JPH09198608A - Voice reproducing circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce a voice by running a magnetic tape faster than the speed at the time of an ordinary reproduction by providing a data reproduction rate counting circuit, reshuffle circuits, etc. SOLUTION: This voice circuit is applied to such a magnetic tape that voice data of a left channel (a Lch) are recorded in plural tracks of the first halved of respective blocks and voice data of a right channel (a Rch) are recorded in plural track of later halves of the respective blocks in the unit of blocks each consisting of plural lines of tracks. A data reproducing rate counting circuit 3 inputs the voice data of the left channel and the voice data of the right channel of one frame to be outputted from a voice data extracting circuit 2 to count the number of pieces of normal data and calculates a data reproduction rate by dividing the result by the total number of data. When the data reproducing rate of the channel of one of the left channel and the right channel of voice data to be inputted from the data reproduction rate counting circuit 3 is lower than a prescribed threshold value, circuits 5a, 5b replace the voice data of the channel of one side with the voice data of the channel of the other side.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an audio reproducing circuit for reproducing audio from a magnetic tape on which digital audio data is recorded.

[0002]

2. Description of the Related Art HD (High Definition) Digital VCR
At the conference, a digital VTR for recording and reproducing a video signal and an audio signal as digital data is standardized. Here, when recording a signal on a magnetic tape,
As shown in FIG. 5, a plurality of tracks are repeatedly formed by helical scanning, and digital video data and digital audio data within a period corresponding to one frame of a video signal are recorded over 10 tracks in the NTSC specification. It will be.

An audio data recording area S is formed at the beginning of each track, and in the 2-channel mode,
In the audio data recording area S of 5 tracks in the first half of 10 tracks, 1 frame of left channel audio data,
In the latter half of the 5-track audio data recording area S, one frame of right channel audio data is recorded. still,
To the audio data recorded in one audio data recording area, a sequence number for identifying a frame, a track pair number for identifying a track, a sync block number, and a parity are added as ID data.
Shuffling is performed for each frame in units of 6-bit data and then recorded in each audio data recording area.
Image-compressed video data is recorded in the video data recording area following the audio data recording area S of each track.

By the way, in the above-mentioned digital VTR, the magnetic tape is run at a higher speed than during normal reproduction.
Special playback such as fast-forward playback can be performed. For example, in a 180-degree opposite two-head VTR, two azimuth tracks A and B are repeatedly formed as shown in FIG. 5, and when performing double-speed reproduction, the magnetic tape is reproduced at twice the normal speed. By running, both heads scan two adjacent tracks diagonally, and A,
B: Signal reproduction by two azimuths is alternately performed. As a result, the audio data recording areas (12a) (12b) (12c) (12d) (12e) where the azimuth during recording and the azimuth during reproduction match ...
The audio data will be read only from the audio data. Here, the data read from the audio data recording areas (12a) (12b) (12d) is the left channel audio data, and the data read from the audio data recording areas (12c) (12e) is the right channel audio data. is there.

Further, since the audio data recorded in each audio data recording area is shuffled, there is no continuity on the time axis in the read order. Therefore, at the time of audio reproduction, it is necessary to perform a process of returning the read data to the original time series data for each channel.

[0006]

However, during special reproduction, only a part of the audio data of each frame is reproduced as shown in FIG. 5, and the audio data of the area shown by hatching in the figure is reproduced. Will be missing.

Further, FIG. 6 shows a data reproducing state when it is assumed that the data can be correctly reproduced when the head traces a track of the same azimuth with an overlapping width (trace rate) of 50% or more at 1.75 times speed ( Simulation results). Here, the "reproducible data number" represents the sampling number (0 to 1600) of the audio data that was normally reproducible. As is clear from this figure, the audio data of most of the frames can be reproduced every two or three channels on any channel, but the right channel of the frame number "2" and the frame number "4". In the left channel of "", the right channel of frame number "5", the right channel of frame number "9", etc., only every fifth data is reproduced, and many missing data are generated.

