JPS58213581A - Still picture transmitting method - Google Patents

Abstract

PURPOSE:To display a preliminary picture which is a rough picture at the first place and gradually becomes a detailed picture as received picture elements increase and make the judgement of the necessity of the preliminary picture at the receiving side before receiving the whole picture elements when the preliminary picture is used for retrieving a still picture film, etc., by overlapping a fixed pattern upon picture elements successively sent by the dot interlace system. CONSTITUTION:An AD converter 3 makes a sampling on a TV signal (a) with a sampling frequency fs=13.5MHz and quantize the signal (a) into an 8-bit, and then, sends a digital TV signal (b). In addition to the above, a freeze signal (c) is added from an input terminal 2. Upon receiving the freeze signal (c), a memory controlling circuit 5 sends a write signal (d) to a frame memory 4. An input terminal 10 receives a transmit signal (g) from the transmission line. A decoding circuit 11 decodes the transmit signal (g) and obtains a decode signal (p). A memory controlling circuit 13 delivers a write signal (q) in accordance with the transmitting order and writes the code signal (p) in a frame memory 12. Moreover, the memory controlling circuit 13 adds a block discriminate signal (s) which indicates the kind of blocks read out from the frame memory 12 to a fixed pattern generator 14.

Description

[Detailed Description of the Invention] The present invention relates to a method for transmitting still images using the dot interlace method. When transmitting still images using a low bit rate transmission path, the transmission of the entire screen is completed. This increases the psychological burden on recipients as the waiting time increases. In addition, especially when searching for a required still image, receiving the entire screen one by one reduces efficiency. Therefore, it is necessary to display a rough image in a short time even if it is not clear at first.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a transmission method in which intermediate results of reception are displayed using easy-to-see pixels in the dot interlace system.

As mentioned above, there is a method using random scanning as a dot-increment method that takes into consideration displaying an intermediate state on the receiving side. This method consists of 1
The pixels on the screen are randomly scanned and transmitted (however, the same pixels are not duplicated)0 When the receiving side receives this, the entire display screen appears little by little,
It is possible to judge the image even while it is being received. However, in this method, when the number of received pixels is small compared to the number of pixels on the entire screen, the visual integration effect is small, making it difficult to obtain a sufficient image on the receiving side. Therefore, the reception side can only judge the screen after most of the pixels have been received, which has the drawback of not increasing efficiency.

Furthermore, although it is not a dot-increse method, there is a method using orthogonal transformation as a transmission method to obtain a similar display effect on the receiving side.

As shown in Figure 2, this method divides one screen into blocks of n pixels, divides the entire screen into iXj blocks, performs n-th orthogonal transformation on each block, and applies the transformation output to each block. The output is transmitted in order starting from the lowest order output. On the receiving side, the conversion outputs are displayed sequentially starting with the low-order conversion output, and one screen gradually changes from a rough screen to a detailed screen.

As an example of n-order orthogonal transformation, it is assumed that 16-order Hadamard transformation is performed on a block consisting of 4×4 pixels. In this case, in order to obtain the converted outputs H1 to H16 of each order, 16 additions and subtractions and division by /16 must be performed. If the value of each pixel is expressed in 8 bits, the number of effective bits after the above calculation will be 12 bits. Therefore, even if the bandwidth is not compressed, the PG
Even if it is transmitted at the same bit rate as M, 12 bits must be rounded to 8 bits, resulting in a rounding error. Furthermore, since similar calculations are performed on the receiving side when performing the Hadamard inverse transform, rounding errors accumulate on both sides of transmission and reception. Therefore, there is a drawback that the image quality deteriorates even after receiving the converted outputs of all orders.

SUMMARY OF THE INVENTION Therefore, it is an object of the present invention to provide a still image transmission method that eliminates the above-mentioned conventional drawbacks.

In order to achieve this purpose, the present invention deals with the case where still images are digitized and transmitted.

Until the transmission and reception of the entire screen is completed, a pseudo screen is displayed that starts with a rough image and becomes a more detailed image as the number of received pixels increases, and after all pixels have been received, the original still image (digitized) is displayed. It is characterized by a transmission method that does not cause any deterioration in image quality.

The principle of the transmission system according to the present invention is most simply as follows.

