JP3335080B2 - Digital audio data reproduction speed conversion method and digital audio data reproduction apparatus - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a method for changing the pitch without changing the pitch.
Digital audio data playback speed conversion method for changing digital audio data playback speed and digital audio data
It relates to a playback device .

[0002]

2. Description of the Related Art Conventionally, in order to change the reproduction speed of digital audio data recorded on a recording medium, generally, an apparatus for rotating or transporting a recording medium to reproduce the digital audio data is used in a device.
A method of changing the rotation speed or the transport speed of the recording medium is employed. In such a digital audio data reproduction speed conversion method, the reproduction speed is changed because the sampling frequency at the time of recording and the frequency at which D / A conversion is performed at the time of reproduction differ depending on the rotation speed or the transport speed of the recording medium. In this case, there is a problem that the pitch at the time of reproduction changes.

For example, when digital audio data is reproduced at twice the normal speed, as shown in FIG. 2, which is an explanatory diagram of the present invention, the digital audio data on the time axis is converted to times T ₀ , T ₁ , T _2, T _3, separated by a certain period of ...,
_{T 1 ~T 2, T 3 ~T} 4, thinning the digital audio data present on the time axis, delimited in ... and every other remaining _{T 0 ~T 1, T 2 ~T} 3, · .. Temporally join the digital audio data present on the time axis of. And
By reproducing the spliced digital audio data at a normal reproduction speed, the apparent reproduction speed is doubled. As described above, since the digital audio data is only reproduced by setting the rotation speed or the transport speed of the recording medium to the normal speed and doubling the apparent reproduction speed, it is possible to eliminate a change in the pitch during reproduction. .

[0004] By the way, data is discontinuous at the junction of the digital audio data after thinning. For this reason, at the time of reproduction, noise occurs at this joint. In order to suppress the generation of this noise, the following three types of methods have been proposed.

[0005] A method of reducing the occurrence of noise using a low-pass filter.

A search is made for a zero-cross point near the delimiter position of digital audio data, the waveform phase thereof is checked, and near the next delimiter position, a zero-cross point having the same phase as the previously checked waveform phase is searched for. A method of reducing the occurrence of noise by joining audio data.

As disclosed in Japanese Patent Application Laid-Open No. Hei 6-36462, a waveform phase near a break position of digital audio data is checked, and a phase having the highest correlation is connected with a sound level near the next break position. , A method for reducing the occurrence of noise by performing cross-fade processing on the connection part.

According to the above-mentioned method of converting the reproduction speed of digital audio data, it is possible to reduce the occurrence of noise due to the joint of digital audio data without changing the pitch during reproduction.

[0009]

By the way, the joint portion of digital audio data contains various frequency components. Therefore, the above-described method for converting the reproduction speed of digital audio data is not effective because there is a possibility that not only unnecessary noise but also data of necessary frequency components may be removed.

In the above-described method for converting the reproduction speed of digital audio data, when the frequency component of the digital audio data is low, there is a possibility that there is no zero-cross point in phase near the separation position. In addition, there is a problem that the data thinning interval becomes irregular and the reproduction speed of digital audio data does not always double.

Further, in the above-described method of converting the reproduction speed of digital audio data, the time axis ratio of the cross-fade portion for performing the cross-fade process changes, so that the reproduction speed does not always double.

Therefore, in the above-mentioned conventional method for converting the reproduction speed of each digital audio data, the time axis of the digital audio data can be compressed and reproduced without changing the pitch of the reproduced sound, but the digital audio data cannot be reproduced at the joint. There is a problem in that the playback speed cannot be fixed when the playback speed is changed or when the playback speed is changed.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and its object is to compress the time axis of digital audio data and reproduce the digital audio data without changing the pitch of the reproduced sound. Digital audio data reproduction speed conversion method and digital audio data reproduction speed can be fixed when the reproduction speed of digital audio data is changed without causing discontinuity at the joint of digital audio data
An object of the present invention is to provide a data regeneration device .

[0014]

Means for Solving the Problems] reproduction speed conversion method for a digital audio data of the present invention, in order to solve the above problems, the playback speed by extending the compressed digital audio data
Digital audio data playback speed conversion method
Of the continuous n compressed digital audio data
Select and expand m (n> m) from the digital audio
The data is at least when the digital audio data is reproduced.
A scale factor that indicates the magnitude of the dynamic range
M digital audio data, including scale factor
Are selected in descending order of the maximum value of .

