JPH1079671A - Compression data storage device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a compression data storage device capable of preventing interruption of storage of an analog signal and attaining a long time storage by changing compression rate during the storage operation. SOLUTION: An audio signal converted into an A/D converter circuit 1 is compressed by a compression rate among a plurality of compression rates at a coding circuit 3, the compressed data are stored in a storage medium such as a semiconductor memory 5 and a recording lapse time and a remaining recording time in the semiconductor memory 5 are detected by a timer 11 and a control circuit 12 and a recording mode changeover circuit 19 and a control circuit 12 are used to select the compression rate. As the recording time elapses, the compression rate is changed to attain a long time recording. In the case of reproduction, the compression data read from the storage medium 5 are expanded by an expansion rate reverse to the compression rate to reproduce the audio signal.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a compressed data storage device for storing compressed data of analog signals such as audio in a storage medium such as a semiconductor memory.

[0002]

2. Description of the Related Art In a compressed data storage device that stores compressed data in a semiconductor memory or the like, the storage time is determined by the storage capacity,
It is known that the sampling frequency and the data compression ratio are determined by the sampling frequency and the compression ratio before the storage operation is started.

Conventionally, in a compressed data storage device of an audio signal, when the recording time can be estimated, the recording time is assumed to be surely stored in a storage device having a limited storage capacity. The recording is performed after setting the apparatus in advance so as to lower the sampling frequency or increase the compression ratio in advance. However, when recording audio information such as an interview in which the recording time cannot be estimated, if the recording time becomes longer than expected, there is a case where the memory capacity becomes insufficient at some point and recording may not be completed to the end.

As described in Japanese Patent Application Laid-Open No. 4-301699, in a compressed data storage device using a solid-state recording element for speech synthesis, sampling is performed by detecting the number of inflection points of an inputted speech signal. Set the frequency, set the compression rate of the differential PCM coding method based on the absolute value of the maximum amplitude of the audio signal in one input frame, and change the sampling frequency and compression rate during the recording operation, It is known that the recording time is extended as compared with the case where the sampling frequency and the compression ratio are fixed. However, this prior art also cannot arbitrarily change the sampling frequency or compression ratio during the recording operation.

[0005]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and in the case where the storage time cannot be estimated, the compression ratio is changed during the storage operation to store the analog signal. It is an object of the present invention to provide a compressed data storage device capable of preventing data interruption and enabling long-term storage.

[0006]

According to the present invention, in the first aspect of the present invention, in a compressed data storage device, A / D conversion means for converting an analog signal into a digital signal and differentiating the digital signal from each other. Compression means for compressing compressed data at one of a plurality of compression rates, means for storing the compressed data in a storage medium, and compression rate switching means for switching the compression rate at a predetermined arbitrary timing during a storage operation It is characterized by having.

According to a second aspect of the present invention, in the compressed data storage device, A / D conversion means for converting an analog signal to a digital signal, and the compressed data stored in the compressed data storage device at one of a plurality of different compression ratios. Compression means, compression means for storing the compressed data in a storage medium, and compression rate switching means for switching the compression rate when an operator is operated at an arbitrary timing during the storage operation. Is what you do.

According to a third aspect of the present invention, in the compressed data storage device according to the first or second aspect, the compression rate switching means has a switching order setting means for setting a switching order of the compression rates in advance. It is characterized by the following.

According to a fourth aspect of the present invention, in the compressed data storage device according to the third aspect, the switching order setting means sequentially switches the compression ratio from a small value to a large value. It is.

According to a fifth aspect of the present invention, in the compressed data storage device according to any one of the first to fourth aspects, means for outputting the remaining storage time of the storage medium; It has a display means.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a block diagram of a memory recording / reproducing apparatus according to an embodiment of the present invention. In the figure, 1 is an A / D conversion circuit, 2 is a sub-band filter, 3 is a coding circuit, 4 is an error detection and correction circuit, 5 is a semiconductor memory, 6 is a decoding circuit, 7 is a signal synthesis circuit, and 8 is D / A. A conversion circuit, 9 is an operation unit, 10 is a recording mode switching circuit, 11 is a timer, and 12 is a control circuit.

