JPH05303400A - Method and device for audio reproduction - Google Patents

Abstract

PURPOSE:To provide an audio reproduction method and a device which reduces a data discarding rate and the amount of delay while keeping the same interval as in the recording during a higher speed reproduction of acoustic signals than the recording. CONSTITUTION:By operating a signal reproducing means 201, an AD transforming unit 202, a digital memory 203 and a clock rate setting means 205, acoustic signals sampled at a sampling period Tn/Rt which is a higher speed than the one during a recording are stored in the digital memory 203. A time region expanding processing means 10 time region compresses the output signals of the memory 203 with a compression ratio S given by a compression ratio setting means 12. A comparing means 13 compares a relative speed Rt and a speed threshold value Rs and when Rt is larger than Rs, sets the compression ratio to 1/Rs and controls the operations of a memory control means 11 and the setting value of the means 12.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio reproducing apparatus and an audio reproducing method for reproducing the speed of a recorded audio signal faster than that at the time of recording.

[0002]

2. Description of the Related Art Conventionally, various devices having a function of varying the reproduction speed of a recorded audio signal have been proposed. The simplest examples are cue (fast forward playback) and review (rewind playback) of an analog tape recorder, but these high-speed playback voices have both pitch and speed changed compared to the voice at the time of recording, It is almost impossible to listen to the content or to cue. There is also proposed a device that performs compensation so that the pitch does not change during high-speed reproduction. Hereinafter, a conventional audio reproducing device that performs pitch compensation will be described with reference to the drawings.

FIG. 11 shows the structure of a conventional audio reproducing apparatus. In the figure, 201 is a signal reproducing means,
202 is an AD converter, 203 is a digital memory, 20
4 is a DA converter, 205 is a clock rate setting means, 2
Reference numeral 06 is a memory control means.

The operation of the audio reproducing apparatus having the above structure will be described below. Here, in the case of reproducing at a speed higher than the reproducing speed at the time of recording, an apparatus for returning to a normal speed and pitch and reproducing is shown.

An acoustic signal is reproduced at a relative speed that is Rt times (Rt> 0) the recording speed. The signal reproducing means 201 converts an acoustic signal recorded on a magnetic tape or the like into an electric signal and extracts it as a signal having an appropriate level. It is difficult to understand the content because the pitch and speed of this signal are Rt times as high as usual. Then, the output of the signal reproducing means 201 is converted into a digital signal by the AD converter 202. The sampling cycle of the AD converter 202 is converted by the clock rate setting means 205 into a sampling cycle Tn / Rt which is inversely proportional to the relative speed Rt. The digital signal has a cycle Tn / Rt under the control of the memory control means 206.
Then, it is written in a predetermined address of the digital memory 203. The digital memory 203 functions as a buffer memory that temporarily stores data. Then, the digital signal recorded in the digital memory 203 sequentially reads out the data of the address indicated by the memory control means 206 at the cycle Tn, and is converted into an analog signal at the sampling cycle Tn by the DA converter 204 and output.

Next, it will be described whether the pitch and speed changing during high-speed reproduction are returned to the normal pitch and speed during recording. When a VTR, a cassette tape recorder, or the like is reproduced at a higher speed than during recording, the reproduced frequency shifts toward a higher direction. Now, assuming that the sampling period that satisfies the sampling theorem for the acoustic signal at the time of recording is Tn, at the time of AD converting the acoustic signal reproduced at high speed to 1 / It is necessary to sample by Rt times, that is, Tn / Rt. On the contrary, when performing high-speed reproduction at the relative speed Rt, a signal obtained by AD-converting the sampling cycle with Tn / Rt is DA-converted with the sampling cycle Tn, whereby an acoustic signal having a normal pitch is restored. Since it is naturally impossible to reproduce all the AD-converted data in terms of time, only a part of the input voice is continuously reproduced at a normal speed and pitch, and most of the rest is discarded. The operation will be repeated.

