JP3371462B2 - Audio signal recording / playback device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention records audio signals.
Audio signal recording / playback device for recording and playing (hereinafter,
"Audio recorder").

[0002]

2. Description of the Related Art At present, a tape recorder using a magnetic tape is widely used as a small audio recorder. However, since the tape recorder includes complicated mechanical parts and electromagnetic conversion parts, there is a limit to miniaturization, it is weak against vibration, the battery life is short, the mechanical part is worn repeatedly, and random access is difficult. However, there are drawbacks such as a limited start-up speed for recording / playback.

On the other hand, the recent progress in semiconductor technology has been remarkable, and the capacity of semiconductor memories has been significantly increased. Along with this, various applications to the AV field such as audio recording and image recording of a semiconductor memory have been considered. The application examples of the semiconductor memory to voice recording are used for various products such as answering machines, various toys, and station announcement machines, although the recording time is still short.

[0004]

Since an audio recorder using a conventional semiconductor memory as a recording medium is configured to record an audio signal with a constant amount of information, the recording time is determined by the capacity of the semiconductor memory. If the memory runs out during recording, it will be necessary to temporarily stop recording and replace it with a new semiconductor memory, and important information will be lost or the music signal will be interrupted halfway. There was a problem such as.

Further, since a conventional tape recorder using a magnetic tape and an audio recorder using a semiconductor memory as a recording medium are configured to record an audio signal in a fixed length frame, the audio data to be recorded is fixed. The high-efficiency coding method of compressing to the rate is also MPEG
As in the audio encoding method of, the audio data of one frame (for example, 384 samples) is encoded so as to be a fixed-length encoded frame. However, when the audio data is compressed with a predetermined sound quality, the information amount of each frame is different. For example, the silent portion has almost no information amount, and the information amount increases at the portion where abrupt changes such as attack sounds occur. Therefore, in an encoding method in which a signal of one frame is encoded by a fixed length frame, more bits than necessary are allocated to a frame having a small amount of information and conversely, necessary bits are allocated to a frame having a large amount of information. There is a problem that it is not possible.

The present invention has been made to solve the above-mentioned problems, and a semiconductor memory having a predetermined capacity can be recorded even if no recording time is provided (although there is a recording time as a guide). It is an object of the present invention to obtain a semiconductor memory audio recorder capable of continuously recording without interruption of music or interruption of music signal.

It is another object of the present invention to obtain a semiconductor memory audio recorder which can record in a semiconductor memory with high sound quality more efficiently (recording time can be lengthened).

It is another object of the present invention to reproduce recorded data at high speed from a semiconductor memory recorded in variable length frames.

Furthermore, "quick listening" is performed by skipping unnecessary portions such as silent portions from the data recorded in the semiconductor memory and reproducing only the portion in which the necessary data is recorded.
It is an object of the present invention to obtain a semiconductor memory audio recorder capable of performing.

[0010]

An audio device according to the present invention
The signal recording device converts the audio signal into a digital signal.
Audio signal recording apparatus for encoding and recording on recording medium
And the audio signal into multiple hierarchical code blocks
Even if there is a lack of hierarchical code blocks
Audio signal with only high priority hierarchical code blocks
Has a priority in each hierarchical code block so that
A layered encoding means for performing additional encoding, and the recording medium described above.
Hierarchical code with lower priority when the storage capacity reaches a predetermined amount
The recording area where the audio signal of the block is written.
Audio from hierarchical code blocks with higher priority
Control means for overwriting the audio signal and recorded on the recording medium.
The identification signal of the hierarchical level of the audio signal to be recorded
An identification signal recording means for recording on the body,
To do.

Audio signal reproducing apparatus according to the present invention
Converts the audio signal into a digital signal and
Codes in order from the hierarchical block with the lowest priority.
Divided into a plurality of hierarchical blocks by the hierarchical coding means
Audio that plays back audio signals recorded on a recording medium
A signal reproducing device, the reading speed of the recording medium
Variable speed reproduction control means that can change the
Decoding only signals with low audio data hierarchy levels
Takes less time to decrypt and higher levels of decryption
According to the hierarchical decoding means
Based on the reproduction speed of the variable speed reproduction control means, the hierarchical decoding
Find the decoding time assigned to the stage and decode within this time
Judge the possible hierarchy levels and instruct the above hierarchy decoding means.
And a decoding hierarchy level determining means for outputting an indication.
And

Audio signal recording apparatus according to the present invention
Records audio signals encoded into digital signals
In an audio signal recording device for recording on a medium,
Divide the audio signal into multiple hierarchical blocks and
Priorities to the hierarchy and the lowest priority hierarchy block.
Audio quality deteriorates even if the
Although it is a hierarchical code that can decode a normal audio signal
A coding means is provided, and the data is input in the hierarchical coding means.
Split a digital audio signal into multiple frequency bands
Sub-band dividing means, input digital audio
The signal is orthogonally transformed into the frequency domain and audible based on auditory characteristics
Audible component extraction means for extracting components,
The first information that calculates the amount of information for each subband for each
Each is based on the information volume calculation means and the total amount of information for each sub-band.
A second information amount calculating means for calculating the information amount of the frame,
The final average allocated information amount approaches the desired bit rate.
Control the amount of allocated information to determine the allocated bandwidth.
Control means, and the amount of information and allocation information for each sub-band.
The total amount of bandwidth information allocated to each tier is
From the low frequency side so that it matches the amount of assigned information for each layer
It has a band deciding unit that decides the allocated band of each tier.
It is possible to change the allocation bandwidth and allocation information amount for each frame.
Characterize.

Audio signal recording apparatus according to the present invention
Divides the audio signal into multiple hierarchical blocks,
Hierarchical blocks are given priority so that they have the lowest priority.
Audio products even if they are lacking in order from the highest hierarchical block
Normal quality audio signal can be decoded although quality is degraded
Audio signal recording apparatus equipped with an effective hierarchical encoding means
The input digital audio signal
Sub-band dividing means for dividing into wave number bands, input di
The digital audio signal is orthogonally transformed into the frequency domain and
Audible component extraction means for extracting audible components based on sex,
Calculate the amount of instantaneous information using the audible component for each frame
Instantaneous information amount calculation means, several frames with constant allocated bandwidth
Is set as 1 cycle, and from the average value of the audible components of 1 cycle
Calculate the average information amount to calculate the average information amount for each subband
Means, the final average allocation information amount to the desired bit rate
One cycle for the amount of instantaneous information in each frame
Increase or decrease the section allocation information amount according to the average allocation information amount.
Control means to control so that each sub-band
Assigned to each layer based on the average amount of information and section allocation information amount
The total amount of bandwidth information is the section allocation information for each tier
To match the amount of each layer for one cycle from the low frequency side
Each cycle has a bandwidth determining means for determining the allocated bandwidth.
For each bandwidth allocated to each layer,
For each audible component in each allocated band according to its magnitude
Allocate every cycle by reallocating bits
It is possible to change the amount of allocated information for each frame
Characterize.

Audio signal recording apparatus according to the present invention
Divides the audio signal into multiple hierarchical blocks,
Hierarchical blocks are given priority so that they have the lowest priority.
Audio products even if they are lacking in order from the highest hierarchical block
Normal quality audio signal can be decoded although quality is degraded
Audio signal recording apparatus equipped with an effective hierarchical encoding means
The input digital audio signal
Sub-band dividing means for dividing into wave number bands, input di
The digital audio signal is orthogonally transformed into the frequency domain and
Audible component extraction means for extracting the audible component based on sex,
The amount of information for each subband for each frame from the listening component
Information amount calculation means to calculate, from the information amount for each sub-band
Instantaneous information amount calculation that calculates the instantaneous information amount for each frame
First means for smoothing changes in the amount of information for each subband
Smoothing means, the final average allocation information amount is the desired bit
For the instantaneous information amount of each frame to approach the rate,
Increase or decrease the instantaneous allocation information amount according to the average allocation information amount.
Control means to control like this
A second smoothing means for smoothing
Based on the smoothed information amount and the smoothed assigned information amount
Information amount of the bandwidth allocated to each layer for each frame
Is low so that the total of
Bandwidth determination means to determine bandwidth allocation for each layer from the area side
However, the allocation band of each layer that changes slowly for each frame
Audible components in each allocated band for each frame
On the other hand, reallocating bits according to its size
Change the allocated bandwidth gently in each frame,
The feature is that the amount of allocation information in the allocated bandwidth is variable
It

In addition, the frame according to the desired bit rate
Extract the difference between the amount of information per program and the amount of bit allocation information
Comparison means, third smoothing means for smoothing the extracted difference
Stage, and the difference from the third smoothing means is the coding ratio.
It has a conversion means to convert to the desired bit rate and allocation
Coding ratio that changes gently according to the cumulative value of the information difference
Is calculated by multiplying the information amount of each frame by
In variable-length frame coding by controlling the amount of information
Control the amount of information to be averaged to a predetermined bit rate
Is characterized by.

[0016]

[0017]

[0018]

[0019]

[0020]

According to the audio signal recording apparatus of the present invention,
Recording medium by encoding audio signals into digital signals
When recording the audio signal on the
Divide into locks and give priority to each hierarchical code block
If the storage capacity of the recording medium reaches a specified amount,
Audio signal of hierarchical code block with low priority
From the recording area in which the
Overwrite the audio signal of the hierarchical code block and
Identification of hierarchical levels of audio signals recorded on recording media
The signal was recorded on the recording medium.

According to the audio signal reproducing apparatus of the present invention
For example, an audio signal is converted into a digital signal,
Encode signal in order of lowest priority hierarchical block
Is divided into multiple hierarchical blocks by hierarchical coding
When playing back the audio signal recorded on the recording medium
The read speed of the recording medium is variable, and
Only signals with low hierarchical level of encrypted audio data
Decoding process takes a short time, and the hierarchical level
Hierarchical recovery is performed so that the decoding processing time becomes longer as it gets higher.
Playback speed for encoding and reading the above recording medium for playback
Degree to obtain the decoding time assigned to hierarchical decoding.
Determining the level that can be decoded within the time
To determine the decodable hierarchy level that should be
It was

According to the audio signal recording apparatus of the present invention
For example, audio signals are encoded into digital signals and recorded
When recording on a medium, the audio signal is
Divide into locks, give priority to each hierarchical block,
The hierarchical blocks with the lowest priority are missing in order.
Audio quality is degraded, but normal audio
In the hierarchical coding that can decode the
The digital audio signal is divided into multiple frequency bands (subbands).
Input) and divides the input digital audio signal.
Orthogonal transform to the wave number domain and extract audible components based on auditory characteristics
From each audible component for each sub-band for each frame
Calculate the first amount of information and total the amount of information for each subband
The second information amount of each frame is calculated by
Allocation so that the amount of information uniformly allocated approaches the desired bit rate
It controls the amount of allocated information to determine the bandwidth and
Each layer based on the amount of information and the amount of assigned information for each subband
The total amount of bandwidth information allocated to each layer
Allocate the bandwidth of each layer from the low frequency side to match the amount of information.
Decide and change allocation bandwidth and allocation information amount for each frame
I decided to.

