JPH02308476A - Digital signal recording and reproducing method - Google Patents

Abstract

PURPOSE:To enable the influence of a reproducing video signal on a reproducing audio signal to be neglected by attaching the low-order bit side of a digital video signal on a digital audio signal so as to form the low-order bit side of the digital audio signal. CONSTITUTION:The digital audio signal DSo is mixed with the digital video signal DSv, and a mixed digital signal DS is recorded/reproduced with a rotary magnetic head. The high-order M (10) bits of the signal DS is occupied with the signal DSo, and the low-order (N-M) (6) bits of it is occupied with the signal DSv. When the signal DSv of low-order 6 bits is inserted, the signal DS is comprised by attaching the signal DSv on the signal DSo at a state where the MSB of the signal DSv can form the least significant low-order bit data V0 and the LSB can form the most significant bit data V5. As the result, the reproducing level difference of the signal DSo and the signal DSv is increased, and a trouble such that the signal DSv is incongruous as a noise can be prevented from occurring even when the signal DSo and the signal DSv are reproduced simultaneously.

Description

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

[Prior art] Current digital audio tape 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 signals, such as video signals for still images, could be recorded and played back simultaneously.

In order to record and play back video signals, it is conceivable to record each signal one channel at a time, for example by recording audio (No. 8) 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.

[Problems to be Solved by the Invention] However, when an audio signal is recorded on one channel and a video signal is recorded on the other channel in the current audio format, it is necessary to use a playback device that can play back the video signal. Otherwise, the video signal will also be played back at the same time.

If a DAT that has only a co-diode signal reproducing device is able to reproduce video No. 148, it will be reproduced with excessive noise, making it unusable.

If a video signal is recorded in a format other than the current audio format, it will not be compatible with the current DAT, and therefore the general DAT will not be able to reproduce even the audio signal.

Therefore, the present invention solves the above-mentioned problems with a simple structure, and provides a digital device that is compatible with current models and that can record and play back video signals without adversely affecting audio signals. This paper proposes a method for recording and reproducing signals. More specifically, the present invention proposes a digital signal recording and reproducing method in which the influence of a reproduced video signal on a reproduced audio signal can be almost ignored.

[Means for Solving the Problems] 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 rotating magnetic head. When using, recording, and reproducing digital signals, audio signals and video signals are used, and the audio signal is a digital audio signal with M pits (where N>M is an integer). is converted into a video 148 or (N-M) bit digital video signal, and is added to the least significant bit side of the converted digital video signal or the least significant bit side of the digital audio signal, It is particularly noteworthy that it is possible to record and reproduce a total of N bits of digital signals.

[Function] Digital audio No. 13 DSo and digital video signal DSv are mixed in the mixing/separating means 90, and the mixed digital signal DS is recorded and reproduced by the rotating magnetic head.

Digital 15 recorded and reproduced by a rotating magnetic head
The signal is a P CM signal conforming to the DAT audio format and has an N-bit configuration.

Among them, the upper M pit is the digital audio signal DS
o, and the remaining (N-M) bits, that is, the lower (N
-M) bits are occupied by the digital video signal DSv. Digital video signal DSv of lower (N-M) bits
When inserting, the lower bit side is added so that it becomes the lower bit side of the digital audio signal DSO.

When this digital signal is reproduced by the current DAT, the video signal Sv also becomes 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 M is set to about 10, the reproduction level difference between the audio signal So and the video signal Sv will increase.

Furthermore, the lower bits of the digital video signal DSV are the digital audio signal DS.

It is added so that it is on the lower bit side of .

As a result, simultaneously with the audio signal So, the video signal Sv
Even if the video signal Sv cannot be reproduced, the video signal Sv will hardly be bothersome 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.

Figure 1 shows the format (bit configuration) of the digital signal DS, which is a mixture of the audio signal So and the video signal Sv.
- Give an example.

In this invention, in consideration of both compatibility with conventional models and the playback quality of audio signals, the D
Although the number of bits of the digital signal DS original to AT is used, it is divided into two as shown in the same figure and Figures 1A to 1C, and the digital audio signal DSo is on the upper bit side and the digital audio signal DSo is on the lower bit side. is a digital video signal DS
Is V your husband? It is assigned.

According to the audio format, the number of bits N (N is an integer) is N = 16, the number of bits of the digital audio signal DSo is M (M is an integer'!19.), and the remaining number of bits (N - M ) is a digital video (No. 8 DSv), better results can be obtained by selecting M≧1/2N.Among them, a practical value is M=8 to 10 (1st As a result, the digital video signal DSV has a 6- to 8-bit configuration (FIG. 1B).

Then, if the digital audio No. 18 DSo and the digital video signal DSv 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 Digital Video No. 43 DSV (FIG. 1C).