FIG. 12 is an example of data processing showing an outline of processing when the relative speed is 5. In the figure, Tf is the repetition cycle of the processing when high-speed reproduction is performed, and Tc is the time required to write the AD-converted data in the required amount in the digital memory. As can be seen from the diagram of the unprocessed data in Fig. 12 (b), the ratio of the data actually used and the data discarded without being used at the time of high speed reproduction is Tc: (Tf
-Tc), i.e. 1: 4. Therefore, the acoustic signal during recording 5T
Of the time of f, the time that can be actually heard is Tf, and the data of the remaining time of 4Tf is discarded. This processing is reproduced at high speed and repeated at the cycle Tf. Here, when the amount of data stored in the digital memory is 64 K words, the relative speed is 5 and the reference sampling period is 50.
If it is [μsec], Tf will be 3.2768 [sec]. That is,
During high-speed reproduction at a relative speed of 5, it means that the audio signal at the time of recording is taken out for every 3.2384 [sec] every 16.384 [sec] for listening. Further, when the ratio of the amount of data to be discarded in the reproduced signal is the discard rate Ra, it is expressed by the following equation.

[0008]

[Equation 5]

Since the relative speed is set to 5 in the example of FIG. 12, the discard rate Ra is 0.8, and most of the reproduced signal cannot be used and is discarded. Since a delay time is generated between the acoustic signal that is next heard as the output and the input signal that is actually being reproduced, if a desired signal portion is searched based on the acoustic signal that is heard as the output, a large deviation will occur. Will occur. Let Td be the maximum delay between the input and output signals.

[0010]

[Equation 6]

From this equation, since Td is also a function of Tf, it is possible to reduce the maximum delay by making it smaller, but if Tf is made too small, the content cannot be recognized and the acoustic Search by signal cannot be performed. In the example of FIG. 12, the maximum delay amount Td is 13.08 [sec] while Tf is 3.2768 [sec]. FIG. 13 shows the relationship among the relative speed Rt, the compression rate Sc, the discard rate Ra, and the maximum delay amount Td.

[0012]

[Problems to be Solved by the Invention] As shown above,
In the conventional example, most of the audio signals to be reproduced are discarded without being used at all. Then, the ratio of the amount of data to be discarded increases as the relative speed Rt for high speed reproduction increases. Also, as the discard rate increases, the probability of missing the information contained in the input signal increases, and the maximum delay amount between the audio signal being listened to and the audio signal currently being reproduced increases. Therefore, it becomes difficult to search for a desired signal portion based on the reproduced sound.

The present invention solves the above-mentioned problems of the prior art. A voice generation apparatus and a voice reproduction capable of reducing the discard rate and the delay amount between input and output signals while maintaining the same pitch as during recording. The purpose is to provide a method.

[0014]

To achieve this object, in a voice reproducing apparatus according to a first aspect of the present invention, a time domain expansion / compression processing means for expanding / compressing a digital signal read from a digital memory in a time domain, a relative speed and a threshold value. And a comparison means for comparing

In the audio reproducing apparatus according to the second aspect, the operation mode of the compression ratio setting means and the selecting means is determined, and the digital signal read from the mode control means and the digital memory for obtaining the value of the compression ratio to be expanded / contracted in the time domain. The time domain expansion / contraction processing section is configured to have a selection section for selecting whether to expand / contract the time domain or output as it is.

In the voice reproducing method according to the third aspect, the digital signal read from the digital memory is used as the relative speed Rt.
Depending on the value of

[0017]

[Equation 7]

An algorithm for performing time domain compression with a compression ratio Sc shown in is used. In the voice reproducing method according to claim 4, the digital signal read out from the digital memory is output according to the value of the relative speed Rt.

[0019]

[Equation 8]

An algorithm for performing time domain compression with a compression ratio Sc shown in is used. In the voice reproducing method according to claim 5, the digital signal read from the digital memory is changed in accordance with the value of the relative speed Rt.