According to the audio signal recording apparatus of the present invention
For example, divide the audio signal into multiple hierarchical blocks,
Hierarchical blocks are given priority so that they have the lowest priority.
Audio products even if they are lacking in order from the highest hierarchical block
Normal quality audio signal can be decoded although quality is degraded
When recording an audio signal with effective hierarchical coding
The input digital audio signal at multiple frequencies.
It is divided into bands (subbands) and the input digital audio
Orthogonal transform of Dio signal to frequency domain and based on auditory characteristics
To extract the audible component, and use the audible component for each frame
The instantaneous amount of information is calculated by
The average of the audible components in the 1 cycle
The average amount of information for each subband is calculated from the values, and the final
The average allocation information amount is adjusted so that it approaches the desired bit rate.
1-cycle section allocation information for instantaneous information amount of frame
Control to increase / decrease the amount of information according to the average amount of assigned information.
And the average amount of information and section allocation information for each subband.
The total amount of bandwidth information allocated to each tier is
Low-frequency side to match the section allocation information amount for each layer
To determine the allocated bandwidth of each layer for one cycle from
For each bandwidth allocated to each layer, each frame
For each audible component in each allocated band,
Therefore, by re-allocating bits,
The allocation bandwidth is made variable for each frame.
I did it.

According to the audio signal recording apparatus of the present invention
For example, divide the audio signal into multiple hierarchical blocks,
Hierarchical blocks are given priority so that they have the lowest priority.
Audio products even if they are lacking in order from the highest hierarchical block
Normal quality audio signal can be decoded although quality is degraded
When recording an audio signal with effective hierarchical coding
The input digital audio signal at multiple frequencies.
It is divided into bands (subbands) and the input digital audio
Orthogonal transform of Dio signal to frequency domain and based on auditory characteristics
To extract the audible components, and to support each frame from the audible components.
Information for each subband is calculated by calculating the amount of information for each band.
The amount of instantaneous information is calculated for each frame from
The first smoothing that smoothes the change in the amount of information for each
The final average allocated information amount approaches the desired bit rate
The instantaneous allocation information amount for each frame
Control to increase / decrease according to the average allocation information amount
Second smoothing for smoothing changes in the instantaneous allocation information amount
, And smoothed information amount and sub-band for each sub-band.
Each floor for each frame based on the amount of allocated information
The total amount of bandwidth information allocated to each layer is the percentage of each layer.
Allocated bandwidth of each layer from the low frequency side to match this information amount
Of each layer that gradually changes for each frame
The audible signal within each allocated band for each frame
Re-allocate components according to their size
This allows the allocated bandwidth to be changed gently in each frame.
In this case, the amount of allocation information within the allocated bandwidth is variable.
To collect.

In addition, the frame according to the desired bit rate
Extract the difference between the information amount per bit and the bit allocation information amount,
Performing a third smoothing to smooth the extracted difference, and
The third smoothed difference is converted into a coding ratio, and the desired
Gradually according to the cumulative value of the difference between the bit rate and the allocation information
Multiply the amount of information in each frame by the changing coding ratio
By controlling the amount of information allocated by
The amount of information in ram coding is averaged over a predetermined bit rate.
Configured to control.

[0026]

[0027]

[0028]

[0029]

[0030]

[0031]

[0032]

[0033]

[0034]

[0035]

[0036]

EXAMPLES Example 1. Embodiment 1 of the present invention will be described below with reference to the drawings. In the first embodiment, in order to simplify the description, the number of hierarchical code block divisions for audio encoding is set to 2, but the basic idea is the same even when the number of divisions increases. Figure 1
, 1 is an audio signal input terminal, 2 is an audio amplifier for adjusting the audio level required in the next stage,
3 is an A / D for converting an audio signal into a digital signal
A converter, 4 is a hierarchical encoder for hierarchically encoding a digital audio signal, 5 is a semiconductor memory which is a recording medium of an audio signal, 6 is a semiconductor memory 5 and a hierarchical encoder 4
The memory address controller for writing the audio signal from the specified address to the specified address, and reading the audio signal from the specified address and sending it to the hierarchical decoder 7, and 7 is for decoding the audio signal encoded by the hierarchical encoder 4. Hierarchical decoder, 8 is a D / A converter for converting a digital audio signal into an analog audio signal, and 9 is a D / A
An audio amplifier 10 for adjusting the output of the converter to an audio level required for negotiations, 10 is an output terminal of an audio signal, and 14 is a clock generator.

FIGS. 2 and 3 show that in the hierarchical encoder 4,
It is the figure which showed the example of a structure which performs the 2 division encoding of the digitized audio signal. In the configuration example of FIG. 2, 16
The high-order 8 bits of the bit digital audio signal are divided into the hierarchical code block 1 and the lower 8 bits are divided into the hierarchical code block 2.

Further, in the configuration example of FIG. 3, the audio frequency is divided into four subbands by the four-division subband division filter 15, and the bit allocator 16 makes the hierarchical code block 1 and the hierarchical code for each subband. Bit allocation to block 2 is determined, and control is performed so that the sum of the signal amounts of hierarchical code block 1 and hierarchical code block 2 for each subband is divided into two.

In both the configuration examples of FIGS. 2 and 3, by assigning the higher-order bit side of the quantized bit to the higher-order hierarchical code block 1, even if the lower-order hierarchical code block 2 is missing. ,, although the sound quality is deteriorated, the audio signal can be reproduced.

Further, in the band division method of FIG. 3, the bit allocation is optimized in consideration of human hearing characteristics, so that the sound quality is deteriorated even when the audio signal is only the hierarchical code block 1. Can be reduced as much as possible.

FIG. 4 shows a memory map on the semiconductor memory 5, which is composed of a control data area for recording an identification code of an audio hierarchical code block, an audio area A for recording an audio signal, and an audio area B. FIG. 5 shows how an audio signal is recorded in the semiconductor memory 5 with the lapse of time.

Next, the operation of the recording system will be described first. In FIG. 1, the audio signal input to the input terminal 1 is amplified to a predetermined level by the audio amplifier 2, converted into a digital signal by the A / D converter 3, and input to the hierarchical encoder 4. In the hierarchical encoder 4, a signal for recording the digitized audio signal in the hierarchical code block 1 by the method shown in FIG. 2 or 3,
It is divided into two signals to be recorded in the hierarchical code block 2.

The coded signal divided into two is recorded in the semiconductor memory 5 as shown in the memory map of FIG. At the start of recording, as shown in FIG. 5A, the recording flow is such that the hierarchical code block 1 encoded by the encoder 4 is present in the audio area A and the hierarchical code block 2 is present in the audio area B. It is recorded in order. FIG. 5B shows a state where the audio signals are sequentially recorded and the memory 5 is almost full.

FIG. 5C shows that the audio signal writing area (audio area B in this case) of the hierarchical code block 2 having a lower priority is overwritten in order to record a more continuous audio signal. , Only the hierarchical code block 1 of the audio signal is recorded.

FIG. 5D shows a state where the recording area is full due to such overwriting. The memory address controller 6 controls the memory address according to the signal from the memory capacity detector 13 so that the flow described in FIG. In the case of FIGS. 5A and 5B, the hierarchy level identification code is "hierarchical level 1", which means that the hierarchical code block "00"
In the case of FIGS. 5C and 5D, the layer code block "01" is recorded because it is "layer level 2".

At the time of reproduction, first, the hierarchy level identification code reproducer 12 checks the identification code of the hierarchy level. In the case of "00", that is, "hierarchical level 1", the audio area A and audio area of the semiconductor memory 5 are checked. B
Are sequentially accessed to output the reproduced audio signal to the hierarchical decoder 7. When the identification code of the hierarchy level is "01", that is, "hierarchy level 2", the semiconductor memory 5 is sequentially accessed from the audio area A (when the audio area A ends, the audio area B is continuously accessed. ), And outputs the reproduced audio signal to the hierarchical decoder 7.

The hierarchical decoder 7 is configured to decode the reproduced signal from the semiconductor memory 5 into a digital audio signal in both cases of "layer level 1" and "layer level 2"("layerlevel"). In the case of the reproduction signal of "2", zero may be input to the signal of the hierarchical code block 2 by the hierarchical level identification code.

The output of the hierarchical decoder 7 is the D / A converter 8
Is converted into an analog audio signal by the audio amplifier 9, amplified by the audio amplifier 9 to a predetermined audio level, and output from the output terminal 10. It should be noted that a clock required for the entire system during recording / reproduction such as a sampling clock is supplied from the clock generator 14.

Example 2. FIG. 6 is a block circuit of a second embodiment of the present invention, in which the same reference numerals as those in FIG. 1 indicate the same parts, and 17 is a recording capacity capable of recording all of the audio signals encoded by the hierarchical encoder 4. First semiconductor memory with room to spare, 18
Is a second semiconductor memory having a predetermined capacity for storing audio data (a removable memory card or the like), 1
Reference numeral 9 denotes a hierarchical level converter which, when dubbing an audio signal from the first semiconductor memory 17 to the second semiconductor memory 18, determines the second semiconductor memory according to the audio recording time output from the memory capacity detector 13. The total signal amount is controlled by dropping the hierarchical code blocks having the low priority of block coding so as to exactly match the memory capacity of 18.

Reference numeral 20 is a first memory address controller which controls the first semiconductor memory 17 to record the audio signal from the hierarchical encoder 4 at a predetermined address, and the first memory address controller 20.
When dubbing from the semiconductor memory 17 to the second semiconductor memory 18, the transfer speed is increased to control the reading of the data of the first semiconductor memory 17. Reference numeral 21 denotes a second memory address controller, which controls to read an audio signal from a second semiconductor memory at a predetermined address, and
When dubbing from the first semiconductor memory 17 to the second semiconductor memory 18, the transfer speed is increased to control writing of data to the second semiconductor memory.

Next, the operation of the recording system will be described. The audio signal input to the input terminal 1 is amplified to a predetermined level by the audio amplifier 2, converted into a digital signal by the A / D converter 3, and input to the hierarchical encoder 4. As shown in FIG. 2 or 3, the hierarchical encoder 4 encodes the signals of two hierarchical code blocks having priorities. Similar to the first embodiment, the audio signal can be normally reproduced even though the sound quality is deteriorated even when the hierarchical code block having the low priority is omitted and only the hierarchical code block having the high priority is left. The audio signal divided into two blocks and encoded is recorded in the first semiconductor memory 17 according to the address signal from the first memory address controller 17. First
Since the semiconductor memory 17 has a sufficient capacity, all the input audio signals will be recorded.

Next, the dubbing operation from the first semiconductor memory 17 to the second semiconductor memory 18 will be described.
The memory capacity detector 13 detects the recording time of the audio signal written in the first semiconductor memory 17, and sends this detection signal to the hierarchical level converter 19, where the memory capacity of the second semiconductor memory 18 and Are compared to determine whether or not the signal needs to be reduced, and if so, how much to reduce, and when reducing, the hierarchy level is changed according to the ratio. That is, the hierarchical code block with the lower priority is dropped.

In the second embodiment, the number of divisions of the data is set to 2. However, the larger the number of divisions, the finer the control of the recording time and the deterioration degree of the sound quality, and the more efficient the semiconductor memory is. It can be used often (the recording time and the degree of sound quality deterioration have a linear relationship).

Further, this hierarchical level is sent to the hierarchical level identification code generator 11, and the identification code is simultaneously recorded in the control area of the second semiconductor memory 18. Further, at the time of dubbing, the addressing of the first memory address controller 17 and the second memory address controller 18 is operated at a high speed, and the dubbing is performed at a high speed within the range permitted by the memory access speed. This high-speed dubbing function is an important function to make it appear as if one recording is performed, even though there are two sets of recording media (semiconductor memories).

