JPH09198808A - Voice reproducing circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reproduce a voice even at the time of special reproduction of fast forward, rewind or the like by running a magnetic tape at higher speed than that at the time of normal reproduction and applying interpolation processing to voice data normally read out from the magnetic tape. SOLUTION: Of reproduced data from a magnetic tape running at higher speed than that at the time of normal reproduction, the normal sync block is extracted by an error information detecting circuit 1 and the reproducible voice data is extracted and separated by a voice data extracting circuit 2 and a frame separating circuit 3 and written into a memory 4. They are deshuffled by a left and a right deshuffle circuits 5a, 5b and after that, interpolation processing is applied to data lost due to an error in a left and a right channel interpolation circuits 6a, 6b, and interpolation processing for smoothing the connection part of voice data is applied thereto by interpolation circuits 9a, 9b. Delay circuit 8a, 8b and each interpolation buffer are used for the synchronization of a voice output.

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. 6, 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 case of NTSC specifications. It will be.

An audio data recording area S is formed at the beginning of each track, and in the audio data recording areas S of the first five tracks of the 10 tracks, the audio data of the left channel for one frame and the latter half of the 10 tracks. In the audio data recording area S of 5 tracks, the audio data of the right channel for one frame is recorded. The audio data recorded in one audio data recording area is added with a sequence number for identifying a frame, a track pair number for identifying a track, a sync block number, and a parity as ID data. Shuffling is performed for each frame in units of 16-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 type VTR, two azimuth tracks A and B are repeatedly formed as shown in FIG. 6, 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 audio data recording areas (12a) (12b) (1
The data read from 2d) is the left-channel audio data, and the data read from the audio-data recording areas (12c) and (12e) is the right-channel audio data. Further, since the audio data recorded in these areas 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. 6, and the audio data of the area shown by hatching in the figure is reproduced. Will be missing. Therefore, even if the process to restore the original time series data is performed,
Due to the lack of data, normal voice reproduction cannot be performed. 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 reproducing circuit capable of reproducing audio even during special reproduction.

[0008]

SUMMARY OF THE INVENTION A voice reproducing circuit according to the present invention is a voice which cannot be reproduced as a voice due to an error at the time of data reading by performing interpolation processing on voice data normally read from a magnetic tape. It supplements the data and generates a series of time-sequential audio data.

When a magnetic tape traveling at a speed higher than that during normal reproduction is helically scanned, interlaced scanning is performed on one track among a plurality of tracks corresponding to the tape traveling speed, and audio data of the one track is recorded. When the recording area is scanned with the same azimuth as at the time of recording, the audio data is likely to be read from the audio data recording area without causing an error. In other cases, an error occurs and The data cannot be reproduced as voice. Therefore, data that cannot be reproduced as voice due to an error is compensated by interpolation processing using normal data before and after that. As a result, a series of audio data similar to the original audio data recorded on the magnetic tape can be obtained.

Further, the audio reproducing circuit according to the present invention detects error information added to the audio data read from the magnetic tape, and extracts audio data that can be reproduced as audio based on the detection result. First data processing means for
A second data processing means is provided for performing interpolation processing on the extracted voice data to supplement voice data that cannot be reproduced as voice.

For example, when the voice data is recorded on the magnetic tape together with the error correction code, when the error is detected in the voice data, if the error is minor, the voice data is corrected using the error correction code. You can do it. On the other hand, when the error is serious, the error cannot be corrected, and error information indicating this is added to the voice data. Further, when code data such as a frame number and a parity for error detection for the code data are added to the audio data, when an error in the code data is detected by the parity, this is indicated. Error information is added to the voice data.

After that, when the above-mentioned error information is detected by the first data processing means, the audio data to which the error information is added is not supplied to the second data processing means in the subsequent stage, and the normal audio Only the data is supplied to the second data processing means. As a result, voice data that cannot be reproduced as voice due to an error is supplemented by interpolation processing using normal voice data before and after the voice data.

However, since the amount of data per unit time to be processed at the time of reproducing the voice is increased by the interpolation process and the voice cannot be reproduced in synchronism with the running of the magnetic tape, a fixed amount corresponding to the tape running speed is obtained. Decimate the audio data by a percentage. In addition, necessary data processing is performed in order to avoid changing the pitch due to thinning of the audio data.

For example, in a specific configuration, when the magnetic tape is run at a speed N times (N is an integer of 2 or more) that during normal reproduction, a series of interpolated audio data is 1 / N.
In order to reduce the amount of data, the sampling is performed at a cycle corresponding to the tape running speed, and the audio data obtained by this is subjected to a process of expanding the time axis by N times.