[0021]

[Equation 9]

An algorithm for performing time domain compression with a compression ratio Sc shown in is used.

[0023]

According to the structure of claim 1, when the relative speed is equal to or higher than the predetermined threshold value, the sound signal is reproduced faster than during recording while maintaining the normal pitch by the time domain expansion / contraction processing, so that more sound than before can be produced. Since the signals can be reproduced at the same time, the discard rate and the maximum delay amount between the input and output signals can be made smaller than before while maintaining the same pitch as during recording.

According to the structure of claim 2, by reproducing the acoustic signal faster than during recording while maintaining the normal pitch by the time domain expansion / contraction processing, or by reproducing the acoustic signal at the normal pitch and at the normal speed. Since it is possible to reproduce an acoustic signal equal to or higher than the conventional one in the same time, the discard rate and the maximum delay amount between the input and output signals can be reduced to the conventional level or lower while maintaining the same pitch as during recording.

According to the method of claim 3, by performing time domain compression with the compression ratio Sc given by (Equation 7), it is possible to obtain an acoustic signal reproduced at a normal pitch and a speed of Rs. The discard rate and the maximum amount of delay between input and output signals can be reduced while maintaining the same pitch as during recording.

According to the method of claim 4, by performing time domain compression with the compression ratio Sc given by (Equation 8), the velocity Rs (k) is in the normal pitch and according to the value of the relative velocity Rt.
It is possible to obtain an acoustic signal reproduced at a speed of (k = 1,2, ..., n), and reduce the discard rate and the maximum delay between input and output signals while maintaining the same pitch as during recording. Is something that can be done.

By performing time domain compression with the compression ratio Sc given by (Equation 9) according to the method of claim 5, all the sound is reproduced when the speed for high speed reproduction is the relative speed Rt smaller than the value of the threshold value Rs. Performs time domain compression using the signal, and when the relative velocity Rt is greater than the threshold value Rs, discards a portion of the input acoustic signal and performs time domain compression to record at normal pitch and record. It is possible to obtain an acoustic signal reproduced at a speed less than the relative speed Rt faster than time, and to reduce the discard rate and the maximum delay amount between input and output signals while maintaining the same pitch as during recording. ..

[0028]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a block diagram of an audio reproducing apparatus in a first embodiment of the present invention. In FIG.
Reference numeral 201 is a signal reproduction means, 202 is an AD converter, 203 is a digital memory, 204 is a DA converter, 205 is a clock rate setting means, 10 is a time domain expansion / contraction processing means, 1
Reference numeral 1 is a memory control means, 12 is a compression ratio setting means, and 13 is a comparison means. Of these, 201, 202, 203, 2
The components 04 and 205 are the same as those of the conventional example.

In this embodiment, the processing content is changed based on the relative speed Rt for high speed reproduction and the given speed threshold Rs. First, regarding the definition of the compression ratio, this is defined by the time length ratio between the input signal that undergoes time domain modification (= Time Scale Modification, hereinafter referred to as TSM) and its output signal. Therefore, in the audio reproducing apparatus described below, only the processing at the time of high-speed reproduction is described, so that the compression ratio is always larger than 1.0. The TSM processing is described in, for example, "Digital Audio Processing" (pages 122 to 124, Sadahiro Furui, Tokai University Press). The signal reproducing means 201, the AD converter 202, the digital memory 203, and the clock rate setting means 205 are almost the same as the conventional example.
Is operated, the acoustic signal sampled at the sampling cycle Tn / Rt which is faster than that at the time of recording is stored in the digital memory 203. The time domain expansion / contraction processing means 10 compresses the output signal of the digital memory 203 in the time domain according to the compression ratio Sc given by the compression ratio setting means 12. The comparison means 13 determines the relative speed Rt and the speed threshold value.
Rs is compared, and when Rt is larger than Rs, the compression ratio is 1 /
Setting to Rs controls the operation of the memory control means 11 and the set value of the compression ratio setting means 12.