At the time of reproduction, first, the hierarchy level identification code reproducer 12 determines the identification code from the control area of the second semiconductor memory 18, and sends the result to the second memory address controller 21. Second memory address controller 21
Is the second from the predetermined address in order according to the hierarchy level.
The read signal is read from the semiconductor memory 18 of FIG.

The hierarchical decoder 7 decodes the reproduced signal of any hierarchical level according to each. The output of the hierarchical decoder 7 is converted into an analog audio signal by the D / A converter 8, amplified by the audio amplifier 9 to a predetermined audio level, and output from the output terminal 10. A clock such as a sampling clock required for reproduction is supplied from the clock generator 14.

[0057] real施例3. The third embodiment of the present invention will be described below with reference to FIGS. In the third embodiment, the number of hierarchical code block divisions for hierarchical encoding is four, but the idea is the same even when the number of divisions is different. In FIG. 7, the same reference numerals as those in FIG. 1 denote the same parts, 22 is a digital audio signal hierarchical encoder, 23 is a memory adrel controller, and the audio signal from the hierarchical encoder 22 is stored in the semiconductor memory 5. Is written into a predetermined address for each layer, the audio signal of each layer is read from the predetermined address, and the capacity of the semiconductor memory 5 is detected.
When the semiconductor memory 5 becomes full, the audio signals which have been sequentially written over are sequentially overwritten from the memory area of the data written as the low-priority hierarchical code block by the hierarchical encoder 22 among the already written data. To control. A hierarchical decoder 24 decodes the audio signal encoded by the hierarchical encoder 22.

8 and 9 show the hierarchical encoder 22 in which
It is a figure for demonstrating the content which divides | segments a digital audio signal into 4 and performs hierarchical encoding. First, in FIG.
Signals are classified from the input original audio signals, that is, they are roughly classified into three types: a signal that cannot be heard originally due to the minimum audibility limit which is a human auditory characteristic, a signal that cannot be heard due to a masking effect, and a signal that can be heard further. Next, it is shown that only the signal heard from among these is selected and further divided into four hierarchical levels according to the frequency characteristics shown in FIG.

FIG. 10 shows a hierarchical level 22 hierarchical encoder 22.
2 and a recording method for recording in the semiconductor memory 5, 27 is a division filter for dividing the audio signal converted into a digital signal by the A / D converter 3 into predetermined blocks, and 28 is a division filter. MD of the signal
MDCT converter that performs orthogonal transform by CT, 29 is a block size setting device that sets the conversion block size of MDCT 28 according to the change of the input signal, and 30 is a grouping device that groups the coefficients of MDCT 28 according to the critical band based on auditory psychology. , 31 are shown in FIGS.
According to the classification of the audio signals shown in, a layering / quantizer for removing inaudible signals and layering and quantizing the audible signals into four hierarchical levels, 32 is a method of only audible signals in each frequency band A dynamic bit allocator that determines whether to allocate bits, 33 is a scale factor calculator that determines a scale factor according to a block of the MDCT 28, and 34 is a formatter for recording and formatting for recording in the semiconductor memory 5. The right side of FIG. 10 shows the concept of recording hierarchically encoded data in the semiconductor memory 5.

FIG. 11 is a diagram showing a memory map on the semiconductor memory 5, which is composed of a control data area for recording identification codes of hierarchical levels and an audio area for recording audio signals (hierarchical level 1 to hierarchical level 4). Further, (1) to (4) in FIG. 11 show the recording state of the audio signal in the semiconductor memory 5 with the passage of time. That is, (1) is a state in which the audio signal encoded at the hierarchical level 4 is recorded up to the memory full, (2) is the case where the situation in (1) has passed and the audio signal is continuously recorded. In the state where the recording area of level 4 is overwritten with hierarchical levels 1 to 3, (3) is the case where the situation of (2) has passed and the audio signal is continuously recorded, the hierarchical level up to the recording area of hierarchical level 3 1 to 2 overwriting state, (4) when the situation of (3) has passed and audio signals are continuously recorded, the recording area of hierarchy level 2 is overwritten in hierarchy level 1 (on the memory All the signals of (become the hierarchical level 1).

Next, the operation of the portion different from the first embodiment at the time of recording will be described. The audio signal converted into a digital signal by the A / D converter 3 and input to the hierarchical encoder 22 is hierarchically encoded data by the method shown in FIGS. 8, 9 and 10 in the hierarchical encoder 22. And is recorded in the semiconductor memory 5. In the hierarchical coder 22, first, the audio signal is divided into predetermined blocks by the division filter 27, while the block size setting unit 29 determines the supple size for MDCT. If there is little change in the amplitude of the clipped sample, increase the block size of MDCT, and if the change in amplitude is large, M
The block size of the DCT is reduced to suppress the occurrence of pre-echo.

In the MDCT converter 28, the division filter 2
MDCT conversion is performed for each frequency band divided in 7.
The transform coefficients are grouped into critical bands by the grouping unit 30 based on auditory psychology, and divided into four bands by the layering / quantizing unit 31 according to the following rules. FIG. 9 shows the band and range.

1. First, as hierarchical level 1, coefficients from a low frequency band to a predetermined frequency band f1 are selected from the coefficients divided into a plurality of frequency bands, and the quantization level of the coefficient is also predetermined from the MSB side. The number of bits is selected and used as encoded data S1 of hierarchical level 1.

2. Next, as the hierarchical level 2, a coefficient up to a predetermined frequency band f2 higher than f1 is selected, and the quantization level of the coefficient is also selected from the MSB side by a predetermined number of bits larger than the hierarchical level 1, and this signal is selected. The residual signal obtained by subtracting the signal component of the coefficient of the layer level 1 corresponding to each coefficient from is defined as the encoded data S2 of the layer level 2.

3. Next, as the hierarchical level 3, a coefficient up to a predetermined frequency band f3 higher than f2 is selected, and the quantization level of the coefficient is also selected from the MSB side by a predetermined number of bits larger than the hierarchical level 2, and this signal is selected. To the residual signal obtained by subtracting the signal components of the coefficients of the hierarchical levels 1, 2, and 3 corresponding to each coefficient from the encoded data S3 of the hierarchical level 3.
And

4. Similarly, as hierarchical level 4, coefficients up to a predetermined frequency band f4 higher than f3 are selected,
Also, the quantization level of the coefficient is selected from the MSB side by a predetermined number of bits larger than that selected in the hierarchical level 3, and from this signal, the corresponding hierarchical levels 1, 2, and 3 for each coefficient are selected.
The residual signal obtained by subtracting the signal component of the coefficient is used as the encoded data S4 of the hierarchical level 4.

On the other hand, the dynamic bit allocator 32 determines how to allocate bits for each frequency band in MDCT block units, and the scale factor calculator 33 determines the maximum of each coefficient in MDCT block units. Extract the value and normalize the value of each sample by this maximum value. In the formatter 34, the scale factor, bit allocation, and hierarchical data (S1, S2, S
3, S4) are formatted and sent to the semiconductor memory 5.

The hierarchical audio signal sent to the semiconductor memory 5 is shown in FIG.
As shown on the right side of FIG. 0, first, at the hierarchical level 4, the semiconductor memory 5 is classified and recorded for each hierarchical level. When the semiconductor memory 5 becomes full and the recording memory runs out, the continuous audio signal is overwritten by the hierarchical levels 1 to 3 in the memory area written in the next hierarchical level 4. FIG. 11 shows this state on the memory map. The above description shows the recording state of FIG. 11 (1) → (2). Hierarchical level identification code generator 25
In the state of FIG. 11 (1), the identification code “11” is generated because it is the maximum hierarchy level 4, and in the state of FIG. 11 (2) is the maximum hierarchy level 3, the identification code “10” is generated. It is recorded in the control data area of the memory 5.

Similarly, as the recording state progresses as shown in FIG. 11 (2) → (3) → (4), the hierarchical level becomes 3 → 2 → 1 and the identification code to be recorded is also “10” → “01”. → "0
In this case, the maximum recording time is when the semiconductor memory 5 finally becomes an audio signal of only the hierarchical level 1, and the information amount of each hierarchical level (1 to 4) is the same. If so, the recorded audio quality will be lower than that in the state of FIG. 11A, but the recording time will be four times longer.

At the time of reproduction, first, the code level identification code reproducer 16 checks the hierarchical level identification code. The memory address controller 6 receives this information, and FIG.
The audio signal recorded in accordance with the memory map is read from the semiconductor memory 5. First, when the identification code is “15”, that is, when the hierarchy level is 4,
The signals of hierarchical levels 1 to 4 are read out according to the memory map of (1). When the identification code is "10", that is, level 3, the signals of the hierarchical levels 1 to 3 are read out according to the memory map of FIG. And so on
When the identification code is “01” and the hierarchy level is 2,
According to the memory map of (3), the signals of the hierarchical levels 1 and 2 are identified by FIG.
The signal of the hierarchical level 1 is read according to the memory map of 1 (4).

In the hierarchical decoder 23, the signal read from the semiconductor memory 5 is decoded by the identification signal from the hierarchical level identification code regenerator 16 according to the hierarchical level. ing. Hierarchical decoder 23
The output of is converted into an analog audio signal by the D / A converter 8 and is output from the audio output terminal 10 through the audio amplifier 9 which amplifies a predetermined audio level. A clock required for the entire system such as a sampling clock during recording / reproduction is supplied from the clock generator 14.

Example 4. Next, a fourth embodiment of the present invention will be described with reference to FIGS. FIG. 12 is a block circuit diagram of the fourth embodiment, and the same reference numerals as those in FIG. 7 denote the same parts. In FIG. 12, reference numeral 35 is an address switch, which switches between the memory address from the write address generator 36 and the memory address from the read address generator 37. The write address generator 36 generates an address for writing the hierarchically encoded audio signal in the semiconductor memory 5.
The read address generator 37 generates an address for reading the hierarchically encoded audio signal from the semiconductor memory 5 according to the reproduction clock from the clock frequency divider 39. Reference numeral 38 denotes a hierarchical level determiner, which changes the decoding calculation time given to the hierarchical decoder 24 depending on the reproduction speed of the audio signal (that is, if the reproduction speed increases, the calculation time given for decoding a predetermined number of audio samples will be The shorter the playback speed is, the longer the computation time required for decoding a predetermined number of audio samples is. In general, the hierarchical encoder and the decoder are DSP (Dig).
It is often the case that software processing is performed using an
Confidence is also performing a fairly high-speed operation, so just because the playback speed of the audio signal has become faster, it is not possible to increase the DSP operation time either), and the decoding is performed within the given operation time. It determines the possible hierarchy levels and informs the hierarchy decoder 23. 39 is a clock divider,
The clock generated by the clock generator 14 is frequency-divided by the signal from the reproduction speed setting switch and sent to the read address generator 37. Reference numeral 40 is a switch that constitutes a reproduction speed setting device.

FIG. 13 is a diagram showing the relationship between the audio decoding time and the reproduction speed according to the fourth embodiment.
(B) shows a case where all four hierarchical level signals can be decoded during normal reproduction. On the other hand, FIG.
(D) shows that when the reproduction speed is doubled, the decoding operation can be completed only for the signals of two hierarchical levels.