[0015]

[0016]

[0017]

[0018]

According to the above arrangement, m (n> m) is selected and expanded from n compressed continuous digital music data, thereby converting the digital audio data to m / n.
It can be played at twice the fixed speed. Thus, music data can be more easily reproduced at a fixed speed by changing the normal reproduction speed only by thinning out the digital audio data from the original digital audio data.

Further, m digital audio data to be selected are selected.
Data in each digital audio data.
The maximum value of the scale factor indicating the size of the edge is large
Since so as to select the order or, et al., Sound level
Expands compressed digital audio data with large priority
be able to. As a result, the digital audio data
Dynamic range during playback can be improved
You.

In order to solve the above-mentioned problems, the digital audio data reproducing apparatus of the present invention expands the input digital audio data, separates the digital audio data at regular time intervals, and separates the divided digital audio data. For each time axis corresponding to audio data, digital audio data existing on two adjacent time axes are completely overlapped, cross-fade processing is performed on each overlap portion, and each overlap portion is processed. And a D / A that converts the digital audio data output from the data expansion circuit into analog audio data and outputs the converted audio information as music information. A converter for temporarily storing digital audio data before being transferred to the data decompression circuit. A shock-proof memory, a memory controller for controlling the storage and transfer of digital audio data to and from the shock-proof memory, and a digital audio data stored in the shock-proof memory at a transfer rate twice that of normal playback. The memory controller is controlled so as to be transferred to the data decompression circuit, and the data decompression circuit decompresses the digital audio data transferred at a transfer speed twice as fast as that of normal reproduction, and then decompresses the digital audio data. And a system controller that controls the data decompression circuit so as to output the data to the D / A converter at a transfer speed during normal reproduction.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to FIGS. In the present embodiment, as an apparatus to which the method for converting the reproduction speed of digital audio data is applied, an MD (Mini Disp.) For reproducing digital music data as digital audio data
k) A playback device shall be used.

The MD reproducing apparatus according to the present embodiment has the structure shown in FIG.
As shown in the figure, the optical pickup 1, the objective lens 1a, and the R
F amplifier 2, decoder / signal processing circuit 3, memory controller 4, shock proof memory 5, data decompression circuit 6, D / A converter 7, feed motor 8, spindle motor 9, drive circuit 10, servo circuit 11, overall control And a system controller 12 for performing the following operations, and reproduces a disk 13 as a recording medium.

The optical pickup 1 is a head which irradiates a disk 13 as a recording medium with light through an objective lens 1a and takes in reflected light from the disk 13, and an RF signal (modulated signal) recorded on the disk 13. Data) can be read. The RF amplifier 2 amplifies the RF signal read by the optical pickup 1.

The decoder / signal processing circuit 3 is provided so as to be able to communicate with the system controller 12 for processing sub-codes and the like.
The signal is demodulated and converted into digital music data, and the digital music data is subjected to predetermined processing such as error correction.

The memory controller 4 includes the decoder /
The writing operation and the reading operation of the shock proof memory 5 are controlled in accordance with an instruction of the system controller 12 so that the digital music data passed through the signal processing circuit 3 is stored in the shock proof memory 5.

The memory controller 4 transfers the digital music data output from the decoder / signal processing circuit 3 to the shock proof memory 5 and expands the digital music data output from the shock proof memory 5. The data is transferred to the circuit 6.

The shock proof memory 5 is a semiconductor memory for temporarily storing digital music data output from the decoder / signal processing circuit 3, for example, 1M.
Bit DRAMs are preferably used.

Further, the shock proof memory 5 includes:
It is arranged between the decoder / signal processing circuit 3 and the data decompression circuit 6, and the transfer speed of the digital music data output from the decoder / signal processing circuit 3 and the transmission speed of the digital music data input to the data decompression circuit 6 It is provided for the purpose of absorbing the difference from the transfer speed and protecting digital music data in order to prevent interruption of reproduction due to disturbance such as vibration.

The data decompression circuit 6 is provided with an ATRAC (Adaptive TRansform Acoustic) recorded on the disc 13.
This is a circuit that decompresses digital music data compressed by the coding method and expands the digital music data to its original size.

The D / A converter 7 includes a data decompression circuit 6
Is converted to analog music data and output as a music signal.

The feed motor 8 is a motor for moving the optical pickup 1 in the radial direction of the disk 13.
The spindle motor 9 is a motor for rotating the disk 13.

