JPH0351356B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to still image transmission in which television video signals are transmitted through a narrowband transmission path (telephone line, etc.), and in particular, field images or frame images are selectively transmitted, and the receiving side The present invention relates to a still image transmission device that automatically receives images.

In recent years, still image transmission equipment has been used for meetings with remote locations,
It is being used for dam monitoring, etc. When transmitting images of people, distant views, etc. for meetings or monitoring, the resolution is not so high, so instead of sending one frame worth of images (frame images), one field worth of images (field pictures) is sent. Transmission time is shortened. However, in cases where high resolution is required, such as drawings or texts, frame images are used, which require a long transmission time but have a high resolution because of the large number of scanning lines. In this way, in a conference, people and drawings are often switched between transmissions, so each time a transmission is performed on the sending and receiving sides, the field image/transmission frame image transmission (hereinafter abbreviated as field/frame) is manually performed. The disadvantage of switching is that it is complicated to operate.

For this reason, conventionally, an identification signal indicating whether the transmitted image is a field or a frame is sent at the start of transmission, and the receiving side automatically switches between fields and frames by receiving the identification information. In other words, in a still image transmission device,
When transmitting field images, the image of one of the two fields is transmitted sequentially in the order of the scanning lines. In addition, when transmitting frame images, if the image for the first field and then the image for the second field are transmitted in the order of the scanning lines, the received image will be 1, 2 in the order of the scanning lines shown in Figure 1. ...262, 263, 264, ...52
5 and the image will be rewritten. In other words, the image is rewritten every other line, but at this time, this rewriting is done at a rate of 1/2, like in regular television.
There is no problem if it is done in 30 seconds, but in the case of still image transmission using a narrowband transmission line, it takes about 1 to 1.5 minutes to transmit 525 scanning lines, and this one screen Transmission time (1 minute to 1.5 minutes)
There is a time difference between the current image and the previous image (the image that is being rewritten), causing flickering. Therefore, when transmitting a frame, scanning line 1 of the first field is transmitted first, and then scanning line 2 of the second field is transmitted.
64 is transmitted. In this way, the first field and the second field
If the field image is transmitted by changing the field for each scanning line, the received image will be rewritten sequentially from the top, eliminating flicker. However, if field transmission had been performed until the previous time, the data received last time existed in the memory corresponding to scanning lines 1 to 263, but the data received previously existed in the memory corresponding to scanning lines 264 to 5.
It is unknown what is written in the memory corresponding to number 25. Therefore, if you switch from field transmission to frame transmission and set the receiving side to frame reproduction when the receiving side detects the field/frame identification signal, scanning lines 1 to 525 will be reproduced, so the previously received image and the other Since an image is played back in which it is unclear what has been written, the playback screen has the disadvantage that the memory contents of each scanning line overlap, resulting in a double image and visible flickering. In addition, in order to eliminate the above drawback, during field transmission, scanning line 1 is added to the portion corresponding to scanning lines 264 to 525 in the receiving side memory.
There is also a method of writing ~263 pieces of information, but this is equivalent to 2 frames even in field image transmission.
Writing to and reading from the field memory must be performed in pairs, and the disadvantage is that the same amount of power to the memory is required during the field as during the frame.

The object of the present invention has been made in view of these drawbacks, and is to provide a still image transmission device that transmits a field/frame identification signal, automatically performs field/frame switching, and transmits a single horizontal field during frame transmission. In addition to transmitting data by switching fields for each line, on the receiving side, field playback is performed at the start of reception, and frame playback is performed at the end of reception, thereby eliminating flickering caused by frame playback.Still image transmission It provides equipment.

Next, the present invention will be explained in detail with reference to the drawings showing embodiments. FIG. 2 shows one embodiment of the present invention, and is a block diagram of the receiving side. Receive input terminal 1
The input serial data signal is separated into a control signal and an image data signal by a control signal detector 2. From the control signal, a reception start pulse 101 and a reception end pulse 102 are generated, and a field/frame is detected. , “0” for field, “1” for frame
A field/frame signal 103 is output. Further, the image data signal is sent to the serial/parallel converter 3, converted into a parallel signal of 8 bits per pixel, and sent to the image memory 4. Image memory 4 is scan line 1
Memory corresponding to ~263 and scan line 264~
It is composed of two sets of memories corresponding to 525. In other words, it is a memory that has a capacity for a frame. The image memory 4 has slow addressers (write address generators) 5, 6, and 7.
Then, a write address and a read address are supplied from TV addressers (read address generators) 8, 9, and 10, respectively, and during reception, image data is written according to the write address according to the speed of the transmission line, and the TV rate (high-speed TV reading is performed at a scanning speed).