Next, the operation of the portion different from that of the third embodiment at the time of recording will be described. In the audio signal hierarchically encoded by the hierarchical encoder 22, the write address generated by the write address generator 36 is selected by the address switch 35, is applied to the semiconductor memory 5, and is recorded at a predetermined address.

At the time of reproduction, first, the address switch 3
5, the read address of the semiconductor memory 5 is switched to the read address generator 37. In the read address generator 37, it is set by the reproduction speed setting device 40.
A clock divider 39 produces a clock for the read address generator 37 according to the read speed (configured to be controlled by N). An audio signal is read from the semiconductor memory 5 according to the set reproduction speed, and is decoded by the hierarchical decoder 24. The decoding hierarchy level in this case changes the decoding operation time given to the hierarchy decoder 24 depending on the reproduction speed of the audio signal as shown in FIG. It is determined by the hierarchy level determiner 40.

In the normal reproduction shown in FIGS. 13 (a) and 13 (b),
All four hierarchical level signals can be decoded, while FIG.
It is shown that when the reproduction speeds of (c) and (d) are doubled, the decoding operation can be normally performed up to the signals of two hierarchical levels. If the playback speed is doubled, the playback audio signals will all have twice the frequency, ie 5k.
Since the signal component of Hz shifts to 10 kHz and the signal component of 10 kHz shifts to 20 kHz, it is practically 10 k.
Signals above Hz will exceed the audible range,
Decoding of hierarchical levels 3 or 4 having many high frequency components is almost unnecessary. From this, it can be said that the method of decoding only the hierarchical levels 1 and 2 as shown in FIGS. 13C and 13D is a very suitable method. The output of the hierarchical decoder 24 is converted into an analog audio signal by the D / A converter 8 and is output from the audio output terminal 10 through the audio amplifier 9 which amplifies a predetermined audio level.

Example 5. Embodiment 5 of the present invention will be described below with reference to the drawings. The Brook circuit diagram of the fifth embodiment is similar to that of the third embodiment shown in FIG. In addition, the conceptual diagram of the hierarchical encoding of the semiconductor memory audio recorder according to the fifth embodiment is also the third embodiment.
Since it is the same as FIG. 8 of FIG.

FIG. 14 is a hierarchical encoder 22 according to the fifth embodiment.
FIG. 10 is a diagram showing a mode of division of the hierarchical level of FIG. Hereinafter, the number of code block divisions of hierarchical coding is set to 4 as in the third embodiment, and the classification of the input original audio signal is the minimum audibility limit which is a human auditory characteristic as in FIG. 8 of the third embodiment. Therefore, the signals that cannot be heard, the signals that cannot be heard due to the masking effect, and the signals that can be heard are roughly divided into three, and only the signals that can be heard are selected. To divide.

That is, in FIG. 14, the audible components exceeding the masking level are divided into four in the frequency direction from hierarchical level 1 to hierarchical level 4 so that the information amount becomes equal, and the total information amount is the desired bit rate. To meet.

FIG. 15 is a diagram showing the structure of the hierarchical encoder 22 of the fifth embodiment and the method of recording in the semiconductor memory 5. In the figure, 41 is a sub-band n division filter, which is an A / D
The audio signal converted into the digital signal by the converter 3 is band-divided into a plurality of subbands. Reference numeral 42 denotes an audible component extracting means that transforms the audio signal into a frequency domain by FFT conversion and extracts only the audible component by masking based on the auditory characteristics. Reference numeral 43 is an information amount calculating means for each sub-band of each frame, and the information amount of each sub-band is calculated by allocating an information amount of 1 bit per 6 dB to the audible component extracted by the audible component extracting means 42. .. 44 is an information amount calculation means for each frame,
The information amount of each sub-band obtained by the information amount calculation means 43 for each sub-band is summed to calculate the information amount per one encoded frame.

Reference numeral 45 is an information amount setting unit per frame based on the coding rate for setting the information amount C per frame based on the desired coding rate, and 46 is an information amount control circuit, which is used by the information amount calculating means 44 of the Laem. According to the average allocation information amount, which is the average value of the calculated information amount of each frame and the information amount allocated to the frames encoded up to that point, the final average information amount is the information per frame based on the encoding rate. The allocation information amount assigned to each frame is calculated so as to match the setting information amount C obtained by the amount setting unit 45. Reference numeral 47 is a band determining means for each layer, which gives the allocated information amount by the information amount for each sub-band of each frame calculated by the information amount calculating means 43 and the allocated information amount calculated by the information amount control circuit 46. The optimum coding band of each layer (K1 to K4) is determined. Reference numeral 48 is a bit allocation circuit, which performs re-bit allocation according to the size of the audible component in the allocated band for each layer according to the band information allocated to each layer obtained by the band determining unit 47 of each layer. The quantization circuit quantizes each subband data according to the bit allocation information obtained by the bit allocation circuit 48.

Numeral 50 is a hierarchical coding formatter, which is allocated band information of each layer obtained by the band determining means 47 of each layer, bit allocation information obtained by the bit allocation circuit 48, and obtained by the quantizer 49. The encoded data is hierarchically encoded and formatted. Also, FIG.
The right side of 5 shows the concept of recording hierarchically encoded data in the semiconductor memory 5.

Since the memory map on the semiconductor memory 5 and the procedure for writing the audio signal are the same as those in FIG. 11 described in the third embodiment, the description thereof will be omitted.

Next, a part of the operation at the time of recording different from that of the third embodiment will be described. In the hierarchical encoder 22, the audio signal is converted into hierarchical encoded data by the method shown in FIGS. 8 and 14 and recorded in the semiconductor memory 5. In the hierarchical encoder 22, first, the audio signal is divided into n sub-bands by the sub-band n division filter 41, and at the same time, the audible component extracting means 42 orthogonally transforms the audio signal into the frequency domain by the FFT transformation, and The masking level based on the auditory characteristics is obtained in the region, and the audible component is extracted. As shown in FIG. 16A, the difference between the frequency spectrum and the masking level is the audible component. Furthermore, the audible components are grouped into subband bands by subband division, and the audible components of each subband are extracted as shown in FIG. 16 (b).

Next, in the information amount calculating means 43, the amount of information of 1 bit is given to the audible component of 6 dB, as shown in FIG.
As shown in 6 (c), the amount of information for each subband band is calculated. Then, the information amount calculation means 4 of each frame
At 4, the information amount of n subbands is added to calculate the information amount of one frame. The information amount per frame setting unit 45 based on the coding rate sets the desired coding rate to calculate the information amount C per frame based on the bit rate and sends it to the information amount control circuit 46.

In the information amount control circuit 46, according to the average information amount per frame assigned to the frames encoded up to that time, the final average assigned information amount is the information amount per frame setting unit based on the encoding rate. The allocated information amount used for determining the allocated bandwidth is determined with respect to the information amount calculated by the information amount calculation means 44 of each frame so as to match the information amount C set in (4). For example, let s be the total number of bits assigned to the previously encoded frames.
If um and the number of encoded frames are count, then sum
Average allocation information amount (M bar)
Is larger than the information amount C per frame converted from the encoding bit rate, the information amount control coefficient (K = C / M-bar)
Is multiplied by the information amount (assumed to be m) calculated by the information amount calculation means 44 for each frame to calculate the allocated information amount (assumed to be M = mK).

Next, in the band determining means 47 of each layer, the information amount for each sub-band obtained by the information amount calculating means 43 and the allocated information amount obtained by the information amount control circuit 46 are used for each layer. A band that can be covered by the amount of allocated information is calculated and used as the band of each layer. For example, if the value obtained by dividing the audio signal into 16 sub-bands and calculating the information amount for each sub-band has a value as shown in FIG. 17, the assigned information amount for that frame is 4
When the number of bits is 3 bits, the amount of information that can be assigned to each layer is determined by setting the amount of information that is assigned to each layer level from layer level 1 (K1) to layer level 4 (K4) to be equal information amount. It will be 10 bits.

The information amount is assigned to each frame in the following procedure. First, the allocated bandwidth of K1 is obtained. Since the information amount of subband 1 of the lowest band is 10 bits, the allocation information amount of K1 is 10 bits only in this subband, and the band that can be allocated as the coding band of K1 is 1 subband. . Next, the allocated bandwidth of K2 is obtained. When the information amounts of subband 2 and subband 3 are added from subbands equal to or more than the band allocated to K1, 1
It becomes 0 (6 + 4) bits, which corresponds to 10 bits allocated to K2. Therefore, the bands that can be allocated as the K2 coding band are a few subbands. Similarly, when the information amounts from subband 4 to subband 6 which are subbands equal to or more than the band allocated to K2 are added, 1
It becomes 0 bits, which matches the allocation information amount of K3, and when the information amounts from subband 7 to subband 10 are added, it becomes 10
It becomes a bit and matches the allocation information amount of K4.

As a result, the bands that can be allocated to the respective layers are 1 subband, 2 3 subbands, 4 to 6 subbands, and 7 to 10 subbands, as shown in FIG. In the bit allocation circuit 48,
Based on the band allocation information for each layer obtained by the band determining unit 47 of each layer and the audible component obtained by the audible component extracting unit 42, for the audible component in the band allocated for each layer,
Re-bit allocation is performed according to the size. For example,
As shown in FIG. 17, when bands are allocated to the respective hierarchical levels K1 to K4, the K1 band is one subband of only subband 1, the K2 band is subbands 2 and 3 of 2 subbands, and the K3 band is subband. Band 4-6, 3 subbands, K4
The bands are 4 subbands of subbands 7 to 10.

Therefore, at the hierarchical level 1, 1 bit per 6 dB is allocated to the audible component of the subband 1, and then at the hierarchical level 2, the audible component of the subbands 2 and 3 is larger than the audible component. 1 per 6 dB according to
Bits are re-bit-allocated and further sub-bands 4, 5 and 6 audible components at hierarchical level 3 and sub-bands 7, 8, 9, 10 audible components at hierarchical level 4 are re-allocated. The quantizer 49 quantizes the subband data obtained by the subband n division filter 41 according to the bit allocation information for each subband obtained by the bit allocation circuit 48. In the layered coding formatter 50, the band determination means 47 of each layer.
The bit allocation information and the quantized data are formatted for each layer according to the allocation band information of each layer obtained as described above, and are sent to the semiconductor memory 5. In the data encoded by the layer encoder 22 as described above, the information amount of each frame has a variable length, but the information amount of each layer included in one frame is an equal amount of information.

The hierarchical audio signal sent to the semiconductor memory 5 is output by the memory address controller 23 as shown in FIG.
As shown on the right side of FIG. 5, the semiconductor memory 5 is first classified and recorded in the semiconductor memory 5 at the hierarchy level 4. When the semiconductor memory 5 becomes full, a continuous audio signal is overwritten in the memory area in which the layer 4 is written at the layer level 3. This FIG. 15 shows the concept, and it is written so that the information amount of each frame is equal, but since it is actually encoded with a variable length frame, the semiconductor memory 5 is
It is controlled so that it can be stored according to the information amount of each frame.

FIG. 11 shows this state on the memory map, and the above description shows the recording state of FIG. 11 (1) → (2). In the hierarchy level identification code generator 25, in the state of FIG. 11 (1), the identification code "15" is given because the maximum hierarchy level is 4.
Since the state of (2) is the maximum hierarchy level 3, the identification code "10" is recorded. Similarly, FIG. 11 (2) → (3)
→ (4) As the recording status progresses, the hierarchy level also increases from 3 → 2 →
It becomes 1 and the identification code to be recorded is also “10” → “01” →
It becomes "00". In this case, the maximum recording time is when the audio signal of only the layer 1 finally becomes the semiconductor memory, and if the information amount of each layer (1 to 4) is the same, the state of FIG. However, although the recorded audio quality is deteriorated, the recording time is quadrupled.