Then, when adding the digital video signal DSV,
When ■O is the least significant bit data and ■5 is the most significant bit data, the bits are usually added with the bits reversed so that the lower bit side of the digital video signal DSV becomes the lower bit side of the digital audio signal DSo. Ru.

That is, as shown in 1l8, the digital video signal D
Looking at the SV itself, its 14sB is the least significant bit data ■0, and its LSB is the most significant bit data V5.
The position of each bit is swapped and the direction of the weight of the bit is reversed so that the digital audio signal D is
The digital signal DS is added to So (FIG. 1C).

The reason why the bit weighting relationship is changed and added in this way will be described later.

When mixing the audio signal So with the video signal SV after applying noise countermeasures such as noise reduction, the relationship between the audio signal SO and the video signal Sv does not follow the above-mentioned relational expression. The number of bits of the audio signal SO may be roughly reduced.

The digital signal DS having such a bit configuration is supplied to the rotary magnetic head, is completely recorded, and is 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 DATIO 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 subjected to noise reduction, the case where M=10 will be exemplified.

The audio signal So supplied to the audio in terminal 12 is supplied to the low-pass filter 16 via the amplifier 14 to be band-limited, and then supplied to the A/D converter 18 where it is converted into a 10-bit digital audio signal DSo. Ru.

The digital audio signal DSo is supplied to the mixing means 20 constituting the mixing and separating means 90 and mixed with digital video No. 48 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 the rotating magnetic head via the terminal 24 and is recorded.

The digital signal DS that has been completely 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 pit clock BCK.

Based on this master clock, a signal 131 for separating the digital audio signal DSo and the digital video signal DSv is generated, and the digital audio signal DSO and the digital video signal DSv are separated from the separating means 36 at the next stage. (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 input terminal 50 is supplied to an A/D converter 54 via an amplifier 52, and is converted into a 6-bit digital video signal DSv in this example.

The digital video signal DSv is supplied to the memory means 6o via the 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 pit clock BCK, and for the time axis expansion of the reproduced digital video signal DSv. Used for time axis compression.

The memory means 60 has a pair of memories 62 and 64, and 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 corresponds to each field (or frame).
2.64.

A pair of output changeover switches 68 and 70 that are switched in conjunction with each other are provided downstream of the memory 62 and 64.
Digital video signals can be read out alternately from 2.64 onwards.

One output selector switch 68 can be used only when recording signals.
The other output selector switch 7o 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 fSC of the analog video signal extracted by the subcarrier extraction circuit 78.

Based on this subcarrier fsc, the control means 76
For example, a write clock WCK of 3 fsc is generated. Based on this write clock \/CK, the digital video signal DSv is written into the corresponding memory 62, 64.

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

As a result, the digital audio signal DSo and the digital video signal DSV are input to the mixing means 2o in complete synchronization with this pit clock BCK.

Further, in the digital out processing circuit 22, the detailed explanation is omitted, but based on the pit clock BCK,
The 0 bit and 6 bit pit switching signal BS has been created,
This pit switching signal BS is supplied 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, one field of digital video signal is read out in about 2 seconds, and the digital audio (g
It is designed to be mixed into No. D So.

The digital video signal DSv read from the memories 62 and 64 is also roughly supplied to the vertical synchronization signal separation circuit 74, and the changeover switch 66 is selected 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 storing the digital video signal DSv first, for example, the digital video signal D is stored in the memory 62.
When storing Sv, a necessary switching signal cannot be obtained from the separation circuit 74 because no signal is stored in the other memory 64.

Therefore, a timer (not shown) is provided inside the separation circuit 74, and when the vertical synchronization signal V-SYNC is not obtained even after a predetermined period of time has elapsed from the start of reading in the initial state, the switch 66 to 74 I am trying to force the switch.

When reproducing the digital signal, the separating means 36 separates the signal into a digital audio signal DSo and a digital video signal DSv.

Therefore, the digital input processing circuit 34 also generates a switching signal BS similar to that described above based on the reproduced digital signal, and supplies this to the separating means 36.

The separated digital video signal DSv is supplied to the signal changeover switch 56 and also to the above-mentioned vertical synchronization signal separation circuit 74, from which the changeover switch is synchronized with the separated vertical synchronization signal No. 43 V-SYNC. 66-7
0 is controlled.

The reproduced digital video signal DSv is the pit clock BC
It is written in by a write clock WCK synchronized with K, and can be read out based on a read clock RCK associated with a fixed subcarrier fsc. Further, a vertical synchronization signal separation circuit 86 is provided at the subsequent stage of the memory means 60, and extracts and separates the vertical synchronization signal 'J-S Y N C
is supplied to the control means 76 to form a write start timing (write enable signal) to the memory means 60.

