JP3189587B2 - Audio time base converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio system capable of arbitrarily compressing and expanding the length of the audio time axis required for high-speed and low-speed audio reproduction by a video tape recorder (VTR) or the like. The present invention relates to a time axis conversion device.

[0002]

2. Description of the Related Art Conventionally, there is an audio time base conversion apparatus capable of reproducing an audio signal from a recording medium at a speed different from that at the time of recording. For example, a fast-forward playback function of a cassette tape recorder is very difficult to listen to, because in this case, even if the reading speed is increased, even the pitch is changed. Therefore, there has been proposed an audio time base conversion apparatus capable of changing the reproduction speed while keeping the pitch at the time of recording.

[0003] A conventional audio time base converter will be described below with reference to the drawings. FIG. 7 is a block diagram showing a configuration of a conventional audio time base conversion apparatus. 7, reference numeral 1 denotes a recording / reproducing unit for recording and reproducing an audio signal;
Is an A / D converter for converting a reproduced analog signal into a digital signal, 3 is a buffer memory for storing digital data, 4 is a D / A converter, and 5 is a controller for writing data to the buffer memory. The writing control unit 6 is a reading control unit that controls reading of data from the memory.

[0004] The operation of the audio time base conversion apparatus configured as described above will be described below. Here, a description will be given of an audio time base conversion apparatus that reproduces an audio signal at a recording speed that is higher than the recording speed, and reproduces the sound by returning the pitch to that at the time of recording.

First, the recording / reproducing unit 1 reproduces an audio signal at M times the recording speed. Here, the recording / reproducing unit is, for example, VT
R, cassette tape recorder, and the like. Next, the audio signal reproduced from the recording / reproduction unit 1 is converted into a digital signal by the A / D converter 2 at a sampling period T / M inversely proportional to the reproduction speed. T is a sampling period that satisfies the sampling theorem for an audio signal at the time of recording. In order to convert an audio signal reproduced at M-speed into a digital signal, at least 1 / M times the sampling period T, that is, T / M Must be sampled at The A / D-converted digital signals have a period T
/ M are sequentially stored in the buffer memory 3. If these signals are read out and reproduced in a cycle T, they return to the pitch at the time of recording. However, it is impossible in terms of time to output all data. Therefore, the read control unit 6 sequentially reads the digital signals stored in the buffer memory 3 at a period T and discards the remaining data at a rate of | 1-M | / M for each fixed amount of sample values, The signal is converted into an analog signal by the D / A converter 4 at a sampling period T. Here, || represents an absolute value. Usually, the interval between discarding and regeneration is a short unit of several milliseconds or less. Through a series of these processes, high-speed reproduction can be realized while maintaining the pitch at the time of recording.

FIG. 8 shows an example of processing at a double speed (M = 2). (A) shows data at the time of recording.
By reading at double speed, the time axis becomes 1 / as shown in (b).
It becomes 2. Reproduction at the sampling period T while discarding 1/2 of the data of (b) results in the data sequence of (c), the pitch is the same as the data sequence of (a), and the time axis is (b)
Can be the same as the data string.

[0007]

In the above-mentioned prior art, however, the pitch returns to the pitch at the time of recording, but since only a uniform reproduction speed can be controlled, the speed of the sound becomes faster in proportion to the reproduction speed. It was very difficult for humans to hear. Also, in order to align the time axis with the playback speed during high-speed playback, an amount of data proportional to the playback speed must be discarded. For example, at the time of double speed reproduction, half of the data is rejected. Therefore, the higher the speed, the more the reproduced sound deteriorates. If the interval of discarding information is increased to several seconds,
Although it is easy to listen at the same speed as at the time of recording without deterioration, there is a disadvantage that information is lost in a large block, and it is difficult to understand the meaning of the word as a whole.

[0008] The present invention solves the above-mentioned problems, and when reading from a recording medium at a reproduction speed higher than the recording speed,
It is an object of the present invention to provide an audio time base conversion apparatus capable of automatically changing the conversion speed to an easy-to-listen conversion speed while minimizing the loss of information.

