Data processing: speech signal processing – linguistics – language – Speech signal processing – For storage or transmission
Reexamination Certificate
1999-05-06
2002-03-19
Dorvil, Richemond (Department: 2641)
Data processing: speech signal processing, linguistics, language
Speech signal processing
For storage or transmission
C704S265000, C704S500000
Reexamination Certificate
active
06360198
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an audio processing method, audio processing apparatus, and recording and reproduction apparatus, which, in an apparatus such as a VTR apparatus for business use, 6-mm tape recorder apparatus, or the like, arranged to output a sound whose pitch has changed in proportion to the reproduction speed, enables a sound, whose pitch is normal regardless of the reproduction speed, to be output when reproducing the recorded sound at this given reproduction speed. Particularly, the invention concerns an audio processing method, audio processing apparatus, and recording and reproduction apparatus, which, when applied to a VTR apparatus, enables the production of a high quality of sound that matches with a wanted reproduction speed and that is synchronized with the image.
BACKGROUND ART
In general, in a case where reproducing at a given speed a sound that has been recorded in an analog recording medium such as a magnetic tape, the pitch of the sound is also changed in proportion to this reproduction speed.
Also, regarding a VTR apparatus for business use, recording of both an image and a sound has in recent years been performed predominantly by the use of a digital system. However, regarding the output of a sound, for the sake of increasing the efficiency of the editing operation, a sound whose pitch has changed is output in proportion to the reproduction speed as in the case of a VTR apparatus of analog system.
Meanwhile, regarding a VTR apparatus, although an image has hitherto been changeable speed reproduced, there has hitherto existed no VTR apparatus that has the function of, while synchronizing a sound with the changeable speed reproduced image, correcting the pitch of the sound to a normal level.
Also, if imposing a limitation on means for correcting the pitch of the sound, there is known a pitch shifter (pitch changer) which has been presently being used in a “karaoke” apparatus or the like. However, if using such a pitch shifter in the correction of the pitch in the above-described VTR apparatus, when the object sound is a human voice or the correction range therefor is wide, such as, for example, when restoring to the original pitch the sound whose pitch has been lowered 1 octave as in the case of a ½ time speed reproduction, there existed the problem with the quality of the sound, such as the problem that a large amount of distortion or echo feeling follows the corrected sound.
As will be understood from the above-described problems, when correcting a change in the sound pitch, if considering the quality of broadcasting, there has hitherto existed no suitable apparatus. Namely, when performing slow reproduction of a VTR apparatus that is used in, for example, broadcasting, there was the problem that it was impossible to use the sound that had been reproduced simultaneously with the reproduction of the image excepting a case where use was made of a non-realistic sound whose pitch had been intentionally changed.
The present invention has been made in view of the above-described problems and has an object to provide an audio processing method, audio processing apparatus and recording and reproduction apparatus which take in a sound which has been changeable speed reproduced within a practical use range of changeable speed as when having reproduced at a speed that is ½ time, or 2 times, higher and whose pitch has changed, and which, while the clearness of the sound is being maintained as is, enables the pitch of the sound to be restored to its original level within a range of ±1 octave or so in a state where the sound is synchronized highly accurately with the image.
DISCLOSURE OF INVENTION
To achieve the above object, according to an audio processing method as described in claim
1
, the gist is that, in an audio processing method of, when reproducing, at a reproduction speed different from that at which an audio signal has been recorded in a recording medium, the audio signal on the recording medium, adjusting the pitch of the reproduced audio signal, wherein a sampling frequency f
i
, which is used when performing A/D conversion of the audio signal that has been reproduced from the recording medium at a changeable speed ratio r with respect to a normal reproduction speed to thereby produce audio data, and a sampling frequency f
o
, which is used when performing, after having performed digital signal processing on the audio data, D/A conversion thereof to thereby produce an audio signal, are respectively set so that these frequencies and the changeable speed ratio r may satisfy prescribed conditions.
According to an audio processing method as described in claim
2
, the gist is that, in the audio processing method as described in claim
1
, when performing digital signal processing on the audio data that has been obtained by performing A/D conversion, at the sampling frequency f
i
, of the audio signal that has been reproduced from the recording medium at the changeable speed ratio r, the digital signal processing comprising the steps of: performing a series of processes of performing analysis processing on the attribute of the audio data, dividing as the next step the audio data into blocks each having a prescribed time width according to data that has been obtained through the performance of the analysis processing and if necessary performing interpolation or thinning of the audio data in units of a block to thereby make a time length of the audio data if necessary 1/r time greater and thereby produce output audio data, and thereafter performing D/A conversion of the output audio data at the sampling frequency f
o
, to thereby produce an audio signal.
According to the audio processing method as described in claim
3
, the gist is that, in the audio processing method as described in claim
1
, as the prescribed conditions, when the sampling frequencies f
i
and f
o
and the changeable speed radio r satisfy the relationship of f
i
/f
o
=r, there is used the sampling frequency f
i
which is represented by an expression f
i
=r·f
o
; and when the sampling frequencies f
i
and f
o
and the changeable speed ratio r are in the relationship of f
i
/f
o
≠r, there is used the sampling frequency f
i
that is represented by an expression f
i
=r·f
o
/c that includes a sampling frequency conversion coefficient c.
According to the audio processing method as described in claim
4
, the gist is that, in the audio processing method as described in claim
2
, as the prescribed conditions, when the sampling frequencies f
i
and f
o
and the changeable speed radio r satisfy the relationship of f
i
/f
o
=r, there is used the sampling frequency f
i
which is represented by an expression f
i
=r·f
o
; and when the sampling frequencies f
i
and f
o
and the changeable speed ratio r are in the relationship of f
i
/f
o
≠r, there is used the sampling frequency f
i
that is represented by an expression f
i
=r·f
o
/c that includes a sampling frequency conversion coefficient c.
According to the audio processing method as described in claim
5
, the gist is that, in the audio processing method as described in claim
4
, when performing digital signal processing on the audio data that has been obtained by performing A/D conversion, at the sampling frequency f
i
, of the audio signal that has been reproduced from the recording medium at the changeable speed ratio r, the digital signal processing comprising the steps of: monitoring time data of the audio signal read out from the recording medium and time data of the output audio data that has been obtained through the performance of the series of processes to thereby correct time non-coincidence that occurs between the audio signal and the output audio data.
According to the audio processing apparatus as described in claim
6
, the gist is that, in an audio processing apparatus for, when reproducing, at a reproduction speed different from that at which an audio signal has been recorded in a recording medium, the audio signal on the recording mediu
Imai Atsushi
Seiyama Nobumasa
Takagi Tohru
Dorvil Richemond
Nippon Hoso Kyokai
Olson & Hierl Ltd.
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