The compressed data storage device of this embodiment is
The audio signal converted to a digital signal by the A / D conversion circuit 1 is compressed by the encoding circuit 3 at one of a plurality of compression ratios prepared, and the compressed data is stored in a storage medium such as the semiconductor memory 5. The elapsed recording time and the remaining recording time of the semiconductor memory 5 are detected by the timer 11 and the control circuit 12, and the compression ratio is switched by the recording mode switching circuit 10 and the control circuit 12. The compression ratio changes with the lapse of the recording time. This makes it possible to record for a long time. At the time of reproduction, the audio signal is reproduced by decompressing the compressed data read from the storage medium of the semiconductor memory 5 at a decompression rate opposite to the above-mentioned compression rate.

The audio signal is input to the A / D conversion circuit 1. The sub-band filter 2 divides the output of the A / D conversion circuit 1 for each sub-band. The encoding circuit 3 performs sub-band encoding, has a compression rate corresponding to several kinds of auditory characteristics, and encodes audio data divided for each sub-band at a predetermined compression rate. The error detection and correction circuit 4 converts the sub-band coded data into a code capable of error detection and correction.

The semiconductor memory 5 sequentially writes the output of the error detection and correction circuit 4 at a predetermined address by a writing circuit (not shown) and stores it. At the time of reproduction, data is sequentially read from a predetermined address from a semiconductor memory 5 by a read circuit (not shown) and output to an error detection / correction circuit 4 to detect and correct data errors. The decoding circuit 6 performs decoding corresponding to the sub-band encoding in the encoding circuit 3 on the data on which the error has been detected and corrected, and decompresses the compressed data to restore the original data. The signal synthesizing circuit 7 synthesizes data for each sub-band to restore audio data. The D / A conversion circuit 8
The reproduced audio data is converted into an analog signal and reproduced data is output.

The operation section 9 has various input buttons and a display section which will be described later with reference to FIG.
Then, the operation function of the control circuit 12 is controlled via the timer 11. In cases where the recording time cannot be assumed,
As described later with reference to FIGS. 4 to 7, as a mode for changing the compression ratio as the recording time elapses, an auto and manual recording mode is prepared, and is switched by the recording mode switching circuit 10. Of course, a mode in which the compression ratio is not changed as the recording time elapses may be provided.

The timer 11 detects the elapsed recording time from the start of recording and outputs the same to the control circuit 12. Control circuit 1
2 is an operation unit 9, a recording mode switching circuit 10, a timer 1
In response to the output of 1, the encoding circuit 3, the decoding circuit 6, the semiconductor memory 5 and the like are controlled to perform time management, remaining storage capacity management, compression rate switching, and other controls.

In the auto mode, the control circuit 12
The current remaining recording time is calculated by subtracting the elapsed recording time from the maximum recordable time that can be recorded in the semiconductor memory 5. The maximum recordable time is determined by the storage capacity of the semiconductor memory 5 and a predetermined compression ratio pattern.

In the manual mode, the current remaining recording time can be calculated from the remaining storage capacity on the assumption that the encoding circuit 3 will maintain the current compression ratio. The maximum recordable time is obtained by adding the current remaining recording time to the recording elapsed time. The remaining storage capacity is obtained by calculating the used storage capacity from the value of the compression ratio up to the present and the recording time at that compression ratio.

A timer 1 for detecting the elapsed recording time
Instead of 1, the used storage capacity, the remaining storage capacity, the elapsed recording time, and the remaining recording time can be calculated from the current write address of the semiconductor memory 5 or the like.

As the semiconductor memory 5, RAM, ROM
, But the EEPROM (electric
all erasable and program
It is preferable to use a nonvolatile memory such as a table read only memory (CMOS) or a CMOS-SRAM capable of backing up memory with low power.

The outline of the signal processing operation for an audio signal will be described with reference to the block diagram of FIG. The analog-valued audio signal is converted into a digital signal by the A / D conversion circuit 1, and the sub-band filter 2 converts the audio signal into a digital signal having an equal bandwidth.
Is divided into subbands. In this filtering, the data is quantized by 24 bits / data, and 12 data are processed as one unit per one subband. When the sampling frequency is 48 kHz, 8
Milliseconds are the unit of signal processing.