[0009]

According to a first aspect of the present invention, there is provided an audio time base converting apparatus for reading an audio signal from a recording medium at a reproduction speed higher than a recording speed, and a reproducing unit for reproducing the audio signal. A / D converter for converting an analog signal into a digital signal, a sound / silence determining unit for determining a silent part and a sound part in the input signal, a buffer memory for storing the input signal, and a buffer memory A write control unit that controls writing of data to and from the buffer, a read control unit that controls reading of data from the buffer memory, and a read control unit that controls the address, and a current writing address and reading by the writing control unit and the reading control unit. A memory remaining amount monitoring unit that measures the remaining amount of memory in the buffer memory from the address location An adaptive speed control unit that determines the speed of the time axis conversion based on the rules described above, a time axis control unit that compresses the audio time axis according to the conversion speed determined by the adaptive speed control unit, and And a D / A converter for converting into an analog signal.

According to a second aspect of the present invention, there is provided an audio time base conversion device including an adaptive speed control unit for determining a time base conversion speed in proportion to the remaining memory capacity.

According to a third aspect of the present invention, there is provided an audio time base conversion apparatus including an adaptive speed control unit for determining a time base conversion speed based on a conversion rule nonlinearly corresponding to the remaining memory capacity.

According to a fourth aspect of the present invention, there is provided an audio time axis conversion apparatus, wherein a value obtained by multiplying a fixed number of adjacent sample value sequences by a monotonically decreasing weighting factor and a value obtained by multiplying a monotonically increasing weighting factor are respectively used. And a crossfade section to add
A time axis control unit is provided for converting the length of the non-processing section for directly outputting the sample value to a desired time axis conversion speed by adjusting the length.

According to a fifth aspect of the present invention, when the remaining memory capacity is equal to or more than a certain value, only the sound interval is stored in the buffer memory, and when the remaining memory capacity is less than a certain value, all data is stored. It is provided with a write control unit that accumulates in a buffer memory.

[0014]

According to the first aspect of the present invention, only the section determined to be sound is stored in the buffer memory as a result of the sound / silence determination, and the remaining memory is measured from the write and read address positions. , The speed can be automatically adjusted according to the amount of silence, such that when the remaining amount is large, the speed becomes low as much as possible, and as the remaining amount decreases, the speed gradually increases. In particular, it becomes possible to reproduce sound at an easy-to-listen speed for an input signal having a lot of silence. In the case of an input signal with little silence, the reproduction speed changes according to the remaining amount of memory, so that loss of information can be prevented. Also, if some information loss is allowed and the maximum value of the speed of the sound that is adaptively changed is set to a value smaller than the playback speed, the voice can be heard at a speed that is easy to hear as far as it can be understood as words although there is slight information loss. It becomes possible to reproduce. Also, when playing back at the same speed as the recording speed (1x speed), if the time axis conversion speed is controlled to be lower than the recording speed in accordance with the amount of silence, it is possible to hear the voice of the fast-talking voice and Listening can be facilitated. .

According to the configuration of the second aspect, since the remaining memory capacity and the conversion speed change in proportion to each other, a rapid change in the voice speed is suppressed, and the voice becomes easy to hear.

According to the third aspect of the present invention, if a non-linear conversion rule is set so as to stay at a low conversion speed for a long time, the effect of suppressing the conversion speed to a low level enables stable voice output at a low speed. It is possible to realize a sound time axis conversion device that can reproduce and is very easy to hear.

According to the fourth aspect of the present invention, an arbitrary time base conversion speed can be obtained only by adjusting the length of the non-processing section for directly outputting the data stored in the buffer memory. An audio time axis conversion device capable of converting to an arbitrary speed with a simple configuration can be realized.