Next, how data is output during high speed reproduction will be described with reference to a schematic diagram. FIG. 2 is a schematic diagram of data processing when the relative speed is 2 and 5 in the first embodiment. In this embodiment, the threshold Rs is 2.
It is assumed that the time domain compression process with a compression ratio of 0.5 is performed when the relative speed to the recording speed is 2.0 or more, that is, 2.0 or more. In the case of the relative speed 2, FIG. 2B is unprocessed data and FIG. 2C is processed data. Further, in the case of the relative speed 5, FIG. 2 (d) is the unprocessed data and (e) is the processed data. As is clear from the figure, when the relative speed is 2, the output is calculated using all the data. Data disposal rate Ra in this example
1 is generally expressed by the following equation.

[0032]

[Equation 10]

In the example of FIG. 2 (c), the relative speed is 2 and the compression ratio is
Since it is set to 0.5, the disposal rate Ra1 is
It becomes 0.0. In the example of Fig. 2 (e), the relative speed is 5 and the compression ratio is 0.
Since it is set to 5, the disposal rate Ra1 is 0 according to (Equation 10).
6

Next, the maximum delay amount Td1 between the input and output signals in this embodiment is expressed by the following equation.

[0035]

[Equation 11]

In order to calculate Td1, Tf is calculated as in the conventional example.
When calculated with 3.2768 [sec], a relative speed of 5, and a compression ratio Sc of 0.5, it is 0.0 [sec] in the case of FIG. 2C and 9.8304 [sec] in the case of FIG. 2E.

FIG. 3 shows the relative speed Rt, the compression ratio Sc, the discard rate Ra,
It is a figure showing the relationship with the maximum delay amount Td. It can be seen that the larger the relative speed, the larger the discard rate and the maximum delay amount.

As described above, according to the present embodiment, it is easily understood that the reproduced sound can be obtained in which both the discard rate Ra1 and the maximum delay amount Td1 are smaller than those in the conventional example while maintaining the same pitch as during recording. To be done.

In the present embodiment, the VTR is the same as the conventional example.
However, the recording medium may be a semiconductor memory, an optical disk, or the like, although it is described as being applied to acoustic signal information recorded on a magnetic recording medium such as a cassette tape recorder.

The second embodiment of the present invention will be described below with reference to the drawings. FIG. 4 shows a block diagram of an audio reproducing apparatus in the second embodiment of the present invention. In FIG. 4, 201 is a signal reproducing means, 202 is an AD converter, 203 is a digital memory, 204 is a DA converter,
Reference numeral 205 is a clock rate setting means, 10 is a time domain expansion / contraction processing means, 11 is a memory control means, 12 is a compression ratio setting means, 20 is a mode control means, and 21 is a selection means. Of these, 201, 202, 203, 204, and 205 are the same constituent elements as the conventional example.

In this embodiment, the processing contents are changed based on the relative speed Rt for high speed reproduction and the given compression ratio Sc. Signal reproducing means 201 and AD converter 20 are almost the same as in the conventional example.
2. By operating the digital memory 203 and the clock rate setting means 205, the acoustic signal sampled at the sampling cycle Tn / Rt which is faster than that at the time of recording is stored in the digital memory 203. The time domain expansion / contraction processing means 10 compresses the output signal of the digital memory 203 in the time domain according to the compression ratio Sc given by the compression ratio setting means 12. The mode control means 20 determines that the compression ratio Sc
In the case of 1.0, control for operating in the conventional mode without time domain compression, and control for operating in the time compression mode using the time domain compression processing means when the compression ratio Sc is greater than 1, the memory control means 11, This is performed for the compression ratio setting means 12 and the selection means 21. When the compression ratio is greater than 1, that is, when operating in the time compression mode, the relative speed
Rt is compared with the compression ratio Sc, and when Rt is smaller than 1 / Sc, the compression ratio is set to 1 / Rt, and when Rt is larger than 1 / Sc, the compression ratio is set to Sc as it is, and the memory control means 11,
The compression ratio setting means 12 and the selection means 21 are controlled.