The digital audio signal divided into sub-bands is then subjected to compression encoding in the encoding circuit 3 in which the compression ratio can be changed. In this embodiment, audio compression processing using human auditory characteristics is performed. The bit allocation for each subband is specified and quantized for each subband. As will be described later with reference to FIG. 2, by providing several types of minimum audible characteristics, compression encoding with different compression ratios is possible. Then, a maximum value of the 12 data is uniformly quantized with 6 bits, and a scale factor, which is a value, and information on the number of the subband and the number of quantization bits is added and output. After that, the error detection and correction circuit 4 adds an error detection and correction bit, and writes the result into the semiconductor memory 5.

At the time of reading from the semiconductor memory 5, the error detection and correction circuit 4 performs error detection and correction of the data using the error detection and correction bits, decodes the data with the decoding circuit 6, and synthesizes with the signal synthesis circuit 7. , A D / A conversion circuit 8 converts the digital signal into an audio signal having an analog value.

FIG. 2 is an explanatory diagram of the minimum audible characteristic of the sub-band coding of the encoding circuit. FIG. 2A is an example of the minimum audible characteristic when a single frequency signal is input, and FIG. Is 2
It is an example of the minimum audible characteristic when a frequency signal is input. The horizontal axis is the frequency axis, and the sub-band division is omitted.
The vertical axis represents the level of sound intensity (sound pressure). The sub-band encoding is a frame processing of a time-axis waveform for each frequency band of a plurality of sub-bands.
PASC (Precision Adapted) adopted in al Compact Casette
SubbandCoding), MPEG (Movin)
g ISO / IEC / IS11172-3 (MP used in Picture ExpertGroup)
EG1 audio).

As shown in FIG. 2A, the minimum audible characteristic at the time of inputting a single frequency signal has frequency dependence, and a sound having a sound pressure lower than the minimum audible characteristic cannot be heard. The number of bits allocated to encoding is reduced for the amplitude of a sub-band having a high level. In this embodiment, three types of the minimum audible characteristics are prepared in advance corresponding to the low compression mode a, the medium compression mode b, and the high compression mode c.

Since the level of the minimum audible characteristic is increased over all the sub-bands in the order of the low compression mode a, the middle compression mode b, and the high compression mode c, the low compression mode a, the middle compression mode b, and the high compression mode c. The number of bits used for encoding is reduced, and the rate of consuming memory capacity is reduced.
In the simplest specific example, the level of the minimum audible characteristic can be increased by uniformly reducing the number of bits assigned to encoding by a predetermined number of bits for each subband.

As shown in FIG. 2B, when two audio signals of different frequencies are inputted simultaneously, the audio signal of a small amplitude is masked by the audio signal of a large amplitude, so that the minimum audible characteristic changes. I do. In this embodiment, also in this case, as in FIG. 2A, three compression modes a, medium compression mode b, and high compression mode c are used.
The kinds of minimum audible characteristics are prepared in advance, and the level of the minimum audible characteristics is sequentially increased.

FIG. 3 is an external view of a memory recording / reproducing apparatus according to one embodiment of the compressed data storage device of the present invention. In the figure, 21 is a main display, 22 is a selection button, 23 is a power button, 24 is a remaining time display, 25 is a compression button, 2
6 is a confirm button, 27 is a microphone jack, 28 is a line-out jack, 29 is a headphone jack, 30 is a volume control button, 31 is a confirm button, 32 is a button lock button, 33 is a compression button, 34 is a record button, 35 is Display mode switching button, 36 is memory clear button, 3
7 is a compression rate pattern memory selection button, 38 is a playback button, 39 is a compression mode selection button, 40 is a card slot, 41 is a stereo microphone, and 42 is a stereo headphone.

The overall structure of the memory recording / reproducing apparatus has a flat rectangular parallelepiped shape, and the main display section 21 and various operation buttons are arranged on the front surface having a large area. On the upper side, remaining time display 24, microphone jack 27,
A compression button 25 and an enter button 26 are provided in addition to jacks such as a line-out jack 28 and a headphone jack 29. A card slot 40 is provided on the lower surface. The remaining time display section 24 is provided on the main display section 2 so that when the memory recording / reproducing device is put in a breast pocket or the like for recording, the remaining recording time can be confirmed without leaving the pocket.
1 is provided in duplicate. Also, the compression button 25,
The enter button 26 is used to select and confirm the memory recording / playback device without taking it out of the pocket.
3, provided separately from the confirmation button 31.

