency axis is sent to the energy calculation circuit 22 for each band, and the energy for each critical band (critical band) is calculated, for example, the sum of the amplitude values in the band. It is required by things. Instead of the energy for each band, a peak value or an average value of the amplitude value may be used. As an output from the energy calculation circuit 22, for example, the spectrum of the sum value of each band is generally called a bark spectrum. FIG. 7 shows such a bark spectrum SB for each critical band. However, in FIG. 7, the number of the critical bands is represented by 12 bands (B _{1 to} B ₁₂ ) to simplify the illustration.

Here, in order to consider the influence of the bark spectrum SB on so-called masking, a convolution process is performed such that the bark spectrum SB is multiplied by a predetermined weighting function and added. Therefore, the output of the energy calculation circuit 22 for each band, that is, each value of the bark spectrum SB is sent to the convolution filter circuit 23. The convolution filter circuit 23 includes, for example, a plurality of delay elements for sequentially delaying input data,
It is composed of a plurality of multipliers (for example, 25 multipliers corresponding to each band) for multiplying the output from these delay elements by a filter coefficient (weighting function) and a sum adder for summing the outputs of the multipliers. Things. By this convolution processing, the sum of the parts shown by the dotted lines in FIG. 7 is obtained. In addition,
The masking refers to a phenomenon in which a certain signal masks another signal and makes it inaudible due to human auditory characteristics.The masking effect includes a time-axis masking effect by an audio signal on a time axis. At the same time by the signal on the frequency axis.
Due to these masking effects, even if there is noise in the masked portion, this noise will not be heard. For this reason, in an actual audio signal, noise within the masked range is regarded as acceptable noise.

Here, a specific example of the multiplication coefficient (filter coefficient) of each multiplier of the convolution filter circuit 23 will be described. When the coefficient of the multiplier M corresponding to an arbitrary band is set to 1, the multiplier M-1 is a coefficient of 0.15, multiplier M-2 is a coefficient of 0.0019, and multiplier M-3 is a coefficient of 0.00000.
086, a coefficient 0.4 by a multiplier M + 1, and a multiplier M + 2
By multiplying the output of each delay element by the coefficient 0.06 by the multiplier M + 3 and the coefficient 0.007 by the multiplier M + 3, the convolution process of the bark spectrum SB is performed. However, M is 1
It is an arbitrary integer of 25.

Next, the output of the convolution filter circuit 23 is sent to a subtractor 24. The subtracter 24 calculates a level α corresponding to an allowable noise level described later in the convolved area. The level α corresponding to the permissible noise level (permissible noise level)
Is a level which becomes an allowable noise level for each of the critical bands by performing the inverse convolution processing as described later. Here, an allowance function (a function expressing a masking level) for obtaining the level α is supplied to the subtractor 24. The level α is controlled by increasing or decreasing the allowable function. The permissible function is (n−
ai) It is supplied from the function generation circuit 25.

That is, the level α corresponding to the allowable noise level can be obtained by the following equation (1), where i is a number sequentially given from the lower band of the critical band. α = S− (n−ai) (1) In the equation (1), n and a are constants, a> 0, S is the intensity of the convolution-processed Bark spectrum, and (1)
In the equation, (n-ai) is the allowable function. In this embodiment, n = 38,
Since a = 1, there was no deterioration in sound quality at this time, and good encoding was performed.

In this way, the level α is obtained, and this data is transmitted to the divider 26. The divider 26 is for inversely convolving the level α in the convolved region. Therefore, by performing this inverse convolution processing,
The masking threshold can be obtained from the level α. That is, this masking spectrum becomes an allowable noise spectrum. Note that the above inverse convolution process requires a complicated operation, but in the present embodiment, the inverse convolution is performed using the simplified divider 26.

Next, the above-mentioned masking threshold is transmitted to the subtracter 28 via the synthesizing circuit 27. Here, the output from the energy detection circuit 22 for each band, that is, the above-described bark spectrum SB is supplied to the subtracter 28 via a delay circuit 29. Therefore, the subtraction operation of the masking threshold and the bark spectrum SB is performed by the subtracter 28, as shown in FIG.
Is masked below the level indicated by the level of the masking threshold MS.

The output from the subtracter 28 is taken out via an allowable noise correction circuit 30 and an output terminal 31.
For example, the assigned bit number information is sent to a ROM or the like (not shown) in which the information is stored in advance. The ROM or the like assigns each band in accordance with the output (the level of the difference between the energy of each band and the output of the noise level setting means) obtained from the subtraction circuit 28 via the allowable noise correction circuit 30. Output bit number information. By transmitting the allocated bit number information to the adaptive bit allocation coding circuit 18, the MDC
Each spectrum data on the frequency axis from the T circuits 13, 14, and 15 is quantized by the number of bits assigned to each band.