Therefore, even if the process of restoring the original time-series data is performed, the normal voice cannot be reproduced due to the lack of the data. Therefore, conventionally, a method has been adopted in which only video is displayed during special reproduction, and audio is not output by mute processing.

Therefore, an object of the present invention is to provide an audio reproduction circuit capable of reproducing audio even during special reproduction.

[0010]

In the audio reproducing circuit according to the present invention, the audio data is updated in units of a block composed of a plurality of tracks, and the audio data of the first channel is recorded in a plurality of tracks in the first half of each block. As recorded,
A circuit for reproducing a voice by running the magnetic tape at a speed higher than that during normal reproduction by targeting a magnetic tape on which second-channel audio data is recorded in a plurality of tracks in the latter half. , It is determined whether or not the error occurrence frequency in the audio data of each channel exceeds a predetermined threshold value, and when the error occurrence frequency of any one of the channels exceeds the predetermined threshold value, After replacing the audio data of the other channel with the audio data of the other channel, the audio data of both channels is subjected to interpolation processing to compensate for the missing data.

In the audio reproduction circuit, when the audio data of each block is normal data in both the first channel and the second channel, it is output as it is as the audio data of two channels. In addition, even if the audio data of both channels is error data, it is 2 as it is.
Output as channel audio data. On the other hand, when only the audio data of one channel is error data and the audio data of the other channel is normal, the audio data of the one channel is replaced with the normal audio data of the other channel. Then, the output signals of both channels become normal audio data.

In this way, a series of audio data that is less likely to be lost due to an error is output from both channels.
The data missing due to the error is supplemented by the interpolation process using the normal data before and after the error. As a result, a series of audio data very similar to the original audio data recorded on the magnetic tape can be obtained.

Further, the audio reproducing circuit according to the present invention determines the number of error data included in the audio data of each channel or the number of normally reproducible data for each block based on the error information included in the audio data. Index data creating means for creating index data according to the above, and when the index data of any one of the channels indicates an increase exceeding the threshold of the error occurrence frequency, the audio data of the one channel is changed to the audio data of the other channel. The data replacing means for replacing the data and outputting the data, the interpolation processing for performing the interpolation processing on the audio data of both channels after the replacement processing, and the data which cannot be reproduced as a voice due to an error, and the interpolation processing are performed. Data processing that applies data processing to the audio data of both channels to reproduce audio with the same pitch as during normal playback And it includes a stage.

In the above audio reproduction circuit, the number of error data contained in the audio data of each channel read from the magnetic tape is counted for each block, and the result is subjected to necessary calculation to obtain an index. Data is calculated. For example, as the index data, the data reproduction rate obtained by dividing the number of normal data included in the audio data per unit time by the total number of audio data within the unit time, and the error occurrence frequency inversely proportional to this Can be adopted.

When the index data of one of the channels indicates an increase in the error occurrence frequency exceeding the threshold value, the audio data of the one channel is replaced in block units with the audio data of the other channel.
As a result, a series of audio data with less omission due to an error can be obtained. The data missing due to the error is supplemented by the interpolation process using the normal data before and after the error.

However, since the interpolation processing is performed,
Since the amount of audio data increases and it becomes impossible to reproduce audio in synchronization with the running of the magnetic tape, the audio data is thinned out at a constant rate according to the tape running speed. In addition, necessary data processing is performed in order to avoid changing the pitch due to thinning of the audio data.

For example, a magnetic tape is played N times (N
Is a random number), the data processing means samples a series of interpolated audio data in a cycle corresponding to the tape running speed in order to reduce the data amount to 1 / N. The audio data thus obtained is subjected to a process of expanding the time axis N times.

In this specific configuration, the audio data is thinned out by the sampling so that the audio can be reproduced in synchronism with the running of the magnetic tape, and the change of the pitch can be avoided by the conversion of the time axis. .

Further, in another specific configuration, the data processing means extracts a series of audio data extracted in a period of 1 / N of a predetermined constant cycle for each constant cycle,
This is to connect the extracted audio data.