The semiconductor memory 5 shown in FIG. 1 is, for example, in the form of a large-capacity IC memory card, is stored in a card slot 40, and can be inserted and removed and replaced. The main display unit 21 displays the maximum recordable time and the elapsed recording time in a bar graph. The left and right volume levels are also displayed in a bar graph. The recording title name, guide display of each operation function, and the like are displayed in characters. The elapsed time of recording or reproduction, the remaining time of recording or reproduction, the remaining time of the battery, and the like are alternatively displayed on an eight-shaped display portion. The display is switched by the display mode switching button 35.

The volume adjustment button 30 adjusts the volume of the headphones 42 connected to the headphone jack 29.
The microphone jack 27 is compatible with stereo, and a stereo microphone 41 is connected. When recording in monaural, double recording time is possible. A small speaker and a small microphone may be built in.

FIG. 4 is a flowchart showing the operation in the auto mode. The operation in the auto mode will be described with reference to the block diagram shown in FIG. 1 and various operation buttons shown in FIG. First (T ₀ ), the auto button of the compression mode selection button 39 shown in FIG. 3 is pressed to set the recording mode switching circuit 10 shown in FIG. 1 to the auto mode. In the control circuit 12, the switching timing of the compression ratio of the encoding circuit 3 is set in advance based on the maximum storage capacity of the semiconductor memory 5, the compression ratio pattern, and the like.

When the record button 34 and the play button 38 shown in FIG. 3 are pressed at the same time, the process proceeds to S51, the recording is started in the low compression mode, and the process proceeds to S52. In S52, when the timer 11 and the control circuit 12 shown in FIG. 1 detect that the remaining recording time has reached a time point (T ₁ ) which is equal to or less than の of the maximum recordable time of the semiconductor memory 5, S53. The process proceeds to step S52, and if not, the process returns to step S52. In recording in the low compression mode, subband encoding is performed at a low compression ratio.

In S53, the control circuit 12 shown in FIG. 1 switches the characteristics of the encoding circuit 3 to the medium compression mode,
The process proceeds to 54. In S54, the timer 11 and the control circuit 12 shown in FIG. 1 detect when the remaining recording time has reached a time point (T ₂ ) of さ ら に or less of the maximum recordable time, ie, １ ／ or less. Then, the process proceeds to S55, and if not, returns to S54. In recording in the medium compression mode, subband encoding is performed at the next highest compression rate.

In S55, the control circuit 12 shown in FIG. 1 switches the characteristic of the encoding circuit 3 to the high compression mode,
The process proceeds to 56. In S56, when the remaining recording time is further reduced to 以下 or less, that is, １ ／ or less by the timer 11 and the control circuit 12 shown in FIG.
_{If 3} ) is detected, the process proceeds to S57, and if not, returns to S56. In recording in the high compression mode, subband encoding is performed at the next highest compression ratio.

In S57, the control circuit 12 shown in FIG. 1 switches the characteristic of the encoding circuit 3 to the maximum compression mode,
The process proceeds to S58. In S58, when the timer 11 and the control circuit 12 shown in FIG. 1 detect that the remaining recording time has become 0, the recording is terminated, and if not, the process returns to S58. In recording in the maximum compression mode, subband encoding with the highest compression ratio is performed.

FIG. 5 is an explanatory diagram of an example of a compression ratio pattern in the auto mode. In the figure, the horizontal axis is a time axis, and the maximum recordable time that can be recorded until the storage capacity of the semiconductor memory 5 becomes full is shown as a reference length. The first
Although the third to third compression rate patterns are illustrated, since the compression rate patterns have different histories of the compression rates, the values of the maximum recordable time of each compression rate pattern are different.

The first compression ratio pattern shows the case of the flowchart shown in FIG. In the first compression ratio pattern, timings T ₁ ,
T ₂ and T ₃ are set to timings at which the recording time in each compression ratio period with respect to the maximum recordable time decreases exponentially by (１ ／) times. Therefore, the timings T ₁ , T ₂ , and T _{3 at} which the compression ratio is switched are 1/2, 3/4, and 7/8 of the maximum recordable time.

The timing T ₁ for switching the compression ratio,
If a plurality of sets of T ₂ and T ₃ are preset in the memory of the control circuit 12 at the time of factory shipment or by a user's manual setting, the user selects a different compression ratio pattern depending on the content of the recording. It becomes possible.

