JP2826332B2 - Audio time axis compression method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a voice recording / reproducing function, and more particularly to a voice time axis compression system for shortening a calculation time.

[Conventional technology]

Conventionally, in this type of audio time axis compression system, in the analog system, generally, audio is recorded on a magnetic tape, and the tape traveling speed is increased by increasing the rotation speed of the capstan during reproduction, or This was done by slightly reducing the tape running speed during recording. In the digital method, a method of compressing a time axis by increasing a sample frequency at the time of reproduction is employed.

[Problems to be solved by the invention]

In the above-mentioned system using a recording / reproducing apparatus using a magnetic tape or the like and the digital system, since the frequency at the time of reproduction shifts to a higher side, the problem that the fidelity deteriorates, such as a change in pitch with respect to the original sound. Atsuta.

[Means for solving the problem]

An audio time axis compression method according to the present invention comprises a plurality of data storage memories for collecting a fixed number of samples of digital audio data converted into digital audio data and storing the data for each group, and a level difference detector for detecting a level difference between the data. A first comparator for comparing the level difference detection result data obtained by the level difference detector with predetermined level difference reference data; and a level range for detecting the level range of the digital audio data. A detector; a second comparator for comparing the level range detection result data obtained by the level range detector with predetermined level range data; and a result of the first and second comparators A deleter for deleting digital audio data based on the data, wherein the level difference data is equal to or less than the set level difference reference data absolute value and is set. Data stored in the memory while deleting the digital audio data below the data value, and at the time of playback, the digital audio data including the partially deleted part is read out of the memory, and this is D / A converted so that the audio compressed on the time axis Is played.

[Action]

In the present invention, the level difference before and after the digital audio data is detected, the detected data is compared with the level difference reference data, and the level range of the data is detected. Are compared with each other, and data deletion control is performed based on a logical product condition of the level difference comparison result data and the level range comparison result.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

 FIG. 1 is a block diagram showing one embodiment of the present invention.

In the figure, 1-1, 1-2... 1-N are a plurality of data storage memories for collecting a fixed number of samples of digital audio data converted into digital audio data and storing the collected data for each group. , 2-2 ... 2- (N-1)
Is a level difference detector for detecting a level difference between data, and 3 is a level difference detection result data obtained by the level difference detectors 2-1 to 2- (N-1) and level difference reference data given in advance. For comparing (for level comparison),
4-1, 4-2,..., 4N is a level range detector for detecting the level range of the digital audio data, and 5 is the level range detection result data obtained by the level range detectors 4-1 to 4N. A comparator (for level range comparison) for comparing with predetermined level range data, 6 is a deleter for deleting digital audio data based on the result data of the comparators 3 and 5, and 7 is digital audio data. A group counter for counting the number, 8 is a block counter for determining the number of groups in one block for collecting M groups into one group, and 9 is the number of audio data to be deleted based on the given compression rate data C. , An adder 10 for adding the deletion counter data d output from the deletion counter 9 and the compression ratio data c for each block, and 11 an adder. A logic circuit for calculating the logical product of the level difference comparison result data q output from the comparator 3 and the level range comparison result data p output from the comparator 5; and 12, a block counter control signal output from the group counter 7. h and the deletion counter control signal i output from the deletion counter 9
A deletion controller for controlling whether or not to delete by the comparison result data g output from the logic circuit 11; a memory 13 for storing the data processed by the deleter 6; and a conversion 14 for converting the analog voice a into a digital voice. A / D converter, 15 is memory 1
D / A that reads audio data from 3 and converts it to analog audio
It is a converter.

Then, the digital audio data that is equal to or less than the set level difference reference data absolute value and equal to or less than the set level range data value is stored in the memory while deleting the digital audio data. And performs D / A conversion on the read data to reproduce a sound compressed on the time axis.

 Next, the operation of the embodiment shown in FIG.

