JPH06338861A - Method and device for processing digital signal and recording medium - Google Patents

Abstract

PURPOSE:To efficiently perform coding with the minimum hardware scale by providing respective steps for information compression processing and information expansion processing and sub-sampling the frequency band component at the high frequency side obtained as a time axis signal. CONSTITUTION:An ATC encoder 63 performs the bit compression processing corresponding to the various modes in a prescribed ATC system to the digital audio PCM data at a prescribed transmission speed prepared by quantizing an input signal AIN by an A/D converter 62. The operation mode is specified by a system controller 57. In this case, operation modes are specified by a system controlled 57. An ATC decoder 73 corresponds to an encoder 63 and the operation mode is specified by the controller 57. For example, the stereo mode ATC data of a mode B is expanded by eight times to reproduce the 16-bit digital audio data. Then it is supplied to a D/A converter 74 and converted into the analog signal. Thus, the analog audio output signal AOUT is formed and outputted from a terminal 76 through an LPF 75.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital signal processing apparatus and method and recording medium for recording and / or reproducing or transmitting and / or receiving compressed data obtained by bit-compressing a digital audio signal or the like, and particularly to a plurality of bits. The present invention relates to a compressed data recording and / or reproducing apparatus and method for recording in a rate compression mode, and a recording medium.

[0002]

2. Description of the Related Art The applicant of the present invention has previously disclosed a technique for bit-compressing an input digital audio signal and burst-recording a predetermined data amount as a recording unit, for example, Japanese Patent Application No. 2-221364. , Japanese Patent Application No. 2-22136
No. 5, Japanese Patent Application No. 2-222821, Japanese Patent Application No. 2-2228
No. 23 specification, drawings, etc.

This technique uses a magneto-optical disk as a recording medium, and records and reproduces AD (adaptive difference) PCM audio data defined in audio data formats of so-called CD-I (CD-interactive) and CD-ROM XA. For example, 32 sectors of this ADPCM data and several sectors for linking for interleave processing are recorded as a recording unit on the magneto-optical disk in a burst manner.

Several modes can be selected for the ADPCM audio in the recording / reproducing apparatus using this magneto-optical disk, and for example, the compression is twice as long as the reproducing time of an ordinary CD (compact disk). Rate, sampling frequency is 37.8 kHz level A, 4 times compression rate and sampling frequency is 37.8 kHz level B,
A level C of 8 times compression rate and a sampling frequency of 18.9 kHz is defined. That is, for example, in the case of the above level B, the digital audio data is approximately 1
The reproduction time (play time) of the disc compressed in / 4 and recorded in this level B mode is four times as long as that in the standard CD format (CD-DA format). This is a smaller disc with a standard diameter of 12c
Since the recording / reproducing time is the same as that of the m-thick disk, the device can be downsized.

However, the rotation speed of the disk is standard C
Since it is the same as D, for example, in the case of the above level B, compressed data for a reproduction time that is four times that of the predetermined time is obtained. Therefore, for example, the same compressed data is read four times in a time unit such as a sector or a cluster, and only the compressed data for one time is sent to the audio reproduction. Specifically, when scanning (tracking) a spiral recording track,
A reproduction operation is performed in such a form that a track jump is performed to return to the original track position for each rotation, and the same track is repeatedly tracked four times. This means that normal compressed data only needs to be obtained at least once out of, for example, four times of redundant reading, is resistant to errors due to disturbances, etc., and is particularly preferable when applied to a portable small device.

Further, it is considered that a semiconductor memory will be used as a recording medium in the future, and it is desirable to perform additional bit compression in order to further improve the compression efficiency. Specifically, it is the one in which an audio signal is recorded and reproduced using a so-called IC card.
The compressed data that has been bit-compressed is recorded and reproduced on the card.

IC cards and the like using such a semiconductor memory are expected to have an increased recording capacity and a reduced price with the progress of semiconductor technology, but at the initial stage when they are supplied to the market. It is thought that the capacity is low and expensive. Therefore, it is sufficiently conceivable to transfer the contents from another inexpensive and large-capacity recording medium such as the above-mentioned magneto-optical disk to an IC card or the like for frequent rewriting and use. Specifically, for example, of a plurality of songs recorded on the magneto-optical disk, a favorite song is dubbed to an IC card, and when it is no longer needed, it is replaced with another song. By frequently rewriting the contents of the IC card in this manner, various songs can be enjoyed outdoors, etc., with a small number of IC cards held in hand.

[0008]

By the way, at the time of recording / reproducing an audio signal, there are various applications.
The required bandwidth and noise-to-signal characteristics are different. For example, when high quality audio is required, the bandwidth is 1
5 kHz to 20 kHz is required, and good noise-to-signal characteristics are also required. A higher bit rate to achieve this is acceptable. Usually, the bit rate is 256 kbps to 64 kbps / channel. On the other hand, when mainly handling a voice signal, the bandwidth may be 5 kHz to 7 kHz, and the noise-to-signal characteristic does not need to be so high. However, in order to lengthen the recording / reproducing time as much as possible, it is required to reduce the bit rate from 64 kbps to several kbps. For this reason, it is necessary to provide a recording / reproducing apparatus which is satisfactory for a plurality of applications having different requirements as described above and has the economical load as small as possible.

However, if a plurality of modes having different bandwidths are to be provided, until now, there is no choice but to support a plurality of sampling frequencies, which complicates the sampling frequency signal generating circuit and increases the LSI scale. Is inevitable. Even if there is only one recording mode, considering dubbing from a CD, which has the most opportunity for digital dubbing, setting the sampling frequency to 44.1 kHz means that even if the band is much narrower than 20 kHz. It will be useful. Further, when the sampling frequency of each mode is different, it is difficult to move information between the modes, and the high bit rate mode information on the large capacity magneto-optical disk is written in the small capacity IC card in the low bit rate mode. When it is desired, it is necessary to completely cancel the compression mode, restore the signal on the time axis, and then perform the compression process again in the low bit rate mode, which requires a large amount of processing calculation and makes real-time processing difficult. In addition, as the mode becomes lower, the number of usable bits decreases and the sound quality deteriorates. For example, when the bandwidth is narrowed and the frequency division width for compression is constant regardless of the frequency, the division bandwidth is 70 when the 20 kHz band is divided into 32 parts with respect to the low critical bandwidth of 100 Hz.
It becomes as wide as 0 Hz and becomes wider than the critical band in most of the middle and low ranges, and the compression efficiency is remarkably lowered. Further, when the bit rate is reduced, if the bit amount is reduced so that only one of the main information and the sub information of the high rate code is biased, the sound quality is significantly deteriorated. Therefore, it is necessary to reduce not only the main information but also the sub information.

The present invention has been made in view of such circumstances. First, when it is desired to have a plurality of bit rate modes, the sampling frequency signal generating circuit is prevented from becoming complicated and the LSI scale from increasing. Secondly, when dubbing bit-compressed data from one recording medium such as a magneto-optical disk or an optical disc onto another recording medium such as an IC card, or when compressing bit-compressed data from another recording medium such as an IC card. To provide a compressed data recording and / or reproducing apparatus capable of performing a small amount of calculation when reproducing, thirdly, to prevent sound quality deterioration in a low bit rate mode as much as possible, and fourthly, It is another object of the present invention to provide a recording device capable of efficiently recording from a CD when the band is narrow.

[0011]

In order to achieve the above-mentioned object, a first digital signal processing device of the present invention decomposes a digital signal into a plurality of frequency band components which are signals on a time axis, An information compression unit that obtains a plurality of signal components in a two-dimensional block regarding time and frequency, quantizes the signal components and records or transmits the information, and / or a plurality of information compression units that perform time and frequency compression. It has an information expansion means for reproducing or receiving the signal component in the dimensional block, and is adapted to sub-sample the frequency band component on the high frequency side obtained as a time axis signal.

The second digital signal processing apparatus of the present invention decomposes the digital signal into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks with respect to time and frequency. Information compression means for quantizing and compressing information for each two-dimensional block regarding the time and frequency, and recording or transmitting the information compression parameter for each two-dimensional block regarding the time and frequency, and / or a plurality of information compressed time and frequency related information. An information decompression unit for reproducing or receiving a signal component in a two-dimensional block using information compression parameters for each of the two-dimensional blocks concerning the time and frequency, and recording and / or recording of a plurality of information bit rates. Play mode, or
The lower information bit rate mode, which has a mode of transmitting and / or receiving, also sub-samples a frequency band component on the high frequency side obtained as a time axis signal.

A third digital signal processing apparatus of the present invention decomposes a digital signal into a plurality of frequency band components which are signals on a time axis to obtain a plurality of signal components in a two-dimensional block concerning time and frequency. An information compression means for quantizing the signal component and compressing the information for recording or transmission;
And / or information decompression means for reproducing or receiving signal components in a plurality of two-dimensional blocks relating to information-compressed time and frequency, the frequency band component on the high frequency side obtained as a time axis signal , Not to be transmitted to the information signal means to be reproduced or received, and sub-sampling the time axis signal in the lower frequency band adjacent to the frequency band not transmitted.

A fourth digital signal processing apparatus of the present invention decomposes a digital signal into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks with respect to time and frequency. Information compression means for quantizing and compressing information for each dimensional block, and recording or transmitting the information compression parameter for each two-dimensional block regarding the time and frequency, and / or a plurality of two-dimensional information compressed for time and frequency An information decompression unit for reproducing or receiving a signal component in a block by using information compression parameters for each of the two-dimensional blocks regarding the time and frequency, and recording and / or reproducing at a plurality of information bit rates. Mode, or a mode having a transmission and / or reception, and a lower information bit rate, Do not send the frequency band component on the high frequency side obtained as the inter-axis signal to the information expansion means for reproducing or receiving, and sub-sample the time axis signal on the lower frequency band adjacent to the frequency band that is not transmitted. It was done like this.

A fifth digital signal processing apparatus of the present invention decomposes a digital signal into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks with respect to time and frequency. Information compression means for quantizing and compressing information for each dimensional block, and recording or transmitting the information compression parameter for each two-dimensional block regarding the time and frequency, and / or a plurality of two-dimensional information compressed for time and frequency An information decompression unit for reproducing or receiving a signal component in a block by using information compression parameters for each of the two-dimensional blocks regarding the time and frequency, and recording and / or reproducing at a plurality of information bit rates. A mode, or a mode for transmitting and / or receiving, and the time between at least two modes. Those having different at least frequency width of 2-dimensional blocks with respect to frequency.

Here, the second or fourth digital signal processing device, when converting the signal mode from the higher bit rate mode to the lower bit rate mode, the frequency width of the two-dimensional block with respect to the time and frequency. Widen. Further, when converting the signal mode from the higher bit rate mode to the lower bit rate mode, the frequency width of the two-dimensional block with respect to time and frequency is widened by an integral multiple.