The second compression ratio pattern is such that the recording time in each compression stage decreases exponentially by × (２) times. In the third compression ratio pattern, recording starts in the middle compression mode b from the beginning, and when the recording elapsed time in the middle compression mode b becomes half of the maximum recordable time, the low compression mode a is set. elapsed recording time of the mode a is at the time of T _2, which was the sixth of the maximum recording time,
The mode is returned to the middle compression mode b again.

In the above description, the compression rate is switched by detecting the elapsed recording time. However, the compression rate may be switched by detecting the recorded storage capacity or the remaining recordable capacity.

FIG. 6 is a flowchart showing the operation in the manual mode. Similar to FIG. 4, the operation in the manual mode will be described with reference to FIGS. At first,
The manual button of the compression mode selection button 39 shown in FIG. 3 is pressed to set the recording mode switching circuit 10 shown in FIG. 1 to the manual mode. In this mode, the user refers to the remaining recording time of the main display unit 21 or the remaining time display unit 24 shown in FIG. 3 or the bar graph display of the maximum recordable time and the elapsed recording time of the main display unit 21, Each time the compression button 25 or 33 is pressed, the compression ratio is sequentially changed.

When the record button 34 and the play button 38 shown in FIG. 3 are simultaneously pressed, the process proceeds to S61, where recording is started in the low compression mode, and the process proceeds to S62. In S62, when it is detected that the compression button 25 or 33 has been pressed, the process proceeds to S63.
The process proceeds to 64. In S64, the timer 1
1. When the control circuit 12 detects that the remaining recording time has become 0, the recording is terminated, and if not, the process returns to S62.

In S63, the control circuit 12 shown in FIG. 1 switches the characteristics of the encoding circuit 3 to the medium compression mode,
Proceed to 65. In S65, the compression button 2
If it is detected that 5 or 33 has been pressed, the process proceeds to S66, and if not, the process proceeds to S67. S
In 67, when the timer 11 and the control circuit 12 detect that the remaining recording time has become 0, the recording is terminated, and if not, the process returns to S65.

In S66, the control circuit 12 shown in FIG. 1 switches the characteristics of the encoding circuit 3 to the high compression mode,
The process proceeds to 68. In S68, the compression button 2
If it is detected that 5 or 33 has been pressed, the process proceeds to S70, and if not, the process proceeds to S69. S6
In 9, when the timer 11 and the control circuit 12 detect that the remaining recording time has become 0, the recording is terminated,
If not, the process returns to S68.

In S70, the control circuit 12 shown in FIG. 1 switches the characteristic of the encoding circuit 3 to the maximum compression mode,
The process proceeds to S71. In S71, the timer 1
1. When the control circuit 12 detects that the remaining recording time has become 0, the recording is terminated, and if not, the process returns to S71.

FIG. 7 is an explanatory diagram of the compression ratio pattern in the manual mode. In the figure, the horizontal axis is the time axis, which is shown based on the maximum recordable time. Note that the first to first
Although the third compression rate pattern is illustrated, since each compression rate pattern has a different history of the magnitude of the compression rate, the value of the maximum recordable time in each compression rate pattern is different.

In the first compression ratio pattern, recording is first started in the low compression mode a, and then sequentially switched to the medium compression mode b and the high compression mode c, and the remaining recording time is reduced to zero in the high compression mode c. The recording has ended. In the second compression ratio pattern, recording is first started in the medium compression mode b, and is sequentially performed.
The mode is switched between the high compression mode c and the maximum compression mode d. In the maximum compression mode d, the remaining recording time becomes 0 and the recording is completed. In the third compression ratio pattern, recording is first started in the low compression mode, and sequentially switched to the medium compression mode b, the high compression mode c, and the maximum compression mode d, and the remaining recording time becomes zero in the maximum compression mode d. Recording has ended. It is not necessary to use all of the plurality of compression ratios of the encoding circuit 3, and the same compression ratio mode may be used a plurality of times or may be used continuously.

The same applies to the case of the auto mode. However, as in the case of the conventional tape recorder, the recording is ended before the remaining recording time becomes zero by pressing the stop button, or the pause button is pressed. Thus, the recording can be temporarily stopped.

The order of the compression ratio in the compression ratio pattern of the above-described compression ratio is preset in a compression ratio pattern memory in the control circuit 12 in advance at the time of factory shipment or by manual setting by the user. Is possible.