First, the image signal 2 of the input still image is digitized on the transmitting side, and then the entire screen is divided into blocks of a plurality of different sizes. At this time, a large block is composed of an integral number of smaller blocks. This blocking method will be described later using a specific example.

Next, for each block, one pixel is selected from among the pixels in the block, and this is made the representative surface element of that block. At this time, it is assumed that a pixel selected in a certain block is not duplicately selected in another block.

The transmission method is as follows: 1. First, all representative values X are transmitted for the largest block, and then all representative values X for the second largest block are transmitted. Then, after transmitting all the representative values of the smallest block, the values of the unselected pixels are sequentially transmitted.

Next, on the receiving side, the pixel values X transmitted using the above method are received and sequentially written into the memory. Here, the size of the block to which the received representative plane element belongs is KXQ
Then, consider a fixed pattern A of first order.

The values of unreceived pixels in each block, rK, and Q, are obtained from the following equations.

xK,Q=X+aK,Q(2) Using the values xK, Q of the unreceived pixels thus obtained and the value X of the received pixels, a pseudo screen of the still image received on the monitor television is reproduced.

Then, as time passes and representative plane elements of smaller blocks are received, the size of the fixed pattern is also reduced. By doing this, the image quality of the pseudo screen gradually approaches the image quality of the original image. After all pixels are received, the calculation with the fixed pattern is completed and the still image is reproduced using only the received pixel values.

Next, an embodiment in which still images are transmitted according to the transmission method according to the present invention described above will be specifically described.

First, consider a black and white television signal (Y signal of an NTSC color television signal) as an example of a still image input signal to be transmitted. Sampling frequency f8 = 13 for this black and white television signal
．． 5 MH2 and quantization with 98 bits per pixel. When digitized as above,
When configuring one screen, the number of bits is approximately 3.6 Mbits. Here, one frame of the NTSC color TV signal is one screen. For example, if this still image is transmitted over a transmission line with a transmission bit rate of 64 Kbps (called P' CM O order group), it will take approximately 56 seconds to transmit all the pixels of one screen. . .

Next, all pixels of one screen are divided into phases for transmission by dot interlacing. Hereinafter, this one phase will be referred to as one frame. That is, the entire still image screen is composed of dot-interlaced frames. It is desirable that the transmission time of one frame be 1 second or less, depending on the requirements of the receiver.

Therefore, in this embodiment, K=64. At this time, 1
The frame transmission time is approximately 0.9 seconds.

An example of a block configuration for an input still image as described above will be explained using FIG. 3.

First, as the smallest block/unit, the entire screen is divided into blocks of 2 lines x 2 pixels, as shown in Figure 3a.
Let this be a small block 5B(i,j)(i+]'integer).Next, as shown in FIG.
j).

The medium block is composed of 4×4 pixels.Furthermore, as shown in FIG.

j). The large block is composed of 8×8 pixels.

As shown in Figure 3d, the effective part of the input still image (hereinafter referred to as
If the total screen (this is called a full screen) is 512 lines x 768 pixels/line, the number of large blocks in the full screen is 96 x 64 blocks.

Perform the block division as described above and create each professional.

Select the value of one pixel from among the pixels as the representative value;
As already explained, transmission begins with the largest program. Let the representative value of block B(i, i) be X (B(
i! j) ) and the value of the pixel not selected as a representative value is represented as X (m, n), then the transmission order is as shown in Table 1 below.

Table 1 FIG. 4 shows the transmission order when the left two corner pixels of each block are selected as representatives. At this time, if the same pixel is duplicated in some blocks, it is transmitted only the first time,
It shall not be transmitted thereafter.

In FIG. 4, the numbers attached to each pixel correspond to the transmission order in Table 1. Moreover, among the representative values belonging to the same transmission order, it is sufficient to sequentially scan and transmit them from the upper left of the screen.

Next, an embodiment of the transmitting side that performs still image transmission using the method described above will be explained using the block diagram of FIG. 5. In FIG. 6, an input image signal is supplied from input terminal 1. . In this embodiment, a television camera or VTR is used.
Assume that black-and-white television signal a is added. A/
The D converter 3 converts this television signal a into a sampling frequency f, .
= 13.6 MHz, quantized to 8 bits, and sent out as a digital television signal. Additionally, a freeze signal C is applied from the input terminal 2. When memory control circuit 5 receives freeze signal C, it sends write signal d to frame memory 6. When the frame memory 5 receives the write signal d, it writes one frame of the digital television signal. Further, the memory control circuit 5 sends out a read signal e, reads out the value of each pixel from the frame memory 4 in the above-described transmission order, and sends it out as an output signal f.