At the time of reproduction, first, the hierarchy level identification code reproducer 26 checks the hierarchy level identification code. This information is received by the memory address controller 23, and FIG.
The audio signal recorded according to the memory map 1 is read from the semiconductor memory 5. When the identification code is "15", that is, the layer level 4 is shown in FIG.
The signals of layers 1 to 4 are read out according to the memory map of. When the identification code is “10”, that is, level 3, the hierarchy level 1 is set according to the memory map of FIG. 11 (2).
Read the signals of ~ 3.

Similarly, when the identification code is "01" and the hierarchy level is 2, the signals of the hierarchy levels 1 and 2 are identified by the identification code "00" in the hierarchy level 1 according to the memory map of FIG. In this case, the signal of the hierarchical level 1 is read out according to the memory map of FIG. 11 (4). The hierarchical decoder 24 is configured so that the signal read from the semiconductor memory 5 is decoded according to the hierarchical level by the identification signal from the hierarchical level identification code regenerator 26. The output of the hierarchical decoder 24 is the D / A converter 8
Is converted into an analog audio signal by the audio amplifier 9 and is output from an audio output terminal 10 through an audio amplifier 9 which amplifies a predetermined audio level.

Example 6. Next, a sixth embodiment of the present invention will be described. FIG. 18 is a diagram showing the configuration of the hierarchical encoder of the semiconductor memory audio recorder according to the sixth embodiment. In the figure, reference numeral 41 denotes a subband n division filter, which divides the audio signal converted into a digital signal by the A / D converter 3 into a plurality of subbands. Reference numeral 42 denotes an audible component extracting means that transforms the audio signal into a frequency domain by FFT conversion and extracts only the audible component by masking based on the auditory characteristics.
Reference numeral 45 is an information amount setting unit per frame based on the coding rate, and sets the information amount C per frame based on the desired coding rate. Reference numeral 48 denotes a bit allocation circuit, which is based on the band information allocated to each layer of one cycle obtained by the band determining unit 54 of each layer, and according to the size of the audible component in the band allocated to each layer for each frame. Perform re-bit allocation. Reference numeral 49 is a quantizing circuit, which quantizes each subband data in accordance with the bit allocation information obtained by the bit allocation circuit 51.

Reference numeral 50 denotes a hierarchical coding formatter, which is obtained by a quantizer 49, and allocation bandwidth information of each layer obtained by the band determining means 47 of each layer, bit allocation information obtained by the bit allocation circuit 48. The data is hierarchically encoded and formatted. Reference numeral 51 denotes an average information amount calculating means, which takes an average value of the audible components extracted by the audible component extracting means 42 for a certain period of time, and assigns an information amount of 1 bit per 6 dB to the average value, so Calculate the average amount of information for each subband. Reference numeral 52 denotes an instantaneous information amount calculating means for each frame, which calculates the information amount for each encoded frame from the maximum subband information SBmax having an audible component obtained by the audible component extracting means 42. Reference numeral 53 denotes an information amount control circuit, which determines the final average information amount according to the instantaneous information amount obtained from the instantaneous information amount calculating means 52 of each frame and the average assigned information amount assigned to the frames encoded up to that point. In order to match the setting information amount C obtained by the information amount setting unit 45 per frame based on the coding rate,
The section allocation information amount for one cycle is calculated. Reference numeral 54 is a band determining means for each layer, which is an average information amount for each sub-band of each frame calculated by the average information amount calculating means 51.
Based on the section allocation information amount calculated by the information amount control circuit 53, the optimum coding band of each layer of one cycle of each layer level (K1 to K4) for giving the allocation information amount is determined.

FIG. 19 is a flow chart showing the average information amount calculating operation for each sub-band by the average information amount calculating means according to the sixth embodiment.

FIG. 20 is a flow chart showing the section allocation information amount calculation operation in the information amount control means according to the sixth embodiment.

FIG. 21 is a flow chart showing the allocated bandwidth determining operation in the bandwidth determining means 54 of each layer according to the sixth embodiment.

FIG. 22 is a flow chart showing the bit allocation operation in the bit allocation circuit 48 according to the sixth embodiment.

Next, the operation will be described. In the hierarchical encoder 22, first, the audio signal is divided into n subbands by the subband n division filter 41, and at the same time, the audio signal is F
The FT transform orthogonally transforms into the frequency domain, the masking level based on the auditory characteristics is obtained in the frequency domain, and the audible component is extracted. As shown in FIG. 16A, the difference between the frequency spectrum and the masking level is the audible component.
Furthermore, the audible components are grouped into subband bands by subband division, and the audible components of each subband are extracted as shown in FIG. 16 (b).

Next, in the average information amount calculating means 51, as shown in FIG.
As shown in the flowchart of FIG. 9, the audible component for each sub-band extracted by the audible component extracting means 42 is X.
The average value for X frames of the audible component is calculated by cumulatively adding for frames and dividing by X after addition, and the average information for X frames is given by giving the information amount of 1 bit per 6 dB to the average audible component. The quantity is calculated and used for bandwidth determination for the next cycle (X frames). The instantaneous information amount calculating means 52 for each frame estimates the instantaneous information amount from the maximum band (SBmax) in which the audible component exists, which is obtained by the audible component extracting means 42, by the following method.

23 to 25 show the maximum band SBma in which the audible component exists in the instantaneous information amount determining means according to the sixth embodiment.
Although it is a diagram showing the relationship between x and the information amount, as can be seen from these data, SBmax and the information amount are in a substantially proportional relationship, so the information amount can be estimated from SBmax. In the sixth embodiment, the instantaneous information amount is obtained by estimation using the relationship between SBmax and the information amount.
It may be calculated by giving an information amount of 1 bit per dB and adding the information amount of each subband.

The information amount per frame setting unit 45 based on the coding rate calculates the information amount C per frame based on the bit rate by setting a desired coding rate and sends it to the information amount control circuit 46. To be In the information amount control circuit 53, the final average assigned information amount is set by the information amount per frame setting unit based on the encoding rate according to the average information amount per frame assigned to the frames encoded so far. The section allocation information amount of one cycle is determined with respect to the instantaneous information amount calculated by the instantaneous information amount calculating means 52 of each frame so as to match the information amount C.

The operation of the information amount control circuit 53 is shown in FIG.
0 is shown in the flowchart. Section allocation information amount MN bar
Is calculated according to, for example, the following equation in accordance with the average allocation information amount M bar of the frames that have been encoded for each cycle of X frames and each cycle. MN bar = C + (CM bar) where C is the information amount per frame based on the coding rate, and the MN bar is controlled so that the average allocated information amount finally becomes this value. It In addition, the instantaneous allocation information amount M is calculated by multiplying the information amount control coefficient K by the instantaneous information amount m calculated by the instantaneous information amount calculation circuit 52 for each frame during one cycle. Further, the average allocation information amount M bar and the information amount control coefficient K based on the average value of the instantaneous allocation information amount are updated every cycle.

Next, in the band determining means 54 of each layer, as shown in the flow chart of FIG. 21, the average information for each sub-band obtained by the average information amount calculating means 51 for each sub-band for each cycle. Amount and the section allocation information amount for one cycle obtained by the information amount control circuit 53 are input, and the section allocation information amount is divided into four to calculate the allocation information amount for each hierarchy, and the allocation information is allocated for each hierarchy. The bandwidth that can be covered by the amount of information is calculated from the low frequency side, and this is used as the allocated bandwidth of each layer. Bit allocation circuit 4
In 8, the band allocation information for one cycle for each layer obtained by the band determining unit 54 of each layer and the audible component obtained by the audible component extracting unit 42 are input. Re-allocation is performed according to the size of the audible component in the allocated band of each layer.

The quantizer 49 quantizes the subband data obtained by the subband n division filter 41 according to the bit allocation information for each subband obtained by the bit allocation circuit 48. The hierarchical coding formatter 53 formats the bit allocation information and the quantized data for each layer according to the allocated band information for each layer obtained from the band determination unit 54 for each layer, and sends it to the semiconductor memory 5.

Example 7. Next, a seventh embodiment of the present invention will be described. FIG. 26 is a block circuit diagram showing the configuration of the hierarchical encoder of the memory audio recorder according to the seventh embodiment, and the same reference numerals as those in FIG. A low-pass filter that smoothes the information amount for each sub-band calculated by 43 to calculate the average information amount for each sub-band, and 56 smooths the instantaneous allocation information amount obtained by the information amount control circuit 46 and averages the allocation information amount. Is a low-pass filter that calculates

FIG. 27 is a diagram showing the configuration of the information amount control circuit 46 of the seventh embodiment. Reference numeral 57 denotes a comparator, which is an information amount per frame and bit allocation according to a desired bit rate obtained from the information amount setting unit 45. Circuit 5
The difference in the bit allocation information amount obtained from 1 is extracted. 5
8 is a low-pass filter for smoothing the extracted difference, 5
Reference numeral 9 is a converter for converting the difference value smoothed by the low-pass filter into a coding ratio, 60 is a multiplier, and the coding ratio K calculated by the coding ratio converter 59 is used as the information amount calculation means 44 for each frame. The information amount obtained by is multiplied to calculate the assigned information amount.

Next, the operation of the seventh embodiment will be described.
In the hierarchical encoder 22, first, the audio signal is divided into n subbands by the subband n division filter 41, and at the same time, in the audible component extracting means 42, the audio signal is orthogonally transformed into the frequency domain by the FFT transformation, and the frequency domain is obtained. At, the masking level based on the auditory characteristics is obtained, and the audible component is extracted. As shown in FIG. 16A, the difference between the frequency spectrum and the masking level is the audible component. Furthermore, the audible components are grouped into subband bands by subband division, and the audible components of each subband are extracted as shown in FIG. 16 (b). Next, the information amount calculation means gives the amount of information of 1 bit to the audible component of 6 dB to calculate the amount of information for each subband band as shown in FIG.

Then, the low pass filter 55 smoothes the information amount for each sub-band and obtains the average information amount for each sub-band. On the other hand, in the instantaneous information amount calculating means 52 of each frame, the information amount of n subbands is added to obtain 1
The information amount of the frame is calculated. The information amount per frame setting unit 45 based on the coding rate sets the desired coding rate to calculate the information amount C per frame based on the bit rate and sends it to the information amount control circuit 53. Information amount control circuit 53
Then, according to the average information amount per frame assigned to the encoded frames so far, the final average assigned information amount matches the information amount C set by the information amount per frame setting unit based on the encoding rate. Thus, the instantaneous allocation information amount is determined with respect to the information amount calculated by the information amount calculation means 44 of each frame.

Then, the low-pass filter 56 smooths the instantaneous allocation information amount and calculates the average allocation information amount. Next, in the band determination means 47 of each layer, the low pass filter 5
5 is input, and the smoothed allocation information amount obtained by the low-pass filter 56 is input, and the average allocation information amount is divided into four to divide the average allocation information amount into four. The allocation information amount is calculated, the band that can be covered by the allocation information amount for each layer is calculated from the low band side, and this is set as the allocation band for each layer.