Further, in the digital signal processing apparatus of the present invention, the input signal is an audio signal, and the frequency width of the block for controlling the generation of at least most of the quantization noise is made wider in the higher range. ing.
In addition, do the following: That is, the information compression means uses orthogonal transformation to decompose the digital signal into a plurality of frequency band components and obtain signal components in a plurality of two-dimensional blocks regarding time and frequency, and / or information decompression. By means of two or more
The inverse orthogonal transform is used to transform the signal components in the dimensional block into digital signals on the time axis. In the information compression means,
In order to decompose a digital signal into a plurality of frequency band components and obtain signal components in a plurality of two-dimensional blocks with respect to time and frequency, first divide into a plurality of bands, and each divided band consists of a plurality of samples. Each block of each band is formed by forming a block and performing orthogonal transformation for each block of each band to obtain coefficient data, and / or in the information expansion means, for conversion from a plurality of bands on the frequency axis to a time axis signal. The inverse orthogonal transform is performed on the above, and the outputs of the respective inverse orthogonal transforms are combined to obtain a combined signal on the time axis. The mode having a smaller information rate has a mode in which the maximum orthogonal transform block length of a signal to be recorded and / or reproduced or the maximum orthogonal transform block length of a signal to be transmitted and / or received is increased. The information compression means determines the division frequency width in the division from the signal on the time axis before orthogonal transformation into a plurality of bands on the frequency axis, and / or the information decompression means determines the division frequency width from the plurality of bands on the frequency axis after inverse orthogonal transformation. The combined frequency widths from a plurality of bands in the combination into the time axis signal are the same in the two lowest continuous bands. The information compression means determines the division frequency width in the division from the signal on the time axis before orthogonal transformation into a plurality of bands on the frequency axis, and / or the information decompression means determines the division frequency width from the plurality of bands on the frequency axis after inverse orthogonal transformation. The synthesis frequency width from a plurality of bands in the synthesis into the signal on the time axis is made wider in a higher frequency band.
In any information rate mode, the length of the maximum orthogonal transform block of the signal to be recorded and / or reproduced on the high frequency side in the information compression means, or the maximum orthogonal transform of the signal to be transmitted and / or received in the information expansion means The blocks have the same length. The sampling frequency is the same in all modes. The main information and / or the sub information of the compression code is not assigned to the signal component in the band substantially above the signal pass band.

Next, according to the first digital signal processing method of the present invention, the digital signal is decomposed into a plurality of frequency band components which are signals on the time axis, and a plurality of signals in a two-dimensional block relating to time and frequency are decomposed. An information compression processing step of obtaining a component, quantizing the signal component, and compressing and recording or transmitting the information, and / or reproducing or receiving the signal component in a plurality of two-dimensional blocks relating to the time and frequency at which the information is compressed. And a sub-sampling of a high frequency band component obtained as a time axis signal.

According to a second digital signal processing method of the present invention, a digital signal is decomposed into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks with respect to time and frequency. An information compression processing step of quantizing and compressing information for each dimension block and recording or transmitting the information compression parameter for each two-dimensional block regarding the time and frequency, and / or a plurality of two information compression time and frequency information. An information decompression processing step of reproducing or receiving a signal component in a three-dimensional block by using information compression parameters for each two-dimensional block concerning the time and frequency, and recording and / or recording of a plurality of information bit rates. Has a mode to play, or a mode to transmit and / or receive,
In the mode of lower information bit rate, the frequency band component on the high frequency side obtained as the time axis signal is sub-sampled.

In the third digital signal processing method, the digital signal is decomposed into a plurality of frequency band components which are signals on the time axis to obtain a plurality of signal components in a two-dimensional block relating to time and frequency. An information compression processing step of quantizing a component to compress and record or transmit the information, and / or an information decompression processing step of reproducing or receiving signal components in a plurality of two-dimensional blocks relating to the time and frequency at which the information is compressed. The frequency band component on the high frequency side obtained as a time axis signal is not sent to the information expansion processing step for reproduction or reception, and the lower frequency band adjacent to the frequency band not transmitted is Try to subsample the time axis signal.

In a fourth digital signal processing method, the digital signal is decomposed into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks regarding time and frequency, and the two-dimensional block regarding time and frequency. Information compression processing step of recording or transmitting the information, which is quantized and information-compressed for each two-dimensional block for each two-dimensional block regarding the time and frequency, and / or a plurality of two-dimensional blocks regarding the information-compressed time and frequency Mode for recording and / or reproducing a plurality of information bit rates, the information decompression processing step of reproducing or receiving a signal component of the information component using the information compression parameter for each two-dimensional block regarding the time and frequency. , Or has a mode for transmitting and / or receiving and has a lower information bit rate. Do not send the frequency band component on the high frequency side obtained as a time axis signal to the information expansion processing step for reproduction or reception, and the time axis signal of the lower frequency band adjacent to the frequency band that is not transmitted. Is subsampled.

A fifth digital signal processing method is to decompose a digital signal into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks with respect to time and frequency.
Information compression processing step of quantizing and compressing information for each two-dimensional block regarding the time and frequency, and recording or transmitting the information together with information compression parameters for each two-dimensional block regarding the time and frequency, and / or the information compressed time. And an information decompression process step of reproducing or receiving the signal components in a plurality of two-dimensional blocks regarding the frequency and the frequency using the information compression parameter for each two-dimensional block regarding the time and the frequency. , Recording and / or playback mode, or
It has a mode of transmitting and / or receiving, and at least the frequency width of the two-dimensional block regarding the time and the frequency is made different between at least two modes.

Here, in the second or fourth digital signal processing method of the present invention, when converting the signal mode from the higher bit rate mode to the lower bit rate mode, the frequency of the two-dimensional block relating to the time and frequency is Widen. Furthermore, when converting the signal mode from the higher bit rate mode to the lower bit rate mode, the frequency width of the two-dimensional block with respect to time and frequency is widened by an integral multiple.

Further, in the digital signal processing method of the present invention, the input signal is an audio signal, and the frequency width of the block for controlling the generation of at least most of the quantization noise is made wider in the higher frequency range. In addition, the following is also performed. That is, in the information compression processing step, orthogonal transformation is used to decompose the digital signal into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks regarding time and frequency, and / or information. In the decompression processing step, the inverse orthogonal transform is used to transform the signal components in a plurality of two-dimensional blocks regarding time and frequency into digital signals on the time axis. In the information compression processing step, the digital signal is decomposed into a plurality of frequency band components, and first divided into a plurality of bands in order to obtain signal components in a plurality of two-dimensional blocks regarding time and frequency. A block composed of a plurality of samples is formed, and orthogonal transformation is performed for each block in each band to obtain coefficient data, and / or in the information expansion processing step, conversion from a plurality of bands on the frequency axis to a time axis signal is performed. Then, the inverse orthogonal transform is performed for each block in each band, and the outputs of the inverse orthogonal transforms are combined to obtain a combined signal on the time axis. The mode having a smaller information rate, the maximum orthogonal transform block length of the signal to be recorded and / or reproduced in the information compression processing step, or the maximum orthogonal transform block length of the signal to be transmitted and / or received in the information expansion processing step. To
Has a lengthened mode. The division frequency width in dividing the time axis signal before the orthogonal transformation in the information compression processing step into a plurality of bands on the frequency axis and / or the plurality of frequency bands on the frequency axis after the inverse orthogonal transformation in the information decompression processing step. The composite frequency widths from a plurality of bands in the composition from the band of 1 to the time axis signal are the same in the continuous two bands of the lowest region. The division frequency width in division into a plurality of bands on the frequency axis from the time axis signal before orthogonal transformation in the information compression processing step,
And / or, the synthesis frequency width from the plurality of bands in the synthesis from the plurality of bands on the frequency axis after the inverse orthogonal transform in the information expansion processing step to the time-axis signal is made wider as it becomes higher. In any information rate mode, the length of the maximum orthogonal transform block of the signal to be recorded and / or reproduced on the high frequency side or the length of the maximum orthogonal transform block of the signal to be transmitted and / or received is the same. To do. The sampling frequency is the same in all modes. The main information and / or the sub information of the compression code is not assigned to the signal component in the band substantially above the signal pass band.

In the digital signal processing apparatus and method of the present invention, a modified discrete cosine transform is used as the orthogonal transform. Also, after canceling at least one orthogonal band in the low frequency band, the orthogonal transform size is expanded and orthogonal transform is performed, and a mode in which the rate is reduced is obtained. Further, after canceling at least one orthogonal transform, the orthogonal transform size is expanded and orthogonal transform is performed to obtain a mode with a reduced rate.

Finally, the recording medium of the present invention records compressed data compressed by the digital signal processing method of the present invention.

Here, examples of the recording medium include a magneto-optical disc, a semiconductor recording medium (for example, an IC memory card), an optical disc recording medium and the like.

That is, for example, the compressed data recording and / or reproducing apparatus and method to which the above-mentioned present invention is applied, and the recording medium efficiently code a band narrower than the pass band width determined by the sampling frequency. ,
By sub-sampling the high band, coding can be achieved efficiently and with minimal hardware scale. Further, in the case of having a plurality of modes, by using the same sampling frequency regardless of the bit rate difference between the modes, the sampling frequency signal generation circuit becomes complicated when the plurality of sampling frequencies are provided, and the LSI scale is increased. Prevent the increase of. Further, when the sampling frequency of each mode is different, information transfer between each mode, which was difficult, can be easily performed, and high bit rate mode information on a large capacity magneto-optical disk can be transferred to a small capacity IC.
When you want to write to the card in low bit rate mode, you do not need to completely cancel the compression mode and return to the signal on the time axis, you can obtain the low bit rate mode compression processing only by additional processing, processing amount Is minimized and real-time processing is possible. In addition, the reduction of the signal pass band in the low bit rate mode is performed by not performing the calculation processing of the unnecessary band on the high frequency side. Can be used for additional calculation processing. The existence of band division before orthogonal transformation is useful in order to prevent unnecessary calculation processing of the high band. That is, if the entire high frequency side divided band is unnecessary, it is not necessary to process the divided band at all, and even if it is partially used, the subsampling process that utilizes only the used band makes it possible to calculate for the unused band. Processing can be avoided.

Next, as the mode becomes lower in bit rate, the number of usable bits decreases, and it becomes necessary to prevent deterioration of sound quality. In the present invention, the maximum processing time block is extended. This improves the compression efficiency. To increase the maximum processing time block, the orthogonal transform block size is increased.

As described above, by increasing the time length of the orthogonal transform block, it is possible to accurately perform signal conversion from the time axis to the frequency axis, and the amount of sub information such as scale factor and word length information. Can be reduced. Further, in a band in which the maximum time length of the orthogonal transform block is not increased, particularly in a band on the high frequency side, in order to reduce sub information, a block for block floating on the frequency axis having sub information and / or quantization Increase the frequency width of the noise generation block. In addition, by increasing the frequency width of the block for block floating and / or the quantization noise generation block on the frequency axis, which has sub information in the higher frequency band in at least most of the blocks, for example, in the low bit rate mode. Even if the bandwidth is narrowed, the frequency division close to the critical band can be performed in the middle and low frequencies, so that it is possible to prevent the compression efficiency from being lowered as in the case of equal division. In the low bit rate mode, useless bit use can be prevented by not allocating main and sub information to a band above the used band. When the bandwidth is narrowed, the frequency division width only for controlling the quantization noise is
When the frequency is constant regardless of the frequency, if the 20 kHz band is divided into 32, the critical band width in the low frequency range is about 100 Hz, which is very wide, about 700 Hz, which is wider than the critical band in the middle and low frequencies. Significant reduction in efficiency.
Therefore, in the present invention, the frequency division width for controlling the quantization noise is selected so that it becomes close to the critical bandwidth, and becomes wider as the frequency becomes higher in at least most of the frequency division bands.

When dubbing bit-compressed data from one recording medium such as the magneto-optical disk onto another recording medium such as the IC card, at least complete bit expansion is not performed, and the bit compression data is directly or additionally compressed. And dubbing. In the case of additional compression, only the limited orthogonal transform on the low frequency side is subjected to inverse orthogonal transform to obtain the time axis signal on the low frequency side, and when performing the next orthogonal transform, the orthogonal transform output is output with a longer orthogonal transform size. Obtaining helps to reduce the throughput. In the band where the orthogonal transform size is not changed, in order to reduce the sub information, the frequency width of the block for the block floating on the frequency axis having the sub information and / or the quantization noise generating block is widened.

