JPH0223078B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION A still image reproducing and transmitting apparatus is known that encodes (PCM) a color video signal, records it on a disk-shaped recording medium, and reproduces the same. Since the amount of information recorded in encoded video signals increases dramatically, it is necessary to greatly increase the relative scanning speed between the recording medium and the recording/reproducing head, or to increase the number of tracks recorded in parallel. For example, it is difficult to record/reproduce at the same speed as the video signal. Increasing the relative scanning speed leads to a reduction in the quality of the reproduced signal, and increasing the number of tracks leads to an increase in the complexity of the device.

Therefore, as a simple still image playback and transmission device,
It is known that the recording/playback time for one frame is significantly slower by about 30 times. In such a device, a video signal in which the time axis of the regular video signal is expanded can be obtained, so the video signal is formed by writing this into a memory and reading the memory so as to return to the regular time axis. is used.

As such a conventional still image reproducing and transmitting apparatus, those shown in FIGS. 1 to 3 are known.

The one in Fig. 1 reproduces the encoded video signal recorded on disk 1, which is a recording medium, at a speed of about 0.4 seconds per field, and writes the reproduced video signal to memory 2, which has a storage capacity for one field. information is transferred. The video signal is read out from this memory 2 on a regular time axis, but it has a sequential nature of 4 fields from the signal of 1 field.
A color framing circuit 3 is used to form an NTSC color video signal.

That is, the frequency of the color subcarrier of the NTSC signal
f _SC is an odd multiple of _1/2 (455
(double) has been selected. Therefore, within the same field, the chroma phase is inverted for each scanning line. Further, the chroma phase of the same scanning line is reversed between the first frame and the second frame. Therefore, NTSC
The signal has the first to fourth fields (two frames) as one unit, and the chroma phase in the fifth field returns to the same state as in the first field.

However, in the device shown in Fig. 1, switching from one still image to the next takes approximately 0.4 seconds, which is the information transfer time of one field's worth of video signals on disk 1; Fritska is relatively inconspicuous. However, since 4 fields (2 frames) of video signals are created from 1 field's worth of video signals, the framing circuit 3
This method has the disadvantage that high-quality still images cannot be obtained due to large signal loss.

In the apparatus shown in FIG. 2, information is transferred from a disk 1 to a video signal for two fields, and this is written to a memory 4 having a storage capacity for two fields.
It is read out on the time axis of the regular video signal. Furthermore,
The color framing circuit 5 converts 2-field video signals into NTSC with 4-field sequentiality.
It forms a color video signal. With this still image reproducing and transmitting device, the image quality is improved compared to the one in Figure 1, but it takes about 0.8 seconds to transfer information for two fields from disk 1, and from one still image to the next. It takes about 0.8 seconds to switch, and flicker is noticeable when switching between still images.

Furthermore, in the apparatus shown in Fig. 3, information is transferred from the disk 1 to the video signal for 4 fields, and this is written into the memory 6, which has a storage capacity for 4 fields, and is read out on the regular time axis to produce NTSC color data. I am getting a video signal. In the reproducing and transmitting device shown in Fig. 3,
Since it is completely reproduced using 4-field video signals, there is no need for a color framing circuit.
Image quality is the best. However, it takes approximately
It takes 1.6 seconds and has the disadvantage that a blank screen appears when switching between still images.

Incidentally, on the disk 1, for example, more than one hundred still images are recorded per disk 1. Further, one still image is usually composed of four fields of video signals.

By the way, there is a device for reproducing and transmitting still images from one disk to multiple terminals (for example, multiple studios in a television station or multiple classrooms in a school) using any of the devices shown in FIGS. 1 to 3. When considering this, the same problem as above arises. In other words, if two terminals request still image playback and transmission at the same time, the requested still image cannot be obtained from the other second terminal until transmission to the first terminal is completed. However, there is a waiting time. This waiting time is the minimum when using the conventional device shown in FIG. 1, and is approximately 0.4 seconds, which is the information transfer time for one field to the first terminal, plus the information transfer time to the second terminal. It is 0.8 seconds. Although this waiting time is relatively short, as described above, the image quality is likely to deteriorate.