According to the fifth and sixth aspects of the present invention, when the remaining memory capacity is low, all data is read out by accumulating in the buffer memory irrespective of the sound / no-sound judgment result of the input signal. It is possible to obtain a natural reproduced sound without a sense of incongruity, because there is no data to be lost and the reproduced sound does not enter a mute state (mute state) on the way.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing the configuration of the audio time axis conversion device according to the first embodiment of the present invention. In FIG. 1, 101 is a recording / reproducing unit that records and reproduces an audio signal, 102 is an A / D converter that converts an analog signal reproduced by the recording / reproducing unit 1 into a digital signal,
Reference numeral 103 denotes a sound / non-speech determining unit that determines whether the converted digital signal sequence is a sound part or a soundless part. 104 denotes a buffer memory 1 for writing the signal sequence determined to be a sound part.
05 is a write control unit for controlling writing on the address and its address, 106 is a read control unit for reading data stored in the buffer memory 105 and controlling its address, and 107 is a current write address and read on the buffer memory 105. A memory remaining amount monitoring unit that measures the remaining amount of memory from the positional relationship between addresses, an adaptive speed control unit that determines a speed for time axis conversion from the remaining amount of memory obtained by the remaining memory amount monitoring unit, and 109 is an adaptive speed controlling unit. A time axis control unit 110 that performs a time axis conversion process according to the conversion speed determined by the speed control unit, and a D / A converter 110 that converts the time axis converted digital data into an analog signal.

The operation of the audio time base conversion device configured as described above will be described in detail below with reference to FIG.

First, M (≧≧) at the time of recording from the recording / reproducing unit 101
1) An acoustic signal is read at twice the speed. Hereinafter, the speed indicates a relative speed with respect to the recording speed (= 1). Here, assuming that the sampling period at the time of recording in the recording / reproducing unit 101 is T, the acoustic signal reproduced by the recording / reproducing unit 101 at the M-times speed is sequentially converted into a digital signal sequence by the A / D converter 102 at the sampling period T / M. Is converted to Based on this digital signal sequence, a sound / non-speech determination unit 103
To determine whether the sample sequence is a sound part or a silent part. The determination of presence or absence of sound is performed, for example, as follows.
Assuming that the sample value sequence of the digital signal is s _i , it is determined that the sample value sequence is sound if the expression (1) is satisfied for the N sample value sequences, and is silent if the expression is not satisfied. Here, P _th is a predetermined threshold value for sound / silence determination.

[0022]

(Equation 1)

Here, assuming that a pointer (hereinafter referred to as a write pointer) pointing to an address in the buffer memory 105 at which data is to be stored next is Pw, if it is determined that there is sound in the above (Equation 1), , The sample value sequence is written by the write control unit 104 to the write pointer.
Pw is sequentially stored at an address position of the buffer memory 105 indicated by Pw, and Pw is incremented each time. Conversely, when it is determined that there is no sound, the write control unit 104 stops the operation of writing data to the buffer memory 105. As a result, only the data of the sound part is accumulated in the buffer memory 105.

In this case, it is determined that there is sound when (Equation 1) is satisfied, and it is determined that there is no sound when it is not satisfied. A short sample string may be included in the sound interval.

The read control unit 106 sequentially reads data from the buffer memory 105 at a period T and sends the data to the time axis control unit 109. Here, a pointer indicating the address of the data on the buffer memory 105 to be read next (hereinafter, referred to as a read pointer) is denoted by Pr. In the memory remaining amount monitoring unit 107, the write pointer Pw
The remaining amount of data that has not yet been read on the buffer memory 105 is sequentially measured from the positional relationship between the data and the read pointer Pr. FIG. 2 is an explanatory diagram showing a method of measuring the remaining amount of memory. There are two cases shown in FIGS. 2A and 2B depending on the positional relationship between two pointers. In FIG. 2, the start address of the buffer memory is a ₀ and the end address is a
_{Assuming that n−1} (where a _n−1 > a ₀ ), the remaining memory capacity Z that has not been read out is indicated by the hatched portion in FIG. 2 and can be calculated as in the following equation.