The encoding circuit 6 encodes the output signal f into a signal suitable for the transmission path, and sends it out to the transmission path from the output terminal 7 as a transmission signal q.

The transmission path described above (transmission bit rate 6, 4
Kbps), the number of frames required to transmit each type of block and the time required from the start of transmission are as shown in Table 2 below.

Table 2 Next, a method of receiving still images transmitted in the manner described above and sequentially displaying them will be described. A block diagram of the receiving side is shown in FIG.

In FIG. 6, the input terminal 10 receives the transmission signal q from the transmission line.
receive. The decoding circuit 11 decodes the transmission signal q to obtain a decoded signal p. This decoded signal p is the same as the output signal f on the transmitting side shown in FIG. 5, and indicates the value of each pixel sent in the transmission order as described above.

The memory control circuit 13 sends the write signal q according to the transmission order and writes the decoded signal p to the frame memory 12. In addition, the memory control circuit 13 sends out a read signal r, and in order to express the value χ of the unreceived pixel by the above equation (2), the value Read from. Furthermore, the memory control circuit 13 applies a block identification signal S indicating the type of block to be read from the frame memory 12 to the fixed pattern generator 14.

In accordance with the block identification signal B, the fixed pattern generator 14 sends the value of Q to each element α of the fixed node shown in equation (1) above. The adder circuit 15 calculates this element αx,1
2 and the representative surface element value −, limit to the maximum and minimum values, respectively.

The value of each pixel I in the block obtained as described above is written into the video memory 1. The values of each pixel are reproduced from the video memory 17 in the scanning order of the television signal.The digital signal U
Read as . The D/person converter 18 converts the reproduced digital signal U into an analog signal, adds it to the monitor television 19 as a reproduced television signal V, and displays the received still image.

Next, a specific example of a fixed pattern for deriving unreceived pixels for transmission of television signals will be described. Here, there are three types of blocks: dog, medium, and small, so the corresponding fixed pattern is the large pattern A0. , medium pattern Am, and small pattern AIII, they are respectively 8X8.4X4.
It consists of 2×2 elements α.

First, as the simplest example, consider a pattern in which all elements are O. In other words, Park-Jeong-Il-MuS-〇In this case, (
2) As is clear from the equation, the values of all pixels within a block are equal to the value of the representative surface element of that block. Fourth
To explain using a diagram, first, in the first frame, the value of the representative surface element (pixel indicated by 1 in Fig. 4) of each dog block is
B(i, i):], the pixel values in each dog block all become indicate. In the fourth frame, the value X (MB (i, j)) of two representative pixels (Fig. 4 (7) 1 (!: 2 display L ta pixels)) of all medium blocks is received. All mosaic patterns are the size of medium blocks, and can show even the smallest details.In addition, 1
6 frames 2 and 3) value X(SB(i,
i)) Receive all. The mosaic pattern of the reproduced pseudo screen is all small block size, making it possible to reproduce a screen that is very close to the original still image. Finally, in the 64th frame, the reception of all pixel values is completed, and the original still image can be reproduced.

As mentioned above, if you use a pattern where each element is all 0,
Fixed pattern generator 14 and addition circuit 16 shown in FIG.
Since it is not necessary, the . . . - code circuit becomes simple. However, depending on the image quality of the still image to be transmitted, image quality deterioration may be easily noticeable at block boundaries or the like. Next, an example of applying the dither pattern will be described.

Among various dither patterns, the two-dimensional dither pattern proposed by +3ayer is famous. This is expressed by the following recurrence formula.

However, CD +) - (0) (Un) is an n×n unit matrix with 1 element.

The dither patterns corresponding to the dog, medium, and small blocks in this embodiment are obtained from the recurrence formula as follows.

...... (9) As shown in equation (9), equation (8), and equation (9), the element α11 of each dither pattern is 0, so as shown in Figure 6, , even if the value of the representative pixel is superimposed with the value of the representative pixel, the value of the representative pixel is reproduced as is.