Next, how data is output during high speed reproduction will be described with reference to a schematic diagram. FIG. 5 is a schematic diagram of data processing when the relative speed is 5 in the second embodiment. When the given compression ratio Sc is 1.0, the same data processing as the conventional example is performed as shown in FIG. On the other hand, the compression ratio
When Sc is a value smaller than 1.0, the TSM processing is performed, so the amount of data used is larger than when the compression ratio Sc is 1.0. FIG. 5D shows a schematic diagram when the compression ratio Sc is 0.5. In the figure, the area described as 1 & 2 represents that the TSM processing is performed using the signal 1 and the signal 2. Here, since the compression ratio Sc is set to 0.5, twice the data amount is used as compared with (c). Therefore, in (c), instead of playing the portion of signal 1 at the time of Tf at the same speed as when recording, at (d) the portion of signal 1 and signal 2 at the time of Tf has the same pitch as that at the time of recording, and It will be played back at twice the speed. That is, in (d), twice as much information as in (c) is heard within the same time. The data discard rate in this embodiment is expressed by (Equation 10) as in the first embodiment.

In the example of FIG. 5D, the relative speed is 5, and the compression ratio is
Since it is set to 0.5, the disposal rate Ra1 is
It becomes 0.6. The larger the relative speed, or the closer the compression ratio value is to 1, the larger the discard rate Ra1. In FIG. 5 (c), the disposal rate is 0.8, which is the same as the conventional example.

Next, the maximum delay amount Td1 between the input and output signals in the device of this embodiment is expressed as in (Equation 11) as in the first embodiment.

Similar to the conventional example, when Tf is 3.2768 [sec], the relative speed is 5, and the compression ratio Sc is 0.5, the maximum delay amount Td1 in the example of FIG. 5D is calculated to be 9.8304 [sec]. The example of FIG. 5 (c) is 13.08 [sec] as in the conventional example.

As described above, according to the present embodiment, not only the same reproduction as in the conventional method but also the discard rate Ra1 and the maximum delay amount Td1 are the same or smaller than those in the conventional example while maintaining the same pitch as during recording. It is easily understood that the reproduced sound can be obtained.

In this embodiment, the VTR is the same as the conventional example.
However, the recording medium may be a semiconductor memory, an optical disk, or the like, although it is described as being applied to acoustic signal information recorded on a magnetic recording medium such as a cassette tape recorder.

The third embodiment of the present invention will be described below with reference to the drawings. FIG. 6 shows a flow chart of the audio reproducing method in the third embodiment of the present invention. The description will be given below.

When the recording medium for recording the acoustic signal is a magnetic recording medium, the acoustic signal is temporarily used as a buffer for RA.
It is necessary to record in M, but when a semiconductor memory is used as a recording medium, the following processing may be performed as it is.
That is, in the case of a magnetic recording medium or the like, it is necessary to perform the following processing separately from the writing of the acoustic signal in the RAM. In this embodiment, it is assumed that a sufficient number of acoustic signals digitized at the sampling period Tn are already stored in the random access memory (hereinafter referred to as RAM) to perform the following processing. That is, the amount of data that can be compressed in the time domain is already in the RAM.
Existence above is a requirement.

Next, the definition of symbols is shown. Let P be a pointer indicating the start address of the memory to be reproduced. It is assumed that the acoustic signal is continuously recorded from the pointer P. For this data string, the reproduction output is output after processing with Nf units as frames, and this is repeated. Na (0 <Na ≦ Nf) indicates the number of data to be output after time domain compression, and Nb (0 ≦ Nb <Nf) indicates the number of data to output silence. Here, Nf is equal to the sum of Na and Nb. If high-speed reproduction is performed at a relative speed of Rt with respect to recording, it is necessary to consume Rt · Nf data during high-speed reproduction during the time of reproducing Nf data during recording.