[0032]

The digital signal processing apparatus and method and recording medium of the present invention can perform digital dubbing from, for example, a CD, can improve coding efficiency in a narrow band, and can reduce the scale of hardware. it can. Further, by using one type of sampling frequency, it becomes possible to prevent the sampling frequency signal generation circuit from becoming complicated and the LSI scale from increasing when a plurality of sampling frequencies are provided. In addition, information transfer between modes with different bit rates can be easily performed without complicated operations such as sampling frequency conversion, and high bit rate mode information on a large capacity magneto-optical disk is written in a small capacity IC card in a low bit rate mode. When it is desired to perform the above, the low bit rate mode compression processing can be obtained only by the additional processing, the increase in the processing calculation amount can be suppressed to the minimum, and the real-time processing can be performed. Further, according to the present invention,
It is possible to prevent deterioration of sound quality in a mode with a low bit rate.

[0033]

Embodiments of the present invention will be described below with reference to the drawings. First, FIG. 1 shows a schematic configuration of an embodiment of a compressed data recording / reproducing apparatus as an example of a signal processing apparatus of the present invention.

The recording / reproducing apparatus of FIG. 1 has two units, that is, the recording / reproducing unit 9 of the magneto-optical disk 1 which is one recording medium and the recording unit 4 of the IC card 2 which is the other recording medium. It is built in the system. When the signal reproduced from the magneto-optical disk 1 by the reproducing system on the side of the magneto-optical disk recording / reproducing unit 9 is recorded on the IC card 2 by the IC card recording unit 4, the optical signal from the magneto-optical disk 1 of the reproducing system is used. Reproduced compressed data (ATC audio data) read by the head 53, sent to the decoder 71 and subjected to EFM demodulation, deinterleave processing, error correction processing, etc. is sent to the memory 85 of the IC card recording unit 4, An additional compressor 8 for performing additional processing such as entropy coding on the memory 85
The variable bit rate coding processing window is added by the I.4, and the I
It is recorded on the C card 2. In this way, the reproduced compressed data is sent to the recording system in the compressed state before being subjected to the decompression processing by the ATC decoder 73 and recorded in the IC card 2.

By the way, during normal reproduction (for audio listening), a predetermined data amount unit (eg 32) is intermittently or bursted from the recording medium (magneto-optical disk 1).
Compressed data is read out with (sector + several sectors), and this is expanded and converted into a continuous audio signal. At the time of so-called dubbing, the compressed data on the medium is continuously read and sent to the recording system for recording. ing. by this,
High-speed (short time) dubbing can be performed according to the data compression rate.

The specific configuration of FIG. 1 will be described in detail below. In the magneto-optical disk recording / reproducing unit 9 of the compressed data recording and / or reproducing apparatus shown in FIG. 1, the magneto-optical disk 1 rotatably driven by the spindle motor 51 is used as the recording medium. When recording data on the magneto-optical disk 1, for example, the optical head 5
By applying a modulation magnetic field according to the recording data with the magnetic head 54 while irradiating the laser beam by 3, the so-called magnetic field modulation recording is performed, and the data is recorded along the recording track of the magneto-optical disk 1. During reproduction, the recording track of the magneto-optical disk 1 is moved to the optical head 53.
Then, it is traced with a laser beam and reproduced magneto-optically.

Here, the recording / reproducing apparatus will be mainly described. The optical head 53 includes, for example, a laser light source such as a laser diode, a collimator lens, an objective lens, a polarization beam splitter, an optical component such as a cylindrical lens, and a photodetector having a light receiving portion of a predetermined pattern. The optical head 53 is provided at a position facing the magnetic head 54 through the magneto-optical disk 1. When recording data on the magneto-optical disk 1, a magnetic head 54 is driven by a head drive circuit 66 of a recording system described later to apply a modulation magnetic field according to the recording data, and at the same time, the optical head 53 drives the magneto-optical disk 1.
By irradiating the target track with laser light, thermomagnetic recording is performed by the magnetic field modulation method. The optical head 53 also detects the reflected light of the laser light 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 it. Generate a signal.

The output of the optical head 53 is supplied to the 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 them to the servo control circuit 56.
The reproduction signal is binarized and supplied to a reproduction system decoder 71 described later.

The servo control circuit 56 is composed of, for example, a focus servo control circuit, a tracking servo control circuit, a spindle motor servo control circuit, a sled servo control circuit, and the like. The focus servo control circuit controls the focus of the optical system of the optical head 53 so that the focus error signal becomes zero. Further, the tracking servo control circuit controls the tracking 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). Further, the sled servo control circuit moves the optical head 53 and the magnetic head 54 to the target track position of the magneto-optical disk 1 designated by the system controller 57. The servo control circuit 56 that performs such various control operations sends information indicating the operating state of each unit controlled by the servo control circuit 56 to the system controller 57.

A key input operation section 58 and a display section 59 are connected to the system controller 57. The system controller 57 controls the recording system and the reproducing system in the operation mode designated by the operation input information from the key input operation unit 58. The system controller 7 also uses the optical head 53 and the magnetic head 54 based on the address information in sector units reproduced from the recording track of the magneto-optical disk 1 by the header time, the Q data of the subcode, or the like.
Manages the recording position and the reproducing position on the recording track traced by the. Further system controller 57
Is 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, and R
The bit compression mode is displayed on the display unit 59 based on the bit compression mode information in the reproduction data obtained from the F circuit 55 through the reproduction system described later, and the data compression rate and the recording track in the bit compression mode are displayed. Based on the above reproduction position information, control is performed to display the reproduction time on the display unit 59.

This reproduction time display is based on the sector unit address information (absolute time information) reproduced from the recording track of the magneto-optical disk 1 by so-called header time or so-called sub-code Q data, and the data in the bit compression mode. By multiplying the reciprocal of the compression rate (for example, 4 in the case of 1/4 compression), the actual time information is obtained and displayed on the display unit 59. In addition,
Even at the time of recording, when absolute time information is recorded (preformatted) in advance on a recording track of a magneto-optical disk, for example, the preformatted absolute time information is read and the reciprocal of the data compression rate is calculated. By multiplying, it is possible to display the current position with the actual recording time.

Next, in the recording system of the recording / reproducing apparatus of this disc recording / reproducing apparatus, the analog audio input signal AIN from the input terminal 60 is supplied to the A / D converter 62 via the low-pass filter 61, and this A / D converter 62 is supplied. The D converter 62 quantizes the analog audio input signal AIN. A
The digital audio signal obtained from the / D converter 62 is supplied to an ATC (Adaptive Transform Coding) PCM encoder 63. Further, the digital audio input signal DIN from the input terminal 67 is supplied to the ATC encoder 63 via the digital input interface circuit 68. The ATC encoder 63 uses the input signal A
Table 1 shows digital audio PCM data of a predetermined transfer rate obtained by quantizing IN by the A / D converter 62.
The bit compression (data compression) processing corresponding to various modes in the ATC system shown in (1) is performed, and the operation mode is designated by the system controller 57. For example, in the B mode, compressed data (ATC data) having a sampling frequency of 44.1 kHz and a bit rate of 64 kbps is supplied to the memory 64. The data transfer rate in this B mode stereo mode is 1/8 (9.375 sectors / second) of the standard CD-DA format data transfer rate (75 sectors / second).
Has been reduced to.

[0043]

[Table 1]

Here, in the embodiment of FIG. 1, A / D
The sampling frequency of the converter 62 is, for example, the sampling frequency of the standard CD-DA format described above.
The ATC encoder 63 is fixed at 4.1 kHz.
Also in, it is assumed that the sampling frequency is maintained and bit compression processing is performed. At this time, since the signal pass band becomes narrower as the low bit rate mode is set, the cutoff frequency of the low pass filter 61 is also switched and controlled accordingly. That is, the cutoff frequency of the low-pass filter 61 of the A / D converter 62 may be simultaneously switched and controlled according to the compression mode.

Next, in the memory 64, the writing and reading of data are controlled by the system controller 57, the ATC data supplied from the ATC encoder 63 is temporarily stored, and recorded on the disk as needed. It is used as a buffer memory for That is, for example, in the stereo mode of the B mode, the compressed audio data supplied from the ATC encoder 63 has a standard CD-D data transfer rate.
It is reduced to 1/8 of the data transfer rate of A format (75 sectors / second), that is, 9.375 sectors / second, and this compressed data is continuously written in the memory 64. As for the compressed data (ATC data), it is sufficient to record one sector for every eight sectors as described above. However, since recording every eight sectors is practically impossible, the continuous sectors described below will be used. I try to keep a record.

In this recording, a cluster consisting of a plurality of predetermined sectors (for example, 32 sectors + several sectors) is used as a recording unit for the same data transfer rate as the standard CD-DA format (75 sectors / second) during the rest period. ) Is done in a burst. That is, in the memory 64, the ATC audio data in the B mode and the stereo mode continuously written at the low transfer rate of 9.375 (= 75/8) sectors / sec corresponding to the bit compression rate is recorded data. The data is read in bursts at the transfer rate of 75 sectors / sec. The overall data transfer rate of the read and recorded data, including the recording pause period, is as low as 9.375 sectors / sec, but within the time of the recording operation performed in a burst manner. The instantaneous data transfer rate in the above is the standard 75 sectors / sec. Therefore, the CD has a standard disc rotation speed.
-At the same speed as the DA format (constant linear velocity)
Recording with the same recording density and storage pattern as the CD-DA format will be performed.

The ATC audio data, that is, the recording data, which is burst-read from the memory 64 at the (instantaneous) transfer rate of 75 sectors / second, is recorded by the encoder 65.
Is supplied to. Here, from the memory 64 to the encoder 65
In the data string supplied to the above, the unit to be continuously recorded in one recording is a cluster composed of a plurality of sectors (for example, 32 sectors) and several sectors for cluster connection arranged at the front and rear positions of the cluster. This cluster connection sector is set to be longer than the interleave length in the encoder 65 so that interleaved data will not affect the data of other clusters.

The encoder 65 uses the recording data supplied from the memory 64 in bursts as described above.
Encoding processing for error correction (parity addition and interleave processing), EFM encoding processing, and the like are performed. The recording data encoded 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,
The magnetic head 54 is driven so as to apply the modulation magnetic field according to the recording data to the magneto-optical disk 1.

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

Next, the reproducing system of the magneto-optical disk recording / reproducing unit 9 will be described. This reproducing system is for reproducing the record data continuously recorded on the recording track of the magneto-optical disk 1 by the above-mentioned recording system, and the recording track of the magneto-optical disk 1 is laser-driven by the optical head 53. The decoder 71 is provided with a reproduction output obtained by tracing with light, which is binarized and supplied by the RF circuit 55. At this time, not only the magneto-optical disc 1 but also a so-called compact disc (CD:
It is also possible to read the same read-only optical disc as Compact Disc).

The decoder 71 corresponds to the encoder 65 in the recording system described above, and decodes the reproduced output binarized by the RF circuit 55 as described above for error correction and EFM decoding. By performing processing such as processing, the above-described B-mode stereo mode ATC audio data is reproduced at a transfer rate of 75 sectors / second, which is faster than the normal transfer rate in the B-mode stereo mode. The reproduction data obtained by this decoder 71 is
It is supplied to the memory 72.

In the memory 72, writing and reading of data 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 bursts at the transfer rate of 75 sectors / second. Be done. Further, in the memory 72, the reproduction data written in a burst at the transfer rate of 75 sectors / second is the normal 9.37 in the stereo mode of the B mode.
It is continuously read at a transfer rate of 5 sectors / second.