As described above, by superimposing the dither pattern as a fixed pattern, it is possible to reduce blocking noise such as at boundaries between blocks and reproduce the data.

In addition to the tizer pattern, there are also the following θO).

Blocking noise can also be reduced by using two-dimensional vibration patterns as shown in equations (11) and (12) as fixed patterns.

(12) Next, a second embodiment of the receiving side having a plurality of types of fixed pattern generators is shown in FIG. In FIG. 7, 20 is a fixed pattern A generator, 21 is a fixed pattern B generator, and 22 is a fixed pattern D generator. Input terminal 23
Then, a pattern selection signal W is added. The selection circuit 24 selects one output signal from the output signals of the connected fixed pattern generators A to D according to the pattern selection signal W, and applies it to the addition circuit 16. The configurations and operations of other blocks are the same as those in the embodiment shown in FIG. 6), and detailed explanations will be omitted.

The pattern selection signal W is configured such that the receiver selects the pattern according to his or her wishes while viewing a simulated screen reproduced on the receiver side. Alternatively, the configuration may be such that the transmitting side selects an optimal fixed pattern based on the transmitted image, transmits a code indicating the fixed pattern in the same way as a still image, and obtains the pattern selection signal W from the code.

As explained above, using the transmission method according to the present invention,
By superimposing a fixed pattern on pixels that are sent sequentially using the dot-in-place method, it is possible to display a pseudo screen that starts out as a rough image and gradually becomes more detailed as the number of received pixels increases. Therefore, the psychological burden on the receiver during the waiting time until reception of all pixels is completed can be reduced.

In addition, when the transmission method according to the present invention is used to search for still image files, etc., the receiving side can determine whether or not it is necessary even before all pixels are received, and if it is not necessary, the transmission can be aborted even during the transmission and the next one can be started. Search can be performed and efficiency is improved.

The transmission method according to the present invention is characterized in that, since no further conversion is performed on the received signal, no deterioration of the transmitted image quality occurs after all pixels have been received.

Although several types of fixed patterns have been given as examples of the present invention, the present invention is not limited to these patterns. In particular, although Bayet's dither pattern is shown, the dither pattern is not limited to this. Further, the size of the block is not limited to the example, and may be divided into smaller blocks to the largest block.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing a dot interlacing method using random scanning, Fig. 2 is a schematic diagram showing block division in orthogonal transformation, and Fig. 3 is a method for dividing an image into blocks in an embodiment of the still image transmission method of the present invention. FIG. 4 is a schematic diagram showing the pixel transmission order in the same embodiment. FIG. 6 is a block diagram of a transmitting device of an embodiment implementing the still image transmission method of the present invention. FIG. 6 is an example thereof. Block diagram of the receiving device, No. 7
The figure is a block diagram of the main parts of the second flJ receiving device. 3... A/D converter, 4, 12... Frame memo IJ, 5, 13... Memory control circuit, 6... Encoding circuit, 11... ...Decoding circuit, 14.20.21.22.Fixed pattern generator, 15.Adder, 17.Video memory, 18.D/M converter. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure 3 Figure 4 Figure 5

Claims (2)

[Claims] (1) The digitized input image signal is divided into blocks for each plurality of pixels, and each block is sequentially transmitted pixel by pixel using the dot interlace transmission method, so that one screen of the above input image signal is divided into n blocks. Divide into small blocks consisting of pixels, m1 small blocks form a medium block, m2 medium blocks form a large block, and so on, so that the blocks become successively larger. One of the pixels in the large block is selected as a representative, and the value of the representative surface element is sequentially transmitted for the large block for one screen, and then the representative surface element within the medium block is sequentially transmitted, and so on. The value of the representative surface element of each block is transmitted sequentially from the largest block to the smallest block, and on the receiving side, for each corresponding block, the value of the received representative surface element and a preset fixed pattern corresponding to the size of the block are transmitted. A still image transmission method characterized in that the values of unreceived pixels in the block are determined from the block, and a pseudo screen consisting of these pixels is displayed. (2) Still image transmission method 0 according to claim 1, characterized in that a dither pattern corresponding to the size of the block is superimposed as the fixed pattern.