JP2805800B2 - Image data transmission device and image data transmission method - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image data transmission apparatus and an image data transmission method suitable for use in, for example, a still image transmission system or a videotex.

[Summary of the Invention]

The present invention relates to an image data transmission apparatus that compresses and transmits image data suitable for use in, for example, a still image transmission system or a videotex, and a first video memory capable of storing image data having a first pixel density. A second video memory capable of storing image data having a second pixel density higher than the first pixel density connectable to the image data transmission device; a first video memory; and a second video memory. Control means for controlling writing / reading of image data to / from the video memory; and compression coding means for compressing and transmitting the image data, the control means comprising a storage area of the second video memory. Is sequentially read out from the designated storage area, and the read image data for each designated storage area is stored in the first video memory. The first and second video memories are controlled so as to be supplied next, and the compression / encoding means compresses and encodes the image data stored in the first video memory and transmits it. Thus, the memory unit and the transmission unit are separated from each other, so that various types of image data having a higher pixel density can be transmitted by using a standard image transmitter in common.

[Conventional technology]

As the transmission bit rate in telephone lines and the like has been improved, and the image data of still images with a large amount of information can be transmitted in a relatively short time, image data for transmitting and receiving image data of still images has been developed. Various transmission devices are being developed. FIG. 9 shows a videotex (interactive character / graphic information system) constructed on a digital telephone network as an example of a system using such an image data transmission apparatus. In FIG. 9, (1) Is a digital exchange,
(2) is a communication line, (3a) and (3b) are telephones,
(4a) and (4b) are terminal devices, (5a) and (5b) are input / output sources of still images such as video tape recorders, and (6) and (7) are information centers.

In the videotex on the digital telephone network, the transmission bit rate can be used up to 64 kbps in both the upstream and downstream directions.
In addition to transmitting image information to (a) and (4b)}, the terminal devices (4a) and (4b)} can exchange image information in a relatively short time.

[Problems to be solved by the invention]

Recently, the input / output source of still images is NTSC or PA
SHR (Super High Resolution) which has 4 times the standard pixel density in addition to the standard pixel density such as L method
Input / output sources that have image data with a pixel density higher than the standard pixel density and thus a larger total number of pixels have been developed, as seen in electronic cameras of the HDTV system and so-called HDTV (High Definition TV) TV receivers. It is getting.

However, when an input / output source of a high-definition still image having image data of such a high pixel density is connected to a terminal device for transmitting and receiving image data of a still image, the entire terminal device is connected in accordance with the pixel density. It had to be re-created, which required a long period of development and high manufacturing costs.

Furthermore, some of the still image input / output sources are, for example, 2000 × 20
There are also special devices that have 00 pixels. Developing dedicated terminal devices for each of these special devices also leads to small-volume production of various types of products, lowering manufacturing efficiency and further increasing manufacturing costs. There is an inconvenience of becoming high.

In view of the above, an object of the present invention is to propose an image data transmission device and an image data transmission method capable of transmitting various image data having a higher pixel density without largely changing the configuration of the entire device.

[Means for solving the problem]

An image data transmission apparatus according to the present invention is, for example, an image data transmission apparatus for compressing and transmitting image data as shown in FIG. 1, wherein a first video memory capable of storing image data of a first pixel density is provided. A second video memory (23a) capable of storing image data having a second pixel density higher than the first pixel density connectable to the image data transmission device; and a first video memory (23a). 1
6) and control means (9) for controlling writing / reading of image data to / from the second video memory (23a).
And compression encoding means for compressing and transmitting the image data and transmitting the image data. The control means (9) includes a designated storage area obtained by dividing the storage area of the second video memory (23a) into a predetermined number. The first and second image data are sequentially read out from the area, and the read image data for each of the designated storage areas is sequentially supplied to the first video memory (16).
This compression encoding means compresses and encodes the image data stored in the first video memory (16) and transmits it.

Also, the image data transmission method of the present invention is larger than the first pixel density for an image data transmission terminal (4a) having a first video memory (16) capable of storing image data of a first pixel density. A second video memory (23a) capable of storing image data having a second pixel density is connectable, and the storage area of the second video memory (23a) is divided into a predetermined number of designated storage areas. The image data is sequentially read, the read image data for each designated storage area is sequentially supplied to the first video memory (16), and the image data stored in the first video memory (16) is read. The data is compressed and transmitted.