[0026]

(Equation 2)

This is equivalent to treating the buffer memory 105 as a so-called cyclic memory. Here, in order to read and output data from the normal memory, the write pointer Pw must precede the read pointer Pr on the cyclic memory,
When Pw and Pr overlap (Pw = Pr), the read control unit 106 stops the read operation and the read pointer
Pr maintains the address value at that time. Where Pw and Pr
2 can be considered as two cases, that is, when Pr catches up with Pw in FIG. 2A and when Pw catches up with Pr in FIG. 2B. In the latter case, the remaining memory capacity actually corresponds to the capacity of the buffer memory 105, that is, n, but also in this case, the remaining memory capacity Z is reset to zero.

On the basis of the value of the memory remaining amount Z obtained by the memory remaining amount monitoring unit 107, the adaptive speed control unit 108
When the remaining memory capacity is small, the speed of the time axis conversion is set to a slow speed as close as possible to the recording speed, and when the remaining capacity is large, the time axis conversion speed is set to an appropriately high speed so that the read pointer Pr cannot catch up with the write pointer Pw. Hereinafter, the operation of the adaptive speed control unit 108 will be described for a case where the recording / reproducing unit 101 reproduces data at a speed twice (M = 2) the recording speed. Here, it is assumed that the maximum value of the conversion speed is 2, which is the same as the reproduction speed, and the minimum value is 1, which is the same as the recording speed. FIG. 3 shows the relationship between the remaining memory capacity and the conversion speed with respect to it.
This is the rule for setting the conversion speed. FIG.
(A) shows a rule for linearly associating the remaining memory capacity with the conversion speed. In this case, the conversion speed V can be calculated by the following equation.

[0029]

(Equation 3)

FIG. 3B shows an example of a rule for nonlinearly associating the remaining memory capacity with the conversion speed. Here, assuming that the conversion is made by a quadratic curve, the conversion speed V can be calculated by the following equation.

[0031]

(Equation 4)

In the case of FIG. 3A, the conversion speed can be smoothly changed according to the increase or decrease of the remaining memory capacity, while in the case of FIG. 3B, data is accumulated to some extent in the buffer memory 105. Until the above, there is a characteristic that the recording speed can be stabilized as close as possible to 1.

FIG. 3C shows an example in which the non-linear correspondence is defined on the steps, and the conversion speed V can be calculated by the following equation.

[0034]

(Equation 5)

According to the rule shown in FIG. 3C, it is possible to realize substantially the same control as the rule shown in FIG. 3B with a small amount of calculation and a small circuit scale.

As described above, by determining the conversion speed based on the corresponding rule in FIG. 3, even if the signal is reproduced at the double speed, an input signal having a certain amount of silence or more is heard at a recording speed close to 1. It is possible to set an easy speed, and when a signal that does not include silence continues, the maximum conversion speed 2 is set, so that data loss does not occur. Here, the maximum value of the conversion speed is 2 and the minimum value is 1
But the maximum value is smaller than 2 (for example, 1.8),
The same rule can be set even if the minimum value is set to a value larger than 1 (for example, 1.5). However, when the maximum value is set to a value smaller than 2, when a signal that does not include silence continues, a signal reproduced at twice the recording speed is set to a speed less than at most twice the maximum. Therefore, it may be necessary to reject a part of the data because the data cannot be read. This is, for example, Pw in FIG.
Corresponds to Pr, but in this case, as described above, by resetting the remaining memory to 0, the data corresponding to the capacity of the buffer memory accumulated so far is discarded. Become. For example, if the capacity of the buffer memory is 256 kbits and 8-bit data per sample is handled at 10 kHz sampling, 32 kbits is used.
The point (about 3.2 seconds) of sound data is discarded. By performing such a setting, part of the data is lost due to the amount of silence, but by suppressing the maximum value of the conversion speed, it becomes possible to reproduce the entire data at a slower and easier to hear speed. .