The 6-bit digital video signal DSv read from the memories 62 and 64 is converted into an analog video signal by a D/A converter 80, and this is outputted to a video out terminal 84 via an amplifier 82.

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 a 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 digital signal DS, which is a mixture of the audio signal S○ and the video signal Sv, is to be played back using the current DAT, that is, as shown in FIG. When the signal DSV is reproduced as the digital audio signal DSo, there is almost no influence on the audio signal SO.

In that case, for the audio signal SO, the video signal Sv
is nothing but a noise component. However, as is clear from FIG. 1C, since the digital video signal DSv is inserted into the lower bit side of the digital audio signal DSo, the audio signal SO has an S/
N ratio can be obtained. Therefore, as mentioned above, the quantization B
If &M is selected to be about 10 pits, the S/N ratio will be comparable to compact cassette or Dolby B (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, and no deterioration in sound quality occurs.

Moreover, even when synthesizing the digital video signal DSv to generate the digital signal DS, the upper bits and lower pits are reversed to generate the digital audio signal D.
Since it is added to So, the influence of the reproduced video signal Sv on the reproduced audio signal SO can be almost completely eliminated.

The reason for this will be explained below.

When adding the digital video signal DSv to the lower bit side of the digital audio signal DSo, the fifth
As shown in Figures B and C, the most significant bit data V5 of the digital video signal DSv is added to the MSB side, and the lowest pit data VO is added to the LSB side, so the digital video signal DS is as shown in Figure 6. The configuration is as follows.

When digitizing the video signal Sv,
As shown in FIG. 7, the intermediate brightness level (shown by the chain line) is used as a reference, and the brightness level higher than that is determined by its MSB (=
V5) is digitized as "1" and the following as "0".

On the other hand, the video signal Sv is a periodic signal that is repeated in units of horizontal periods. Since one horizontal period is approximately 63.5 μsec and recording is performed at a speed 120 times that, the reproduction frequency of the most significant bit data V5 at that time is approximately 130 Hz.

FIG. 8 shows the spectrum of this reproduction frequency, and it can be seen that there is a noise peak approximately every 130 Hz. FIG. 9 shows the spectrum when θ11 is constant up to 20 KHz.

During playback, approximately 60 dB of the playback frequency level is mixed into the playback audio No. 3 So as noise.

Therefore, the reproduced video signal may be heard as noise, albeit slightly.

On the other hand, when the digital video signal DSv is added to the digital audio signal DSo with the bit weights swapped as described above, the following occurs.

In other words, if the bits are swapped so that the original most significant bit data V5 is on the least significant bit side and the least significant bit data 0 is on the most significant bit side, even if the most significant bit data v5 is reproduced, it will not be reproduced. Since the level is extremely small, it is not a problem at all.

Furthermore, since the lowest bit data VO itself changes very rapidly even within one horizontal period, when the lowest bit data VO is reproduced, the reproduction frequency is extremely high and is output as white noise. .

However, since the reproduction frequency is very high and the reproduction output level is very low, this is not a problem at all. As a result, the reproduction noise mixed into the audio signal So can be reduced to a greater extent than in the case of the configuration shown in FIG. 5C.

Note that FIGS. 10 and 11 are reproduction frequency spectra when the configuration shown in FIG. 1 is used, respectively, and FIG.
FIG. 11 corresponds to FIG. 9.

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.

[Effect of the invention] As explained above, according to the present invention, the audio
In addition to No. 3, when recording and reproducing video signals such as still images at the same time, the two are mixed in accordance with the current audio format.

In this case, in addition to ensuring compatibility with current models, efforts have been made to ensure that the sound quality of the reproduced audio signal 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.
The present invention is extremely suitable for use in recording and reproducing digital signals in, for example.

In general, since the bit positions of the digital video signal are changed and added to the digital audio signal, the noise mixed into the reproduced audio signal (the reproduced video signal) can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an example of the audio format of a digital signal that can be adopted in the digital signal recording and reproducing method according to the present invention, FIG. 2 is a block diagram of a DAT audio format, and FIG. 3 embodies the present invention. FIG. 4 is a system diagram of the main parts showing an example of a digital audio chip recorder, FIG. 4 is a system diagram showing an example of a current DAT, FIGS. The waveform diagrams of the video signal, FIGS. 8 to 11, are characteristic diagrams for explaining the present invention. 1o...Digital audio recorder (DA)
T) 20...Mixing means 22...Digital out processing circuit 34...Digital in processing circuit 36...Separation means 60...Video signal memory means 74.86...Vertical synchronization signal separation circuit S○...Audio signal DSo...Digital audio signal Sv...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 least 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.