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

Further, in another specific configuration, a series of audio data extracted during a period of 1 / N of a predetermined constant cycle is extracted for each constant cycle, and the extracted audio data is extracted. To connect.

In the specific configuration, the audio data is extracted at regular intervals, so that the audio data is thinned out and the pitch of the audio data within the constant cycle is prevented from changing. Also, by connecting the extracted audio data, it is possible to reproduce the audio in synchronization with the running of the magnetic tape.

However, since data discontinuity occurs at the concatenation portion of the audio data, it is desirable to filter the data at the concatenation portion to smooth the change in the data.

[0019]

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.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment in which special reproduction at double speed is performed in a digital VTR having two 180-degree facing type heads will be specifically described below 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 assumed that any one of the sequence number, track pair number, or sync block number is unknown in the sync block, and error information indicating that fact 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 contains audio data or video data, only the sync block containing audio data is extracted, and the subsequent frame separation circuit
Output to (3).

By the way, during double-speed special reproduction, the magnetic tape runs at twice the normal speed, so that the audio data obtained from the audio data extraction circuit (2) is converted into two frames by scanning for one frame period. A sync block spanning the entire range will be included. Therefore, if audio is reproduced using all sync blocks that are read out,
A time axis shift occurs between the reproduction of the voice and the running of the magnetic tape, and the reproduction of the voice cannot keep up with the running of the magnetic tape.

Therefore, the frame separation circuit (3) separates the sync block of either one of the sync blocks of the two frames based on the sequence number, and stores the data of the sync block in the memory (4). Store to. The sync block of the other frame is discarded. It is assumed that audio data is written to the memory (4) at an address corresponding to a sync block number and a track pair number included in ID data, and a sync block having an error in the ID data is a non-reproducible sync block. ,
The voice data is discarded and is not written in the memory (4). As a result, only reproducible sync blocks are written in the memory (4). An error code for recognizing that it is a non-reproducible sync block is written in an address where no data has been written.

The audio data for one frame written in the memory (4) is original data having continuity with respect to the time axis by the deshuffle circuit (5a) for the left channel and the deshuffle circuit (5b) for the right channel. The data is sequentially read and deshuffled.

The deshuffled data is shown in FIG.
Although they are arranged in chronological order as shown in (a), a lot of data loss occurs as indicated by an X mark in the figure due to an error in voice data or ID data, and the voice cannot be reproduced as it is. Therefore, in the present embodiment, as shown in FIG. 1, the output data of the left-channel deshuffle circuit (5a) and the right-channel deshuffle circuit (5b) is converted to the left-channel first interpolation circuit (6a) and the right-channel first interpolation circuit. The data is supplied to the circuit (6b) and the data missing due to the error is compensated by the interpolation process.

For example, for the two missing data indicated by arrows in FIG. 2A, one or a plurality of normal data before and after indicated by double circles in FIG. Interpolation processing such as interpolation method or Newton interpolation method is performed, and the data generated by interpolation as shown by the square marks in the figure is supplemented to the data missing portion. As a result, Fig. 2 (c)
As shown in, a series of audio data similar to the original audio data recorded on the magnetic tape can be obtained.

The first interpolation circuit (6
a) and the right channel first interpolation circuit (6b) include a left channel first interpolation buffer (7a) and a right channel first interpolation buffer (7a) for temporarily storing data during the interpolation process. 7b) are connected respectively. First interpolation circuit (6a)
From (6b), it is necessary to output the data after interpolation processing at a fixed time interval, whereas the time interval of the data obtained from the deshuffle circuits (5a) and (5b) is not constant and is still normal. Interpolation calculation cannot be performed until a predetermined number of data are collected. Therefore, the time difference between the input and output data of the first interpolation circuits (6a) (6b) is absorbed by the first interpolation buffers (7a) (7b). As a result, from the first interpolation circuit (6a) (6b),
A series of data strings that can be recognized as voice are obtained.

FIGS. 3A and 3B show the relationship between a series of audio data obtained during normal reproduction at 1 × speed and a series of audio data obtained during special reproduction at 2 × speed. In the present embodiment, for example, the audio data of even-numbered frames is thinned out by the frame separation circuit (3) described above, and only the audio data of odd-numbered frames is supplied to the subsequent circuit to perform deshuffling and interpolation processing for each frame. Then, the audio data of the odd-numbered frames are connected to each other as shown in FIG. 3 (b). As a result, the running of the magnetic tape and the audio reproduction are synchronized with each other, and at the same time, the audio reproduction with no change in pitch is realized.

However, as shown in FIG. 3B, the connecting portion of the audio data becomes discontinuous, which causes noise.
Therefore, in this embodiment, as shown in FIG. 1, the first interpolation circuit (6a) for the left channel and the first interpolation circuit (6b) for the right channel.
The second interpolation circuit for the left channel from the audio data obtained from
(9a) and the second interpolating circuit (9b) for the right channel, respectively, to perform an interpolating process for smoothing the connection part of the audio data.