The value of the conversion speed V determined by the adaptive speed control unit 108 is sent to the time axis control unit 109, and the time axis is converted according to the conversion speed V. FIG. 4 is a block diagram showing a detailed configuration of the time axis control unit 109. In FIG. 4, reference numeral 401 denotes a control circuit for performing overall control;
Reference numeral 2 denotes a switching circuit for switching between a cross-fade processing section in which weighted addition is performed according to a command from the control circuit and a non-processing section, 403 a latch circuit for temporarily holding data,
Reference numeral 04 denotes a cross-fade circuit for performing a weighted addition process. The other blocks are the same as the blocks having the same names in FIG. Hereinafter, along FIG.
The operation of the time axis control unit 109 will be described.

The control circuit 401 first determines the cross-fade section length K and the non-processing section length S to realize the conversion speed V.
To determine. Here, the crossfade section length is fixed value K
However, it is of course possible to make the value of K variable according to the conversion speed V. FIG. 5 is a schematic diagram for explaining the time axis conversion processing. FIG. 5A shows data before the processing,
FIG. 5B shows the data after the processing. FIG.
The part corresponding to the data length K in (b) is data A and B
Indicates that the cross-fade processing has been performed. here,
In order to realize the conversion speed V, the data A,
The length S may be determined so that 1 / V of the total length (2K + S) of B and C becomes the data length (K + S) after the time axis processing. Therefore, the non-processing section length S is determined by the following equation.

[0039]

(Equation 6)

Now, assuming that the read pointer Pr points to the head of the data string A in FIG. 5A, the crossfade processing will be described first. The control circuit 401 switches the switching circuit 402 to the cross-fade processing side,
It instructs the read control unit 106 to read the data indicated by the pointer Pr. This data is input to the latch circuit 403 and held. Next, the control circuit 401 instructs the read control unit 106 to read data indicated by the address of Pr + K which is k samples ahead, and this data is directly input to the crossfade circuit 404. Crossfade circuit 4
04 performs weighted addition using these two data.

[0041] Here, the data string A in FIG. 5 (a) d _0,
d ₁ ,..., d _k−1 , and the data string B are d _k , d _{k + 1} ,.
_2k-1 . The weighting function that monotonically increases is w ₁ (t) (where 0 ≦ w ₁ (t) ≦ 1, t = 0, 1,..., K−1), and the weighting function that monotonically decreases is w ₂ (t). = 1-w ₁ (t), the value c _t of the weighted sum is obtained by the following equation.

[0042]

(Equation 7)

Thereafter, the read pointer Pr is incremented, and thereafter, the control circuit continues the same processing as described above K times, and after all the cross-fade processing between the data strings A and B in FIG. Is the current Pr
The value of + K is set. When the cross-fade processing is completed, the control circuit 401 switches the switching circuit 402 to the non-processing side, and the data read from the buffer memory 105 is directly the D / A data of the length S determined by (Equation 6).
Input to converter 110. Thereafter, by alternately repeating the cross-fade processing of the length K and the output of the unprocessed data of the length S, time axis conversion giving the conversion speed V can be realized. If the conversion speed set by the adaptive speed control unit 108 is changed at a certain point in time, the non-processing section length is changed according to (Equation 6), and thereafter the same processing is continued to change the conversion speed at any time. I do.

The data sequence that has been subjected to the time axis conversion processing in this manner is finally converted into an analog signal by the D / A converter 110 with a period T, so that the pitch is the same as during recording and the reproduction speed is M or less. Thus, an audio signal whose speed is adaptively switched can be obtained.

As described above, according to the first embodiment, the sound / non-speech judging unit 103, the memory remaining amount monitoring unit 107 for measuring the remaining memory from the positional relationship between the write pointer and the read pointer, and the memory By providing an adaptive speed control unit 108 that determines the speed of the time axis conversion according to the remaining amount, by gradually lowering the conversion speed when the remaining memory amount is small, and gradually increasing the conversion speed when the remaining memory amount is large, Depending on the amount of silence contained in the audio signal played at high speed, the playback speed is slower than the playback speed,
Moreover, there is almost no loss of information, and it is possible to listen at high speed. In addition, by providing the time axis control unit 109 that converts the time axis at a desired conversion speed by adjusting the cross fade section length and the non-processing section length, high-quality time axis conversion can be realized. If the crossfade section length is fixed to a preset value, an arbitrary time axis conversion speed can be achieved only by changing the length of the non-processing section, and an audio time axis conversion apparatus can be realized with a very simple configuration. be able to. Particularly, in a recording / reproducing unit accompanied by an image such as a VTR, for example, an image can be reproduced at a double speed and only an audio can be reproduced at a slow speed of 2 times or less, which is highly effective.