In the specific configuration, the audio data is extracted at regular intervals to thin out the audio data, and to avoid a change in pitch of the audio data within the constant cycle. Further, by connecting the extracted audio data, it is possible to reproduce the audio in synchronization with the running of the magnetic tape.

More specifically, the interpolating means includes filter means for smoothing the change of the data between the channels with respect to the audio data of the different channels continuously output from the data replacing means. . According to this specific configuration, the discontinuity of the data caused by the data replacement is smoothed, and the generation of noise due to the discontinuity is avoided.

[0022]

According to the sound reproducing circuit of the present invention, sound can be reproduced even when special reproduction is carried out by running the magnetic tape at a higher speed than during normal reproduction.

[0023]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an embodiment in which the present invention is applied to a digital VTR will be specifically described with reference to the drawings.
FIG. 1 shows the configuration of a signal reproduction system equipped in a digital VTR. The reproduction data read from the magnetic tape goes through a well-known sync protection circuit and error correction circuit (both not shown) to compensate for the missing sync signal and correct the reproduction data error. 1 is input to the signal reproduction system.

Here, the reproduction data includes audio data, video data, code data, etc., and is sent in units of one sync block. At the beginning of each sync block, as the ID data, a sequence number for identifying a frame, a track pair number for identifying a track, a sync block number for identifying a sync block, and these data Parity for error detection is added. Further, error information indicating that fact is added to a sync block that cannot be error-corrected beyond the error correction capability of the error correction circuit.

The reproduced data is first of all an error information detection circuit.
Input to (1), the presence or absence of error information is detected, the sync block to which the error information is added is discarded, and only a normal sync block that has no error or is error-corrected is extracted, Subsequent voice data extraction circuit (2)
Output to The error information detection circuit (1) determines whether the parity included in each sync block matches the parity generated from the sequence number, track pair number, and sync block number included in the sync block. If they do not match, it is determined that the sequence number, the track pair number, or the sync block number is unknown in the sync block, and error information indicating that is unknown is added to the sync block, and then the audio data extraction circuit (2 ). Voice data extraction circuit (2)
Then, based on the sync block number, it is determined whether the input sync block includes audio data or video data, and only the sync block including audio data is extracted and output to the subsequent stage.

One frame of left channel audio data and right channel audio data extracted as a sync block containing audio data is stored in the memory (4). Here, it is assumed that the audio data is written in the memory (4) at an address corresponding to the sync block number and the track pair number, and the sync block in which the ID data has an error is a non-reproducible sync block. The voice data is discarded and is not written in the memory (4). As a result,
In the memory (4), normal left-channel audio data read from the first half 5 tracks of 10 tracks corresponding to one frame is written, and normal right-channel audio data read from the latter half 5 tracks is written. Will be written. An error code for recognizing that it is a non-reproducible sync block is written in an address where no data has been written.

Further, one frame of left channel audio data and right channel audio data output from the audio data extraction circuit (2) is supplied to the data reproduction rate counting circuit (3) to count the number of normal data. Then, the data reproduction rate is calculated by dividing the result by the total number of data. The calculated data reproduction rate is the deshuffle circuit for the left channel (5a) and the deshuffle circuit for the right channel (5
It is supplied to b).

On the other hand, one frame of audio data written in the memory (4) is stored in the left channel deshuffle circuit (5
a) and the right channel deshuffle circuit (5b) read in the original data order with continuity to the time axis,
Deshuffling is applied. At this time, the left-channel deshuffle circuit (5a) determines that the data reproduction rate of the left-channel audio data is below a predetermined threshold based on the data reproduction rate input from the data reproduction rate counting circuit (3). Replaces the audio data and applies deshuffling to the audio data of the right channel. The deshuffle circuit (5b) for the right channel is the data reproduction rate counting circuit (3).
If the data reproduction rate of the audio data of the right channel is below a predetermined threshold value based on the data reproduction rate input from, the deshuffling is applied to the audio data of the left channel instead of the audio data. . As a result, the audio data is replaced on a frame-by-frame basis.