The system controller 57 writes the reproduced data in the memory 72 at a transfer rate of 75 sectors / second, and also writes the reproduced data from the memory 72 in the above 9.37.
Memory control is performed so that data is continuously read at a transfer rate of 5 sectors / second. Further, the system controller 57 performs the above-mentioned memory control on the memory 72, and continuously reproduces the above-mentioned reproduction data written in burst from the memory 72 from the recording track of the magneto-optical disk 1 by the memory control. Controls the playback position. This playback position is controlled by the system controller 5
By controlling the reproduction position of the reproduction data read out from the memory 72 in burst by 7 and supplying a control signal for designating the reproduction position on the recording track of the magneto-optical disc 1 or the optical disc 1 to the servo control circuit 56. Done.

Stereo mode ATC audio data of B mode obtained as reproduction data continuously read from the memory 72 at a transfer rate of 9.375 sectors / second is supplied to the ATC decoder 73. The ATC decoder 73 corresponds to the ATC encoder 63 of the recording system, the operation mode is designated by the system controller 57, and, for example, the B mode stereo mode ATC data is expanded eight times (bit expansion). As a result, 16-bit digital audio data is reproduced. The digital audio data from the ATC decoder 73 is supplied to the D / A converter 74.

The D / A converter 74 is the ATC decoder 73.
The digital audio data supplied from the converter is converted into an analog signal to form an analog audio output signal AOUT. The analog audio signal AOUT obtained by the D / A converter 74 is output from the output terminal 76 via the low pass filter 75.

Next, the IC card recording unit 4 of the compressed data recording and / or reproducing apparatus will be described.

The analog audio input signal AIN supplied to the recording unit 4 is passed through the low pass filter to A
It is supplied to the / D converter and quantized. The digital audio signal obtained from the A / D converter is sent to an additional compressor 84 that performs so-called entropy coding, which is a kind of variable bit rate encoder, and is subjected to processing such as entropy coding. Here, the signal sent to the additional compressor 84 is, specifically, the analog audio input signal AIN via the input terminal 60, the low-pass filter 61 and the A / D converter 62, and the ATC encoder 63. The signal is stored in the memory 85 via the.
Therefore, the processing such as entropy coding in the additional compressor 84 is executed while reading / writing data from / to the memory 85. The variable bit rate compression-encoded data from the additional compressor 84 that performs entropy encoding or the like is transmitted via the IC card interface circuit 86 to I
It is recorded on the C card 2. Of course, in the present invention, the variable bit rate compression of the entropy code is not performed, but the orthogonal transform size is increased or the block for the block floating on the frequency axis having the sub information and / or the quantization noise generating block is used. By widening the frequency range,
Recording may be performed at a constant bit rate with a lower bit rate.

Here, compressed data (AT) from the decoder 71 of the reproducing system of the magneto-optical disk recording / reproducing unit 9 is described.
C data) is sent to the memory 85 of the IC card recording unit 4 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. Recording on an IC card from a magneto-optical disk or optical disk by changing the bit rate mode and decreasing the bit rate is suitable for recording on an IC card having a high price per recording capacity. This is convenient without the need for sampling frequency conversion where it is unnecessary for the sampling frequencies to be the same regardless of the bit rate mode. The actual additional compression is performed by the additional compressor 84.

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 57 executes a predetermined high-speed dubbing control processing operation by operating a dubbing operation key or the like of the key input operation unit 58. Specifically, the compressed data from the decoder 71 is directly applied to the IC.
The data is sent to the memory 85 of the card recording system, subjected to variable bit rate coding by the additional compressor 84 that performs entropy coding, and recorded in the IC card 2 via the IC card interface circuit 86. Here, for example, when the stereo mode ATC data of the B mode is recorded on the magneto-optical disk 1, eight times compressed data is continuously read from the decoder 71. In addition, IC
The IC card detection circuit 52 determines whether or not the card 2 is inserted (loaded) in the recording unit 4. When the IC card detection circuit 52 detects that the IC card 2 has been inserted into the recording unit 4, it outputs a signal to that effect to the recording / reproducing unit 9, and the recording / reproducing unit 9 concerned.
Receives the signal and performs the process for the dubbing.

Therefore, at the time of high-speed dubbing, compressed data corresponding to 8 times (in the case of the B-mode stereo mode) in real time is continuously obtained from the magneto-optical disk 1, which is entropy as it is. Since it is encoded and converted to a constant bit rate of a low bit rate and recorded in the IC card 2, it is possible to realize 8 times high-speed dubbing. If the compression mode is different, the magnification of the dubbing speed is also different. 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 is driven to rotate at high speed at a speed several times the steady speed.

By the way, as shown in FIG. 2, the bit-compressed data is recorded on the magneto-optical disk 1 at a constant bit rate, and at the same time, the additional compression / expansion block 3 compresses the data. Information of the amount of data when encoded (that is, the data recording capacity required for recording in the IC card 2) is recorded. By doing so, for example, the number of songs that can be recorded in the IC card 2 among the songs recorded on the magneto-optical disc 1, the combination of the songs, and the like can be immediately known by reading the data amount information. . Of course, the additional compression operation may be performed by the additional compression / expansion block 3 not to the variable bit rate mode but to the fixed bit rate lower bit rate mode.

On the contrary, in the IC card 2, not only the data bit-compressed and encoded at the variable bit rate,
By recording the data amount information of the data bit-compressed and encoded at a constant bit rate, it is possible to quickly know the data amount when the data such as music is transmitted from the IC card 2 to the magneto-optical disc 1 for recording. it can. Of course, not only the data bit-compressed and encoded at the variable bit rate but also the data bit-compressed and encoded at the constant bit rate can be recorded in the IC card 2.

FIG. 3 shows the external appearance of the compressed data recording and / or reproducing apparatus 5 having the structure shown in FIG. Has been. Of course, the disc and the IC card may be separate sets and a signal may be transmitted between them with a cable.

Next, the high-efficiency compression encoding used in the compressed data recording and / or reproducing apparatus of this embodiment will be described in detail. That is, refer to FIG. 4 and subsequent figures for a technique for highly efficient encoding of an input digital signal such as an audio PCM signal using band division encoding (SBC), adaptive transform encoding (ATC) and adaptive bit allocation techniques. While explaining.

In the concrete high-efficiency encoder shown in FIG. 4, the input digital signal is divided into a plurality of frequency bands, and the adjacent two bands in the lowest band have the same bandwidth.
In the higher frequency band, the higher the frequency band, the wider the bandwidth is selected, the orthogonal transformation is performed for each frequency band, and for the obtained frequency axis spectrum data, the human auditory characteristics described later are considered in the low frequency band. In each of the so-called critical bandwidths (critical bands), in the middle and high frequencies, so-called block floating efficiency is taken into consideration, and the critical bandwidths are subdivided into bands to adaptively allocate bits for coding. Usually, this block is the quantization noise generation block. Furthermore, in the embodiment of the present invention, the block size (block length) is adaptively changed according to the input signal before the orthogonal transformation, and the floating process is performed for each block.

That is, in FIG. 4, at the input terminal 10, for example, when the sampling frequency is 44.1 kHz, 0
An audio PCM signal of .about.22 kHz is supplied. This input signal is converted into a band of 0 to 11 kHz by a band splitting filter 11 such as a so-called QMF filter.
Divided into 1 kHz-22 kHz band, 0-11 kHz
Similarly, the signal in the z band is supplied to a band division filter 12 such as a so-called QMF filter, which has a band of 0 to 5.5 kHz and a band of 5.5.
It is divided into a band of kHz to 11 kHz. A signal in the 11 kHz to 22 kHz band from the band division filter 11 is sent to the MDCT circuit 13 which is an example of an orthogonal transformation circuit, and a signal in the 5.5 kHz to 11 kHz band from the band division filter 12 is sent to the MDCT circuit 14, The signals in the 0 to 5.5 kHz band from the division filter 12 are sent to the MDCT circuit 15 to be subjected to MDCT processing.

Here, as a method of dividing the above-mentioned input digital signal into a plurality of frequency bands, for example, QMF is used.
With filter, 1976 RECrochiere Digital coding
of speech in subbands Bell Syst.Tech. J. Vol.55, No.
8 1976. Also ICASSP 83, BOSTON Po
lyphase Quadrature filters-A new subband codingtec
hnique Joseph H. Rothweiler describes an equal bandwidth filter partitioning technique. Here, as the above-mentioned orthogonal transform, for example, an input audio signal is divided into blocks in a predetermined unit time (frame), and fast Fourier transform (FFT), cosine transform (DCT),
There is orthogonal transformation in which the time axis is transformed into the frequency axis by performing modified DCT transformation (MDCT) or the like. M
For DCT, ICASSP 1987 Subband / Transform Codin
g Using Filter Bank DesignsBased on Time Domain Al
iasing Cancellation JPPrincen ABBradley Univ.
of Surrey Royal Melbourne Inst. of Tech.

Next, FIG. 5 shows a concrete example of blocks for each band supplied to the MDCT circuits 13, 14, 15 in each mode for a standard input signal. In the specific example of FIG. 5, the three filter output signals from the band division filters 11 and 12 of FIG. 4 each have a plurality of orthogonal transform block sizes independently for each band,
The time resolution can be switched according to the time characteristic of the signal. In addition, the smaller the bit rate, the longer the maximum processing block time and the narrower the signal pass bandwidth.

That is, in the case of A mode, when the signal is quasi-stationary in time, the orthogonal transform block size is increased to 11.6 ms, and when the signal is non-stationary, the orthogonal transform block is in the band of 11 kHz or less. The size is further divided into four, and the orthogonal transform block size is divided into eight in the band of 11 kHz or more.

In the B mode, the time length of the maximum orthogonal transform block is twice as long as in the A mode, which is 23.2.
ms, and the signal pass bandwidth is narrowed to 13 kHz. When the signal is quasi-stationary in time, the orthogonal transform block size is increased to 23.2 ms, and when the signal is more non-stationary, it is divided into two to 11.6 ms. Furthermore, when the non-stationarity of the signal becomes stronger, 11
In the band below kHz, the orthogonal transform block size is set to 4
The division is made into a total of 8 divisions, and in the band of 11 kHz or more, the orthogonal transformation block size is further divided into 8 divisions to make a total of 16 divisions.

In the C mode, the maximum processing time block has a time length of up to 34.8 ms. The pass band is 5.5
Limit to kHz.

In the D mode, the maximum processing block time length of 46.4 ms is provided.

Here, each MDCT circuit 13, 14, 15
By increasing the time length of the maximum orthogonal transform block by a factor of 2 in each of the bands supplied to
Conversion from A mode to B mode becomes easy. In other words, the low-frequency side orthogonal transform of the A mode is subjected to inverse orthogonal transform, and the orthogonal transform having a double orthogonal transform size is performed again. This is easier than performing inverse orthogonal transform of a plurality of bands forming the entire band and then performing orthogonal transform again for each band.
Further, this is convenient for executing high-speed transfer from the magneto-optical disk to the IC memory card while converting from the A mode to the B mode. This is based on the fact that the acoustic signal in the high frequency range has a larger temporal variation and the signal-to-noise ratio may be smaller than that in the low frequency range.

At this time, the signal pass bandwidth is 13
Up to kHz. In this case, as shown in FIG.
By ½ or ¼ sub-sampling the filter output signal before orthogonal transformation in the signal of the band from kHz to 22 kHz, it is possible to avoid useless signal processing for the band above the signal pass band.

The maximum orthogonal transform block length becomes longer and the signal pass bandwidth can be made narrower in the C mode and D mode. Of course, the length of the maximum processing time block and the signal pass bandwidth do not have to be different between all modes, and may have the same value.

Further, even if the length of the maximum orthogonal transform block is longer in the low bit rate mode,
For the purpose of shortening the time delay, the object can be achieved by selectively using a short orthogonal transform block among a plurality of orthogonal transform blocks of the mode to perform an encoding process.