When using the conventional device of FIG. 2, the image quality is improved, but the waiting time is doubled. Furthermore, the third
When the conventional example shown in the figure is used, the image quality is the best, but the maximum waiting time is 2.4 seconds.

When still image reproduction and transmission requests from two or more terminals overlap in time, the waiting time further increases.

SUMMARY OF THE INVENTION In view of the above problems, it is an object of the present invention to provide a still image reproducing and transmitting device with less waiting time and good image quality.

An example of a specific embodiment of the present invention will be described below based on drawings.

FIG. 4 is an overall block circuit diagram.

A disk 1, which is an example of a recording medium, has a plurality of reproduction output systems 1, 2, 3, . . . 7, which will be described later, with the same configuration.
A, 7B, 7C, . . . are connected to enable information transfer of video signals reproduced from this disk 1.

These multiple playback output systems 1, 2, 3...7
Each of A, 7B, 7C... has a plurality of corresponding terminals 1, 2, 3... having a corresponding monitor screen, etc.
...8A, 8B, 8C... are connected.

Information transfer of the video signal is performed even with a video signal whose time axis is slower than that of the regular video signal.
The video signals whose information has been transferred to the playback output systems 1, 2, 3...7A, 7B, 7C... are written to the respective memories 10 of the playback output systems 1, 2, 3...7A, 7B, 7C... which will be described later. is read out on the regular time axis,
Motue terminals 1, 2, 3...8A, 8B, 8C...
sent to.

On the other hand, terminals 1, 2, 3...8A, 8B, 8C...
A still image request command signal OUT ORDER is issued based on each still image reproduction and transmission request.
This still image request command signal OUT ORDER is given to the reproduction output system control section 9. As a result, the reproduction output system control signal OUT CONTROL is formed.
This playback output system control signal OUR CONTROL is
For example, if the still image reproduction transmission request is from the terminal 18A, this is a control signal for writing the video signal of the requested still image from the disk 1 into the memory 10 of the corresponding reproduction output system 17A. Furthermore, if the still image reproduction/transmission request overlaps with another request in time, the writing of the video signal from the disk 1 is interrupted.

The reference synchronization signal Ref.SYNC is a pulse that determines the timing for writing, writing rate, reading, etc., and is also a reference signal when creating address signals for writing and reading of the memory 10.

FIG. 5 shows the reproduction output system 1, 2, 3...7A,
A detailed block circuit diagram of 7B, 7C... is shown.

The memory 10 is composed of four first to fourth memory blocks 10a to 10d each having a storage capacity of one field. Information is transferred from the disk 1 to encoded video signals for four fields to this memory 10, and one field is sequentially written to each of the first to fourth memory blocks 10a to 10d. There is.
The write clock of the memory 10 is formed by a write clock forming circuit 11, and is adapted to write one field's worth of video signal in about 0.4 seconds as in the conventional case.

The video signal written in the memory 10 is read out using a clock pulse output from the read clock forming circuit 12. This clock pulse has the same frequency as the sampling pulse used when encoding a video signal. As a result, an encoded video signal having a regular time axis is obtained from the memory 10. Note that the write clock formation circuit 11, the read clock formation circuit 12, and the switch circuit 16 (described later) are connected to a timing circuit 15.
It is controlled by a write command signal WRITE, a read command signal READ, and a switching command signal CHANGE, respectively.