That is, in summary, the adaptive bit allocation coding circuit 18 calculates the number of bits in each band according to the level of the difference between the energy of each band of the critical band and the output of the noise level setting means. Each spectrum data is quantized. The delay circuit 29 is provided to delay the bark spectrum SB from the energy detection circuit 22 in consideration of the amount of delay in each circuit before the synthesis circuit 27.

By the way, at the time of synthesizing in the synthesizing circuit 27 described above, data indicating a so-called minimum audible curve RC, which is a human auditory characteristic as shown in FIG. The above-mentioned masking threshold MS can be synthesized. At this minimum audible curve, if the absolute noise level is below this minimum audible curve, the noise will not be heard. This minimum audible curve may differ, for example, due to differences in playback volume during playback, even if the coding is the same, but in a realistic digital system, the way in which music enters the 16-bit dynamic range, for example, varies significantly. If there is no quantization noise in the most audible frequency band around 4 kHz, for example, it is considered that quantization noise below the level of the minimum audible curve will not be heard in other frequency bands. Therefore, it is assumed that a method is used in which noise near the word length of the system, for example, around 4 kHz is not heard.
If the allowable noise level is obtained by combining C and the masking threshold MS together, the allowable noise level in this case can be up to the shaded portion in FIG. In this embodiment, the 4 kHz level of the minimum audible curve is adjusted to the lowest level corresponding to, for example, 20 bits. FIG.
Also shows the signal spectrum SS at the same time.

The allowable noise correction circuit 30 corrects the allowable noise level in the output from the subtractor 28 based on, for example, information on the equal loudness curve sent from the correction information output circuit 33. Here, the equal loudness curve is a characteristic curve relating to human auditory characteristics. For example, the loudness curve is obtained by calculating the sound pressure of sound at each frequency that sounds as loud as a pure tone of 1 kHz, and is connected by a curve. Also called a sensitivity curve. Further, this equal loudness curve draws substantially the same curve as the minimum audible curve RC shown in FIG. In this equal loudness curve, for example, the sound pressure near 8 kHz is 8
Even if it drops by 10 dB, it sounds the same as 1 kHz. Conversely, the sound pressure around 50 kHz is about 15 dB lower than the sound pressure at 1 kHz.
If it is not high, it will not sound the same size. For this reason, it can be seen that noise exceeding the level of the minimum audible curve (allowable noise level) preferably has a frequency characteristic given by a curve corresponding to the equal loudness curve.
From this, it can be seen that correcting the allowable noise level in consideration of the equal loudness curve is suitable for human auditory characteristics.

Here, as the correction information output circuit 33, the detection information of the output information amount (data amount) at the time of the quantization in the encoding circuit 18 and the bit rate target value of the final encoded data are used. The allowable noise level may be corrected based on the error information. This is because the total number of bits obtained by previously performing temporary adaptive bit allocation for all bit allocation unit blocks is a fixed number of bits (target value) determined by the bit rate of the final encoded output data. May have an error, and the bits are allocated again so that the error becomes zero. That is, when the total number of allocated bits is smaller than the target value, the difference bit number is allocated to each unit block and added. When the total allocated bit number is larger than the target value, the difference bit number is set to each unit block. It is to be allocated and cut.

To do this, an error of the total allocated bit number from the target value is detected, and the correction information output circuit 33 corrects each of the allocated bit numbers according to the error data. Is output. Here, when the error data indicates that the number of bits is insufficient, it is possible to consider a case where the data amount is larger than the target value by using a large number of bits per unit block. Further, when the error data is data indicating the remainder of the number of bits, a case where the number of bits per unit block is small and the data amount is smaller than the target value can be considered. Therefore, from the correction information output circuit 33, the allowable noise level in the output from the subtractor 28 is corrected based on the information data of the equal loudness curve, for example, according to the error data. Data will be output. By transmitting the correction value as described above to the allowable noise correction circuit 30, the allowable noise level from the subtractor 28 is corrected. In another embodiment, the bits of the target value may be fixedly assigned to each block from the beginning. At this time, a large reduction in the amount of calculation can be obtained. In still another embodiment, bits can be assigned depending on the signal size of each block. In this case, the noise energy can be minimized.