Referring again to FIG. 4, each M in the A mode
Spectral data or MDCT on the frequency axis obtained by the MDCT processing in the DCT circuits 13, 14 and 15
The coefficient data is grouped into so-called critical bands in the low band, and the critical band width is divided into sub bands in the middle and high bands in consideration of the effectiveness of block floating, and sent to the adaptive bit allocation coding circuit 18. Has been. The critical band is a frequency band divided in consideration of human auditory characteristics, and when the pure tone is masked by a narrow band noise of the same strength in the vicinity of the frequency of a pure tone, the noise of that pure tone is masked. It is the bandwidth that you have. The critical band has a wider bandwidth in a higher frequency range, and the entire frequency band of 0 to 22 kHz is divided into, for example, 25 critical bands.

In the B mode, in a band in which the maximum orthogonal transform block size is not doubled in the A mode, the frequency width of the block having the sub information is set to, for example, double the frequency width of the A mode. The number of blocks is halved and sub-information is reduced. In this way
By doubling the orthogonal transform block size in the low range,
In the other bands, the sub-information in the entire band can be reduced by increasing the frequency width of the block having the sub-information.

Further, the bit allocation calculating circuit 20 uses the spectral data divided in consideration of the critical band and block floating, for each divided band in consideration of the critical band and block floating in consideration of so-called masking effect and the like. The masking amount for each band is calculated based on the masking amount and the energy or peak value for each divided band in consideration of the critical band and block floating, and this information is adaptive bit allocated. It is sent to the encoding circuit 18. The adaptive bit allocation encoding circuit 1
In No. 8, each spectrum data (or MDCT coefficient data) is requantized according to the number of bits assigned to each band. The data encoded in this way is taken out via the output terminal 19.

Next, FIG. 6 shows the bit allocation calculating circuit 20.
It is a block circuit diagram which shows schematic structure of one specific example. In FIG. 6, the input terminal 21 is supplied with spectrum data on the frequency axis 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 of each divided band in consideration of the masking amount, the critical band and the block floating is, for example, each energy in each band. It can be obtained by calculating the sum of amplitude values. Instead of the energy for each band, a peak value, an average value, etc. of the amplitude value may be used. As the output from the energy calculating circuit 22, for example, the spectrum of the sum value of each band is shown as SB in the drawing of FIG. However, in FIG. 7, in order to simplify the illustration, the number of divided bands in consideration of the masking amount, the critical band, and the block floating is expressed by 12 bands (B1 to B12).

Here, in order to consider the influence of the so-called spectrum SB on so-called masking, a convolution process for multiplying and adding the spectrum SB by a predetermined weighting function is performed. Therefore, the output of the energy calculation circuit 22 for each band, that is, each value of the 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, and a plurality of multipliers (for example, 25 corresponding to each band, for multiplying outputs from these delay elements by a filter coefficient (weighting function)). Number of multipliers), and a sum adder that sums the outputs of the multipliers. By this convolution processing, the sum total of the portion indicated by the dotted line in FIG. 7 is obtained. Note that the masking is a phenomenon in which one signal is masked by another signal and becomes inaudible due to human auditory characteristics, and this masking effect includes a time axis masking by an audio signal on the time axis. There are an effect and a simultaneous masking effect by a signal on the frequency axis. Due to these masking effects, even if there is noise in the masked portion, this noise cannot be heard.
Therefore, in the actual audio signal, the noise within the masked range is regarded as an 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 1, the multiplier is M-1 gives a coefficient of 0.15, multiplier M-2 gives a coefficient of 0.0019, and multiplier M-3 gives a coefficient of 0.0000.
086, multiplier M + 1 gives a coefficient of 0.4, multiplier M + 2
By multiplying the output of each delay element by a coefficient of 0.06 with a coefficient of 0.007 with a multiplier M + 3, the convolution processing of the spectrum SB is performed. However, M is an arbitrary integer of 1 to 25.

Next, the output of the convolution filter circuit 23 is sent to the subtractor 24. The subtractor 24 obtains a level α corresponding to an allowable noise level described later in the convoluted area. The level α corresponding to the permissible noise level (permissible noise level)
Is a level at which an allowable noise level is obtained for each critical band by performing inverse convolution processing, as will be described later. Here, the subtractor 24 is supplied with an allowance function (function expressing a masking level) for obtaining the level α. The level α is controlled by increasing or decreasing this allowance function. The permissible function is (n-
ai) It is supplied from the function generating circuit 25.

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

In this way, the level α is obtained, and this data is transmitted to the divider 26. The divider 26 is for inverse convolution of the level α in the convolved area. Therefore, by performing this inverse convolution process,
The masking spectrum can be obtained from the level α. That is, this masking spectrum becomes the allowable noise spectrum. Although the above-mentioned inverse convolution processing requires a complicated operation, in the present embodiment, the inverse convolution is performed using the simplified divider 26.

Next, the masking spectrum is transmitted to the subtractor 28 via the synthesizing circuit 27. Here, the subtractor 28 includes an energy detection circuit 22 for each band.
From the output signal, that is, the spectrum SB described above is supplied via the delay circuit 29. Therefore, the masking spectrum and the spectrum SB are obtained by the subtractor 28.
By performing the subtraction operation with and, the spectrum SB is masked below the level indicated by the level of the masking spectrum MS, as shown in FIG.

The output from the subtractor 28 is taken out through the allowable noise correction circuit 30 and the output terminal 31,
For example, the allocation bit number information is sent to a ROM or the like (not shown) in which it is stored in advance. The ROM or the like is assigned to 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. Outputs bit number information. By transmitting this allocation bit number information to the adaptive bit allocation encoding circuit 18, each spectrum data on the frequency axis from the MDCT circuits 13, 14, 15 is quantized by the number of bits allocated for each band. Is done.

In summary, in the adaptive bit allocation encoding circuit 18, the masking amount, the energy of each divided band considering the critical band and the block floating, and the level of the difference between the output of the noise level setting means are determined. The spectrum data for each band is quantized by the allocated number of bits. In addition,
The delay circuit 29 considers the amount of delay in each circuit before the synthesis circuit 27 and the spectrum S from the energy detection circuit 22.
It is provided to delay B.

By the way, at the time of synthesizing by 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 masking spectrum MS can be combined. In this minimum audible curve, if the absolute noise level is below this minimum audible curve, the noise will not be heard. Even if the coding is the same, the minimum audible curve differs depending on, for example, the difference in the reproduction volume at the time of reproduction. However, in a realistic digital system, for example, the way of inputting music to the 16-bit dynamic range is very different. Therefore, if the quantization noise in the most audible frequency band around 4 kHz is not heard, it is considered that the quantization noise below the level of the minimum audible curve is not heard in other frequency bands.

Therefore, it is assumed that the system is used in such a manner that noise near the word length of 4 kHz possessed by the system cannot be heard, and the allowable noise level is obtained by synthesizing the minimum audible curve RC and the masking spectrum MS together. In this case, the allowable noise level in this case can be up to the shaded portion in the drawing of FIG. In this embodiment, the level of 4 kHz of the minimum audible curve is set to the minimum level equivalent to 20 bits, for example. Further, FIG. 9 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 the information of 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, and is obtained by, for example, obtaining the sound pressure of sound at each frequency heard at the same loudness as a pure tone of 1 kHz and connecting them with a curve. Also called sensitivity curve. Further, this equal loudness curve draws a curve substantially the same as the minimum audible curve RC shown in FIG. In this equal loudness curve, for example, in the vicinity of 4 kHz, even if the sound pressure is lowered by 8 to 10 dB from that at 1 kHz, it sounds as loud as 1 kHz. It doesn't sound the same. Therefore, it is understood that it is preferable that the noise (allowable noise level) exceeding the level of the minimum audible curve has a frequency characteristic given by a curve corresponding to the equal loudness curve. From this, it can be seen that correcting the permissible noise level in consideration of the equal loudness curve is suitable for human hearing characteristics.

Here, as the correction information output circuit 33, the detection output of the output information amount (data amount) at the time of quantization in the adaptive bit allocation encoding circuit 18 and the bit rate target value of the final encoded data are set. The allowable noise level may be corrected based on the information on the error between the two. This is because the total number of bits obtained by performing temporary adaptive bit allocation in advance 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 bit allocation is performed again so that the error becomes 0. That is, when the total number of allocated bits is smaller than the target value, the difference bit number is allocated and added to each unit block, and when the total number of allocated bits is larger than the target value, the difference bit number is set in each unit. Allocate to blocks and delete.

In order to do this, the correction information output circuit 33 detects an error in the total number of allocated bits from the target value, and the correction information output circuit 33 corrects each allocated bit number in accordance with the error data. Is output. here,
When the error data indicates a shortage of the number of bits, it can be considered that the amount of data is larger than the target value due to the large number of bits used per unit block. Further, when the error data is data indicating a surplus of the number of bits, it can be considered that the number of bits per unit block is small and the amount of data is smaller than the target value. Therefore, the correction information output circuit 33 outputs the correction value for correcting the allowable noise level in the output from the subtracter 28 based on the error data, for example, based on the information data of the equal loudness curve. 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 the system as described above, the data obtained by processing the orthogonal transform output spectrum with the sub information as the main information and the scale factor indicating the block floating state and the word length indicating the word length as the sub information are obtained and sent from the encoder to the decoder. To be

Here, the bit allocation calculation circuit 20 is
It is also possible to adopt a configuration as shown in FIG. The following effective bit allocation method different from the bit allocation method described above will be described with reference to FIG.

The MDCT circuits 13 and 1 shown in FIG.
The outputs of 4 and 15 are input through the input terminal 301 of FIG.
It is sent to the energy calculation circuit 303 which calculates the energy for each band. In the energy calculation circuit 303 for each band,
In the critical band or the high band, the energy of each band obtained by further dividing the critical band is obtained by, for example, calculating the square root of the root mean square of each amplitude value in the band. Instead of the energy for each band, it is possible to use the peak value or average value of the amplitude values.

As the output from the energy calculation circuit 303, for example, the spectrum of the sum value for each critical band (critical band) or for each band obtained by further dividing the critical band in the high frequency band is, for example, the spectrum shown in FIG. Burk spectrum) SB.

In the present embodiment, the number of bits that can be used for transmission or recording by expressing MDCT coefficients is, for example, 10
Assuming 0 Kbps, 100 K of them in this embodiment.
Create a fixed bit allocation pattern using bps. In this embodiment, a plurality of bit allocation patterns for the fixed bit allocation are prepared, and various selections can be made depending on the characteristics of the signal. In the present embodiment, the fixed bit allocation circuit 305 has various patterns in which the bit amount of a short-time block corresponding to 100 Kbps is distributed in each frequency. In the fixed bit allocation circuit 305,
We have prepared a number of patterns with different bit allocation ratios for the low and middle frequencies. And the smaller the signal size,
Make sure to select a pattern that has a small allocation to the high range. By doing so, the loudness effect in which the sensitivity in the high frequency range decreases as the signal becomes smaller can be used. As the signal magnitude at this time, the magnitude of the signal in the entire band may be used, but for example, the output of the non-blocking frequency division circuit using a filter or the MDCT output may be used. it can. In addition, MDCT
The number of bits that can be used for transmission or recording by expressing the coefficient (100 Kbps, which is the number of usable bits) is set by the total usable bit number output circuit 302, for example. This total number of usable bits can be input from the outside.

