JP2693848B2 - Playback signal monitoring method for digital audio tape recorder - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital audio tape recorder capable of recording a still image.

[Prior Art] A digital audio tape recorder (DAT) is a dedicated device for recording and reproducing an audio signal. Recently, a DAT capable of superimposing and recording a video signal on the audio signal and reproducing the video signal has been developed. ing.

This normally records and reproduces an N-bit (N is an integer) digital audio signal as it is. On the other hand, the newly developed method of using the DAT is as shown in FIG. 3, in which the upper M bits (M is an integer, M> N), for example N
When = 16 bits, the digital audio signal is assigned to the upper 10 bits, and the digital video signal for still picture is assigned to the remaining (N−M) bits, and thus the lower 6 bits for recording and reproduction.

When reproducing this synthesized digital signal, even if it is reproduced as an audio signal with N bits, the digital video signal of (N−M) bits has almost no effect. This is because the digital video signal is assigned to the lower (NM) bits.

A digital video signal obtained by separating the composite digital signal is supplied to a monitor. Then, not only the audio signal but also the video signal can be recorded and reproduced at the same time, and the DAT function can be further increased.

The composite digital signal is recorded / reproduced in units of one frame, and thus the screen is reproduced (monitored) in units of one frame.

FIG. 3 is a format showing an example of the data structure of one frame, and various control signals (ID signals) are inserted in the preceding stage and the final stage of the composite digital signal (shown as data in the figure).

Here, S-ID is the start ID indicating the start of data
, And the MD ID is a mode ID, which is used to distinguish between an odd field and an even field.

The LS ID (last start ID) is an ID for distinguishing from the data, and is the last ID inserted in the preceding stage. E · ID (end ID) is an ID added to the end of data. The total ID insertion time is approximately 80 msec, and data is inserted for approximately 2.48 sec. Therefore, one frame is approximately 5 seconds.

[Problems to be Solved by the Invention] When reproducing a composite digital signal as described above, since the recording is performed on a frame-by-frame basis, the first reproduced composite digital signal is completely stored in the memory. You can't see the screen until.

Since the playback time for one frame takes about 5 seconds, at the playback timing a in FIG. 5A, the first playback screen cannot be monitored until 5 seconds have elapsed after switching to the playback mode (FIG. B). .

Also, in the case of storing a composite digital signal, when the system is configured so that it can be stored for the first time when the MD / ID of the odd field added to this is detected, if the MD / ID is not detected, the next Since the frame is written in the memory, it will be monitored with a delay of about 10 seconds at worst.

This is because, for example, when the reproduction mode is entered from the time point b in FIG.

As described above, the conventional configuration has a drawback that it takes time to reproduce the first screen.

Therefore, in the present invention, such a problem is solved, and when reproducing a composite digital signal with a DAT,
This is to propose a method for monitoring a reproduction signal that can monitor the first image quickly.

[Means for Solving the Problems] In order to solve the above-mentioned problems, in the present invention, N
Of the digital signal composed of bits (N is an integer), the upper M bits (M is an integer, N> M) are assigned a digital audio signal, and the remaining (N−M) bits are assigned a digital video signal. In a digital audio tape recorder in which a composite digital signal is formed and recorded / reproduced in units of one frame, an odd field of the composite digital signal reproduced by a magnetic head and an even field following the odd field are written in a memory. , It is assumed that the one-frame playback screen is monitored by the odd field and the even field written in the memory, and after storing this stored odd field, it is detected that this odd field playback screen is the first playback screen. When this happens, the playback image of this odd field And it is characterized in that the writing of the next even-numbered field was to monitor until the end.

[Operation] The reproduction mode is selected, the composite digital signal is reproduced from the magnetic head, and this is temporarily buffered in the memory.

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

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

However, from the second time onward, the frame is monitored as a unit. By doing so, the time until the first playback screen is monitored can be reduced to less than half that of the conventional method.

[Embodiment] Next, an example of a reproduction signal monitoring method of the digital audio tape recorder according to the present invention will be described in detail with reference to the drawings.

In this example, the digital audio signal and the digital video signal are synthesized by selecting N = 16 and M = 8, but this is only an example.