In the bit allocation circuit 51, the audible band within each layer is audible by the band allocation information for each layer obtained by the band determining unit 47 of each layer and the audible component obtained by the audible component extracting unit 42. The components are re-bit-allocated according to their magnitude. Quantizer 49
Then, according to the bit allocation information for each sub-band obtained from the bit allocation circuit 48, the sub-band n
The subband data obtained by the division filter 41 is quantized. In the hierarchical coding formatter 50,
The bit allocation information and the quantized data are formatted for each layer according to the allocated band information for each layer obtained from the band determining unit 47 for each layer and sent to the semiconductor memory 5.

Next, the information amount control operation in the information amount control circuit 53 will be described. In the information amount control circuit 53, first, the information amount per frame and the bit allocation circuit 48 according to the desired bit rate obtained from the information amount setting unit 45 by the comparator 57.
The difference in the obtained bit allocation information amount is extracted, and the difference extracted by the low-pass filter 58 is smoothed. Next, the coding ratio converter 59 uses the low pass filter 58.
The difference value smoothed by is converted into a coding ratio, and the multiplier 60 multiplies the coding ratio K calculated by the coding ratio converter 59 by the information amount obtained by the information amount calculating means 44 of each frame. Then, the allocation information amount is calculated. By the above operation, the information amount in variable-length frame coding is controlled to a predetermined bit rate on average by gently controlling the information amount according to the accumulated value of the difference between the desired bit rate and the allocation information.

As described above, by using the hierarchical coding in which the code of each layer is configured by variable bit allocation and variable band based on the input audio signal, it is possible to efficiently record with high sound quality and to be captured in the recording time. It is possible to obtain a memory audio recorder that can record and reproduce with optimum sound quality without having to do so.

Example 8. 28 is a block circuit diagram of an eighth embodiment of the present invention, and the same reference numerals as those in FIG. 1 denote the same parts. In the eighth embodiment, the case where the data obtained by converting the audio signal into the frequency domain is quantized will be described, but the quantized data may be subband data. In FIG. 28,
Reference numeral 61 is digital audio data input to the encoder 62, and 63 is a time-frequency domain conversion circuit (hereinafter referred to as "frequency domain conversion circuit"), which converts the input digital audio data 61 into a frequency domain. Reference numeral 64 is transform coefficient data converted by the frequency domain transform circuit 63, and 65 is a bit allocation circuit, which determines bit allocation for the transform coefficient data 64 so as to obtain a predetermined sound quality based on the characteristics of the input audio signal. Reference numeral 66 is bit allocation information defined by the bit allocation circuit 65, and 67 is a quantization circuit, which quantizes the transform coefficient data 64 obtained by the frequency domain conversion circuit 63 with the number of bits given by the bit allocation circuit 65. Reference numeral 68 is quantized data quantized by the quantization circuit 67, 69 is a formatting circuit that formats the bit allocation information 66 and the quantized data 68, 70 is a frame length calculation circuit that calculates the frame length based on the bit allocation information 66, 71 Is a write address control circuit for controlling the write address according to the frame length calculated by the frame length calculation circuit 70.
An encoder 62 is composed of 3, 65, 67, 69, 70 and 71.

Reference numeral 5 is a semiconductor memory for storing coded data, 72 is bit allocation information extracted from the semiconductor memory 5, 73 is bit allocation information and a frame length calculation circuit, which stores the bit allocation information 72 in a temporary buffer. The frame length is calculated from the bit allocation information 72. A read address control circuit 74 controls the read address so that the required quantized data 75 is read from the semiconductor memory 5 in accordance with the input frame length. Reference numeral 75 is quantized data read from the semiconductor memory 5, and 76 is an inverse quantization circuit for inversely quantizing the quantized data 75 having the number of bits given by the bit allocation information 72.
And constitutes the decoder 77.

FIG. 29 shows the bit allocation circuit 6 shown in FIG.
5 shows the configuration of No. 5. In FIG. 29, a band division energy calculation circuit 78 divides the coefficient data 64 into a plurality of frequency bands and calculates the energy of each band. 7
An allowable noise level calculation circuit 9 calculates an allowable noise level of each band based on the energy of each band calculated by the band division energy calculation circuit 78. Reference numeral 80 denotes a bit allocation calculation circuit, which determines the number of bits allocated to the conversion coefficient divided into each band according to the difference between the allowable noise level of each band calculated by the allowable noise level calculation circuit 79 and the energy of each band.

FIG. 30 is a format diagram showing coded data of one frame, which is coded by the encoder 71 with high efficiency. One frame of encoded data is composed of fixed-length bit allocation information and variable-length quantized data.

FIG. 31 is a diagram showing the relationship between the masking threshold and the minimum audible limit, which is used for bit calculation in the bit allocation circuit 65. FIG. 32 is a diagram showing the energy of each band and the calculated allowable noise level.

FIG. 33 shows a case where the bit allocation information 66 and the quantized data 68 are separately recorded in the auxiliary information recording area and the quantized data recording area when the encoded data is recorded in the semiconductor memory 5. It is a figure which shows operation | movement at the time of performing a high speed reproduction.

Next, the recording operation of the eighth embodiment will be described. The audio signal 61 converted into digital data by the A / D converter 3 is input to the time-frequency domain conversion circuit 63 of the encoder 62, and the time-frequency domain conversion circuit 63 forms a block for each fixed sample. The converted coefficient data 64 is converted into a frequency domain in frame units, and the converted coefficient data 64 is input to the bit allocation circuit 65. The bit allocation circuit 65 performs bit allocation based on the characteristics of the input audio signal so as to satisfy a predetermined sound quality. The bit allocation information 66 determined by the bit allocation circuit 65 is input to the quantization circuit 67. In the quantization circuit 67, the transform coefficient data 6 is generated based on the input bit allocation information 66.
4 is quantized with the allocated number of bits. The bit allocation information 66 and the quantized data 68 are formatted by the formatting circuit 69. Further, the bit allocation information 66 is input to the frame length calculation circuit 70, and in the frame length calculation circuit 70, according to the number of bits assigned to the transform coefficient and the number of transform coefficients quantized by the number of bits,
The total number of bits assigned to the quantized data is calculated,
The number of bits of fixed-length bit allocation information sent as auxiliary information is added to this to calculate the length of one encoded frame, which is sent to the write address control circuit 71.

As described above, by recording the quantized data that is bit-allocated so as to obtain a predetermined sound quality and quantized by the number of bits and the allocated bit allocation information, one frame of a fixed length is recorded. An encoding method for encoding audio data in a variable length is hereinafter referred to as "frame length variable encoding". In the write address control circuit 71, a write address is generated according to the input frame length, the formatted compressed data is written in the semiconductor memory 5, and the write address is moved according to the frame length. As a result, encoded data is continuously recorded in the semiconductor memory 5 with a variable frame length.

Next, at the time of reproduction, the fixed-length bit allocation information 72 is read from the semiconductor memory 5 and stored in the bit allocation information buffer 73. In the bit allocation information buffer 73, the number of bits allocated to the quantized data is calculated from the input bit allocation information and sent to the read address control circuit 74. Read address control circuit 74
Then, a read address is generated according to the code length of the input quantized data, and the quantized data 75 is read from the semiconductor memory 5. The quantized data 75 read out is inversely quantized and decoded by the inverse quantization circuit 76 according to the bit allocation information input from the bit allocation information buffer 73. . The output of the decoder 77 is the D / A converter 8
Is converted into an analog audio signal by the audio amplifier 9 and is output from an audio output terminal 10 through an audio amplifier 9 which amplifies a predetermined audio level.

Next, the bit allocation operation in the bit allocation circuit 65 in the encoder 62 of the semiconductor memory recorder will be described with reference to FIG. The input conversion coefficient data 64 is divided into a plurality of frequency bands by the band division energy calculation circuit 78, and the average energy is calculated from the conversion coefficient of each band. The calculated energy of each band is input to the allowable noise level calculation circuit 79, and the allowable noise level is calculated. To calculate the allowable noise level, a masking effect, a minimum audible limit characteristic, etc. are used in order to perform compression with little deterioration in hearing in consideration of human auditory characteristics. Here, the masking effect is an effect in which a sound with a high level in a certain frequency band masks a sound in another frequency band, and the minimum audible limit is a sound with a minimum level that a human can hear.

FIG. 31 shows an example in which the allowable noise level is calculated by the masking effect and the minimum audible limit for the energy in each band. In FIG. 31, S1 to S10 represent energy in each frequency band when divided into 10 frequency bands. The diagonal lines extending from the energy of each band to the left and right are:
The area masked by the sound in that band is shown. Also, the dashed characteristic curve indicates the minimum audible limit. As the allowable noise level of each frequency band, the maximum level of the masking level from other frequency bands and the minimum audible limit is selected. In the example of FIG. 31, the allowable noise level of each selected frequency band is shown by a horizontal line in FIG. The allowable noise level calculated by the allowable noise level calculating circuit 79 and the energy of each band are input to the allocated bit calculating circuit 80.
Since the allocated bit calculation circuit 80 does not hear the sound below the allowable noise level, it calculates the number of bits corresponding to the difference between the energy of each frequency band and the allowable noise level for the sound in the band exceeding the allowable noise level. The allocation information 66 is output. The number of bits allocated in this way is based on the property of the input audio signal, and the number of bits allocated for encoding one frame is variable.

As described above, the bit-assigned encoded data of one frame is the fixed-length bit assignment information and the variable-length quantized data quantized by the assigned number of bits as shown in FIG. Is encoded and formatted. By using the fixed-length bit allocation information as the auxiliary information in this way, the number of bits allocated to the quantized data can be calculated, so that coding in a variable-length frame is possible. Further, in the semiconductor memory 5, since the recording position can be randomly determined at high speed by controlling the address, it is possible to record the code of the variable length frame.

The variable length frame code is not recorded in the format as shown in FIG. 30, but an area for recording auxiliary information and an area for recording quantized data are provided on the semiconductor memory 5, and auxiliary information is recorded. The bit allocation information 66 is continuously recorded with a fixed length in the area
Variable length quantized data is continuously recorded in the area for recording 8. As a result, the address at which the quantized data is recorded is calculated based on the fixed-length bit allocation information of the auxiliary information area, and the quantized data is read out and decoded at a predetermined frame interval, which enables high-speed reproduction.

FIG. 33 shows an example of this. In the example of FIG. 33, addresses 0 to 999 are auxiliary information (bit allocation information) recording areas and addresses 1000 are quantized data recording areas, and bit allocation information is recorded in 20 bits from address 0. The number shown in the bit allocation information is the number of bits in one frame of the quantized data calculated from the bit allocation information, and the quantized data indicated by this number is variable in the quantized data recording area. It has been recorded continuously for a long time. The numbers circled in the figure indicate frame numbers. Therefore, the number in the bit allocation information is set to the first address 1000 of the quantized data recording area.
By adding, the first address in which the quantized data is recorded can be calculated. Therefore, first, the bit allocation information in the auxiliary information is read, the address where the quantized data is recorded is calculated from the read bit allocation information, and the quantized data is read from the address calculated every 5 frames, Decoding enables high-speed reproduction at 5 times speed. Reading of the quantized data is performed by using frames 1, 6, 11, 16 ... With numbers surrounded by double circles in FIG.
The addresses of the frames that are read out in this order are 1000, 1378, 1723, 2112 ...
Becomes

As described above, a variable frame length encoding method is used in which bit allocation is performed with variable frame length so as to obtain a predetermined sound quality based on the input audio signal, and bit allocation information and quantized data are encoded. By using it and storing it in a semiconductor memory capable of high-speed random access in a variable length frame, it is possible to obtain a semiconductor memory recorder capable of recording with high sound quality and with high efficiency and capable of recording for a long time.