In the present embodiment, the energy-dependent bit allocation is performed by weighting the dB value of the energy of the block in a short time corresponding to 100 Kbps by multiplying a predetermined coefficient for each block, It is performed in proportion to the value thus obtained. Here, by setting the weighting coefficient so that it has a large value in the low frequency band, more bits are allocated to the low frequency band. The energy-dependent bit allocation is performed by the energy-dependent bit allocation circuit 304 to which the output of the energy calculation circuit 303 is supplied.

That is, in the energy-dependent bit allocation circuit 304, a plurality of patterns of the weighting coefficient are prepared similarly to the fixed bit allocation, and the plurality of patterns are switched according to the input signal, or
For example, the energy-dependent bit allocation is calculated using a weighting pattern obtained by interpolating two weighting patterns with the input signal. Thus, in this embodiment, by changing the weighting coefficient depending on the input signal,
It is possible to allocate bits that are more suitable for the sense of hearing and improve sound quality.

In FIG. 10, the division ratio between the above-mentioned allocation to the fixed bit allocation pattern and the bit allocation depending on the Bark spectrum (spectrum SB) is determined by the index indicating the smoothness of the signal spectrum. That is, in the present embodiment, the output of the energy calculation circuit 303 is sent to the spectrum smoothness calculation circuit 308, and in the spectrum smoothness calculation circuit 308, the sum of the absolute values of the differences between adjacent values of the signal spectrum is calculated. A value obtained by dividing the sum is calculated as an index, and this index is sent to the bit division rate determination circuit 309 for obtaining the division rate of the bit allocation.

The division rate data from the bit division rate determining circuit 309 is supplied to the multiplier 312 to which the output of the fixed bit allocation circuit 305 is supplied and the multiplier 311 to which the output of the energy dependent bit allocation circuit 304 is supplied. Sent to. The outputs of these multipliers 312 and 311 are sent to the sum calculation circuit 306. That is, the sum of the fixed bit allocation and the critical value (critical band) of each band or the value of the bit allocation that depends on the spectrum of each band obtained by further dividing the critical band in the high frequency band is calculated by the sum calculation circuit 306, The result of this calculation is sent from the output terminal (bit allocation amount output terminal of each band) 307 to the configuration of the subsequent stage, and is used at the time of quantization.

The state of bit allocation at this time is shown in FIGS. The states of quantization noise corresponding to this are shown in FIGS. Note that FIGS. 11 and 12 show the case where the spectrum of the signal is flat, and FIGS.
4 shows the case where the signal spectrum shows high tonality. In addition, Q _{S in} the diagrams of FIGS. 11 and 13 indicates the bit amount corresponding to the signal level, and Q _F in the diagrams indicates the bit amount corresponding to the fixed bit allocation. 12 and 14
In the figure, L indicates the signal level, N _{S in} the figure indicates the noise reduction due to the signal level dependence, and N _F in the figure indicates the noise level due to the fixed bit allocation.

In FIGS. 11 and 13, which show the case where the spectrum of the signal is fairly flat, bit allocation by a large amount of fixed bit allocation is usually useful for obtaining a large signal-to-noise ratio over the entire band. .
However, in the case of FIGS. 11 and 13, relatively few bit allocations are used in the low band and the high band. This is because this band is acoustically less important. Further, at this time, as shown by Q _S in the drawing of FIG. 11, the noise level in the band in which the signal magnitude is large is selectively lowered by a bit (bit) which is slightly signal level dependent bit allocation. . Therefore, if the spectrum of the signal is relatively flat, this selectivity also works over a relatively wide band.

On the other hand, when the signal spectrum exhibits a high tonality as shown in FIGS. 12 and 14, a large amount of signal level-dependent bit allocation is performed as indicated by Q _S in the diagram of FIG. The reduction of quantization noise by minutes (bits) is used to reduce noise in a very narrow band (band indicated by N _S in the drawing of FIG. 14). This achieves improved performance with isolated spectrum input signals. In addition, the noise level in a wide band is non-selectively lowered by the bit allocation that is performed by a bit of fixed bit allocation at the same time.

Next, signal processing between modes having different bit rates will be described by taking the conversion from A mode to B mode as an example.

As shown in FIG.
The processing content is decided while watching the signal for 6 ms. Here, when converting to the B mode, as shown in FIG. 16, two adjacent blocks of 11.6 ms are simultaneously viewed, and the two blocks are both the maximum block length in the A mode of 11.6 ms. Confirm that the scale factor and word length are similar, and in this case only 11.6m
By reducing the sub information amount and increasing the main information amount by making the scale factor and word length of two adjacent blocks of s common, it is possible to prevent deterioration of sound quality due to a decrease in bit rate.

Here, in FIG. 15, the number of spectrum division blocks considering the critical band and block floating in 11.6 ms is 52 in all bands. Of these, 20 exist in the low range and 16 in the middle range and 16 in the high range. In the same mode, when the signal becomes more transient, and the length of the processing block on the time axis is reduced by half, the frequency width is doubled so that the number is the same.

Further, in FIG. 16, 20 in 11.6 ms in the A mode for low frequencies and 23.
The sub information is halved by having 20 scale factors and word lengths in 2 ms.
In the middle and high frequencies, the maximum processing block size is not expanded, and the frequency width of the block having sub information is doubled,
The number of sub-information has been halved. As a result, in the mid range,
It has 16 scale factors and word length sub information in 23.2 ms. Furthermore, in the high band, the bandwidth is reduced in addition to the above.

Next, the reduction of the bandwidth at the time of mode conversion to the low bit rate mode will be described. In order to obtain a B-mode compressed signal, first, a case of directly compressing an analog or digital time axis signal into a B-mode, and a second case
There are two possible methods for additional compression from the A mode compressed signal to the B mode.

The specific structure is as shown in FIG. In FIG. 17, when the signal on the time axis having the sampling frequency of 44.1 kHz via the input terminal 120 is compressed from the beginning, the cutoff frequency 13 corresponding to the reduction of the bandwidth is set.
The low-pass filter (LPF) 121 of kHz reduces the signal band of the signal on the time axis.

Next, the same QMF filter 122, as described above,
Of the signals band-divided by 123, the QMF filter 1
The signals excluding the high frequency side output from 22 are the QMF filter 1
23, and is further band-divided to the MDCT circuit 12
Sent to 7,128. Due to this, the signal excluding the high frequency side output from the QMF filter 122 is 23.3 ms,
From the 3 types of MDCT of 11.6ms and 2.9ms,
It receives the MDCT selected according to the time characteristic of the signal.

On the other hand, the high-frequency side output from the QMF filter 122 is down-sampled by the down-sampling circuit 125 of the band signal processing circuit 124 at a ratio of 1/2. The signal whose number of samples has been halved by the downsampling circuit 125 is sent to the next MDCT circuit 12
MDCT conversion is performed by 6. That is, in the MDCT circuit 126, the number of samples is reduced by half due to the downsampling and then 23.3 ms, 11.6 ms.
The MDCT selected according to the time characteristic of the signal is performed from among three kinds of orthogonal transforms (MDCT) of ms and 2.9 ms. For example, between 11 kHz and 15 kHz, MDC
If the time length of T is 23.2 ms, 8 bands having sub information in it, if the time length of MDCT is 11.2 ms, 4 bands having sub information in it, MDCT
If the time length of 2.9 ms is 2.9 ms, then one band having sub-information will be included therein. At this time, the band signal processing circuit 124 can also perform downsampling at a ratio of 1/4.

The outputs of these MDCT circuits 126 to 128 are sent to the adaptive bit allocation encoding circuit 129 similar to the above, and output from the terminal 19. When the bandwidth is not 13 kHz as described above but is reduced to, for example, 11 kHz, the band signal processing circuit 124 provided on the high frequency side may be deleted.

Next, the case of additionally compressing the A-mode compressed signal to the B-mode compressed signal will be considered with reference to FIG.

In the configuration shown in FIG. 18, when the MDCT blocks having the time length of 11.6 ms in the A mode are continuous and the change in the floating information on the time axis is less than or equal to a certain value, two blocks each. Solving MDCT, MDCT with a time length of 23.2 ms in B mode is performed. This makes it possible to reduce the amount of sub information.

That is, in FIG. 18, first, for example, the A-mode compression circuit 224 for performing the A-mode compression compresses the signal on the time axis of 20 kHz at the sampling frequency of 44.1 kHz supplied through the input terminal 221. To be done. In this A-mode compression circuit 224, the signal is band-divided by the QMF filters 222 and 223 similar to the above, the high frequency side output from the QMF filter 222 is sent to the MDCT circuit 225, and the QMF filter 2
The low-frequency side output of 22 is further band-divided by the QMF filter 223 and sent to the MDCT circuits 227 and 228, respectively. These MDCT circuits 226 to 228 perform MDCT on the supplied signal with a block time length of 11.6 ms in the A mode. After that, the MDCT output of each of these bands is bit-allocated by the bit allocation circuit 126.

The output for each band from the A-mode compression circuit 224 is used as a judgment unit (high band judgment unit 421, middle band judgment unit 422, low band judgment) corresponding to each band of the orthogonal transform size judgment circuit 400. Part 423). These determining units 421, 422, and 423 determine the block size of the MDCT based on the scale factor of the sub information. In the example of FIG. 18, it is determined to be 11.6 ms.

The output for each band from the orthogonal transform size determination circuit 400 is divided into sub information and MDCT coefficient data and output after the previous bit assignment is released by the bit assignment release circuit 401. The MDCT coefficient data is the IMDCT circuit 40 corresponding to each band.
2, 405, 407 and is subjected to inverse MDCT to be converted into a signal on the time axis.

The above IMDCT circuits 402, 405, 4
Of the 07, the output of the IMDCT circuit 402 on the high frequency side is
The downsampling circuit 403 downsamples at a ratio of 1/2. The signal whose number of samples has been halved by the downsampling circuit 403 is the next MDC.
MDCT conversion is performed by the T circuit 404. That is, in the MDCT circuit 404, the signal whose number of samples is reduced by half by the down sampling is 23.3 ms.
MDCT is performed with the block size of. Also, IMDCT
The MDCT circuit 406 performs MDCT on the mid-range signal from the circuit 405 with a block size of 23.3 ms, and the low-range signal from the IMDCT circuit 407 is MDCT.
The circuit 408 allows M with a block size of 23.3 ms.
DCT is performed.

Thereafter, in the bit allocation circuit 409, adaptive bit allocation is coded together with the sub information, and the terminal 41
It is output from 0. As a result, the conversion from the A mode compressed signal to the B mode compressed signal is realized. In the configuration shown in FIG. 18, it is possible to keep the A-mode orthogonal transform size (block size) in the middle and high frequencies.

The present invention is not limited to the above-described embodiments, and for example, the one recording / reproducing medium (magneto-optical disk 1) and the other recording / reproducing medium (IC
The units 9 and 4 for the card 2) do not have to be integrated, and it is possible to connect the units with a data transfer cable or the like. Further, for example, audio PCM
It can be applied not only to signals but also to signal processing devices such as digital audio (speech) signals and digital video signals.

Further, the above-mentioned minimum audible curve synthesizing process may be omitted. In this case, the minimum audible curve generating circuit 32 and the synthesizing circuit 27 shown in FIG. Will be transmitted.

Further, there are various kinds of bit allocation methods, and the simplest is to use fixed bit allocation, simple bit allocation by each band energy of a signal, or bit allocation combining fixed and variable components.

Further, by driving the magneto-optical disk 1 at a rotation speed higher than the steady speed, dubbing at a speed higher than the bit compression rate may be performed. In this case, high-speed dubbing can be performed within the range permitted by the data transfer rate.