For example, when interpolation is applied to the connecting portion between the first frame and the third frame as shown in FIG.
The last plural data of the frame and the first plural data of the third 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.

The second interpolating circuit for the left channel (9
a) and the second interpolation circuit for the right channel (9b) include a second interpolation buffer for the left channel (10a) and a second interpolation buffer for the right channel (10a) for temporarily storing data during the interpolation process. 10b) are connected to each other and perform the same time difference absorbing function as the first interpolation buffers (7a) and (7b).

The left channel first interpolation circuit (6a) and the right channel first interpolation circuit (6b) are provided at the output ends thereof in parallel with the second interpolation circuits (9a) and (9b), and a delay for the left channel is provided. Circuit (8a)
And a delay circuit (8b) for the right channel are connected to the output data of the first interpolation circuits (6a) (6b) and the second interpolation circuits (9a) (9b).
Delay processing corresponding to the processing time according to b) is performed. The output data of the delay circuits (8a) and (8b) and the output data of the second interpolation circuits (9a) and (9b) which are synchronized in this way are selected by the selection circuit (11
a) (11b), the audio data interpolated by the first interpolation circuits (6a) (6b) and the audio data interpolated by the second interpolation circuits (9a) (9b) are It is synthesized as shown in FIG. As a result, double-speed audio data for the left channel and double-speed audio data for the right channel in which the connection portion between frames changes smoothly can be obtained.

The left channel double speed audio data and the right channel double speed audio data thus obtained are D / A
After the conversion, if it is supplied to the speaker device, the sound with the same pitch as in the normal reproduction is reproduced.

The description of the above embodiments is for the purpose of illustrating 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, FIG.
Although the audio data is thinned out in frame units as shown in (a) and (b), it is also possible to adopt a configuration in which the audio data is thinned out at a cycle twice the sampling cycle as shown in FIG. In this case, in order to obtain the same pitch as in normal reproduction, it is necessary to double the time axis by well-known voice speed conversion or the like.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an audio reproducing circuit according to the present invention.

FIG. 2 is a diagram illustrating an interpolation process by a first interpolation circuit.

FIG. 3 is a diagram illustrating a data thinning process by a frame separation circuit.

FIG. 4 is a diagram illustrating an interpolation process by a second interpolation circuit.

FIG. 5 is a diagram illustrating another example of data thinning processing.

FIG. 6 is a diagram showing an audio data recording area of a track formed on a magnetic tape and a scanning locus during special reproduction.

[Explanation of symbols]

 (1) Error information detection circuit (2) Audio data extraction circuit (3) Frame separation circuit (6a) First interpolation circuit for left channel (6b) First interpolation circuit for right channel (9a) Second interpolation circuit for left channel (9b) Second interpolation circuit for right channel

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Claims (5)

[Claims] 1. A voice reproducing circuit for reproducing a voice by running the magnetic tape at a speed higher than that at the time of normal reproduction for a magnetic tape on which digital voice data is recorded by a helical scan. By performing interpolation processing on the normally read audio data, the audio data that cannot be reproduced as audio due to an error during data reading is supplemented, and a series of time-series audio data is generated. Audio playback circuit. 2. A voice reproducing circuit for reproducing a voice by running the magnetic tape at a speed higher than that during normal reproduction, which is intended for a magnetic tape on which digital voice data is recorded by a helical scan. First data processing means for detecting error information added to the read voice data and extracting voice data reproducible as voice based on the detection result, and an interpolation process for the extracted voice data. And a second data processing means for supplementing voice data that cannot be reproduced as voice. 3. When reproducing audio, the magnetic tape is run at a speed N times (N is an integer of 2 or more) that during normal reproduction, and a series of interpolated audio is provided after the second data processing means. 3. A sampling means for sampling data at a constant cycle according to a tape traveling speed, and a time axis conversion means for performing a process of expanding the time axis by N times the audio data obtained by sampling. The voice reproduction circuit described. 4. A magnetic tape is made to travel at a speed N times (N is an integer of 2 or more) that during normal reproduction at the time of voice reproduction, and N minutes of a predetermined constant cycle are provided after the first data processing means. A series of audio data extracted in the period 1) is extracted for each fixed period, and the extracted audio data is concatenated, and the concatenated audio data is supplied to the second data processing means. The audio reproduction circuit described in 2. 5. A filter means for smoothing a change in the data of the connection portion at the time of connection of the audio data extracted at the fixed cycle is provided at a stage subsequent to the second data processing means. The audio reproduction circuit according to item 4.