These signals WRITE, READ, CHANGE are
The reproduction output system control signal OUT CONTROL applied to the timing circuit 15 and the reference synchronization signal Ref.
Formed based on SYNC. Further, this write command signal WRITE controls the selection, writing timing, and amount of the video signal to be written into the memory 10 of the video signal that is requested to be reproduced and transmitted. With this control, multiple terminals 1, 2, 3...8
A, 8B, 8C, . . . make a request for reproducing and transmitting a still image, and when the requests for reproducing and transmitting overlap in time, it is possible to interrupt the writing of a video signal from the disk 1 to the memory 10.

Information transfer of the video signal from the disk 1 to the memory 10 is started due to a write interruption, etc., and the first
When the writing of the first field is completed in the second memory block 10a, the state is switched so that the next field of video signals can be written into the second block memory 10b. When the writing to the first memory block 10a is completed, the first
A read clock is applied to the memory block 10a. As a result, the video signal for one field is read out to the color framing circuit 13 for one field, which is the same as that in FIG. This color framing circuit 13 has four-field sequentiality based on the read video signal for one field.
Forms an NTSC color video signal. At this time, the switch circuit 16 is connected to the contact 16a based on the switching command signal CHANGE. As a result, the output of the color framing circuit 13 is applied to the D/A converter 17 through the switching contact 16a, and is converted into an analog signal. Based on this converted video signal, the selected still image is displayed on terminal 1.
2, 3...8A, 8B, 8C... are displayed on the monitor screens, etc.

1 written in the first memory block 10a
The still image formed based on the video signal for the field is displayed on a monitor screen or the like until the writing of the video signal to the next second memory block 10b is completed.

When writing to the first and second memory blocks 10a and 10b is completed, the two-field color framing circuit 14 forms an NTSC color video signal having four-field order based on the two-field video signal. . this
The NTSC color video signal is sent to the D/A converter 17 through the contact 16b of the switch circuit 16 until the video signal transferred from the disk 1 is written into the third and fourth memory blocks 10c and 10d.
given to.

When the writing of the video signals to the third and fourth memory blocks 10c and 10d is completed, the video signals for four fields have been written to the memory 10. At this point, the read clock forming circuit 12
provides a read clock to the entire memory 10. As a result, video signals for four fields are sequentially read out. The read video signal is already
It has NTSC 4-field sequentiality. Therefore, these video signals are sent through the contact 16c of the switch circuit 16 without color framing processing, and a still image is displayed on a monitor screen or the like via the D/A converter 17. From then on, the same terminal 1,
The contents of the memory 10 are repeatedly read out until there is a request for reproduction and transmission of another still image from 2, 3, . . . 8A, 8B, 8C, .

Next, for example, the memory 10 of the playback output system 17A
The operation will be explained in order when a still image reproduction transmission request is received from another terminal 28B while a video signal is being transferred from the desk 1 and being written.

First, when writing the first field into the memory 10 of the playback output system 17A, write the subsequent fields at an appropriate time after writing that one field. If it is busy, stop writing immediately at an appropriate time. This makes it possible to interrupt the writing of the video signal from the disk 1 into the memory 10 of the reproduction output system 27B corresponding to the terminal 28B.

Next, in the memory 10 of the playback output system 27B,
The writing of the first field of the still image video signal requested to be reproduced and transmitted from the terminal 28B is interrupted. Based on this one-field video signal, the selected still image is displayed on the monitor screen of the terminal 28B.

Next, when the writing is completed, the memory 10 of the playback output system 17A where the writing was stopped is caused to continue writing.

Furthermore, when the writing is completed, the subsequent writing is performed in the memory 10 of the reproduction output system 27B into which only the first one feed was written.

In addition, as mentioned above, the playback output system 1, 27
From the time when the first one field's worth of video signal is written into each memory 10, each terminal 1, 28A, 8B of terminals A, 7B, based on at least this one field's worth of video signal, 28
Still images are displayed on the monitor screens of A and 8B.

As a result, even if still image playback transmission requests are made from the two terminals 1, 28A, and 8B and they overlap, there is little time delay when switching, and in the end, the still image can be played back with good playback quality. Can be sent.

