JPH03276469A - Digital audio tape recorder - Google Patents

Abstract

PURPOSE:To shorten the time required for monitoring the first screen by monitoring a reproducing screen of, for instance, an odd-numbered field when it is detected that the first reproducing screen is the reproducing screen of this odd-numbered field. CONSTITUTION:A digital video signal supplied to a terminal (data-in) 12 of a memory control circuit is distributed in turn via a frame change-over switch 14 and field changeover switches 16 and 18 to store in odd-numbered frame field memories 30 and 32 and even-numbered frame field memories 34 and 36. Then, the digital video signal read out of these memories is outputted via field changeover switches 20 and 22 and a frame changeover switch 24 to the side of an output terminal (data-out) 38, and under a normal reproducing mode, the signal is reproduced in a unit of a frame and monitored, and in the case of the first reproducing screen, the signal is controlled by a CPU 40 so as to be monitored in a unit of a field. By this method, the time from selecting a reproducing mode to monitoring the first screen can be shortened, and hence the reproducing screen can quickly be monitored.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a digital audio tape recorder that can also record still images.

``Prior Technology J Digital audio tape recorder (DAT) is a dedicated device for recording and playing back audio signals, but recently a DAT has been developed that can record and play back a video signal superimposed on the audio signal. ing.

This normally records and reproduces an N-bit (N is an integer) digital audio signal as it is.

In contrast, the newly developed method for using DAT is
As shown in the diagram, the upper N bits (the numbers in between are integers, M<N)
, for example, when N = 16 bits, the digital audio signal is assigned to the top 10 bits, and the remaining (N-M
) bits, ie, the lower 6 bits, are allocated to digital video signals for still images for recording and reproduction.

When this composite digital signal is reproduced, even if it is reproduced as an audio signal with N bits intact, there is almost no influence from the (N-M) bit digital video signal. This is because the digital video signal is assigned to the lower (NM) bits.

A digital video signal from which the composite digital signal has been separated is supplied to a monitor. Then, not only audio signals but also video signals can be recorded and reproduced simultaneously, and the functionality of the DAT can be greatly increased.

The composite digital signal is recorded and played back in units of one frame, so the screen is played back in units of one frame (
monitored).

FIG. 3 is a format showing an example of the data structure of an 1 frame, in which various control signals (No. IIJ) are inserted at the front and end stages of a composite digital signal (shown as data in the figure), respectively.

Here, S ID is START which indicates the start of data.
D, and MD•ID is a mode ID, which is used to distinguish whether an odd field is an even field.

LS-ID (last start ID) is an ID for distinguishing from data, and is the last ID inserted in the previous stage. Further, E-ID (end ID) is an ID added to the end of data. The total time to insert the ID is 8.
0m5ec, and data is inserted for approximately 2.48sec. Therefore, one frame is approximately 5 seconds.

[Problems to be Solved by the Invention] By the way, when reproducing the above-mentioned composite digital signal, since the recording is performed in units of frames,
The screen cannot be viewed until the first reproduced composite digital signal is completely stored in memory.

Since it takes approximately 5 seconds to play one frame, at playback timing a in Figure 5, the first playback screen cannot be monitored until 5 seconds have elapsed after switching to the playback mode (Figure B). .

In addition, when storing a composite digital signal in memory, if the system is configured so that it can be stored only when an odd field MD/ID added to it is detected, if this MD/ID is not detected, the following The frame will be written to memory, so the worst case is 10
It will be monitored with a delay of about seconds.

For example, if the playback mode is entered at the 5th [mA] point, the result will be as shown in C in the figure.

As described above, the conventional configuration has the disadvantage that it takes a long time until the first screen can be reproduced.

Therefore, the present invention solves these problems and proposes a DAT that allows the first screen to be monitored as quickly as possible.

[Means for Solving the Problems] In order to solve the above-mentioned problems, in the present invention, among digital signals composed of N bits (N is an integer),
The digital audio signal is assigned to the upper M bits (M is an integer, N>M), and the digital video signal is shaved off to the remaining (N-M) bits to form a composite digital signal, which is recorded and played back in units of frames. In a digital audio tape recorder configured to perform the following steps, after storing the odd field of the composite digital signal reproduced by the magnetic head, when it is detected that the playback screen of the odd field is the first playback screen, This apparatus is characterized in that the playback screen of the odd field is monitored until the writing of the next even field is completed.

[Operation] The playback mode is selected, a composite digital signal is played back by the magnetic head, and this is temporarily buffered in the memory.

After the odd field is stored in memory, when it is detected that the playback screen of the odd field is the first playback screen, the digital video signal of the odd field written in the memory is read out and monitored.

That is, when it is the first reproduction screen, the screen is reproduced not in frame units but in field units.

However, from the second time onwards, each frame is monitored. By doing so, the time required to monitor the first playback screen can be reduced to less than half of the conventional time.