Next, the second embodiment of the audio time base conversion apparatus of the present invention will be described.
An example will be described. The basic configuration of the audio time axis conversion device of the present embodiment is the same as the block diagram shown in FIG. 1, and only the operation of the writing control unit 104 is different. FIG. 6 is a flowchart illustrating the operation of the write control unit according to the present embodiment. Hereinafter, only the operation of the write control unit will be described with reference to FIG.

The write operation unit 104 sequentially takes in the value of the remaining memory Z measured by the remaining memory monitoring unit 107 (S1) and compares it with a preset threshold value Zth (S2). Here, if Z is larger than Zth, that is, if there is a sufficient remaining memory, the sound / silence determination unit 103
It is determined whether the current input data is voiced or silent based on the result (S3), and if it is voiced, the data is written to the buffer memory 105 (S4), and the write pointer Pw is incremented (S5). ). If the determination condition of S3 is not satisfied, that is, if there is not enough remaining memory, regardless of the determination result of sound / no sound,
The data is written into the buffer memory 105, and the write pointer Pw is incremented. Specifically, the above-described series of processing is performed for a signal including a lot of silence,
In FIG. 2A, control is performed so that the read pointer Pr does not catch up with the write pointer Pw, that is, the remaining memory does not become zero.

As described above, according to the second embodiment, when the remaining amount of memory is smaller than a predetermined amount, the write control unit for accumulating all data in the buffer memory is provided. Can be prevented from being interrupted (becoming a mute state) without causing the sound to be converted to 0, and a sound time base conversion apparatus capable of natural reproduction without a sense of incongruity can be realized.

[0049]

As described above, according to the audio time base conversion apparatus of the present invention, only the sound part is stored in the buffer memory by the sound / non-speech judgment from the sound signal reproduced at M (≧ 1) times the recording speed. Then, the remaining memory is measured from the write and read address positions, and according to the amount of silence, the speed becomes as low as possible when the remaining capacity is low, and gradually increases as the remaining capacity increases. The conversion speed can be automatically adjusted by
It is possible to provide an audio time base conversion apparatus capable of reproducing a sound at the same pitch as that at the time of recording and at an easy-to-listen speed lower than the reproduction speed.

Further, by providing a time axis control unit for converting the time axis to a desired conversion speed by adjusting the cross fade section length and the unprocessed section length, especially when the cross fade section length is kept constant. By simply adjusting the length of the non-processing section, an arbitrary conversion speed can be achieved, and a high-quality time-base converted reproduced sound can be realized with a simple circuit configuration.

When the remaining memory capacity is low, all data is stored in the buffer memory regardless of the presence or absence of sound or no sound, so that there is no data to be output and a mute state occurs during playback. It is possible to provide an audio time base conversion device capable of outputting natural reproduced audio without a sense of incongruity.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an audio time base conversion apparatus according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram of a method of measuring a remaining memory amount according to the embodiment;

FIG. 3 is an explanatory diagram of a speed setting method of an adaptive speed control unit according to the embodiment.

FIG. 4 is a circuit diagram of a time axis control unit according to the embodiment.

FIG. 5 is a principle diagram illustrating an operation of a time axis control unit according to the embodiment;

FIG. 6 is a flowchart showing the operation of a write control unit according to a second embodiment of the present invention;

FIG. 7 is a block diagram of a conventional audio time base conversion apparatus.

FIG. 8 is a principle diagram showing a data processing method of a conventional audio time base conversion apparatus.