Example 9. Next, a ninth embodiment of the present invention will be described with reference to the drawings. Figure 3
In FIG. 4, the same reference numerals as those in FIG. 28 indicate the same parts, and 81 is a reproduction frame selection circuit, which calculates the number of bits allocated to the quantized data by the bit allocation information, and the allocated number of bits is a predetermined value. Only frames that exceed the threshold of are selected as playback frames. 82
Is the reproduction frame selection information and the reproduction frame bit allocation information obtained by the reproduction frame selection circuit 81, and 83 is the code length of the quantized data calculated by the reproduction frame selection circuit 81 and the reproduction frame selection information.

Since the recording operation of the ninth embodiment is the same as that of the first embodiment, its explanation is omitted. Next, the “fast-listening operation” during reproduction will be described. "Fast-listening" is not high-speed playback by continuously skipping data at regular intervals or fast-listening by increasing the playback speed, but a semiconductor memory recorder was used to record conversations such as conference memos. In this case, the quick listening is performed by continuously reproducing only the necessary conversational part by skipping the unrecorded part of the conversation only by the silent part or the ambient noise.

The fixed length bit allocation information 72 is read from the semiconductor memory 5 and input to the reproduction frame selection circuit 81. In the reproduction frame selection circuit 81, the number of bits allocated to the quantized data of one frame is calculated by the bit allocation information 72. Here, when bits are allocated by the method as described in the eighth embodiment, the number of bits allocated to the quantized data is 0 because all the transform coefficients have a level below the minimum audible limit in the silent part. Become.

Further, even in the portion where only noise is recorded, the number of bits assigned to the quantized data is very small because the whole level is small. Therefore, a predetermined threshold value is set for the number of bits assigned to one frame, and a frame whose assigned number of bits does not exceed the threshold value is not reproduced as a silent part or a noise part, and the threshold value is The reproduction frame selection information and the bit allocation information 82 are sent to the dequantization circuit 76 for the frames exceeding.

The code length for the quantized data of one frame calculated by the reproduction frame selection circuit 81 and the reproduction frame selection information 83 are read out by the read address control circuit 7.
Sent to 4. In the read address control circuit 74, when a frame selected as a reproduction frame is input, a read address is generated according to the code length of the input quantized data, and the quantized data 75 is generated from the semiconductor memory 5. Is read out.

In the frame not selected as the reproduction frame, the address is moved by the number of bits assigned to the quantized data. Quantized data read out 7
In the dequantization circuit 76, the quantized data of the number of bits given according to the bit allocation information 82 input together with the frame selection information is dequantized and decoded in the dequantization circuit 76. The output of the decoder 77 is converted into an analog audio signal by the D / A converter 8 and is output from the audio output terminal 10 through the audio amplifier 9 which amplifies a predetermined audio level.

As described above, in frame length variable coding in which bit allocation is performed based on the input signal, a frame with a small amount of information such as a silent part has a very small bit allocation. By playing back only the frames that exceed the threshold value of 1, the silent sections can be skipped, and only the recorded portion of the voice can be played back fast.

[0138]

As described above, the audio signal of the present invention is used.
According to the No. recording device , an audio signal is converted into a digital signal.
Audio signal recording device for encoding into a recording medium and recording to a recording medium
The audio signal into multiple hierarchical code blocks.
And lack of lower priority hierarchical code blocks
Audio signals only with hierarchical code blocks with high priority.
Prioritize each hierarchical code block so that the
A hierarchical encoding means for carrying and encoding the recording medium,
Hierarchical code with lower priority when the storage capacity reaches a certain amount
Signal in which the audio signal of the signal block is written.
The order of hierarchical code blocks with higher priority from the rear
Control means for overwriting the audio signal and recording on the recording medium
The identification signal of the hierarchical level of the audio signal to be recorded
Since the identification signal recording means for recording on the medium is provided,
The recording time of the medium can be extended and the recording capacity can be effectively utilized.
Can be used.

Audio signal reproducing apparatus according to the present invention
Converts the audio signal into a digital signal and
Codes in order from the hierarchical block with the lowest priority.
Divided into a plurality of hierarchical blocks by the hierarchical coding means
Audio that plays back audio signals recorded on a recording medium
A signal reproducing device, the reading speed of the recording medium
Variable speed reproduction control means that can change the
Decoding only signals with low audio data hierarchy levels
Takes less time to decrypt and higher levels of decryption
According to the hierarchical decoding means
Based on the reproduction speed of the variable speed reproduction control means, the hierarchical decoding
Find the decoding time assigned to the stage and decode within this time
Judge the possible hierarchy levels and instruct the above hierarchy decoding means.
Since the decoding hierarchy level determining means for issuing
Decodable for all possible hierarchy levels, variable speed playback
It is possible to output a voice sound when normal.

Audio signal recording apparatus according to the present invention
Records audio signals encoded into digital signals
In an audio signal recording device for recording on a medium,
Divide the audio signal into multiple hierarchical blocks and
Priorities to the hierarchy and the lowest priority hierarchy block.
Audio quality deteriorates even if the
Although it is a hierarchical code that can decode a normal audio signal
A coding means is provided, and the data is input in the hierarchical coding means.
Split a digital audio signal into multiple frequency bands
Sub-band dividing means, input digital audio
The signal is orthogonally transformed into the frequency domain and audible based on auditory characteristics
Audible component extraction means for extracting components,
The first information that calculates the amount of information for each subband for each
Each is based on the information volume calculation means and the total amount of information for each sub-band.
A second information amount calculating means for calculating the information amount of the frame,
The final average allocated information amount approaches the desired bit rate.
Control the amount of allocated information to determine the allocated bandwidth.
Control means, and the amount of information and allocation information for each sub-band.
The total amount of bandwidth information allocated to each tier is
From the low frequency side so that it matches the amount of assigned information for each layer
It has a band deciding unit that decides the allocated band of each tier.
Since the allocated bandwidth and the amount of allocated information can be changed for each frame,
It is divided for each frame according to the amount of information of the signal to be encoded.
Hierarchical coding by variable length coding that makes the amount of information variable
It is possible.

Audio signal recording apparatus according to the present invention
Divides the audio signal into multiple hierarchical blocks,
Hierarchical blocks are given priority so that they have the lowest priority.
Audio products even if they are lacking in order from the highest hierarchical block
Normal quality audio signal can be decoded although quality is degraded
Audio signal recording apparatus equipped with an effective hierarchical encoding means
The input digital audio signal
Sub-band dividing means for dividing into wave number bands, input di
The digital audio signal is orthogonally transformed into the frequency domain and
Audible component extraction means for extracting audible components based on sex,
Calculate the amount of instantaneous information using the audible component for each frame
Instantaneous information amount calculation means, several frames with constant allocated bandwidth
Is set as 1 cycle, and from the average value of the audible components of 1 cycle
Calculate the average information amount to calculate the average information amount for each subband
Means, the final average allocation information amount to the desired bit rate
One cycle for the amount of instantaneous information in each frame
Increase or decrease the section allocation information amount according to the average allocation information amount.
Control means to control so that each sub-band
Assigned to each layer based on the average amount of information and section allocation information amount
The total amount of bandwidth information is the section allocation information for each tier
To match the amount of each layer for one cycle from the low frequency side
Each cycle has a bandwidth determining means for determining the allocated bandwidth.
For each bandwidth allocated to each layer,
For each audible component in each allocated band according to its magnitude
Allocate every cycle by reallocating bits
Since the amount of allocated information is variable for each frame,
Depending on the amount of information of the signal to be encoded,
The amount of allocation information for each frame can be changed with respect to the allocated bandwidth
Hierarchical coding by variable length coding is possible.

Audio signal recording apparatus according to the present invention
Divides the audio signal into multiple hierarchical blocks,
Hierarchical blocks are given priority so that they have the lowest priority.
Audio products even if they are lacking in order from the highest hierarchical block
Normal quality audio signal can be decoded although quality is degraded
Audio signal recording apparatus equipped with an effective hierarchical encoding means
The input digital audio signal
Sub-band dividing means for dividing into wave number bands, input di
The digital audio signal is orthogonally transformed into the frequency domain and
Audible component extraction means for extracting the audible component based on sex,
The amount of information for each subband for each frame from the listening component
Information amount calculation means to calculate, from the information amount for each sub-band
Instantaneous information amount calculation that calculates the instantaneous information amount for each frame
First means for smoothing changes in the amount of information for each subband
Smoothing means, the final average allocation information amount is the desired bit
For the instantaneous information amount of each frame to approach the rate,
Increase or decrease the instantaneous allocation information amount according to the average allocation information amount.
Control means to control like this
A second smoothing means for smoothing
Based on the smoothed information amount and the smoothed assigned information amount
Information amount of the bandwidth allocated to each layer for each frame
Is low so that the total of
Bandwidth determination means to determine bandwidth allocation for each layer from the area side
However, the allocation band of each layer that changes slowly for each frame
Audible components in each allocated band for each frame
On the other hand, reallocating bits according to its size
Change the allocated bandwidth gently in each frame,
Since the amount of allocation information within the allocated bandwidth is variable, it is possible to
Hierarchical coding by frame coding is possible.

Also, the frame rate according to the desired bit rate
Extract the difference between the amount of information per program and the amount of bit allocation information
Comparison means, third smoothing means for smoothing the extracted difference
Stage, and the difference from the third smoothing means is the coding ratio.
It has a conversion means to convert to the desired bit rate and allocation
Coding ratio that changes gently according to the cumulative value of the information difference
Is calculated by multiplying the information amount of each frame by
In variable-length frame coding by controlling the amount of information
Control the amount of information to be averaged to a predetermined bit rate
The average amount of information in variable length frame coding is
You can control to a constant bit rate.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a semiconductor memory audio recorder according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration example of a hierarchical coding system according to a first embodiment.

FIG. 3 is a diagram illustrating another configuration example of the hierarchical encoding system according to the first embodiment.

FIG. 4 is a memory map of the semiconductor memory according to the first embodiment.

FIG. 5 is a diagram showing a recording process of recording an audio signal in Example 1 in a semiconductor memory.

FIG. 6 is a block circuit diagram of a semiconductor memory audio recorder according to a second embodiment of the present invention.

FIG. 7 is a block circuit diagram of a semiconductor memory audio recording / reproducing apparatus according to a third embodiment of the present invention.

FIG. 8 is a diagram for explaining the concept of hierarchical coding according to the third embodiment.

FIG. 9 is a frequency characteristic diagram showing hierarchical levels of hierarchical coding according to the third embodiment.

FIG. 10 is a diagram showing a concept of a configuration of a hierarchical encoder and a recording system in a semiconductor memory according to a third embodiment.

FIG. 11 is a memory map of a semiconductor memory according to a third embodiment.

FIG. 12 is a block circuit diagram of a semiconductor memory audio recording / reproducing apparatus according to Embodiment 4 of the present invention.

FIG. 13 is a diagram showing a relationship between an audio decoding time and an audio reproduction time according to the fourth embodiment.