The drive circuit 10 is a circuit for supplying power to the above-described feed motor 8, spindle motor 9, and a drive device for driving the objective lens 1a of the optical pickup 1 in order to operate them.

The servo circuit 11 feeds back each of the above-described devices driven by the drive circuit 10 so that the operation of causing the light emitted from the optical pickup 1 to follow the target track of the disk 13 accurately is performed. The control circuit determines a control amount based on the output of the RF amplifier 2 in accordance with an instruction from the system controller 12 as control means, and sends the control amount to the drive circuit 10 as a control signal.

The system controller 12 includes a decoder /
It comprises a microcomputer for centrally managing the signal processing circuit 3, memory controller 4, data decompression circuit 6, and servo circuit 11.

The system controller 12 controls the memory controller 4 to transfer digital music data to the data decompression circuit 6 at a transfer speed twice that of normal reproduction. Then, the data decompression circuit 6
After expanding the digital music data transferred at twice the transfer speed from the memory controller 4, the digital music data is subjected to a cross-fade process described later, and the digital music data after the cross-fade process is normally played back. Is output to the D / A converter 7 at a transfer speed of.

Here, the cross-fade processing of digital music data in the data decompression circuit 6 will be described with reference to FIG.
This will be described below with reference to FIG. The digital music data expanded by the data expansion circuit 6 has a sound level as shown in FIG. 2, for example.

First, as shown in FIG. 2, the digital music data on the time axis is divided by fixed period times T ₀ , T ₁ ,. The total number of digital music data existing on the time axis of each cycle is defined as S _n (n> 0). Then, T ₀ through T to _one of the digital music data on the time axis, in order from the beginning of the digital music data in the time axis, the total number of digital music data present in the T ₀ through T ₁ of time axis S A fade _- out process is performed as shown in FIG. 1A by multiplying by a fade-out coefficient S _n-1 / S _{n to} 0 / S _n having _n as a denominator.

Next, for each digital music data on the time axis of T _{1 to} T ₂ , the digital music data existing on the time axis of T _{1 to} T ₂ is sequentially arranged from the first digital music data on the time axis. multiplied by a fade-coefficient _{0 / S n ~S n-1} / S n to the total number S _n of the music data as the denominator, as shown in FIG. 1 (b), performing a fade-in processing. Similarly, T _2-
The fade-out process and the fade-in process are also performed on digital music data existing on each of the time axes of T ₃ , T _{3 to} T ₄ ,.

Next, the _first digital music data on the time axis after the fade-out process on the time axis of T _{0 to} T ₁
T is added to the head of the digital music data between shaft ₁ through T fade-in processing later time on the _second time base. Similarly, the second digital music data,..., S _n- th digital music data are added, and as shown in FIG.
T ₀ ~T _1, T ₁ ~T completely to overlap the digital music data that is present on the _second time base. In this way, the digital music data existing on two adjacent time axes are completely overlapped, and the digital music data are added to each other, thereby completing the cross-fade processing. Since the digital music data after addition present on the time axis subjected to the cross-fade processing has the same weight, even if the digital music data is reproduced at twice the normal speed, the sound level remains unchanged. No clipping.

Similarly, the digital music data is added to the time axes of T _{2 to} T ₃ and T _{3 to} T ₄ , and FIG.
As shown in _{(d), T 2 ~T 3} , T 3 to overlap each digital music data included in the time axis through T ₄ in the time axis throughout. In this way, on each time axis, similarly, digital music data existing on two adjacent time axes are overlapped over the entire time axis.

Next, a waveform showing digital music data subjected to the cross-fade processing shown in FIG.
A waveform indicating digital music data that has been subjected to the cross-fade processing shown in (d) is temporally joined. Hereinafter, in the same manner, the waveforms indicating the digital music data subjected to the cross-fade processing at the overlapped portions on the respective adjacent time axes are temporally joined. As a result, the time axis corresponding to the original digital music data is compressed by half, so that the apparent reproduction speed can be doubled.
Also, since the digital music data is only overlapped, the digital music data can be reproduced at twice the speed without changing the amount of digital music data to be reproduced.

Further, the waveform shown in FIG.
The joint with the waveform shown in (d) is a coefficient S _n− for both the last digital music data on the time axis of T _{1 to} T ₂ and the first digital music data on the time axis of T _{2 to} T _{3. 1} / _Sn
, Is continuous data. Therefore, a discontinuous portion of data does not occur during reproduction.