[Action]

According to the present invention, in order to connect a higher definition still image input / output source having image data with a higher pixel density, only the second video memory (23a) can support the still image. You can replace it with something. Then, assuming that the pixel density is, for example, N times (N is a natural number of 2 or more) the predetermined pixel density of the first video memory (16), the storage area of the second video memory (23a) is N pieces. Divide into designated storage areas. Then, first, the image data in the first designated storage area is transferred to the first video memory (16), and the image data stored in the first video memory (16) is compressed and encoded and transmitted. Second video memory (23
The image data in the second to N-th designated storage areas in a) are sequentially compressed and transmitted via the first video memory (16).

Therefore, according to the present invention, the first video memory (1
By sharing the still image transmission terminal (8a) having 6), various types of image data having a higher pixel density can be transmitted.

〔Example〕

Hereinafter, an embodiment of an image data transmission apparatus and an image data transmission method according to the present invention will be described with reference to FIGS. In this example, the present invention is applied to a still image transmission system that transmits a still image signal via a communication line,
In FIG. 1, parts corresponding to those in FIG. 9 are denoted by the same reference numerals, and detailed description thereof will be omitted.

FIG. 1 shows a still image transmission system. In FIG. 1, a still image is transmitted from a terminal device (4a) to a terminal device (4b) via a communication line (2), a digital exchange (1) and a communication line (2). Is compressed and encoded and transmitted. These terminal devices (4a) and (4b) are equipped with standard transmitters (8a) and (8b), respectively, and these standard transmitters (8a) and (8b) have the same configuration and use standard systems such as NTSC or PAL, respectively. To transmit and receive image data corresponding to the video signal. In this case, as the communication line (2), ISDN (Integrated Services Digital Network), high-speed digital line, DDX (Digital Data
Exchange) networks (there are two types, DDXC and DDXP). Furthermore, it is also possible to use an analog telephone line or a wireless transmission line instead of the digital communication line (2).

To explain the configuration of the standard transmitter (8a), (9) is a microcomputer composed of a central processing unit (CPU), ROM (11) and RAM (12), and (13) is a data bus, an address bus and a control bus. A system bus of a CPU (10) comprising a ROM (11) and a RAM
Connect (12). The microcomputer (9) controls each part of the terminal device (4a).

(14) is a keyboard, (15) is an input / output circuit for connecting the keyboard (14) and the system bus (13), and (16) is a first video signal RA comprising a frame memory having a standard capacity.
M (VRAM1) indicates that the VRAM1 (16) can store image data of the number of pixels of P bits (horizontal direction) × Q dots (vertical direction). Connect to the bus (13). Generally, P = 768, Q
= 480.

(17) denotes a write / read control circuit, (18) denotes an address signal generation circuit, and the microcomputer (9) controls the write / read control circuit (17) via a system bus (13). first and second write / generates a read pulse J ₁ and J _2, and generates an address signal generation circuit (18) first and second address signal by controlling the ADR ₁ and ADR _2. First write / read pulse J ₁ and the first address signal ADR ₁ respectively VRAM1
Fed to (16), a second write / read pulse J ₂ and second address signal ADR ₂ respectively below the input and output circuits of the accessory via (21) a second video signal for RAM (VRAM 2) ( 23a)
To supply. Reference numeral (19) denotes a timing circuit. The timing circuit (19) supplies a synchronizing signal corresponding to a vertical synchronizing signal and a horizontal synchronizing signal of a video signal to an address signal generating circuit (18). 18) The above-mentioned first and second address signals corresponding to pixels at predetermined coordinates in the horizontal and vertical directions based on the synchronization signal
Generate ADR ₁ and ADR ₂ .

(20) indicates a communication control device connected between the communication line (2) and the system bus (13), and the communication control device (20) performs protocol and transmission of a still image signal of the communication line (2). It operates as a communication interface according to the speed.