[Embodiment] Next, an example of a digital audio tape recorder according to the present invention will be described in detail with reference to FIG. 1.

In this example, N=16. The digital audio signal and digital video signal are synthesized by selecting M=8.
This is just an example.

In FIG. 1, reference numeral 10 denotes a composite digital signal (hereinafter, only a digital video signal will be illustrated for convenience of explanation) read out from a magnetic head (not shown) of a digital audio tape recorder (DAT) according to the present invention. ) A specific example of the memory control circuit 10 will be shown.

In the figure, a reproduced digital video signal (8 bits) is supplied to a terminal 12. This digital video signal is sequentially distributed and stored in four field memories 30 to 36 in units of fields via the first frame changeover switch 14 and the first and second field changeover switches 16 and 18.

Therefore, field memory 30.32 is for odd frames and field memory 34.6 is for even frames.

The digital video signals that have been read out from these are transferred to the third
．． The signal is outputted to the output terminal 38 through the fourth field changeover switch 20° 23 and the second frame changeover switch 24.

These plurality of changeover switches 14 to 24 can be appropriately controlled based on commands from the CPU 40 functioning as a control section. Therefore, in order to obtain field information, a reproduced digital video signal is supplied as its input signal.

In the normal playback mode, the CP is monitored in units of frames, but in the first playback screen, the CP is monitored in units of fields.
It is controlled by a control program built into U40.

Therefore, the process flow 40 for monitor display is as shown in FIG.

When the playback mode is selected, the MD/ID is first detected (step 51), and when this is detected, field discrimination is performed, and if it is an odd field, the digital video signal is stored in memory (step 52. 53).

When the E-ID inserted at the last stage of the digital video signal is detected in the memory of the digital video signal (step 54), the presence or absence of the previous screen that has been played back is checked (step 55).

When it is the first screen, the digital video signal of the odd field stored immediately before is read out as is and is monitored (step 56).

In the second and subsequent playback modes, this is step 55.
Since the check can be completed with , there is no transition to the field image display mode at that time (step 56).

When the MD/ID is detected again, field discrimination is performed in the same way (steps 51 and 52). In the example above,
Since the next field will be an even field, it is checked whether the data of the odd field has already been stored in memory (step 55).

If the odd field has already been recorded, memory processing for the even field is executed (Step 58), and the E-ID in the even field is waited for (Step 59).

When the E-ID is detected, the digital video signal for one frame stored immediately before is read out, and monitoring of the frame image is started (step 60). After that, switching processing of the writing frame changeover switch 14.24 is performed (step 61).

If it is determined in step 57 that the odd field has not been memorized, this control program is terminated and the next M, D
-You will have to wait for the ID to arrive.

Therefore, this monitoring process can be summarized as follows.

When the reproduction mode is selected at time a shown in FIG. 5A in the above mode, the screen of the odd field is monitored at the stage when the writing of the odd field is completed as described above. Therefore, the screen can be monitored approximately 2.5 seconds after selecting the playback mode (see diagram 5).

If the playback mode has already been selected at the time shown in FIG. Enters write mode. Therefore, in this case, the screen can be monitored approximately 7.5 seconds after the playback mode is selected (see FIG. 5E).

In this mode, step 56 is skipped, so frames are displayed on the screen. Therefore, the screen can be monitored approximately 5 seconds after selecting the playback mode.

[Effects of the Invention] As explained above, in the present invention, when it is detected that the playback screen of an odd field is the first playback screen, the playback screen of the odd field is replaced with the writing of the next even field. It was designed to monitor the situation until it was completed.

According to this, the time from selecting the playback mode to monitoring the first screen can be reduced to less than half that of the conventional method. Therefore, the user's anxiety can be alleviated to that extent.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of essential parts showing an example of a digital audio tape recorder according to the present invention, FIG. 2 is a flowchart showing an example of a monitor display processing flow, and FIGS. 3 and 4 are diagrams showing its recording format. , FIG. 5 is an explanatory diagram of the monitor operation. 10 ・ 14.24 ・ 16 to 22 ・ 40 ・ ・Memory control circuit・Frame changeover switch・Field changeover switch・Control unit 50: Monitor display processing flow

Claims (1)

[Claims] (1) Of the digital signal composed of N bits (N is an integer), the digital audio signal is assigned to the upper M bits (M is an integer, N>M), and the remaining (NM) bits are assigned to the digital video signal. In a digital audio tape recorder in which a composite digital signal is constructed by allocating signals, and this is recorded and reproduced frame by frame, the odd fields of the composite digital signal reproduced by the magnetic head are stored in memory, and then the odd fields are recorded and reproduced frame by frame. When it is detected that the playback screen of a field is the first playback screen, the playback screen of this odd field is
A digital audio tape recorder characterized in that monitoring is performed until writing of the next even field is completed.