As described above, in the present embodiment, the digital music data is divided at regular time intervals, and each of the time axes corresponding to the divided digital music data exists on two adjacent time axes. Digital music data is completely overlapped, cross-fade processing is performed on each overlap part, and digital music data after cross-fade processing existing in each overlap part is temporally joined. Therefore, cross-fade processing is performed on all digital music data.

As a result, even if the apparent reproduction speed is doubled by halving the time axis, the entire area of the digital music data on the time axis becomes a cross-fade portion subjected to the cross-fade processing. The change of the time axis ratio can be eliminated.

As a result, digital music data can be reproduced at a fixed speed.

Further, since all digital music data are reproduced, the reproduced sound is easy to hear even when reproduced at twice the reproduction speed.

As described above, in the present embodiment, the data decompression circuit 6 performs the cross-fade processing on the digital music data so that the digital music data is always reproduced at twice the speed. As a method for converting the playback speed of digital music data for playback at a fixed speed,
However, the present invention is not limited to this, and a method for converting the reproduction speed of other digital music data (digital audio data) may be used.

As another method of converting the reproduction speed of digital music data, for example, the system controller 12 selects digital music data to be transferred to the data decompression circuit 6 with respect to the memory controller 4 and converts the selected music data to a normal speed. Then, there is a method of transferring the music data, which has been subjected to a decompression process and decompressed here to the D / A converter 7, at a normal speed. In other words, the data decompression circuit 6 performs decompression processing on m (n> m) digital music data selected from compressed digital music data as continuous n digital music data. Has become.

When data is expanded by the data expansion circuit 6, for example, the selected digital music data is
MDCT (Inverse Modified Discrete Cosine Transfo
rm) processing is performed. At this time, as shown in FIG. 4, each digital music data is windowed such that the data partially overlaps at a fixed time period.

According to the above digital music data reproducing speed conversion method, m (n> m) are selected and expanded from n consecutive compressed digital music data, thereby obtaining digital music data. Can be reproduced at a fixed speed of m / n times. Thus, the digital music data can be more easily reproduced at a fixed speed by changing the normal reproduction speed only by thinning out the digital music data from the original digital music data.

Further, in the above-described method for converting the reproduction speed of digital music data, m decompression is performed by selecting m pieces of n pieces of continuously compressed digital music data.
That is, (n−m) digital music data are thinned out from the n digital music data, and the decompression process is performed on the remaining m digital music data. Thus, in the data decompression circuit 6, since only the compressed digital music data is thinned out, the power consumption at the time of decompression can be made the same as at the time of normal reproduction.

Further, as another method of converting the reproduction speed of digital music data, the system controller 12 sends n consecutive compressed digital music data to the memory controller 4 at a transfer speed n times as fast as normal reproduction. Control is performed so that the digital music data is transferred to the data decompression circuit 6.
Before performing the CT processing, m digital data are selected and decompressed in order from the largest scale factor of the digital music data, and the digital music data is transferred to the D / A converter 7 at the transfer speed of normal reproduction. There is a way to do that. The reproduced sound at this time can be reproduced at n / m times.

At this time, the data expansion circuit 6 selects and expands m pieces of digital music data in descending order of the maximum value of the scale factor. In this decompression process, as shown in FIG. 4, windowing is performed on each digital music data.

According to the above digital music data reproduction speed conversion method, the selected m digital music data are sorted in descending order of the maximum value of the scale factor indicating the magnitude of the dynamic range included in each digital music data. Therefore, compressed digital music data having a large sound level can be preferentially expanded. Thereby, the dynamic range at the time of reproducing the digital music data can be improved.

In the present embodiment, a case has been described in which the present digital audio data reproduction speed conversion method is applied to an MD reproduction apparatus that reproduces digital music data as digital audio data. However, the present invention is not limited to this. Instead, a device capable of reproducing digital audio data, for example, a CD
Also, the present invention can be applied to a reproducing apparatus such as an LD or an LD.

[0057]

Reproduction speed conversion method for a digital audio data of the present invention exhibits, as above, compressed digital voice de
Digital audio data that expands data and converts playback speed
In the playback speed conversion method of
M (n> m) from the selected digital audio data
The digital audio data at least
Dynamic range when playing audio data.
M digital audio data with scale factor
Are selected in descending order of the maximum scale factor.
And is a configuration that.