Reference numerals (21) and (22) denote input / output circuits connected to the system bus (13), respectively. In this example, a capacity four times as large as the standard is provided through the input / output circuit (21). Video signal RAM (VRAM) comprising a frame memory having
2) Connect the input / output terminal of (23a) and the system bus (13). This VRAM2 (23a) has 2P dots (horizontal direction) x 2Q
Image data of the number of pixels in the dot (vertical direction) can be stored. In this example, the standard transmitter (8b) of the terminal device (4b) on the receiving side also has a VRAM2 having the same capacity as the VRAM2 (23a).
(23b) is connected. (24) is SHR (Super High R)
o solution) camera, and this SHR camera (24) has a pixel density of 2 in the horizontal direction and in the vertical method, respectively, with respect to the standard method.
A video signal having a total pixel density of four times (the total number of pixels is also four times) is generated. Then, the video signal of one still image generated by the SHR camera (24) is written to the VRAM2 (23a) via the analog / digital (A / D) converter (25). Reference numeral (27) denotes an SHR monitor, which supplies the image data written in the VRAM2 (23a) to the SHR monitor (27) via a digital / analog converter (26) so that the pixel density becomes standard. 4x higher definition image is the SHR
Displayed on the monitor (27).

As shown by the broken line in FIG. 1, this standard transmitter (8
a) The system bus (13) via the input / output circuit (22)
In addition, a digital / analog converter (28) and a standard monitor (29) may be connected. Thus standard monitor (29)
Is provided, a still image corresponding to the image data having the standard pixel density stored in the VRAM 1 (16) can be displayed on the standard monitor (29).

FIG. 2 is a flowchart of an operation in transmitting image data of one still image having a pixel density four times as large as that of a standard image captured by the SHR camera (24) of FIG. 1 to the terminal device (4b). The microcomputer (9) on the side of the terminal device (4a) initializes the value of the variable n written in the RAM (12) to 1 and then takes an image with the SHR camera (24). The image data having a pixel density of 4 times corresponding to the obtained still image is written into the VRAM2 (23a) (steps (90) and (91) in FIG. 2). In this case, as shown in FIG.
AM2 Since the image data of the (23a) the number of pixels of 2P × 2Q dots are written to the storage area in the first block B ₁ ~ fourth block B ₄ having a number of pixels each P × Q dots 4 divided . Therefore, the _first to fourth blocks B ₁ to B ₄
Are equal to the number of pixels in the entire storage area of the VRAM1 (16) shown in FIG. 3B.

Then, the microcomputer (9) executes step (9).
In 2), VRAM2 (23a) determined by the value of variable n
The image data of the n-th block (currently the first block B ₁ ) is written into the VRAM1 (16), and the RAM
After incrementing the value of the variable n written in (12) by one, in step (94), the VRAM1 (1
6) Compression-encodes the image data stored in.

The block coding method (Adapti
ve Block Truncation Coding (ABTC method) will be described with reference to FIGS. 4 to 7. In this block coding method, virtual display is performed on a standard monitor (29). For example, a screen (29a) consisting of P dots (pixels) in the horizontal direction and Q dots in the vertical direction is converted into an 8 dot × 8 dot basic block Bij (1 ≦ i ≦ M, 1 ≦ j ≦
N) (FIG. 4). Then, the compressed transmission of this screen data is first transmitted by compression coding the basic block B _11, the basic block B ₁₂ in the following, ‥‥ B _1N, B _21, and transmits the ‥‥ the respective compression coding . To compress and encode each basic block, the basic block (FIG. 5A)
1/4 block (4x4 block)
After introducing the concept of (FIG. 5B) and the 1/16 block (2 × 2 block) (FIG. 5C) obtained by dividing the basic block into 16, the encoding modes shown in Table 1 are changed to Use in combination.

Also, the processing block unit in the basic block is represented by “mn”, where m indicates an m × m block,
n indicates a position in the basic block shown in FIG. 6B. When the encoding of each encoding mode in Table 1 is performed on the processing block "mn", a "mode flag" shown in FIG. 6A is added before the data information of the basic block. The receiving side can decode the image data based on the "mode flag" information.

FIG. 7 shows an encoding algorithm of a block encoding system for performing compression encoding of an 8 × 8 basic block by combining the above-described encoding modes. In Figure 7, epsilon ₁ and epsilon ₂ shows the standard deviation of the data values of all pixels of each processing block, the threshold E ₁ and E ₂ represent the value of each standard deviation. Further, a ₀ and a ₁ is the upper left corner and upper right corner of the pixel data values divided into four equal parts respectively processing block, d _1, d ₂ and d ₃ are each a ₁ -a _0, i.e. the data value of the kind of variation, The thresholds D ₁ , D ₂ and D ₃ each indicate an allowable value of the variation of the data value. Therefore, when both the standard deviation ε ₁ and the variation d ₁ are smaller than the allowable value, the steps (100) to (10)
Go to 4) and process in A8 mode, 6 of its basic block
The values of all four pixels are transmitted as the same value (for example, an average value). Further, when the standard deviation epsilon ₁ or variation d ₁ is greater than the respective allowable values began to step (105), the standard deviation epsilon ₂ of the 4 × 4 blocks depending on whether less than or greater than the threshold value E ₂ The process proceeds to step (108) and below or step (112) and below, respectively. Step (112) and subsequent steps show the codes of 2 × 2 blocks.
After determining the variation d ₃ in, the variation d ₃ is the threshold
When D is smaller than ₃ proceeds from step (114) to the step (115), when the variation d ₃ is the threshold value D ₃ than the flow proceeds to step (116) from step (114).