It goes without saying that the same thing can be done even if the still image reproduction and transmission request is made from three or more terminals 1, 2, 3...8A, 8B, 8C... and these requests overlap in time. .

Furthermore, if still image reproduction and transmission requests are made from multiple terminals 1, 2, 3, . .

Regarding the writing of the remaining fields after the completion of the interrupt in the above, time-sharing interrupt operations can also be performed. That is, even after the interruption for one field is completed, the remaining video signals may be written into the memory 10 alternately, for example, one field at a time, by the two reproduction output systems 1, 27A, and 7B.

Note that the color framing circuit 14 in FIG. 5 may be omitted. In this case, the switch circuit 16
is a two-contact switch that selects the output from the color framing circuit 13 and the combined output of the first to fourth merry blocks 10a to 10d. With this configuration as well, almost the same effect as the embodiment shown in FIG. 5 can be obtained. Moreover, the circuit configuration becomes simpler. However, after the video signal is written into the second memory block 10b, the third and fourth memory blocks 10c and 1
Until the video signal is written to 0d, the image quality is slightly degraded compared to that shown in FIG. 5, but this is not a problem in practical use.

The color framing circuits 13 and 14 are 1
The video signal for one field or two fields is separated into a luminance signal Y and a chroma signal C, and a chroma signal C or a phase-inverted chroma signal is added or delayed as appropriate to the separated luminance signal Y. However, this is a well-known device configured to obtain a video signal having NTSC field sequentiality.

In summary, the present invention provides a method for transmitting a video signal having NTSC order based on the video signal for at least one field to each terminal when still image reproduction and transmission requests from multiple terminals overlap in time. In order to quickly reproduce and transmit still images, it is possible to interrupt writing from the storage medium to the memory.

As a result, even if still image reproduction and transmission requests from a plurality of terminals overlap in time, a still image based on at least the first field's worth of video signals can be quickly transmitted to each terminal. Therefore, it is possible to shorten the time required for switching still images on the terminal. Furthermore, at the time when four fields' worth of video signals have been written to each memory, a still picture is formed based on the four fields' worth of video signals, so that high quality reproduced picture quality can be obtained.

[Brief explanation of drawings]

1 to 3 are block diagrams showing the main parts of a conventional still image reproducing and transmitting device, respectively. FIG. 4 is an overall block circuit diagram showing an embodiment of the still image reproducing and transmitting device of the present invention. FIG. 5 is a block circuit diagram of the reproduction output system of FIG. 4. FIG. In addition, in the symbols used in the drawings, 1...
...disk, 7A, 7B, 7C...playback output system,
8A, 8B, 8C...terminal, 10...memory,
10a to 10d...1st to 4th memory blocks, 13, 14...color framing circuit, 1
6...This is a switch circuit.

Claims (1)

[Claims] 1 A still image configured to write a video signal obtained from a recording medium in a memory at a time axis slower than the regular video signal, read the video signal from the memory at the regular time axis, and reproduce and transmit it to multiple terminals. In the playback/transmission device, a plurality of playback/output systems are provided corresponding to the plurality of terminals, and each of the playback/output systems includes the memory, and a memory of the other playback/output system is written during a writing operation to the memory of the one playback/output system. each reproduction output system has the memory capable of storing video signals for four fields, and has four-field sequentiality from the memory output for at least one field. A memory for one playback output system, each comprising a color framing circuit that forms an NTSC color video signal, and a switch circuit that selects the combined output of four fields' worth of memory or the output of the color framing circuit and outputs it to the terminal. When a still image reproduction transmission request is received from another terminal during a write operation, the interrupt control is performed so that at least one field worth of video signal corresponding to the requested still image is written into the memory of the latter's reproduction output system. A still image reproducing and transmitting device in which a memory writing interrupt operation is performed by means, and a reproduction output is transmitted to the other terminal through the color framing circuit based on the video signal written in the memory.