FIG. 14 is a frequency characteristic diagram showing hierarchical levels of hierarchical encoding of the semiconductor memory audio recording / reproducing apparatus according to Examples 5 to 7 of the present invention.

FIG. 15 is a diagram showing a configuration of a hierarchical encoder and a concept of a recording system in a semiconductor memory according to a fifth embodiment.

FIG. 16 is a diagram showing how audible components are extracted and the amount of information is calculated in the layered encoders of Embodiments 5 to 7.

[Fig. 17] Fig. 17 is a diagram illustrating a state of determining an allocation band of each layer in a layer encoder of Examples 5 to 7.

[Fig. 18] Fig. 18 is a diagram illustrating the configuration of a hierarchical encoder according to a sixth embodiment.

FIG. 19 is a flowchart showing an average information amount calculation operation for each subband by the information amount calculation means of the sixth embodiment.

FIG. 20 is a flowchart showing the operation of calculating the section allocation information amount in the information amount control means of the sixth embodiment.

FIG. 21 is a flow chart showing the operation of determining the allocated bandwidth in the bandwidth determining means of each layer of the sixth embodiment.

FIG. 22 is a flowchart showing the bit allocation operation in the bit allocation circuit of the sixth embodiment.

FIG. 23 is a diagram showing the relationship between the maximum band SBmax in which an audible component exists and the information amount in the instantaneous information amount determination means of the sixth embodiment.

FIG. 24 is a diagram showing the relationship between the maximum band SBmax in which an audible component exists and the information amount in the instantaneous information amount determining means of the sixth embodiment.

FIG. 25 is a diagram showing the relationship between the maximum band SBmax in which an audible component exists and the amount of information in the instantaneous information amount determination means of the sixth embodiment.

FIG. 26 is a diagram showing the structure of a hierarchical encoder of a semiconductor memory audio recording / reproducing apparatus according to Example 7 of the present invention.

[Fig. 27] Fig. 27 is a diagram illustrating the configuration of an information amount control circuit of a hierarchical encoder according to a seventh embodiment.

FIG. 28 is a block circuit diagram of a semiconductor memory audio recording / reproducing apparatus according to Embodiment 8 of the present invention.

FIG. 29 is a diagram showing the configuration of a bit allocation circuit of the encoder according to the eighth embodiment.

FIG. 30 is a diagram showing a format of a coded frame according to the variable frame length coding method of the eighth embodiment.

FIG. 31 is a diagram showing a manner of calculating an allowable noise level using the masking effect and the minimum audible limit in the bit allocation circuit of the encoder of the eighth embodiment.

FIG. 32 is a diagram showing the permissible noise level and energy of each band in the bit allocation circuit of the encoder of the eighth embodiment.

FIG. 33 is a memory map for explaining high speed reproduction according to the eighth embodiment.

FIG. 34 is a block circuit diagram of a semiconductor memory audio recording / reproducing apparatus according to Embodiment 9 of the present invention.

[Explanation of symbols]

3 A / D converter 4 Hierarchical encoder 5 Semiconductor memory 6 Memory address controller 7 Hierarchical decoder 8 D / A converter 11 Hierarchical level identification code generator 12 Hierarchical level identification code regenerator 13 Memory capacity detector 15 Sub-band division filter 16 Bit allocator 17 First semiconductor memory 18 Second semiconductor memory 19 Hierarchical level converter 20 First memory address controller 21 Second memory address controller 22 Hierarchical encoder 23 Memory address control Device 24 Hierarchical decoder 25 Hierarchical level identification code generator 26 Hierarchical level identification code regenerator 27 Division filter 28 MDCT 29 Block size setting device 30 Grouping device 31 Hierarchization / quantization device 32 Dynamic bit allocation device 33 Scale factor calculator 34 Formatting device 35 Address switching device 36 Built-in address generator 37 Read address generator 38 Hierarchical level determiner 39 Clock frequency divider 40 Reproduction speed setter 41 Subband n division filter 42 Audible component extraction means 43 Information amount calculation means 44 for each subband of each frame Information amount calculating means for frame 45 Information amount setting device per frame based on coding rate 46 Information amount control circuit 47 Band determining means for each layer 51 Average information amount calculating means for each subband 52 Instantaneous information amount calculation for each frame Means 53 Information amount control circuit 54 Band determining means 55 for each layer Information amount smoothing filter 56 for each sub-band Allocation information amount smoothing filter 57 Information amount comparator 58 Difference information amount smoothing filter 59 Coding ratio converter 62 Code 65 bit allocation circuit 67 quantization circuit 70 frame length calculation times Path 71 Write address control circuit 73 Bit allocation information buffer and frame length calculation circuit 74 Read address control circuit 77 Decoder 78 Band division energy calculation circuit 79 Allowable noise level calculation circuit 80 Allocation bit calculation circuit 81 Reproduction frame selection circuit 82 Reproduction Frame selection information and bit allocation information 83 Reproduction frame selection information and code length of quantized data

─────────────────────────────────────────────────── ─── Continuation of the front page (31) Priority claim number Japanese Patent Application No. 5-18050 (32) Priority date January 7, 1993 (Jan. 1, 1993) (33) Priority claim country Japan (JP) Preliminary examination (56) References JP-A-64-53642 (JP, A) JP-A-3-117181 (JP, A) JP-A-3-117921 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) G10L 19/00

Claims (6)

(57) [Claims] 1. An audio signal recording apparatus for encoding an audio signal into a digital signal and recording it on a recording medium, wherein the audio signal is divided into a plurality of hierarchical code blocks, and a hierarchical code block with a low priority is lacking. In the case where the storage capacity of the recording medium reaches a predetermined amount, a hierarchical coding means for coding each hierarchical code block with priority so that an audio signal can be decoded only by a hierarchical code block having a high priority. Control means for sequentially overwriting the audio signals of the hierarchical code blocks of higher priority from the recording area in which the audio signals of the hierarchical code blocks of lower priority are sequentially written, and the hierarchical level of the audio signals recorded on the recording medium. An audio signal recording device, comprising: an identification signal recording means for recording an identification signal on the recording medium. apparatus. 2. An audio signal recorded on a recording medium by dividing an audio signal into a digital signal and dividing the signal into a plurality of hierarchical blocks by hierarchical coding means for sequentially coding from the hierarchical block having the lowest priority. An audio signal reproducing device for reproducing, wherein a variable speed reproduction control means capable of varying a read speed of the recording medium and a decoding process time is short in decoding only a signal having a low hierarchical level of the hierarchical audio data. The hierarchical decoding means that the decoding processing time becomes longer as the hierarchical level becomes higher, and the decoding time assigned to the hierarchical decoding means is obtained from the reproduction speed of the variable speed reproduction control means, and the hierarchy that can be decoded within this time is obtained. A decoding hierarchy level determining means for determining a level and giving an instruction to the hierarchy decoding means. Audio signal playback device. 3. An audio signal recording apparatus for encoding an audio signal into a digital signal and recording it on a recording medium, wherein the audio signal is divided into a plurality of hierarchical blocks,
Each hierarchical block is given a priority, and even if the hierarchical blocks having the lowest priority are lacking in order, the audio quality is deteriorated, but a hierarchical coding unit capable of decoding a normal audio signal is provided, and the hierarchical block is provided. Subband dividing means for dividing the input digital audio signal into a plurality of frequency bands in the encoding means, audible component extracting means for orthogonally converting the input digital audio signal into the frequency domain, and extracting audible components based on auditory characteristics, audible A first information amount calculating means for calculating the information amount for each sub-band for each frame from the component, a second information amount calculating means for calculating the information amount for each frame by the total information amount for each sub-band, and finally Controls the amount of allocation information for determining the allocated bandwidth so that the average allocation information amount approaches the desired bit rate. The allocated bandwidth of each layer from the low frequency side so that the total amount of information of the bandwidth allocated to each layer based on the control means and the amount of information for each subband and the amount of allocated information matches the amount of allocated information for each layer. An audio signal recording apparatus having a band determining unit for determining, and varying an allocation band and an allocation information amount for each frame. 4. An audio signal is divided into a plurality of hierarchical blocks, each hierarchical block is given a priority order, and even if the hierarchical blocks are lacking in order from the lowest priority block, the audio quality is deteriorated, but is normal. In an audio signal recording device equipped with a hierarchical encoding means capable of decoding various audio signals, a subband dividing means for dividing an input digital audio signal into a plurality of frequency bands, and an orthogonal transformation of the input digital audio signal into a frequency domain Then, an audible component extracting means for extracting an audible component based on the auditory characteristics, an instantaneous information amount calculating means for calculating an instantaneous information amount by using the audible component for each frame, and several frames having a fixed allocation band as one cycle, An average information amount calculating means for calculating the average information amount for each subband from the average value of the audible components in one cycle, Control means for controlling to increase or decrease the section allocation information amount for one cycle according to the average allocation information amount with respect to the instantaneous information amount of each frame so that the final average allocation information amount approaches the desired bit rate, and for each subband Based on the average information amount and the section allocation information amount, the total band information amount allocated to each tier matches the section allocation information amount for each layer Has a band determining means for determining,
For the allocated bandwidth of each layer obtained for each cycle, re-bit allocation is performed for each audible component in each allocated bandwidth for each frame according to the size of the audible component, and the allocated bandwidth is determined for each frame for each frame. An audio signal recording device characterized in that the allocation information amount is variable. 5. An audio signal is divided into a plurality of hierarchical blocks, each hierarchical block is given a priority order, and even if the hierarchical blocks are lacking in order from the lowest priority block, the audio quality is deteriorated, but is normal. In an audio signal recording device equipped with a hierarchical encoding means capable of decoding various audio signals, a subband dividing means for dividing an input digital audio signal into a plurality of frequency bands, and an orthogonal transformation of the input digital audio signal into a frequency domain Audible component extraction means for extracting audible components based on auditory characteristics, information amount calculation means for calculating the amount of information for each subband for each frame from the audible components, instantaneous information for each frame from the amount of information for each subband Instantaneous information amount calculating means for calculating the amount, first smoothing for smoothing changes in the information amount for each subband Means, control means for controlling to increase or decrease the instantaneous allocation information amount according to the average allocation information amount with respect to the instantaneous information amount of each frame so that the final average allocation information amount approaches the desired bit rate, instantaneous allocation information amount Second smoothing means for smoothing the change of the, and the sum of the information amount of the band allocated to each layer for each frame based on the smoothed information amount for each subband and the smoothed allocation information amount. Has a band determining means for determining the allocated band of each layer from the low frequency side so that the same as the allocated information amount for each layer, and for each band of the layer that changes gently for each frame, For each audible component in each allocated band, re-bit allocation is performed according to its size, so that the allocated band is gradually changed in each frame, and the amount of allocated information in the allocated band can be changed. Audio signal recording apparatus characterized by a. 6. A comparing means for extracting a difference between an information amount per frame and a bit allocation information amount according to a desired bit rate, a third smoothing means for smoothing the extracted difference, and the third smoothing. By converting the difference from the encoding means into an encoding ratio, and multiplying the information amount of each frame by the encoding ratio that gradually changes according to the cumulative value of the difference between the desired bit rate and the allocation information. 6. The audio signal recording device according to claim 5, wherein the amount of information in variable length frame coding is controlled to a predetermined bit rate on average by controlling the amount of assigned information.