For example, in the example shown in FIG. 6, the right channel of frame number "2", the left channel of frame number "4", the right channel of frame number "5", the right channel of frame number "9", etc. Since the data reproduction rate is low, the right channel of frame number "2" is replaced with the audio data of the left channel, the left channel of frame number "4" is replaced with the audio data of the right channel, and the right channel of frame number "5" is replaced. The channel is replaced with the audio data of the left channel, and the right channel of the frame number "9" is replaced with the audio data of the left channel.

By the way, for example, during 1.75 times special reproduction, the magnetic tape runs at 1.75 times the normal speed, so that it is possible to read out audio data for 1.75 frames by scanning for one frame period. Become. Therefore, if it is assumed that the audio is reproduced using all the read audio data, a time axis shift occurs between the reproduction of the audio and the running of the magnetic tape, and the audio reproduction catches up with the running of the magnetic tape. There will be no.

Therefore, in this embodiment, the output signals of the left-channel deshuffle circuit (5a) and the right-channel deshuffle circuit (5b) shown in FIG. 1 are converted to the left-channel interpolation circuit (6a).
And the right channel interpolation circuit (6b) to thin out audio data at a rate according to the tape running speed. For example 1.
At 75 × speed, the audio data after deshuffling shown in FIG. 2 (a) has a sampling period of 1.
Sampling is performed at a cycle of 75 times. At this time, if the original data to be sampled is missing,
As indicated by a square mark, the missing data is interpolated using the reproducible data before and after. As the interpolation method, averaging,
The Lagrange interpolation method, the Newton interpolation method, or the like can be adopted.

Further, when the audio data of different channels are connected as shown in FIG. 3 (a) by the above-mentioned data replacement, data discontinuity occurs at the connecting portion, which causes noise. In view of this, in the present embodiment, such a data connecting portion is subjected to interpolation processing for smoothing the change of data.

For example, as shown in FIG. 3 (a), when interpolation is applied to the connecting portion between the first frame and the second frame, the first
The last plural data of the frame and the first plural data of the second frame are invalidated, and the Lagrange interpolation method is used by using plural data before and after the invalidated data as shown by a double circle in FIG. And the Newton interpolation method are applied to replace the invalidated data with the data generated by the interpolation as indicated by the square marks in the figure. As a result, a series of smoothly varying audio data is generated as shown in FIG. 3C, and noise is prevented from occurring.

The left-channel interpolation circuit (6a) and the right-channel interpolation circuit (6b) shown in FIG. 1 have a left-channel interpolation buffer (7a) for temporarily storing data during the interpolation process. ) And the interpolation buffer (7b) for the right channel are connected respectively. The interpolator (6a) (6b) needs to output the data after the interpolation processing at a constant time interval, while the time interval of the data obtained from the deshuffle circuit (5a) (5b) is not constant. However, the interpolation calculation cannot be performed until a predetermined number of normal data are prepared. Therefore, the time difference between the input and output data of the interpolation circuits (6a) and (6b) is calculated by the interpolation buffer.
It is absorbed by (7a) and (7b).

FIG. 4 shows the interpolation circuit (6a) (6
This is an example of audio data output from b). As shown in the figure, since the voice data has a frequency higher than usual in proportion to the double speed number, the voice data of both channels is converted into the left channel voice speed conversion circuit (8a) and the right channel voice speed as shown in FIG. The signal is supplied to the conversion circuit (8b), the time axis is expanded in proportion to the double speed number, and then supplied to the speaker device via the D / A converter. As a result, the stereo sound is reproduced with the same pitch as in the normal reproduction.

The present invention is effective when there is a high correlation between the audio data of the left channel and the audio data of the right channel of the same frame, and there is a difference in the reproduction rate of the audio data of both channels. According to the result of the computer simulation, the difference in the data reproduction rate is 1.75 times, 1.8 times, 1.85 times, 1.9 times.
This is during special playback with double speed and 3.0 times double speed.