By sequentially compressing and encoding each basic block Bij in this way, it is possible to compress and encode all the image data stored in the VRAM1 (16). As the software for executing the compression encoding algorithm as shown in FIG. 7, the software that has already been developed for compressing and encoding image data of the standard system such as the NTSC system or the PAL system is used as it is. be able to. Therefore, there is an advantage that it is not necessary to newly develop complicated compression coding software.

Next, in step (95) of FIG. 2, the microcomputer (9) executes the compression-encoded image data and VR.
AM2 supplies code indicating the first block B ₁ of (23a) to the communication control device (20). As a result, the compression-coded image data and the code indicating the block are transmitted in a short time to the terminal device (4b) of the other party via the communication line (2), the digital exchange (1) and the communication line (2). You. In the terminal device (4b), the standard transmitter (8b) decodes the received image data and sends the decoded image data to the VRAM2.
The storage area of (23b) is written in the first block formed by dividing into four.

Then, in step (96), the microcomputer (9) checks whether or not the value of the variable n stored in the RAM (12) has exceeded 4. When the value of the variable n is 4 or less, the n-th block B _n to the fourth block B ₄ of the VRAM 2 (23a)
Since the transmission of the image data up to has not been completed, the operation of the microcomputer (9) is again performed at steps (92) to (92).
Repeat (95). Thus the stored image data in the VRAM 2 (23a) and is transferred to VRAM1 (16) in order of the first blocks B ₁ → ‥‥ → fourth block B _4, respectively are compressed coded terminal device (4b ) Side. In this case, the image data received in the terminal device (4b) is written into the first block B ₁ → ‥‥ → fourth block B ₄ sequential VRAM2 are respectively decoded (23b). When the transmission of all the image data in the VRAM2 (23a) is completed, the value of the variable n becomes 5, and the operation of the microcomputer (9) stops at step (96).

As described above, according to this example, it is possible to transmit image data having a pixel density four times that of a normal pixel by using the standard transmitter (8a) for the NTSC system or the like. Therefore,
There is no need to develop a new transmission unit, and the terminal device (4a) can be developed in a very short time. In addition, the standard transmitter (8a) mass-produced inexpensively can be used as it is, thus reducing the manufacturing cost of the terminal device (4a). There are cheap profits. Furthermore, this example is VR
It is possible to cope with image data having various pixel densities by simply changing the capacity of AM2 (23a).

The above embodiment shows a case where the storage capacity of VRAM2 (23a) is an integral multiple of the storage capacity of VRAM1 (16) of the standard transmitter (8a). That
The present invention can be applied to a case where the storage capacity of VRAM1 (16) is not an integral multiple. To explain the example in this case, VRAM2 (23a)
Instead of (2P + ΔP) × (2Q +
ΔQ) A third video signal RAM (VRAM3) (30a) capable of storing image data of the number of dots is used.

Then, the storage area of the VRAM3 (30a) is divided into _first to fourth blocks B1 to B4 each having a storage capacity of P × Q dots.
And B _4, divided into the fifth block B ₅ having a storage capacity fraction. By dividing this manner, VRAM 3 first blocks B ₁ ~ fourth block B ₄ of (30a) is in Fig. 8 B VRAM1 (1
6) can be transmitted by compression encoding. In this case, writing in the region (31) of VRAM1 (16) in a predetermined order the fifth block image data B ₅ of VRAM 3 (30a), the excess portion (31a) remains in the storage area of the VRAM1 (16) However, for example, data whose value is all 0 is written in the surplus portion (31a). Then, by compressing and encoding the image data of the VRAM 1 (16) and transmitting it, the VRAM 3 (30
image data of the stored fraction to a fifth block B ₅ of a) is also transmitted.