FIG. 10 is a block diagram of the remainder bit reducing circuit 8.
4 shows a specific example of the removable bit reduction circuit 101 corresponding to No. 4. In FIG. 10, A shown in FIG.
The output from the TC encoder 63 is an MDCT coefficient a,
It consists of bit length information b and floating information c. The bit length information “b” indicates what bit length the MDCT coefficient “a” is quantized, and the floating information “c” indicates what normalization processing is performed on the MDCT coefficient “a”. ATC encoder 6
The removal of the audibly redundant portion or the removal of the degree of redundancy contained in the output from 3 is performed as follows.

First, by using the floating information c and the MDCT coefficient a to obtain the coefficient size of each block, the masking threshold calculation circuit 102 uses the method described with reference to FIG. Calculate the threshold. Next, the bit length calculation circuit 103 calculates the bit length in the same manner as described with reference to FIG.
The removable bit calculation circuit 104 extracts a removable bit portion by comparing with the bit length information b of the ATC encoder output. The final bit length determination circuit 106
The bit length information b of the ATC encoder output is compared with the output from the removable bit calculation circuit 104 to determine the final bit length, and the removable bit removal circuit 105 is controlled.
The MDCT coefficient a ′ from which the removable bits have been removed by the removable bits removing circuit 105, the floating information c, and the final bit length information b ′ output from the final bit length determining circuit 106 are, for example, as shown in FIG. To the IC card interface circuit 86 or the like.

Next, a monitoring operation during recording on the IC card 2 will be described with reference to FIG. For example, data recorded on the rotating disk of the magneto-optical disk 1 is as follows.
Before compression, as shown in FIG.
It is a continuous file in time. When recorded on a rotating disk, since the data is compressed, for example, by a factor of four, the rotating disk reproduction data is obtained by compressing the time axis to １ ／ as shown in FIG. 11B. . Next, to remove at least some of the bits that provide a quantization noise level below an allowable noise level determined by a masking threshold and a minimum audibility,
As shown in FIG. 11C, the removable bit reduction circuit 101 (or the residual bit reduction circuit 84) that removes the surplus bits considered from the auditory sense has a variable bit rate for the real-time data as shown in FIG. Data having a compression ratio four times or more than that of the data is obtained. As shown in FIG. 11D, the data bit rate of the data of the IC card 2 is bit-compressed at a variable bit rate and recorded.

Simultaneously with the recording on the IC card 2, the compressed data is read from the head of each file on the IC card 2, and
1 (e), the removable bit reduction circuit 101
, And the bits reduced by the ATC encoder 63 are padded with zeros.
Monitor with fixed bit length PCM data. This monitoring is performed only during the time required to record each file on the IC card. More specifically, for example, when the recording of the file FL1 in FIG.
1 and stops reading and decoding from the IC card 2, and simultaneously reads the compressed data from the head of the file FL 2 of the IC card 2 while writing the next file FL 2 to the IC card 2, and removes the compressed data by the removable bit reduction circuit 101. The reduced bits and the bits reduced by the ATC encoder 63 are padded with zeros, and the ATC decoder 73 monitors 16-bit fixed-length PCM data. The recording of the file FL2 on the IC card 2 is monitored only during the time required to record the file FL2 on the IC card 2.

The present invention is not limited only to the above embodiment. For example, the reproduction system of one recording medium and the recording system of the other recording medium need not be integrated. It is also possible to connect between them with a data transfer cable. When the length of the file to be recorded is long, instead of monitoring only the beginning of each file, real-time data at a certain time in the same file may be monitored. This can be realized by, for example, skipping reproduction data every certain time. Further, the present invention is applicable not only to audio PCM signals but also to signal processing devices for digital voice (speech) signals and digital video signals. Further, the configuration may be such that the above-described minimum audible curve synthesis processing is not performed. In this case, the minimum audible curve generating circuit 32 and the synthesizing circuit 2
7 becomes unnecessary, and the output from the subtractor 24 is deconvolved by the divider 26, and then immediately after the subtractor 2
8 will be transmitted. Further, as the other recording medium, various IC memories such as an IC memory cartridge and an IC memory pack can be used in addition to the IC memory card.

[0072]

As is apparent from the above description, according to the data recording method and apparatus of the present invention, the compressed digital data is recorded on the recording medium while the compressed digital data is recorded on the recording medium. By expanding and reproducing the data, monitor reproduction while recording is possible, and the recorded contents can be efficiently checked in a short time.
Specifically, the compressed digital data recorded on the recording medium is expanded and reproduced, and during the time required for recording the compressed digital data, the compressed digital data is recorded. By expanding and playing back, it is possible to monitor real-time data while recording.