The description of the above embodiments is for the purpose of explaining the present invention, and should not be construed as limiting the invention described in the claims or reducing the scope thereof.
In addition, the configuration of each part of the present invention is not limited to the above-described embodiment, and it goes without saying that various modifications can be made within the technical scope described in the claims. For example, in the above-described embodiment, after the voice data is thinned out at a constant cycle, the change in pitch is avoided by the voice speed conversion circuit. By connecting the audio data of 1 to each other, the running of the magnetic tape and the audio reproduction can be synchronized, and at the same time, the audio reproduction without the pitch change can be realized.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a signal reproducing system of a digital VTR according to the present invention.

FIG. 2 is a diagram illustrating a method of interpolation processing on data in a frame.

FIG. 3 is a diagram illustrating a method of interpolation processing for a data connection portion between frames.

FIG. 4 is a diagram exemplifying a change in a series of audio data that has undergone interpolation processing.

FIG. 5 is a diagram showing an audio data recording area of a track formed on a magnetic tape and a scanning locus during special reproduction.

FIG. 6 is a table showing numbers of reproducible data of each channel.

[Explanation of symbols]

 (1) Error information detection circuit (2) Audio data extraction circuit (3) Data reproduction rate counting circuit (6a) Interpolation circuit for left channel (6b) Interpolation circuit for right channel (8a) Speech rate conversion circuit for left channel (8b) ) Right channel speech speed conversion circuit

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location G11B 20/18 572 9558-5D G11B 20/18 572G 574 9558-5D 574D

Claims (5)

[Claims] 1. Audio data is updated in units of a block composed of a plurality of tracks, audio data of a first channel is recorded in a plurality of tracks in the first half of each block, and second track is recorded in a plurality of tracks in the latter half. This is a circuit for reproducing audio by running the magnetic tape at a speed higher than that during normal playback, targeting a magnetic tape on which audio data of a channel is recorded. Means for determining whether or not the occurrence frequency of a channel exceeds a predetermined threshold, and when the error occurrence frequency of one of the channels exceeds a predetermined threshold, the audio data of the one channel is transferred to the other channel. And the audio data of both channels that have undergone the replacement process are interpolated, and the audio And a sound reproduction circuit having means for compensating unreproducible data. 2. The audio data is updated in units of a block composed of a plurality of tracks, the audio data of the first channel is recorded in a plurality of tracks in the first half of each block, and the second track is recorded in a plurality of tracks in the latter half. Targeting a magnetic tape on which audio data of a channel is recorded, a circuit for reproducing the audio by running the magnetic tape at a higher speed than during normal reproduction, based on error information included in the audio data, For each block, index data creating means for creating index data according to the number of error data included in the audio data of each channel or the number of normally playable data, and the index data of one of the channels is When the increase of the occurrence frequency exceeds the threshold value, the audio data of the one channel is changed to the audio data of the other channel. Data replacement means for replacing and outputting, interpolation means for performing interpolation processing on the sound data of both channels that have undergone the replacement processing, and compensating data that cannot be reproduced as sound due to an error, and both channels subjected to the interpolation processing And a data processing means for performing data processing for reproducing the sound with the same pitch as the normal reproduction. 3. The interpolating means comprises filter means for smoothing a change in data between channels for audio data of different channels continuously output from the data replacing means. The voice reproduction circuit described. 4. When reproducing audio, the magnetic tape is run at a speed N times (N is an arbitrary real number) speed during normal reproduction, and the data processing means sets a series of audio data output from the interpolating means to the tape running speed. The sampling means for sampling at a constant cycle according to the above, and the time axis conversion means for performing processing for expanding the time axis by N times on the audio data obtained by sampling, according to claim 2 or claim 3. Voice reproduction circuit. 5. When reproducing audio, the magnetic tape is run at a speed N times (N is an arbitrary real number) speed during normal reproduction, and the data processing means is set within a period of 1 / N of a predetermined constant cycle. The audio reproduction circuit according to claim 2 or 3, wherein the audio data output from the data replacing means is extracted at every fixed period, and the extracted audio data is connected.