In FIG. 1, VRAM2 (23a) and input / output circuit (21)
By providing a so-called down converter that converts the SHR signal into a standard signal such as an NTSC signal between the VRAM2 (23a)
Is converted to standard signal image data and
(16) may be written. In this case, an upconverter for converting a standard signal into an SHR signal is provided between the standard transmitter (8b) and the VRAM2 (23b) in the terminal device (4b).

In the above embodiment, the terminal device (4b) on the other end
Has a standard transmitter (8b) like the terminal device (4a), but the terminal device (4b) on the other end has an SHR (Super High
The present invention is applicable even when a transmitter compatible with Rosolution is provided. In this case, first, VRAM1 of the terminal device (4b)
In order to transmit the standard format image data stored in (16) to the terminal device (4b), the terminal device (4a) uses a communication protocol exchanged before sending the compressed and encoded image data. Then, a code indicating that the image data has the standard density is transmitted to the terminal device (4b). Accordingly, SHR-compatible terminal device that can support four times the pixel density (4b)
Is written in the built-in frame memory while enlarging the received and decoded image data by a factor of four by zero-order interpolation.

On the other hand, to transmit the image data of the VRAM2 (23a) corresponding to the SHR of the terminal device (4a) to the terminal device (4b) via the VRAM1 (16), the terminal device (4a) uses the image data in the communication protocol. A code indicating that the data has four times the standard pixel density is transmitted to the terminal device (4b). Accordingly
The SHR-compatible terminal device (4b) writes the received and decoded image data as it is into the built-in frame memory.

A code indicating the pixel density of the transmitting terminal is transmitted before the image data compressed and encoded in advance in this way, and the receiving terminal reduces (decimates, etc.) or expands (0-order interpolation) the decoded image data. Etc.) and write it to the memory, image data can be transmitted and received between terminal devices corresponding to different pixel densities.

As described above, the present invention is not limited to the above-described embodiment, and may adopt various configurations without departing from the spirit of the present invention.

〔The invention's effect〕

According to the present invention, the storage area of the second video memory is divided into a predetermined number, and image data for each of the divided areas is sequentially supplied to the first video memory. Since the memory section and the transmission section are separated by compressing and transmitting the data, there is an advantage that the image data having various higher pixel densities can be transmitted using the standard image transmitter in common. is there. Therefore, it is possible to flexibly cope with image data having various pixel densities, and to reduce the manufacturing cost of an image data transmission device that can cope with various pixel densities.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the image data transmission apparatus of the present invention, FIG. 2 is a flowchart showing the operation of the example of FIG. 1, and FIG. 3 is a diagram for explaining the operation of the example of FIG. , Fourth
FIG. 7 to FIG. 7 are diagrams for explaining the compression encoding of the embodiment, FIG. 8 is a diagram for explaining another embodiment of the present invention,
FIG. 9 is a configuration diagram showing an example of Videotex. (8a) is a standard transmitter, (9) is a microcomputer,
(16) is a first video signal RAM (VRAM1), (20) is a communication control device, and (23a) is a second video signal RAM (VRAM1).
2) and (24) are SHR cameras.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-111763 (JP, A) JP-A-63-257825 (JP, A) JP-A-55-21604 (JP, A) JP-A-2- 128582 (JP, A) JP-A-2-101884 (JP, A) JP-A-2-198287 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04N 7/10, 7 / 14,7 / 08

Claims (2)

(57) [Claims] 1. An image data transmission apparatus for compressing and transmitting image data, comprising: a first video memory capable of storing image data having a first pixel density; and a first video memory connectable to the image data transmission apparatus. A second video memory capable of storing image data having a second pixel density higher than the pixel density of the first video memory; and controlling writing / reading of image data to / from the first video memory and the second video memory. And a compression encoding unit that compresses and encodes the image data and transmits the image data. The control unit is configured to divide a storage area of the second video memory into a predetermined number of storage areas. The first and second video memories are sequentially read so as to sequentially supply the read image data for each of the designated storage areas to the first video memory. Controls re, the compression encoding means, the image data transmission apparatus characterized by being adapted to transmit compressed encoded image data stored in the first video memory. 2. An image data transmission terminal having a first video memory capable of storing image data having a first pixel density is provided with image data having a second pixel density higher than the first pixel density. A second video memory that can be stored is connectable, and image data in a specified storage area obtained by dividing the storage area of the second video memory into a predetermined number is sequentially read out. Image data is sequentially supplied to the first video memory, and the image data stored in the first video memory is compression-encoded and transmitted.