[Brief description of the drawings]

FIG. 1 is a block circuit diagram showing a configuration example of a compressed data recording / reproducing apparatus as one embodiment of the present invention.

FIG. 2 is a diagram showing recorded contents of a magneto-optical disk 1 and an IC card 2.

FIG. 3 is a schematic front view showing an example of an external appearance of the embodiment device.

FIG. 4 is a block circuit diagram showing a specific example of a high-efficiency compression encoding device that can be used for constant bit rate compression encoding in the above embodiment.

FIG. 5 is a diagram showing a specific example of divided bands and blocking in the time axis direction in each band in the apparatus of FIG. 4;

6 is a block circuit diagram showing a specific example of an allowable noise calculation circuit 18 of the device shown in FIG.

FIG. 7 is a diagram showing a bark spectrum.

FIG. 8 is a diagram showing a masking spectrum.

FIG. 9 is a diagram in which a minimum audible curve and a masking spectrum are combined.

FIG. 10 is a block circuit diagram showing a specific example of a remainder bit reducing circuit.

FIG. 11 is a timing chart for explaining a monitoring operation at a real-time rate while recording compressed data on an IC card.

[Explanation of symbols]

1 ... Magneto-optical disk 2 ... IC card 11, 12 ... Band splitting filter 13, 14, 15 ... Orthogonal transform circuit (MDCT circuit) 18 ... · Adaptive bit allocation coding circuit 20 · · · · permissible noise calculation circuit 22 · · · Energy detection circuit for each band 23 · · · · convolution filter circuit 27 · · · · synthesis circuit 28 · · · ... Subtractor 30 ... Allowable noise correction circuit 32 ... Minimum audible curve generation circuit 33 ... Correction information output circuit 52 ... IC card detection circuit 53 ... ··· Optical head 54 ···· Magnetic head 56 ···· Servo control circuit 57 ··· System controller 62, 83 ··· A / D converter 63 ··· ATC encoder 64, 72, 85 ..... memory 6 ····· Encoder 66 ··· Magnetic head drive circuit 71 ··· Decoder 73 ··· ATC decoder 74 ··· D / A converter 84 ··· Reduction circuit 86: IC card interface circuit 101: Removable bit reduction circuit 102: Masking threshold calculation circuit 103: Bit length calculation circuit 104: ..Removable bit calculation circuit 105... Removable bit removal circuit 106...

Claims (10)

(57) [Claims] 1. A data recording method for inputting compressed digital data and recording the digital data on a recording medium, wherein a surplus bit of the compressed digital data is deleted.
Hesi and variable bit rate coding, during the time required for the variable bit rate encoded digital data is to be recorded on said recording medium, said recording
A data recording method characterized by expanding and reproducing a predetermined continuous portion of the digital data recorded on a medium . 2. The reproduction of the digital data encoded by the variable bit rate is performed by expanding a continuous portion at the head of digital data recorded on the recording medium. The data recording method according to claim 1. 3. During multiple different variable bit rate coding <br/> is time to record each digital data, each of the variable bit rate recorded on said recording medium
2. The data recording method according to claim 1, wherein a predetermined continuous portion of the digitally encoded digital data is expanded and reproduced. 4. The data recording method according to claim 1, wherein a value of a data amount of the digital data recorded at the variable bit rate is output. 5. The data recording method according to claim 1, wherein said recording medium is a semiconductor memory. 6. A data recording apparatus for recording compressed digital data on a recording medium, comprising: input means for inputting the compressed digital data; and a surplus bit of the compressed digital data.
Means for variable bit rate coding in Hesi, while the variable bit rate encoded digital data is recorded on the recording medium, recorded on the recording medium
And decompressing the digital data and a control means for reproducing the said control means, during the time required to record the variable bit rate encoded digital data to the recording medium, on the recording medium A data recording apparatus for expanding and reproducing a predetermined continuous portion of the recorded digital data. 7. The recording medium according to claim 7, wherein
7. The data recording apparatus according to claim 6, wherein a head continuous part of the obtained digital data is expanded and reproduced. 8. The control means according to claim 7, wherein said plurality of variable variable
During the time required to record each bit rate encoded digital data, the digital data recorded on the recording medium is recorded.
Each variable bit rate encoded data recording apparatus according to claim 7, wherein by expanding the predetermined contiguous portion of the digital data, characterized in that play has been. 9. The data recording apparatus according to claim 6, further comprising means for outputting a value of a data amount of the digital data recorded at the variable bit rate. 10. The data recording apparatus according to claim 6, wherein said recording medium is a semiconductor memory.