The description will be given below with reference to the flowchart of FIG. First, the values of Rt, Nf, Na, and Nb are determined as initial settings. Then, the compression ratio Sc for time compression is obtained according to the value of Rt. Here, as an example represented by (Equation 8), a case of following the following equation will be described.

[0052]

[Equation 12]

The following is the processing for one frame, that is, the portion for repeatedly performing the processing. (a) The data after the pointer P is time-domain compressed at the compression ratio Sc given by (Equation 12), and Na data is output.

(B) Output Nb silent data. This processing is applied when forcibly inserting silence when frames are connected discontinuously.

(C) The address indicated by the pointer P is increased by Rt · Nf to prepare for the next processing. To continue the process, the processes (a) to (c) are repeated.

Next, how data is output during high-speed reproduction will be described with reference to schematic diagrams. FIG. 7 shows a schematic diagram of data processing when the relative speeds are 2, 3, and 5 in the third embodiment. In this embodiment, the threshold Rs
It is assumed that the processing is performed when (1) is 2.0, that is, the relative speed to the recording speed is 2.0 or more. As shown in (Equation 129), the compression ratio Sc is 1/2 when the relative speed is 2 or more and less than 3, 1/3 when the relative speed is 3 or more and less than 4, and 1/4 when the relative speed is 4 or more. , Change the setting according to the relative speed value. In the case of the relative speed 2, FIG. 7B shows unprocessed data and FIG. 7C shows processed data. In the case of the relative speed 3, FIG. 7D shows unprocessed data, and FIG. 7E shows processed data. Further, in the case of the relative speed 5, FIG. 7 (f) is the unprocessed data and (g) is the processed data. As is clear from the figure, when the relative speed is 2 or 3, the output is calculated using all the data. On the other hand, when the relative speed is 5, a part is discarded. The data discard rate Ra in the present embodiment is expressed by the following equation.

[0057]

[Equation 13]

Since the relative speeds are set to 2 and 3 in the examples of FIGS. 7C and 7E, the discard rate Ra is 0.0. In the example of FIG. 7 (g), since the relative speed is set to 5, the discard rate Ra is 0.2. The discard rate varies discontinuously due to the positional relationship between the relative speed and the threshold value. The waste rate Ra is generally expressed as follows based on (Equation 8).

[0059]

[Equation 14]

Next, the maximum delay amount Td between the input and output signals in this embodiment is expressed by the following equation.

[0061]

[Equation 15]

In order to calculate Td, Tf is set to 3.
2768 [sec], 0.0 [se] in the case of Fig. 7 (c) and (e)
c], which is 3.2768 [sec] in the case of FIG. 7 (g). The maximum delay amount also changes discontinuously depending on the positional relationship between the relative speed and the threshold value. The maximum delay amount Td is generally expressed as follows based on (Equation 8).

[0063]

[Equation 16]

FIG. 8 shows the relationship between the relative speed Rt, the compression ratio Sc, the discard rate Ra, and the maximum delay amount Td in this embodiment. The difference can be clearly seen in comparison with the case of the conventional example of FIG.

As described above, according to this embodiment, the waste rate Ra
It is easily understood that the reproduced sound can be obtained with both the maximum delay amount Td and the maximum delay amount Td being smaller than the conventional example.

Next, as an example represented by (Equation 9), the compression ratio
The case where Sc follows the following formula is explained.

[0067]

[Equation 17]

When the compression ratio shown in (Equation 17) is given, when the relative velocity is less than 2, time domain compression using all the input acoustic signals is performed, and when it is more than that, the compression ratio is obtained. Performs a fixed time compression. The disposal rate in this case is expressed as the following equation.

[0069]

[Equation 18]

Then, the discard rate is generally written based on the compression ratio represented by (Equation 9) as follows.

[0071]

[Formula 19]

The maximum delay amount is given by the following equation.

[0073]

[Equation 20]

Then, the maximum delay amount is generally written as follows based on the compression ratio represented by (Equation 9).