To preset a compression ratio pattern, the user specifies a manual button of the compression mode selection button 39 shown in FIG. 3 and a memory to be stored among the memories A, B and C in the control circuit 12. The compression rate pattern memory selection button 37 is pressed simultaneously. Then, the compression ratio in the first period of the compression ratio pattern is selected with the left and right buttons of the select button 22, and confirmed with the confirmation button 31. Similarly, the compression rate for the next period is sequentially selected and confirmed by the select button 22 and the confirm button 31. If the recording button 34 is pressed after the input of the compression pattern of the last period, the determined compression pattern can be preset in the compression rate pattern memory in the designated control circuit 12.

If the input is wrong, the manual button of the compression mode selection button 39 and the compression ratio pattern memory selection button 37 are simultaneously pressed, and the up and down buttons of the select button 22 are pressed to return to the wrong position, and the correct compression is performed. The pattern can be modified by selecting the pattern with the left and right buttons. The clear button 36 is used to erase the stored compression pattern. The compression rate pattern memory is also a nonvolatile memory similar to the semiconductor memory 5 or a COMOS-SR
AM is preferred.

By pressing the lock button 32, a button lock in which the function of the button is not performed even if the button is pressed is performed, and erroneous operation during recording can be prevented. The button lock can be released by pressing the lock button 32 and the confirmation button 31 at the same time.

The data recorded in the above-mentioned auto mode and manual mode are reproduced from the semiconductor memory 5 through a process reverse to that at the time of recording. The number of quantization bits for each subband at the time of encoding is recorded together with sample data in one frame. At the time of reproduction, by reading out the number of quantization bits, the sub-band code can be decoded at an expansion rate corresponding to the compression rate at the time of recording.

When employing a format in which the number of quantization bits for each sub-band is not written in a frame during encoding, the compression rate pattern and switching timing during recording are determined by compressing the encoded audio data and title. The data can be stored together with the data in the semiconductor memory 5, read out at the time of reproduction, and the sub-band code can be decoded at an expansion rate corresponding to the compression rate in each compression period.

In the above description, a device for inputting an audio signal such as a voice signal or a tone signal and storing compressed data has been described. However, as long as compression encoding is possible, another device for inputting another analog signal may be used. Good. Further, the compressed data storage device may be applied to an audio signal recorded accompanying a video. The compression coding method is not limited to the above-described subband coding, and includes various methods such as a differential PCM method described in the related art.
What is necessary is just to employ | adopt suitably considering the characteristic etc. of the input analog signal.

In the above description, an apparatus capable of recording and reproduction has been described, but a recording-only apparatus may be used. Semiconductor memory 5
Is replaceable, but may be built in the device.
Although the apparatus dedicated to storing compressed data is illustrated, the entire apparatus may be incorporated in another audio device, video device, notebook personal computer, or the like.

In the above description, as the storage medium, a semiconductor memory which is particularly effective because of its relatively small storage capacity has been described. However, the storage medium has a smaller storage capacity than a normal recording time length of an input analog signal. The present invention can be applied to storage in a storage medium such as a flexible magnetic disk, which has a limitation.

In order to reduce the storage capacity, the sampling frequency is lowered as described for the prior art, and in the case of a stereo signal, switching to a joint stereo signal (storage of L + R, LR) or a monaural signal is performed. This is also possible. Therefore, only by these means, the amount of information necessary for storing the analog signal per unit time may be reduced over time. However, changing the compression rate of the above-described compression code is relatively less likely to cause deterioration in voice quality. It is also possible to use the above-mentioned means together with the method of changing the compression ratio of the compression code.

[0060]

As is apparent from the above description, according to the first aspect of the present invention, A / D conversion means for converting an analog signal into a digital signal, and a digital signal having a plurality of compression rates different from each other. Compression means for compressing the compressed data into one piece, means for storing the compressed data in a storage medium,
Since the compression ratio switching means for switching the compression ratio at an arbitrary predetermined timing during the storage operation is provided, the remaining storage time can be arbitrarily expanded or contracted during the storage operation. There is an effect that the memory can be stored according to the situation.

Further, since the timing of switching the compression ratio is set in advance, the compression ratio is automatically switched, and there is an effect that the operation is easy. Even if the storage time length of the analog signal is not determined in advance, if the remaining storage time is extended during the storage operation, it is possible to prevent running out of storage and to reliably store the analog signal in the storage medium.