Finally, FIG. 19 shows a schematic block diagram of a decoding device corresponding to the high efficiency coding device of this embodiment. In FIG. 19, input terminals 152, 155, 1
Coded data from the above coding device is supplied to 56, and sub information data from the above coding device is supplied to input terminals 153, 155, and 157. The encoded data and the sub-information data are transmitted to the respective decoding circuits 146, 1
47 and 148, and the decoding circuit performs a process of decoding the encoded data based on the sub information data. The decoded data is, for example, an IMDCT circuit 1 that performs a process (IMDCT process) opposite to the MDCT process in the MDCT circuits 13, 14, 15 of the encoding device.
43, 144, 145. In addition, each IMDCT
The circuits 143, 144 and 145 are also supplied with the sub information data. Therefore, I in the IMDCT circuits 143, 144, 145
MDCT processing is also performed based on this sub information data. The output of the IMDCT circuit 143 is sent to a band synthesizing filter (IQMF) circuit 141 that performs a process reverse to that of the QMF band division filter 11. Also, the above IM
The outputs of the DCT circuits 144 and 145 are band synthesizing filters (IQMs) that perform processing reverse to that of the band dividing filter 12.
F) It is sent to the circuit 142. The output of the band synthesis filter circuit 142 is also sent to the band synthesis filter circuit 141. Therefore, the band synthesis filter circuit 141
From this, a digital audio signal in which the signals divided into the respective bands are combined is obtained. This audio signal is output from the output terminal 130.

[0127]

As is apparent from the above description, according to the digital signal processing apparatus and method and the recording medium of the present invention, a band narrower than the pass band width determined by the sampling frequency is efficiently coded. Then, by sub-sampling the high band, coding can be achieved efficiently and with a minimum hardware scale. In addition, regardless of the bit rates of the plurality of modes, the use of the same sampling frequency complicates the sampling frequency signal generation circuit that occurs when the plurality of sampling frequencies are used.
It is possible to prevent an increase in I scale. Also, when the sampling frequency of each mode is different, it is possible to easily transfer information between the modes, which was difficult, and to transfer the high bit rate mode information on the large capacity magneto-optical disk to the small capacity IC card in the low bit rate mode. When you want to write with, you do not need to completely cancel the compression mode and return to the signal on the time axis, you can obtain the low bit rate mode compression processing with only additional processing, and the increase in the amount of processing calculation is minimal. It can be suppressed by and real-time processing is possible. In addition, the reduction of the signal pass band in the low bit rate mode is performed by not performing the calculation processing of the unnecessary band on the high frequency side so that the processing calculation amount is reduced or the surplus calculation capacity is used to improve the sound quality of the low bit rate mode. Can be used for additional calculation processing. That is, if the entire high-frequency side divided band is unnecessary, it is not necessary to process the divided band at all, and even if it is partially used, sub-sampling of only the used band avoids arithmetic processing for the unused band. be able to.

Next, as the mode becomes lower in bit rate, it becomes necessary to prevent deterioration of sound quality due to a decrease in usable bits. In the present invention, compression is performed by increasing the maximum processing time block. Has gained efficiency. By increasing the time length of the processing block, it is possible to perform accurate signal conversion from the time axis to the frequency axis, and it is also possible to reduce the amount of sub information such as scale factor and word length information. In addition, by increasing the frequency width of the quantization noise generation block on the frequency axis in at least most of the blocks, the frequency division close to the critical band even if the bandwidth is narrowed in the low bit rate mode. Since it can be performed in the low frequency range, it is possible to prevent a decrease in efficiency as in the case of equal division. In the low bit rate mode, useless bit use can be prevented by not allocating main and sub information to a band above the used band.

When the bandwidth is narrowed, and the frequency division width for controlling the quantization noise is constant regardless of the frequency, the 20 kHz band is divided into 32, and the low critical bandwidth becomes 100 Hz. On the other hand, it becomes very wide at about 700 Hz, and it becomes wider than the critical band in most bands, and the efficiency is remarkably lowered. However, in the present invention, the frequency division width for controlling the quantization noise is set to the critical bandwidth. So that it becomes wider as the frequency becomes higher in at least most of the frequency division bands. Further, in order to avoid the deterioration of sound quality due to the decrease of the bit rate as much as possible, the mode having the lower maximum bit rate has the longer maximum compression processing block. When dubbing bit-compressed data from one recording medium such as a magneto-optical disk to another recording medium such as the IC card, the processing operation is performed by performing the dubbing as it is or without performing the bit expansion without performing the bit expansion. The amount can be reduced. In addition, so-called high-speed dubbing can be performed according to the compression rate, and the amount of information is small and dubbing can be performed efficiently in a short time.

[Brief description of drawings]

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

FIG. 2 is a diagram for explaining the recorded contents of a magneto-optical disk and an IC card.

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

FIG. 4 is a block circuit diagram showing a specific example of a high-efficiency compression encoding encoder that can be used for bit rate compression encoding according to the present embodiment.

FIG. 5 is a diagram showing a data structure of a processing block in each mode of bit compression.

FIG. 6 is a block circuit diagram showing a specific circuit that performs a bit allocation calculation.

FIG. 7 is a diagram showing spectra of bands divided in consideration of each critical band and block floating.

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 another specific circuit for performing a bit allocation calculation.

FIG. 11 is a diagram showing bit allocation when the signal spectrum is flat in another specific circuit that performs a bit allocation calculation.

FIG. 12 is a diagram showing a noise spectrum when the signal spectrum is flat in another specific circuit that performs a bit allocation calculation.

FIG. 13 is a diagram showing bit allocation when the tonality of a signal spectrum is high in another specific circuit that performs a bit allocation calculation.

FIG. 14 is a diagram showing a noise spectrum when the signal spectrum in the other specific circuit that performs the bit allocation calculation has a high narrative.

FIG. 15 is a diagram regarding frequency and time showing a frequency band of 52 divisions in consideration of a critical band and a block floating in a processing block of 11.6 ms.

FIG. 16 is an explanatory diagram of a case where the maximum processing time block length is increased between modes having different bit rates.

FIG. 17 is a block circuit diagram showing a specific configuration for narrowing the signal bandwidth between modes having different bit rates.

FIG. 18 is a block circuit diagram showing another specific configuration for increasing the maximum processing time block length between modes having different bit rates.

FIG. 19 is a block circuit diagram showing a specific example of a high-efficiency encoding decoder that can be used for bit rate compression encoding according to the present embodiment.

[Explanation of symbols]

1 --- Optical magnetic disk 2 --- IC card 3 --- Additional compression / expansion block 5 ... ···· Recording / reproducing device 6 ···· Magneto-optical disk insertion part 7 ···· IC card insertion slot 10 ···・ ・ ・ ・ ・ Acoustic signal input terminal 11,12 ・ ・ ・ Band splitting filter 13,14,15 ・ ・ ・ ・ MDCT circuit (orthogonal transformation circuit) 18 ・ ・ ・ ・ ・Bit Allocation Coding Circuit 20 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Bit Allocation Calculation Circuit 21 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Allowable Noise Level Calculation Function Input Terminal 22 ・ ・ ・ ・ ・ ・ ・ ・ Band Energy detection circuit for each 23 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Convolution filter circuit 27 ・ ・ ・ ・ ・ ・ ・ ・ ・ ・ Combining circuit 28 ・ ・ ・ ・ ・・ ・ ・ ・ Subtractor 30 ・ ・ ・ ・ ・ ・ Allowable noise correction circuit 31 ・ ・ ・ ・ ・ ・ Allowable noise level calculation function output terminal 32 ・ ・ ・ ・ ・ ・Minimum audible curve generating circuit 33 ... Correction information output 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 65 ... Encoder 66 ... Magnetic head drive circuit 71 ... Decoder 73 ATC decoder 74 D / A converter 121 -Low-pass filters 122, 123, 222, 223 ... QMF filters (division filters) 124 ... High-frequency signal processing circuit 125, 403 ... Down-sampling circuit 126, 127, 128 , 225, 226, 228 ...
MDCT circuit 129, 226 ... Bit allocation circuit (bit allocation circuit) 141, 142 ... Band synthesis filter 143, 144, 145 ... IDCT circuit 146, 147, 148 ... Decoding circuit 153 155, 157 ... Decoding sub information input terminal 152, 154, 156 ... Decoding main information input terminal 224 ... A mode compression circuit 400 ... Orthogonal transformation Size determination circuit 401 ・ ・ ・ ・ ・ ・ ・ ・ Bit allocation release circuit 402 ・ ・ ・ ・ ・ ・ High band IMDCT circuit 404 ・ ・ ・ ・ ・ ・ ・ ・ High band MDCT circuit 405 ・ ・ ・・ ・ ・ Mid-range IMDCT circuit 406 ・ ・ ・ ・ ・ ・ ・ ・ Mid-range MDCT circuit 407 ・ ・ ・ ・ ・ ・ Low-range IMDCT circuit 408 ・ ・ ・ ・ ・ ・ Low-range MDCT circuit Circuit 4 09 --- bit allocation circuit (re-bit allocation circuit) 410 --- Encoder output terminal 421 --- High frequency determination section 422 ---・ ・ ・ Middle range judgment part 423 ・ ・ ・ ・ ・ ・ Low range judgment part

Claims (41)