[0075]

[Equation 21]

The relationship between the relative speed Rt, the compression ratio Sc, the discard rate Ra and the maximum delay amount Td in the case of this example is as shown in FIG.

As described above, according to this embodiment, the waste rate Ra
It is easily understood that the reproduced sound having a value smaller than that of the conventional example can be obtained for both 3 and the maximum delay amount Td3.

Next, as an example represented by (Equation 22), a case where the compression ratio Sc follows the following equation will be described.

[0079]

[Equation 22]

[0080]

[Equation 23]

When the compression ratio shown in (Equation 23) is given, when the relative velocity is less than 2, time domain compression using all the input acoustic signals is performed, and when it is more than that, the compression ratio is obtained. Performs a fixed time compression. The disposal rate in this case is expressed as the following equation.

[0082]

[Equation 24]

Then, the discard rate is generally written based on the compression ratio represented by (Equation 22) as follows.

[0084]

[Equation 25]

The maximum delay amount is given by the following equation.

[0086]

[Equation 26]

Then, the maximum delay amount is generally written as follows based on the compression ratio represented by (Equation 22).

[0088]

[Equation 27]

The relationship between the relative speed Rt, the compression ratio Sc, the discard rate Ra and the maximum delay amount Td in the case of this example is as shown in FIG.

As described above, according to this embodiment, the waste rate Ra
It can be easily understood that the reproduced sound having a value smaller than that of the conventional example can be obtained for both 4 and the maximum delay amount Td4.

[0091]

The audio reproducing apparatus of the present invention is provided with the time domain expansion / contraction processing means for expanding / compressing the time domain at the compression ratio given by the compression ratio setting means, so that the sound is reproduced faster than during recording while maintaining the normal pitch. The signal can be reproduced, and the discard rate and the maximum delay amount can be reduced to the same level or less. Therefore, V
Even when performing a search based on an audio signal in TR or the like, it is possible to set the content of reproduction and the time lag to be smaller than in the conventional case. Then, it becomes possible to select reproduction at the normal speed. It is also possible to change the operation by changing the threshold value for changing the compression ratio. This is because, for example, in the case of voice whose contents are difficult to understand, if the reproduction speed exceeds twice, the reproduced contents may not be understood, but in the present invention, the speed can be changed only by changing the threshold value. Further, in the audio reproducing method of the present invention, silent data can be inserted for the purpose of reducing discontinuity between frames.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a first embodiment of the present invention.

FIG. 2 is a schematic diagram of data processing in the first embodiment of the present invention.

FIG. 3 is a characteristic diagram showing the relationship between the relative speed, the compression ratio, the discard rate, and the maximum delay amount in the first embodiment of the present invention.

FIG. 4 is a configuration diagram of a second embodiment of the present invention.

FIG. 5 is a schematic diagram of data processing in the second embodiment of the present invention.

FIG. 6 is a flowchart showing an outline of processing in the third embodiment of the present invention.

FIG. 7 is a schematic diagram of data processing in the third embodiment of the present invention.

FIG. 8 is a characteristic diagram showing the relationship between the relative speed, the compression ratio, the discard rate, and the maximum delay amount in the third embodiment of the present invention.

FIG. 9 is a characteristic diagram showing the relationship between the relative speed, the compression ratio, the discard rate, and the maximum delay amount in the third embodiment of the present invention.

FIG. 10 is a characteristic diagram showing the relationship between the relative speed, the compression ratio, the discard rate, and the maximum delay amount in the third embodiment of the present invention.

FIG. 11 is a configuration diagram of a conventional example.

FIG. 12 is a schematic diagram of conventional data processing.

FIG. 13 is a characteristic diagram showing the relationship between the relative speed, the compression ratio, the discard rate, and the maximum delay amount in the conventional example.