[0058]

[0059]

[0060]

Therefore, by selecting and expanding m pieces (n> m) from the compressed n pieces of continuous digital music data, the digital audio data is reproduced at a fixed speed of m / n times. can do. Thus, the digital audio data can be reproduced at a fixed speed more easily by changing the normal reproduction speed only by thinning out the digital audio data from the original digital audio data.

Furthermore, since only the compressed digital audio data is thinned out, the power consumption during decompression can be made the same as during normal reproduction.

Further, m digital audio data to be selected are selected.
Data in each digital audio data.
The maximum value of the scale factor indicating the size of the edge is large
The sound level is selected because it is selected in order.
Expands compressed digital audio data with large priority
be able to. As a result, of the digital audio data
There is an effect that the dynamic range at the time of reproduction can be improved .

Further , as described above, the digital audio data reproducing apparatus of the present invention expands the input digital audio data, separates the digital audio data at regular time intervals, and handles the divided digital audio data. Digital audio data existing on two adjacent time axes are completely overlapped with each other,
A data decompression circuit that performs cross-fade processing on each overlap portion and temporally joins digital audio data after cross-fade processing present in each overlap portion, and digital audio data output from the data decompression circuit A D / A converter for converting the audio data into analog audio data and outputting the audio information as music information, a shock-proof memory for temporarily storing digital audio data before being transferred to the data decompression circuit, and a shock-proof memory. A memory controller for controlling the storage and transfer of digital audio data, and the memory for transferring the digital audio data stored in the shock proof memory to the data decompression circuit at twice the transfer rate of normal reproduction. In addition to controlling the controller, the data decompression circuit Te, after decompressing the digital audio data transferred at double the transfer rate of the normal reproduction, the D / A the digital audio data at a transfer rate of the normal reproduction
And a system controller for controlling the data decompression circuit so as to output the data to the converter.

Therefore, all digital audio data
The time axis of the digital audio data contained on the time axis.
Can be reduced to half the original length without thinning
it can. As a result, digital audio data
It can be played back at twice the speed.

Therefore, the data is thinned out as in the prior art.
Compared to the case of playing at twice the apparent speed,
Since all data is played back,
The digital audio data such as conversation can be easily heard .

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a method for converting the reproduction speed of digital audio data according to the present invention.

FIG. 2 is an explanatory diagram showing a state in which digital audio data is divided at a certain period of time.

FIG. 3 is a schematic block diagram showing an MD reproducing apparatus to which the digital audio data reproducing speed conversion method shown in FIG. 1 is applied.

FIG. 4 is an explanatory diagram showing windowing processing of digital audio data in a data decompression circuit in the MD reproduction device shown in FIG. 3;

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 optical pickup 3 decoder / signal processing circuit 4 memory controller 5 shock proof memory 6 data decompression circuit 7 D / A converter 12 system controller 13 disk (recording medium)

Claims (2)

(57) [Claims] 1. A method for converting a reproduction speed of digital audio data in which compressed digital audio data is expanded to convert a reproduction speed, wherein m (n> m) are selected from n consecutive compressed digital audio data. ) Is selected and decompressed. The digital audio data includes at least a scale factor indicating the size of a dynamic range at the time of reproduction of the digital audio data, and the m digital audio data includes a maximum value of the scale factor. A method for converting the reproduction speed of digital audio data, wherein the reproduction speed is selected in descending order. 2. Decompressing the input digital audio data, dividing the digital audio data at a fixed time period, and setting two time axes corresponding to the divided digital audio data on two adjacent time axes. The digital audio data existing in is completely overlapped, cross-fade processing is performed for each overlap part,
A data decompression circuit that temporally joins digital audio data after cross-fade processing present in each overlap portion, and converts digital audio data output from the data decompression circuit into analog audio data and outputs it as music information A digital-to-analog converter, a shock-proof memory for temporarily storing digital audio data before being transferred to the data decompression circuit, and a memory controller for controlling storage and transfer of digital audio data to and from the shock-proof memory And controlling the memory controller to transfer the digital audio data stored in the shock proof memory to the data decompression circuit at twice the transfer speed of normal reproduction. Digital data transferred at twice the transfer speed when playing And a system controller for controlling the data decompression circuit so as to output the digital audio data to the D / A converter at a transfer rate during normal reproduction after decompressing the audio data. Digital audio data playback device.