[Claims] 1. A digital signal is decomposed into a plurality of frequency band components which are signals on a time axis to obtain a plurality of signal components in a two-dimensional block relating to time and frequency, and the signal components are quantized to compress information. In a digital signal processing device having an information compression means for recording or transmitting the information and / or an information decompression means for reproducing or receiving signal components in a plurality of two-dimensional blocks relating to the time and frequency at which the information is compressed, A digital signal processing device characterized by sub-sampling the frequency band component on the high frequency side obtained as. 2. A digital signal is decomposed into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks regarding time and frequency, and the information is compressed by quantizing each two-dimensional block regarding the time and frequency. Information compression means for recording or transmitting together with the information compression parameters for each two-dimensional block concerning the time and frequency, and / or
In a digital signal processing device having information decompression means for reproducing or receiving information-compressed signal components in a plurality of two-dimensional blocks concerning time and frequency using information compression parameters for each two-dimensional block concerning time and frequency, It has a mode of recording and / or reproducing, or a mode of transmitting and / or receiving of a plurality of information bit rates, and in a mode of a lower information bit rate, a frequency band component on the high frequency side obtained as a time axis signal is obtained. A digital signal processing device characterized by sub-sampling. 3. A digital signal is decomposed into a plurality of frequency band components which are signals on a time axis to obtain a plurality of signal components in a two-dimensional block relating to time and frequency, and the signal components are quantized to compress information. In a digital signal processing device having an information compression means for recording or transmitting the information and / or an information decompression means for reproducing or receiving signal components in a plurality of two-dimensional blocks relating to the time and frequency at which the information is compressed, The frequency band component on the high frequency side obtained as
A digital signal processing device characterized in that it is not sent to an information signal means to be reproduced or received, and sub-sampling a time axis signal in a lower band adjacent to a frequency band that is not transmitted. 4. A digital signal is decomposed into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks regarding time and frequency, and the information is compressed by quantizing each two-dimensional block regarding the time and frequency. Information compression means for recording or transmitting together with the information compression parameters for each two-dimensional block concerning the time and frequency, and / or
In a digital signal processing device having information decompression means for reproducing or receiving information-compressed signal components in a plurality of two-dimensional blocks concerning time and frequency using information compression parameters for each two-dimensional block concerning time and frequency, It has a mode of recording and / or reproducing, or a mode of transmitting and / or receiving of a plurality of information bit rates, and in a mode of a lower information bit rate, a frequency band component on the high frequency side obtained as a time axis signal is obtained. A digital signal processing device, characterized in that it is not sent to an information expansion means for reproduction or reception, and sub-sampling a time axis signal in a lower frequency band adjacent to a frequency band that is not transmitted. 5. A digital signal is decomposed into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks regarding time and frequency, and the information is compressed by quantizing each two-dimensional block regarding the time and frequency. Information compression means for recording or transmitting together with the information compression parameters for each two-dimensional block concerning the time and frequency, and / or
In a digital signal processing device having information decompression means for reproducing or receiving information-compressed signal components in a plurality of two-dimensional blocks concerning time and frequency using information compression parameters for each two-dimensional block concerning time and frequency, It has a recording and / or reproducing mode or a transmitting and / or receiving mode of a plurality of information bit rates, and at least the frequency width of the two-dimensional block regarding the time and the frequency is made different between at least two modes. The digital signal processing device according to claim 2 or 4, characterized in that. 6. The frequency width of the two-dimensional block with respect to time and frequency is widened when converting a signal mode from a higher bit rate mode to a lower bit rate mode. The described digital signal processing device. 7. The frequency width of the two-dimensional block with respect to time and frequency is increased by an integral multiple when converting a signal mode from a higher bit rate mode to a lower bit rate mode. The described digital signal processing device. 8. The input signal is an audio signal, and the frequency width of a block that controls the generation of at least most of the quantization noise is made wider in a higher frequency range. 4. The digital signal processing device according to 4, 5, 6 or 7. 9. The information compression means uses orthogonal transformation to decompose a digital signal into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks with respect to time and frequency, and / or 9. The digital signal processing device according to claim 8, wherein the information decompression means uses an inverse orthogonal transform to transform the signal components in the plurality of two-dimensional blocks regarding time and frequency into digital signals on the time axis. 10. The information compressing means decomposes the digital signal into a plurality of frequency band components, and first divides the digital signal into a plurality of bands in order to obtain signal components in a plurality of two-dimensional blocks regarding time and frequency. Forming a block consisting of a plurality of samples for each band, and performing orthogonal transformation for each block in each band to obtain coefficient data, and / or, in the information decompression means, a time axis signal from a plurality of bands on the frequency axis. For the conversion to, perform the inverse orthogonal transform for each block of each band,
10. The digital signal processing device according to claim 9, wherein each inverse orthogonal transform output is combined to obtain a combined signal on the time axis. 11. A mode having a lower information rate, a maximum orthogonal transform block length of a signal to be recorded and / or reproduced,
Alternatively, the digital signal processing apparatus according to claim 10, wherein the digital signal processing apparatus has a mode in which a maximum orthogonal transform block length of a signal to be transmitted and / or received is increased. 12. The information compressing means sets a division frequency width in dividing the signal on the time axis before orthogonal transformation into a plurality of bands on the frequency axis, and / or the information decompressing means on the frequency axis after inverse orthogonal transformation. 11. The composite frequency width from a plurality of bands in the combination of the plurality of bands into the time axis signal is the same in two consecutive lowest bands.
Alternatively, the digital signal processing device according to item 11. 13. The information compressing means sets a divided frequency width in dividing the signal on the time axis before orthogonal transformation into a plurality of bands on the frequency axis, and / or the information decompressing means on the frequency axis after inverse orthogonal transformation. 13. The synthesis frequency width from a plurality of bands in the synthesis from the plurality of bands to the signal on the time axis is set to be broader in a substantially higher range.
The described digital signal processing device. 14. In any information rate mode, the maximum orthogonal transform block length of a signal to be recorded and / or reproduced on the high frequency side in the information compression means, or transmission and / or reception in the information expansion means. 14. The digital signal processing device according to claim 10, 11, 12 or 13, wherein the maximum orthogonal transform blocks of the signals have the same length. 15. The digital signal processing apparatus according to claim 14, wherein the sampling frequencies of all modes are the same. 16. The digital signal processing apparatus according to claim 15, wherein the main information and / or the sub information of the compression code is not assigned to the signal component in the band substantially equal to or more than the signal pass band. 17. A digital signal is decomposed into a plurality of frequency band components which are signals on a time axis to obtain a plurality of signal components in a two-dimensional block regarding time and frequency, and the signal components are quantized to compress information. In the digital signal processing method, there is provided an information compression processing step for recording or transmitting the information, and / or an information expansion processing step for reproducing or receiving the signal components in a plurality of two-dimensional blocks relating to the time and frequency at which the information is compressed, A digital signal processing method characterized by subsampling a frequency band component on a high frequency side obtained as a time axis signal. 18. A digital signal is decomposed into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks regarding time and frequency, and the information is compressed by quantizing each two-dimensional block regarding the time and frequency. An information compression processing step of recording or transmitting the information compression parameter for each two-dimensional block concerning the time and frequency, and / or a plurality of two information compression time and frequency related information.
A digital signal processing method comprising: an information decompression processing step of reproducing or receiving a signal component in a dimensional block using information compression parameters for each of the two-dimensional blocks relating to the time and frequency, and recording and recording of a plurality of information bit rates. And / or a mode for reproducing and / or a mode for transmitting and / or receiving, and in a mode of a lower information bit rate, a digital feature characterized by subsampling a frequency band component on a high frequency side obtained as a time axis signal. Signal processing method. 19. A data signal is decomposed into a plurality of frequency band components which are signals on a time axis to obtain a plurality of signal components in a two-dimensional block concerning time and frequency, and the signal components are quantized to compress information. In the digital signal processing method, there is provided an information compression processing step of recording and transmitting the information, and / or an information decompression processing step of reproducing or receiving the signal components in a plurality of two-dimensional blocks relating to the time and frequency of the information compression. , The frequency band component on the high frequency side obtained as a time axis signal,
A digital signal processing method characterized in that it is not sent to an information expansion processing step to be reproduced or received, and sub-sampling of a time axis signal in a lower frequency band adjacent to a frequency band not transmitted. 20. A digital signal is decomposed into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks regarding time and frequency, and the information is compressed by quantizing each two-dimensional block regarding the time and frequency. An information compression processing step of recording or transmitting the information compression parameter for each two-dimensional block concerning the time and frequency, and / or a plurality of two information compression time and frequency related information.
A digital signal processing method having an information decompression processing step of reproducing or receiving a signal component in a three-dimensional block using information compression parameters for each two-dimensional block relating to time and frequency, and recording and / or recording a plurality of information bit rates. Or has a mode for reproducing, or a mode for transmitting and / or receiving,
In the lower information bit rate mode, the frequency band component on the high frequency side obtained as the time axis signal is not sent to the information expansion processing step for reproduction or reception, and
A digital signal processing method characterized by sub-sampling a time axis signal in a lower band adjacent to a frequency band not transmitted. 21. A digital signal is decomposed into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks regarding time and frequency, and the information is compressed by quantizing each two-dimensional block regarding the time and frequency. An information compression processing step of recording or transmitting the information compression parameter for each two-dimensional block concerning the time and frequency, and / or a plurality of two information compression time and frequency related information.
In a digital signal processing method having an information decompression processing step of reproducing or receiving a signal component in a dimensional block using information compression parameters for each two-dimensional block relating to the time and frequency, recording and / or recording of a plurality of information bit rates is performed. 21. A reproduction mode or a transmission and / or reception mode, and at least the frequency width of the two-dimensional block regarding the time and the frequency is different between at least two modes. The described digital signal processing method. 22. When converting a signal mode from a higher bit rate mode to a lower bit rate mode,
21. The digital signal processing method according to claim 18, wherein the frequency width of the two-dimensional block regarding the time and frequency is widened. 23. When converting a signal mode from a higher bit rate mode to a lower bit rate mode,
23. The digital signal processing method according to claim 22, wherein the frequency width of the two-dimensional block regarding the time and the frequency is increased by an integral multiple. 24. The input signal is an audio signal, and the frequency width of a block for controlling the generation of at least most of the quantization noise is made wider in a higher frequency range. , 20, 21, 22, or 23, the digital signal processing method. 25. In the information compression processing step, orthogonal transformation is used to decompose the digital signal into a plurality of frequency band components to obtain signal components in a plurality of two-dimensional blocks with respect to time and frequency, and / or Alternatively, in the information expansion processing step, inverse orthogonal transform is used for transforming signal components in a plurality of two-dimensional blocks regarding time and frequency into digital signals on a time axis.
The described digital signal processing method. 26. In the information compression processing step, the digital signal is decomposed into a plurality of frequency band components, and first divided into a plurality of bands in order to obtain signal components in a plurality of two-dimensional blocks regarding time and frequency, Forming a block composed of a plurality of samples for each of the divided bands, performing orthogonal transform on each block of each band to obtain coefficient data, and /
Alternatively, in the information expansion processing step, in the conversion from a plurality of bands on the frequency axis to the time axis signal, inverse orthogonal transform is performed for each block of each band, and each inverse orthogonal transform output is combined to generate a combined signal on the time axis. 26. The digital signal processing method according to claim 25, wherein the method is obtained. 27. The mode having a lower information rate, the maximum orthogonal transform block length of a signal to be recorded and / or reproduced in the information compression processing step, or the maximum orthogonal of a signal to be transmitted and / or received in the information expansion processing step. 27. The digital signal processing method according to claim 26, wherein the conversion block has a mode in which the length of the conversion block is increased. 28. The divided frequency width in dividing the time axis signal before orthogonal transformation in the information compression processing step into a plurality of bands on the frequency axis and / or after the inverse orthogonal transformation in the information expansion processing step. 28. The digital signal processing method according to claim 27, wherein the combined frequency widths from a plurality of bands in the combination of a plurality of bands on the frequency axis into a time axis signal are the same in two consecutive lowest bands. . 29. The divided frequency width in dividing the time axis signal before orthogonal transformation in the information compression processing step into a plurality of bands on the frequency axis and / or after the inverse orthogonal transformation in the information expansion processing step. 29. The digital signal processing method according to claim 28, wherein a combined frequency width from a plurality of bands in combining a plurality of bands on the frequency axis into a time axis signal is made wider toward a higher frequency band. 30. In any information rate mode, the maximum orthogonal transform block length of a signal to be recorded and / or reproduced on the high frequency side or the maximum orthogonal transform block length of a signal to be transmitted and / or received. 30. The digital signal processing method according to claim 27, 28 or 29, characterized in that the heights are the same. 31. The digital signal processing method according to claim 30, wherein the sampling frequencies of all modes are the same. 32. The digital signal processing method according to claim 15, wherein the main information and / or the sub information of the compression code is not assigned to the signal component in the band substantially equal to or more than the signal pass band. 33. The method according to claim 17, 18, 19, 20, 2.
A recording medium characterized by recording compressed data compressed by the digital signal processing method described in 6, 30, or 31. 34. The recording medium according to claim 33, comprising a magneto-optical disk, wherein the compressed data is recorded on the magneto-optical disk. 35. The recording medium according to claim 33, comprising a semiconductor recording medium, wherein the compressed data is recorded on the semiconductor recording medium. 36. The recording medium according to claim 35, wherein the semiconductor recording medium is an IC memory card, and the compressed data is recorded in the IC memory card. 37. The recording medium according to claim 33, comprising an optical disc recording medium, wherein the compressed data is recorded on the optical disc recording medium. 38. The digital signal processing device according to claim 9, wherein a modified discrete cosine transform is used as the orthogonal transform. 39. The digital signal processing device according to claim 25, wherein a modified discrete cosine transform is used as the orthogonal transform. 40. A mode in which at least one band on the low frequency side is canceled, then the size of the orthogonal transform is expanded to perform the orthogonal transform, and a mode in which the rate is reduced is obtained. Alternatively, the digital signal processing device according to item 12. 41. After canceling at least one orthogonal transform, the orthogonal transform size is enlarged and orthogonal transform is performed to obtain a mode with a reduced rate.
The digital signal processing method according to item 7 or 28.