[Explanation of symbols]

 10 time domain expansion / contraction processing means 11 memory control means 12 compression ratio setting means 13 comparing means 20 mode control means 21 selecting means 201 signal reproducing means 202 AD converter 203 digital memory 204 DA converter 205 clock rate setting means

Claims (6)

[Claims] 1. A signal reproducing means for reading out an acoustic signal recorded on a recording medium at a high speed at a relative speed Rt (Rt> Rs ≧ 1) relative to a recording time which is a predetermined threshold value Rs or more, and an acoustic signal read out. To an digital signal, a clock rate setting means for setting the sampling period of the AD converter to Tn / Rt, a digital memory for storing the output of the AD converter under the control of the memory control means, Time domain expansion / contraction processing means for expanding / compressing the digital signal read from the digital memory at the compression ratio given by the compression ratio setting means, and DA for converting the output of the time domain expansion / compression processing means into an analog signal at the sampling cycle Tn. A converter, a comparator for comparing the value of the relative speed Rt and the threshold value Rs to obtain the value of the compression ratio, and the data to the digital memory based on the output of the comparator. The memory control means for controlling the writing and reading, and the compression ratio setting means for setting the compression ratio of the time domain expansion / contraction processing means based on the output of the comparator, An audio reproducing device characterized by performing control so that reproduction is performed at a pitch during recording and at a speed that is Rs times that during recording. 2. A signal reproducing means for reading an acoustic signal recorded on a recording medium at a high speed at a relative speed Rt (Rt ≧ 1) to that at the time of recording, and A for converting the read acoustic signal into a digital signal.
The sampling period of the D converter and the AD converter is Tn /
A clock rate setting means for setting to Rt, a digital memory for storing the output of the AD converter under the control of the memory control means, and a digital signal read from the digital memory at a compression ratio given by the compression ratio setting means in the time domain. Time domain expansion / contraction processing means for expansion / contraction, DA converter for converting into an analog signal at a sampling cycle Tn, the memory control means, the compression ratio setting means and selection in consideration of the value of the relative speed Rt and the compression ratio. The mode control means for determining the operation mode of the means and obtaining the value of the compression ratio to be expanded / contracted in the time domain, and the output of the time domain expansion / compression processing means or the output of the digital memory are selected according to the operation mode given by the mode control means. Based on the output of the selecting means for outputting to the DA converter and the mode control means. High-speed reproduction having the memory control means for controlling writing and reading of data to and from the memory, and the compression ratio setting means for setting the compression ratio of the time domain expansion / contraction processing means based on the output of the mode control means. An audio reproducing apparatus characterized by performing control to reproduce the recorded sound signal at a pitch at the time of recording and at the same speed as or at a high speed at the time of recording. 3. When a sound signal stored in a digital memory is reproduced at a high speed at a relative speed Rt (Rt> 1) to that at the time of recording, a compression ratio is set for a relative speed Rt equal to or higher than a predetermined threshold value Rs. Sc is calculated by the following formula, and Let P be a pointer indicating the start address of the digital memory to be played back, and (a) Na number (0 <0 (Na ≤ Nf) data is output, (b) Nb pieces (Nb = Nf-Na) of silent data are output, and (c) The address indicated by the pointer P is increased by Rt ・ Nf. , The pitch is the same as when recording,
Moreover, a sound reproducing method characterized by reproducing an acoustic signal at high speed. 4. The audio reproducing method according to claim 3, wherein the compression ratio Sc is given by the following equation, and the compression ratio is changed stepwise according to the value of Rt to perform time domain compression. [Equation 2] 5. The speech according to claim 3, wherein the compression ratio Sc is given by the following equation, and when the value of Rt is less than or equal to a predetermined threshold value, the compression is performed in the time domain with a compression ratio inversely proportional to Rt. How to play. [Equation 3] 6. A compression ratio Sc is given by the following formula, and when the value of Rt is less than or equal to a predetermined threshold value, time compression is performed with a compression ratio inversely proportional to Rt. 4. The audio reproducing method according to claim 3, wherein the compression ratio is changed stepwise according to the value to perform time domain compression. [Equation 4]