First, the analog voice a is converted into digital voice data by the A / D converter 14, and the converted digital voice data 1 is stored in the data storage memories 1-1 to 1-N in order. Then, the number of data is counted. Then, the data storage memories 1-1 to 1-N
Are stored in the digital audio data e _{1 to} e _N are level difference detectors 2-1 and 2 for detecting a level difference between data before and after the digital audio data e _{1 to} e _N.
The -2 ····· 2- (N-1) , detected the level difference is supplied to the comparator 3 as a level difference comparison data f ₁ ~f _N-1, prepared in advance based on the audio material Comparison with the level difference reference data b is performed, and the result is output to the logic circuit 11.
Is transmitted as level difference comparison result data q. Further, the digital audio data e _{1 to} e _N are supplied to the level range detectors 4-1 to 4N for detecting the level range, and the level range preset by the comparator 5 as the level range comparison data. A comparison is made as to whether the value falls within the range determined by the upper limit data n and the level range lower limit data o, and as a result, the result is sent to the logic circuit 11 as level range comparison result data p.

In the logic circuit 11, the level difference comparison result data q and
The logical product of the level range comparison result data p is calculated, and the result is sent to the deletion controller 12 as comparison result data g.

At the same time as the above operation, a block counter control signal h is supplied from the group counter 7 to the block counter 8 and the deletion controller 12 for each data number corresponding to one group.
The block counter 8 increases the number of counters by the block counter control h, and increases the number of block counters for each group number corresponding to one block. Then, the adder 10 adds the compression ratio data c and the count data d extracted from the deletion counter 9 by the block counter control signal h for each group number corresponding to one block, and sets the result to the deletion counter 9. The deletion counter 9 sends to the deletion controller 12 a deletion counter control signal i indicating whether the counter value is zero. The deletion controller 12 outputs a deletion control signal j based on the block counter control signal h, the deletion counter control signal i, and the comparison result data g, and the deletion unit 6 performs the deletion based on the deletion control signal j.

Then, when data is extracted, the deletion counter 9 counts down according to the deletion result signal k from the deletion unit 6 and manages the number of deleted data.

Next, the data processed by the deleter 6 is temporarily stored in the memory 13, then D / A converted by the D / A converter 15, and output as a compressed audio signal m which is a compressed analog audio. .

In this way, the level difference and the level range before and after the digital audio data are detected, and the extraction of the data is controlled by the comparison result data obtained by performing the logical product of the level difference result data and the level range result data. It is possible to maintain a state in which it is not necessary to detect a change in the frequency of the sound due to the time axis compression from the viewpoint of audibility without an extreme change in the level difference of.

〔The invention's effect〕

As described above, the present invention detects the level difference before and after the digital audio data, compares the detected data with the level difference reference data, further detects the level range of the data, and sets it in advance. Compared with a certain level range data, the deleted data is controlled under the condition of the logical product of the level difference comparison result data and the level range comparison result data. It has the effect of not changing.

For this reason, there is an effect that it is possible to perform compression that cannot detect a change in the frequency of the sound due to time compression in terms of audibility.

[Brief description of the drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention. 1-1 to 1-N Data storage memory, 2-1 to 2-
(N-): level difference detector, 3: comparator, 4-1 to 4-1
4N: Level range detector, 5: Comparator, 6: Deleter, 7: Group counter, 8: Block counter, 9: Delete counter, 10: Adder, 11: Logic circuit, 12: Delete controller, 13: Memory, 14: D / A converter, 15: A / D converter.

Continuation of the front page (56) References JP-A-50-114904 (JP, A) JP-A-61-75396 (JP, A) JP-A-57-104195 (JP, A) JP-A-60-214399 (JP, A) , A) (58) Field surveyed (Int. Cl. ⁶ , DB name) G10L 3/00-9/18 JICST (JOIS)

Claims (1)

(57) [Claims] 1. A plurality of data storage memories for collecting a fixed number of samples of digital audio data converted into digital audio data and storing them for each group, a level difference detector for detecting a level difference of data, and a level difference detector A first comparator for comparing level difference detection result data obtained by the detector with predetermined level difference reference data;
A level range detector for detecting a level range of the digital audio data, a second comparator for comparing level range detection result data obtained by the level range detector with predetermined level range data; And a deleter for deleting digital audio data based on the result data of the first and second comparators, wherein the digital value is not more than a set level difference reference data absolute value and not more than a set level range data value. Audio data is stored in the memory while deleting it, and at the time of playback, digital audio data including the part that has been partially deleted is read from the memory and D / A converted to play back the audio compressed on the time axis. An audio time axis compression method characterized by: