JPH02161660A - Recording and reproducing method for digital signal - Google Patents

Abstract

PURPOSE:To prevent the sound quality of a reproducing audio signal from deteriorating by mixing an audio signal and a video signal based on a current voice format at the time of performing the recording and reproduction of both signals simultaneously. CONSTITUTION:The audio signal So and the video signal Sv are mixed by conforming to the current voice format by a mixing means 20. In such a case, the number of quantization in the audio signal So is reduced, for example, from the current constitution of 16 bits of constitution of 10 bits, however, deterioration in the sound quality according to the reduction of the number of quantization scarcely occurs. Also, since a video is still picture, it is enough to perform quantization of six bits. In the case of regenerating a digital signal DS in which the audio signal So and the video signal Sv are mixed by a current digital-audio tape recorder 10, no influence when a digital video signal DSv is regenerated as a digital audio signal DSo on the audio signal So is given. In such a manner, it is possible to prevent the deterioration in the regenerating quality of the audio signal from occurring.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a digital signal recording and playback method suitable for application to a digital audio tape recorder, and in particular to a method for simultaneously recording video signals without adversely affecting audio signals. This invention relates to a method for recording and reproducing digital signals that can be reproduced.

[Prior art] Current digital audio recorder (hereinafter referred to as DA)
(referred to as T) is capable of recording and reproducing only audio signals.

However, it would be very convenient if not only audio signals but also other (FI) signals, such as video signals for still images, could be recorded and reproduced simultaneously.

Here, in order to record and reproduce video signals, it is conceivable to record each signal one channel at a time, such as recording audio signals on odd-numbered tracks and recording video signals on even-numbered tracks.

Alternatively, it may be possible to record in a format other than the current audio format.

[Issue to be Solved by the Invention 81 However, if the A-dio code is recorded on one channel and the video signal is recorded on the other channel in the current audio format, there is no playback device that can also play back video No. 143. Unless you use , the video signal will also be played back at the same time.

In a DAT having only an audio signal reproducing device, when a video signal is reproduced, excessive noise is generated in the DAT, making it unusable.

If a video signal is recorded in a format (other than the current audio format), it will not be compatible with current DATs, so even audio signals will not be able to be played back with general DATs.

Therefore, the present invention solves the two problems in a simple structure, and records video signals without adversely affecting audio signals while maintaining compatibility with current models. This paper proposes a method for recording and reproducing digital signals that can be reproduced.

[! Means for Solving IFa] In order to solve the above problems, the present invention converts an input signal into a digital signal with a predetermined number of bits N (N is an integer), and then converts this digital signal into a digital signal using a rotating magnetic head. 74143 and the video signal are used, and the audio signal has M bits (M is an integer), and N>M). The video signal is converted into a (r'l-M) bit digital video signal 198, and the most significant bit of the converted digital video signal is the least significant bit of the digital audio signal. It is characterized in that it is recorded and reproduced in a state in which it is added to a total of N bits of digital signals.

[Function 1] The digital audio signal DSo and the digital video signal DSv are mixed in the mixing/separating means 90, and the mixed digital No. 18 DS is recorded and reproduced by a rotating magnetic head.

The digital signal recorded and reproduced by the rotating magnetic head is a PCM signal conforming to the DAT audio format and has an N-bit configuration.

The upper M bits are the digital audio signal DS.
o occupies the remaining (N-M) bits, i.e. the lower (N
-M) bits are occupied by the digital video signal DSv.

When the current DAT reproduces this digital signal (No. 8), the video signal Sv and the audio signal S.

is played as. However, since the video signal Sv is added to the lower bit side of the audio signal So, the reproduction level difference between the audio signal So and the video signal SV is about 6 MdB.

Therefore, if the interval is set to about 10, the reproduction level difference between the audio signal So and the video signal Sv becomes large.

As a result, simultaneously with the audio signal SO, the video signal Sv
Even when the video signal Sv is played back, the video signal Sv does not become harsh as noise.

[Embodiment] Next, an example of the digital signal recording and reproducing method according to the present invention will be explained in detail with reference to FIG. 1 and subsequent figures.

FIG. 1 shows an example of the format (bit configuration) of a digital signal DS in which an audio signal SO and a video signal Sv are mixed.

In this invention, in consideration of compatibility with conventional models and the playback quality of audio (no. As shown in the figure and Figure 1C, the digital audio signal D
So is the digital video signal DSv on the lower bit side.
are applied to each.

According to the audio format, the bit aN (N is an integer) is N = 16, the number of bits of the digital audio signal DSo is M (M is an integer), and the remaining number of bits (NM) is the digital video signal. When DSv,
Better results can be obtained by selecting M such that M≧1/2N. Among these, a practical value is M=8 to about 10 (FIG. 1A). As a result, the digital video signal DSV has a 6 to 8 bit configuration (FIG. 1B).

Then, if the digital audio signal DSo and the digital video signal 1) SV are mixed so that the digital audio signal DSo is on the upper bit side, the upper 10
The bits become the area of the digital audio signal DSo, and the lower 6 bits become the area of the digital video signal DSv (FIG. 1C).

When mixing the audio signal So with the video signal SV after noise reduction or other noise countermeasures have been applied to the audio signal So, the relationship between the audio signal So and the video signal Sv is expressed by the relational expression described above. , sub-de°
The number of bits of the IO signal So may be roughly reduced.

The digital signal DS having such a bit configuration is supplied to the rotating magnetic head, is recorded thereon, and can be reproduced from the rotary magnetic head.

Figure 3 shows a digital signal D with such a signal form.
An example of the main part of the DAT 10 for recording and reproducing S is shown.

The signal processing system for the audio signal So will be explained first.

However, since the audio signal So has not been completely noise-reduced, the case where M=10 will be exemplified.

The audio signal So supplied to [Audio In terminal] 2 is supplied to the low-pass filter 16 via the amplifier 14, where it is band-limited, and then supplied to the A/D converter 18, where it is converted into a 10-bit digital audio signal DSo. be done.

The digital audio signal DSo is supplied to the mixing means 20 constituting the mixing and separating means 90, and is mixed with a digital video signal DSv, which will be described later.

The mixed digital signal (FIG. 1C) is supplied to the digital out processing circuit 22 and converted into a digital signal DS in a form compliant with the audio format.

As is well known, the digital out processing circuit 22 is provided with clock generation means for bit clock generation.

The digital signal DS formatted into a predetermined format is finally supplied to a rotating magnetic head via a terminal 24 and recorded thereon.

The digital signal DS reproduced by the rotating magnetic head is supplied to a digital-in processing circuit 34 via a reproduction terminal 32 and subjected to digital-in processing.

For example, a PLL circuit (not shown) is driven to generate a master clock synchronized with the reproduced bit clock BCK.

A separation signal for separating the digital audio signal DSo and the digital video signal DSv is generated based on this master clock, and a state in which the digital audio signal DS0 and the digital video signal DSv are separated from the next stage separation means 36 is generated. (Fig. 1 A, B)
).

Separated 10-bit digital audio signal DS
o is converted into an analog signal by a D/A converter 38, limited to a predetermined band by a low-pass filter 40, and then output to an audio out terminal 44 via an amplifier 42.

The signal processing system for the video signal Sv has the following configuration.

For example, a still image video signal Sv supplied to the video in terminal 50 is passed through an amplifier 52 to an A/D converter 1! i! !
The signal is supplied to a converter 54 and converted into a 6-bit digital video signal DSv in this example.

Digital video signal DSv is supplied to memory means 60 via signal changeover switch 56.

This memory means 60 combines the digital video signal DSv with the digital audio signal DSo, and is used for time axis expansion when reading out the digital video signal in synchronization with the bit clock BCK, and for the time axis of the reproduced digital video signal DSv. Used for compression.

The memory means 60 has a pair of memories 62 and 64, in which the digital video signal DSv is alternately switched by an input changeover switch 66 provided in front of the memories 62 and 64, and the memory 6 corresponding to each field (L or frame) is switched alternately.
2.64.

A pair of output changeover switches 68 and 70 are provided after the memories 62 and 64 and are switched in conjunction with each other so that digital video signals are read out alternately from the memories 62 and 64.

One output selector switch 68 is used during signal recording,
The other output selector switch 70 is a switch used during signal reproduction.

Here, 76 is a control means 76 such as a memory, and this is first supplied with the subcarrier fse of the analog video 143 extracted by the subcarrier extraction circuit 78. The control means 76 generates a write clock WCK of, for example, 3 fse based on this subcarrier fsc. Based on this write clock WCK, the digital video signal DSv is written into the corresponding memory 62, 64.

The control means 76 includes a digital output processing circuit 2.
A pit clock BCK is supplied from the digital input processing circuit 2 and the digital input processing circuit 34. Therefore, the read clock RCK for the memory 62, 64 is generated based on this bit clock BCK, and this read clock RCK
Digital video signal DSv is read out in synchronization with .

As a result, the digital audio signal 1) So and the digital video signal DSv are input to the mixing means 20 in complete synchronization with this pit clock BCK.

Further, in the digital out processing circuit 22, a 10-bit and 6-bit bit switching signal BS is created based on the bit clock I cock BCK, although a detailed explanation of the seventh part is omitted, and this bit switching signal BS is sent to the mixing means 20. The 10-bit digital audio signal DSo and the 6-bit digital video signal DSv are mixed as shown in FIG. 1C.

In this case, in this example, the field digital video (
No. 8 is read out in about 2 seconds and mixed into the digital audio signal DSo.

The digital video signal DSv read out from the memories 62 and 64 is further supplied to a vertical synchronization signal separation circuit 74, and the changeover switch 66 is applied based on the vertical synchronization signal V-SYNC extracted and separated from the digital video signal DSV.
-70 switching states are controlled. As a result, the memories 62 and 64 can always store one field's worth of digital video signals DSV with reference to the vertical synchronizing signal V-SYNC.