[Explanation of symbols]

 Reference Signs List 101 recording / reproducing unit 102 A / D converter 103 sound / non-sound determining unit 104 write control unit 105 buffer memory 106 read control unit 107 remaining memory monitoring unit 108 adaptive speed control unit 109 time axis control unit 110 D / A converter

──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Norikazu Ueno 1006 Kazuma Kadoma, Kadoma-shi, Osaka Matsushita Electric Industrial Co., Ltd. (56) References JP-A-7-192392 (JP, A) JP-A-5-192 73089 (JP, A) JP-A-7-191695 (JP, A) JP-A-6-289895 (JP, A) JP-A-3-205656 (JP, A) (58) Fields investigated (Int. ⁷ , DB name) G10L 21/00-21/06

Claims (6)

(57) [Claims] 1. A recording / reproducing section for reading an audio signal stored in a recording medium at a speed M (≧ 1) times that at the time of recording, and converting an analog audio signal read by the recording / reproducing section into a digital signal. An A / D converter, a voiced / silent determining unit for determining a voiced portion and a voiced portion of the input signal, a buffer memory for storing digitally converted data, and a voiced / voiceless sound determining unit. A write control unit that controls a write address so that only data in the determined section is written to the buffer memory; a read control unit that reads data from the buffer memory; and a write control unit that is written to the buffer memory last by the write control unit. By monitoring the positional relationship between the read address and the address on the buffer memory last read by the read control unit, A memory remaining amount monitoring unit for measuring the remaining amount of memory in the memory, and an adaptive speed for determining a time axis conversion speed of data according to a predetermined rule according to the remaining amount of memory obtained from the memory remaining amount monitoring unit. A control unit and an address of the buffer memory indicated by the read control unit according to the conversion speed determined by the adaptive speed control unit.
While reading the data sequentially from the
A time axis control unit that performs compression and outputs the data, and a D / A converter that receives the data after compression processing obtained by the time axis control unit and converts the data into an analog signal. Conversion device. 2. The adaptive speed control section sets the maximum value of the set conversion speed to be equal to or less than the reproduction speed M from the recording medium, sets the minimum value to be equal to or higher than the recording speed of the recording medium, 2. The audio time base conversion device according to claim 1, wherein the conversion speed is determined in proportion to the amount. 3. The adaptive speed control unit sets the maximum value of the set conversion speed to be equal to or less than the reproduction speed M from the recording medium, sets the minimum value to be equal to or higher than the recording speed of the recording medium, 2. The audio time base conversion apparatus according to claim 1, wherein the conversion speed is determined based on a conversion rule that is nonlinearly associated with the quantity. 4. A time axis control unit for adding a value obtained by multiplying a sequence of sample values of a fixed number adjacent to each other by a monotonically decreasing weighting factor and a value obtained by monotonically increasing a weighting factor. The adaptive speed control unit controls the length of the fade processing section and the length of the non-processing section for directly outputting data.
It is adjusted successively so that the time axis conversion speed obtained by
By outputting each section alternately, the time axis
4. The audio time base conversion device according to claim 1, wherein a reduced signal is output . 5. A writing control unit, wherein when the remaining memory amount is equal to or more than a predetermined amount in the remaining memory amount monitoring unit, only the data determined to be sound by the sound / non-sound determining unit is stored in the buffer memory.
If the memory remaining amount monitoring unit determines that the memory remaining amount is equal to or less than a certain amount, the write address is stored so that all data is stored in the buffer memory regardless of the result of the sound / silence determining unit. 2. The audio time axis conversion device according to claim 1, wherein 6. The writing control section stores only data determined to be sound by the sound / non-sound determination section in the buffer memory when the remaining memory amount is equal to or more than a predetermined amount in the memory remaining amount monitoring section,
If the memory remaining amount monitoring unit determines that the memory remaining amount is equal to or less than a certain amount, the write address is stored so that all data is stored in the buffer memory regardless of the result of the sound / silence determining unit. 5. The audio time axis conversion device according to claim 4, wherein