According to the second aspect of the present invention, A / D conversion means for converting an analog signal into a digital signal, and compression means for compressing a digital signal into compressed data at one of a plurality of different compression rates. Means for storing compressed data in a storage medium, and compression ratio switching means for switching a compression ratio when an operator is operated at an arbitrary timing during the storage operation. Since it can be expanded and contracted, there is an effect that storage according to the type and length of the analog signal source can be performed.

Further, since the timing of switching the compression ratio is determined by the operation timing of the operation element, there is an effect that the compression ratio can be switched manually and flexibly. Even if the storage time length of the analog signal is not determined in advance, if the storage time is extended while the storage time has elapsed, interruption of the storage operation can be prevented and the data can be reliably stored in the storage medium.

According to the third aspect of the present invention, since the compression rate switching means has the switching order setting means for setting the compression rate switching order in advance, the compression rate switching order is automatically determined. There is an effect that the operation is easy.

For example, in the case of interview recording, the recording time is prioritized over the sound quality, and the medium compression mode → high compression mode → maximum compression mode is set and stored. And the order in which the compression ratio is selected can be set according to the situation, such as setting the low compression mode → the low compression mode → the high compression mode and storing them.

According to the fourth aspect of the present invention, the switching order setting means sequentially switches the compression ratio from a small value to a large value. Therefore, even when the storage time length of the analog signal is not determined, the switching order setting means changes the compression ratio. There is an effect that interruption of the storage operation can be prevented while deterioration is minimized, and the data can be reliably stored in the storage medium.

According to the fifth aspect of the present invention, since there are means for outputting the remaining storage time of the storage medium and means for displaying the remaining storage time, the remaining storage time of the storage medium can be confirmed during the storage operation. There is an effect that can be. Especially,
This is suitable when the compression ratio is manually switched during the storage operation.

[Brief description of the drawings]

FIG. 1 is a block diagram of a memory recording / playback device according to an embodiment of a compressed data storage device of the present invention.

FIG. 2 is an explanatory diagram of a minimum audible characteristic of subband coding of an encoding circuit. FIG. 2A is an example of a minimum audible characteristic when a single frequency signal is input, and FIG. It is an example of the minimum audible characteristic at the time of signal input.

FIG. 3 is an external view of a memory recording / playback device according to an embodiment of the compressed data storage device of the present invention.

FIG. 4 is a flowchart showing an operation in an auto mode.

FIG. 5 is an explanatory diagram of an example of a compression ratio pattern in an auto mode.

FIG. 6 is a flowchart illustrating an operation in a manual mode.

FIG. 7 is an explanatory diagram of a compression ratio pattern in a manual mode.

[Explanation of symbols]

1 ... A / D conversion circuit, 2 ... Sub-band filter, 3 ...
Code circuit, 4 ... Error detection and correction circuit, 5 ... Semiconductor memory,
6 decoding circuit, 7 signal synthesis circuit, 8 D / A conversion circuit, 9 operation unit, 10 recording mode switching circuit, 11 timer, 12 control circuit, 21 main display unit, 24
Remaining time display section, 25, 33 ... compression button, 37 ... compression rate pattern memory selection button, 39 ... compression mode selection button, 40 ... card slot.

Claims (5)

[Claims] A / D conversion means for converting an analog signal into a digital signal, compression means for compressing the digital signal into compressed data at one of a plurality of different compression ratios, and storing the compressed data in a storage medium. A compressed data storage device comprising: a storage unit; and a compression ratio switching unit that switches the compression ratio at a predetermined arbitrary timing during a storage operation. 2. A / D conversion means for converting an analog signal into a digital signal, compression means for compressing the digital signal into compressed data at one of a plurality of different compression ratios, and storing the compressed data in a storage medium. A compressed data storage device comprising: a storage unit; and a compression ratio switching unit that switches the compression ratio when an operator is operated at an arbitrary timing during a storage operation. 3. The compressed data storage device according to claim 1, wherein the compression ratio switching unit includes a switching order setting unit that sets a switching order of the compression ratio in advance. 4. The compressed data storage device according to claim 3, wherein the switching order setting means sequentially switches the compression ratio from a small value to a large value. 5. The compressed data storage device according to claim 1, further comprising means for outputting the remaining storage time of the storage medium, and means for displaying the remaining storage time. .