Note that when the digital video signal DSv is first stored in the memory, for example, when the digital video signal DSv is stored in the memory 62, since no signal is stored in the other memory 64, necessary signals are sent from the separation circuit 74. Cannot get switching signal.

Therefore, a timer (not shown) is provided inside the separation circuit 74, and if the vertical synchronization signal V-3YNC is not obtained even after a predetermined period of time has elapsed after the start of reading in the initial state, the switch 66 to 70 are forcibly switched.

When the digital No. 43 is reproduced, the separation means 36 separates it into a digital audio signal DSo and a digital video signal DSv.

Therefore, the digital input processing times'#! Also in I34, a switching signal BS similar to that described above is formed based on the reproduced digital signal, and this can be supplied to the separating means 36.

The digital video signal DSv after ts is supplied to the No. 3 changeover switch 56 and also to the vertical synchronization signal separation circuit 74 mentioned above, and is synchronized with the vertical synchronization signal V-3YNC separated from this. Changeover switch 66~
70 is controlled.

The reproduced digital video signal DSv is a pit clock clock B.
It is written based on a write clock WCK synchronized with CK and read based on a read clock RCK associated with a fixed subcarrier fsc. Further, a separation circuit 86 for a double 1σ synchronization signal P is provided at the subsequent stage of the memory means 60, and the extracted and separated vertical synchronization signal V-5YNC is supplied to the control means 76 to start writing into the memory means 60. Timing (write enable signal) is formed.

The 6-bit digital video No. 4g DSv read from the memories 62 and 64 is converted to an analog video (No. 3) by a D/A converter 80, and is sent to a video out terminal 84 via an amplifier 82. Output.

88 is a switch for a video monitor.

With the above configuration, it is possible to mix the audio signal So and the video signal Sv while adapting them to the current audio format. In this case, the number of quantizations of the audio signal So is reduced from the current 16-bit configuration to 10-bit configuration, but there is almost no deterioration in sound quality due to this decrease in the quantization number.

Furthermore, since the video is a still image, 6-bit quantization is sufficient.

When the audio signal So and the video signal Sv are mixed and the t-digital No. 43 DS is played back using the current DAT, that is, as shown in FIG. video signal DSv
When reproduced as a digital audio signal @D SO, there is almost no effect on the audio signal SO.

In that case, the audio signal So and the video signal S
v is nothing but a noise component. However, as is clear from FIG. 1C, since the digital audio signal DSV No. 1113 is inserted into the lower bit side of the digital audio signal DSo, the audio signal No. 4143 So can have an S/N ratio of 6 MdB or more. Therefore, as mentioned above,
If the quantization number M is selected to be about 10 bits, the S/N ratio will be comparable to compact cassette and Dolby 8 (trademark) recording/playback. For this reason, even if the video signal Sv is played back at the same time, there is almost no effect on the audio signal So.
No deterioration in sound quality occurs.

In the above, N=16. Although the description has been made assuming that M=10, the values of N and M are not limited to this as described above.

[Effects of the Invention] As explained above, according to the present invention, when recording and reproducing video signals such as still images in addition to audio signals at the same time, the two are mixed in accordance with the current audio format. It is something.

In that case, in addition to ensuring compatibility with current models, the playback audio (No. 8) has been devised to ensure that the sound quality does not deteriorate.

According to this, it becomes possible to record and play back on both current models and dedicated models, and the effect on audio signals can be practically ignored, so it is possible to use DAT for events.
It is extremely suitable for application to the recording and reproduction of digital No. 48, etc.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing an example of the digital No. 43 audio format that can be adopted in the digital signal recording and reproducing method according to the present invention, FIG. 2 is a block diagram of the DAT audio format, and FIG. FIG. 4 is a system diagram showing an example of a current DAT. 10 ・ 20 ・ 22 ・ 34 ・ 36 ・ 60 ・ 74, 86 ・ So ・ DSo ・ Sv ・ DSV ・ ・Digital audio table recorder (DAT) ・D combination means ・Digital out processing circuit ・Digital in processing circuit ・Separation means ・Video signal memory means, vertical synchronization signal separation circuit, audio signal, digital audio signal, video signal, digital video signal

Claims (1)

[Claims] (1) After converting the input signal into a digital signal with a predetermined number of bits N (N is an integer), this digital signal is recorded using a rotating magnetic head, and when the digital signal is reproduced from this, it is converted into an audio signal. The video signal is used, the audio signal is converted into an M-bit (where M is an integer, and N>M) digital audio signal, and the video signal is converted into an (NM)-bit digital video signal. At the same time, the most significant bit of the converted digital video signal is added to the least significant bit of the digital audio signal, so that the digital signal is recorded and played back with a total of N bits. Features a digital signal recording and playback method.