The slow addresser is composed of a slow horizontal addresser 5, a slow vertical addresser 6, and a slow field addresser 7, and the slow horizontal addresser 5 counts up each pixel of received data to count the number of pixels for 1H. This carry is input to the slow vertical addresser 6. The slow vertical addresser counts the number of lines in one field. The slow-field addresser 7 is a counter (a flip-flop is also possible) that counts based on the carry from the slow horizontal addresser 5, and the output of the slow-field addresser 7 determines which memory in the image memory 4 the data is written to. control That is, by inputting the output of the slow field/frame latch 11, which latches the field/frame signal detected by the control signal detector 2 with the reception start pulse, to the clear of the slow field addresser 7, the latch 11 is cleared when the field is in the field. Since the output is "0", the slow field addresser 7 is cleared and the output becomes "0", and only one side of the image memory 4 is selected and written, but when it is a frame, the output of the latch 11 is "1". , the slow field addresser 7 is inverted every horizontal line, so both memories are alternately selected and writing is performed alternately.

Next, the TV dresser is TV horizontal dresser 8,
It consists of a TV vertical addresser 9 and a TV field addresser 10. The TV horizontal addresser 8 is a counter that operates at high speed (scanning speed of the television) and counts the number of pixels in one horizontal line. This counter is incremented by the carry of addresser 8 and the carry of addresser 9. here
The TV field addresser 10 controls which of the two sets of memories in the image memory 4 is selected. Here TV field addresser 10
If the field/frame is controlled by supplying the same signal as the clear terminal of the slow field addresser 7 to the clear terminal of the slow field addresser 7, both memories of the image memory 4 will be played back when the field transmission changes to the frame transmission. In order to
The image received in the previous field and the image received in the frame before that or an unknown image (because data is erased in dynamic memory if you do not access the memory on the side that is not being played when playing the field) are played back and the flicker is played back. becomes. To avoid this, the slow field/
The output of frame latch 11 is latched by the reception end pulse detected by the control signal detector.
TV field/frame latch 12 output
By inputting to the clear terminal of the TV field addresser 10, if the previous reception was a field, the playback side
is cleared, and a different field image will not be reproduced by field reproduction even during frame signal reception until reception is completed. When frame reception is completed, the output of the TV field/frame latch 12 becomes "1", and the TV field addresser 10 counts up for each field, so that two sets of memories in the image memory 4 are alternately selected. Frame playback can be performed to eliminate flickering. Also, when the frame changes to field reception, if the frame is played back as it is, a different image will be displayed and a flicker will occur because writing is only done in one memory.However, by connecting the input of the latch 12 to the clear terminal of the latch 12, By setting field playback at the start of reception, it is possible to play back images without flickering even when the field changes from frame to field.
Next, the image signal read out from the image memory 4 is converted into an analog signal by the D/A converter 13, and is output as a television video signal at the video signal output terminal 1.
Output from 4.

Although Fig. 2 is a block diagram of the receiving side, on the transmitting side, the video output terminal in Fig. 2 is the video input terminal, and the D/A
The converter is an A/D converter, the TV addresser provides a write address, and the slow addresser provides a read address. The transmitting side is configured by making the serial-parallel converter become a parallel-serial converter, the control signal detector becomes a control signal inserter, and two field/frame latches 11 and 12 are preset at the time of frame. be able to.

As explained above, when transmitting a frame, fields are changed for each line to transmit data, and a field/frame identification signal is transmitted, and on the playback side, by changing the field playback at the start of reception and the frame playback at the end of reception,
This has the effect of automatically detecting fields/frames and avoiding flicker by simultaneously reproducing the contents of two different sets of field memories.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the order of scanning lines of a television video signal, and FIG. 2 is a block diagram of an embodiment of the present invention. In the figure, 1... Receive input terminal, 2... Control signal detector, 3... Serial/parallel converter, 4... Image memory, 5... Slow horizontal addresser, 6...
...Slow vertical addresser, 7...Slow field addresser, 8...TV horizontal addresser, 9...TV vertical addresser, 10...TV
Field addresser, 11...Slow field/frame latch, 12...TV field/frame latch, 13...D/A converter, 1
4...Video signal output terminal.

Claims (1)

[Scope of Claims] 1. In a still image transmission device that transmits and receives television video signals through a narrowband transmission path, the transmitting side is equipped with an image memory that stores images for two fields, and transmission control means, The transmission control means generates an identification signal for switching between field image transmission and frame image transmission, and transmits this identification signal to the receiving side, and when transmitting a field image, scans an odd field or an even field. The receiving side controls the memory so as to send a line image, and in transmitting a frame image, alternately sends an odd field scanning line image and an even field scanning line image, and the receiving side has two memories corresponding to the two fields. an image memory having an area, a write address means for writing the transmitted image into the image memory at a speed corresponding to the bandwidth of the transmission path, and a readout means for reading out the image written in the image memory at a speed corresponding to the display speed. address means, and reception control means for controlling writing and reading of the image memory in accordance with an identification signal sent from the transmitting side, and the reception control means controls one side of the image memory when receiving a field image. Only a memory area is selected for writing and reading, and when receiving a frame image, control is performed so that writing and reading are performed by alternately selecting two memory areas of the image memory for each scanning line, and when receiving a field image. When changing from frame image reception to frame image reception, the reading of the image memory is switched to a read operation for frame image reception when frame image reception is completed, and when frame image reception changes to field image reception, field image reception starts. A still image transmission device characterized in that the reading of the image memory is switched to a reading operation for field image reception at a certain point in time.