In FIG. 1, reference numeral 10 is a digital audio tape recorder (DAT) according to the present invention, and in particular, a composite digital signal read by a magnetic head (not shown) (only a digital video signal will be illustrated below for convenience of explanation). ), A specific example of the memory control circuit 10 for storing

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

Therefore, the field memories 30 and 32 are for odd frames, and the field memories 34 and 6 are for even frames.

The digital video signal read from these is
It is output to the output terminal 38 side via the third and fourth field changeover switches 20 and 23 and the second frame changeover switch 24.

The plurality of changeover switches 14 to 24 are appropriately controlled based on a command from the CPU 40 functioning as a control unit. Therefore, in order to obtain the field information, the reproduced digital video signal is supplied as its input signal.

Then, in the normal playback mode, playback is performed in units of frames and monitored, but in the first playback screen, monitoring is performed in units of fields.
It is controlled by the control program built into U40.

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

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

When the E.ID inserted in the final stage of the digital video signal is detected (step 54), the presence or absence of the reproduced previous screen is checked (step 55). If it is the first screen, the digital video signal of the odd field stored immediately before is read as it is and monitored (step 56).

This is step 55 for the second and subsequent playback modes.
At that time, the mode does not change to the field image display mode (step 56).

When the MD / ID is detected again, the same field discrimination is performed (steps 51 and 52). In the above example, since the current field is an even field, it is then checked whether or not the data of the odd field has already been stored (step 55).

When the odd field is already recorded, the memory processing of the even field is executed (step 58), and the E.ID in the even field is waited (step 58).
59).

When the E.ID is detected, this time the digital video signal for one frame stored in the immediately preceding memory is read out and the monitoring of the frame image is started (step 60). After that, the switching processing of the frame changeover switches 14 and 24 for writing is performed (step 61).

If no odd field memory is stored in step 57, this control program is terminated and the next MD / ID
Will wait for the arrival of.

Therefore, the monitor process is organized as follows.

(1) First reproduction mode When the reproduction mode is selected at the time point a shown in FIG. 5A, the screen of the odd field is monitored 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 reproduction mode (see FIG. 5D).

(2) In the first reproduction mode When the reproduction mode is selected at the time point b shown in FIG. 5A, the MD / ID is not detected and the odd field memory is not stored. The write mode is started for the odd field of. Therefore,
At this time, the screen can be monitored approximately 7.5 seconds after selecting the reproduction mode (see FIG. 5E).

(3) In the second and subsequent reproduction modes At this time, since step 56 is skipped, the frame is displayed on the screen. Therefore, the screen can be monitored approximately 5 seconds after the reproduction mode is selected.

As described above, according to the present invention, when it is detected that the reproduction screen of the odd field is the first reproduction screen, the writing of the reproduction screen of the odd field is completed in the reproduction screen of the odd field. It is designed to be monitored until.

According to this, there is a feature that the time from selecting the reproduction mode to monitoring the first screen can be reduced to half or less as compared with the conventional case. Therefore, the anxiety of the user can be removed accordingly.

[Brief description of the drawings]

FIG. 1 is a block diagram of a main part showing an example of a digital audio tape recorder according to the present invention, FIG. 2 is a flow chart showing an example of a monitor display processing flow, and FIGS. 3 and 4 are views showing its recording format. , FIG. 5 is an explanatory diagram of the monitor operation. 10 …… Memory control circuit 14,24 …… Frame changeover switch 16〜22 …… Field changeover switch 40 …… Control section

Claims (1)

(57) [Claims] 1. A high-order M bits (M is an integer, N> M) of a digital signal composed of N bits (N is an integer)
Is assigned to the digital audio signal, and the remaining (N-
In a digital audio tape recorder in which a digital video signal is allocated to M) bits to form a composite digital signal, and the composite digital signal is recorded / reproduced in 1-frame units, an odd field of the composite digital signal reproduced by the magnetic head and this It is assumed that the even field following the odd field is written in the memory, and the one-frame playback screen is monitored by the odd field and the even field written in the memory, and the playback screen of the stored odd field is the first playback screen. When detected, the reproduction screen of the odd field is monitored until the writing of the next even field is completed, and the reproduction signal monitoring method of the digital audio tape recorder.