JPH01302978A - Transmitting system and receiving device for two-frame television signal - Google Patents

Abstract

PURPOSE:To display an auxiliary picture as looking and listening a TV main program, and to raise the effect of a program by sending the digital information of an auxiliary still picture as multiplexing it in the information channel of a main TV signal after compressing and encoding and packeting it, and reproducing the auxiliary still picture at a receiving side. CONSTITUTION:After a picture is image-picked as and sampled and A/D-converted, one of two-dimensional differential encoding and bit truncation is selected by a still picture encoder 3 so as to adapt it to a pattern, and it is made into a packet. While the presentation time of the auxiliary still picture to be packet-transmitted is synchronized with the TV program, control information capable of instructing is multiplexed to a data channel together with the TV signal by a multiplexing device 4, and is transmitted by a transmitter 5. It is looked and listened by a TV receiver 8 and the packet of a still picture is extracted from a PCM sound by a data channel decoder 9. The still picture encoder 10 extracts the information from the packet through a buffer memory, and operates it so as to decode it, and writes picture information successively in a frame memory, and switches the auxiliary picture in time to the main program. By this constitution, the TV program is complemented by the auxiliary picture, and its effect is raised.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a data broadcasting service that uses a data transmission path multiplexed to a television signal transmission path, and in particular, the invention relates to a data broadcasting service that utilizes a data transmission path multiplexed to a television signal transmission path, and in particular, the invention relates to multiplex transmission and reception of still image data. This relates to a transmission method that displays this on a sub-screen on the side, and a receiving device for the transmission method.

(Summary of the Invention) This invention relates to a broadcasting service that utilizes a data transmission line multiplexed with a television signal transmission line, and includes a digital display of a single character figure or a still image sub-screen that complements the content of a main television program. The data is compressed and encoded, packetized, multiplexed onto the main program television signal, and transmitted, and then played back on the receiving side to obtain a sub-screen that is separate from the main program.

This makes it possible to view the main TV program while displaying five sub-screens, thereby significantly enhancing the effectiveness of the program.

(Prior art) Teletext broadcasting is a conventional method for transmitting still images by multiplexing packets onto television broadcast waves (for example, Murasaki et al.:
Development of teletext pattern transmission system, NHK technology research,
Vol, 36. No, 1. pp, 1. -27(
1984)).

This multiplexes packetized digital data during the vertical blanking period of a television video signal and transmits text or simple pictures.

Furthermore, facsimile broadcasting is a technology that is still being researched (for example, Yasunari et al.: Small special feature, facsimile broadcasting, Journal of the TV Society, Vow, 41. NO, 2, 1)
1+1°1-31 (1987)). This is a method in which a subcarrier is provided in the audio signal of the television signal, and packets of facsimile IJ signals are multiplexed and transmitted thereon.

(Problem to be solved by the invention) In teletext broadcasting, the number of pixels in one multiplexed screen is at most 24.
8×204, the coloring is small, with only 8 colors and 2 gradations (4 bits in total, so-called level Δ) for each 4×4 pixel. In addition, in facsimile broadcasting, the number of pixels is 1728x2376 (
G3 standard), and although the gradation can be expressed to some extent by dithering (65 levels), it is basically a black and white binary image, and it is difficult to transmit natural images in either case.

In the present invention, all images including characters and figures can be sent to NTS
The purpose is to enhance the content of the main program by reproducing the images in C standard standard image resolution and gradation and displaying them on the sub-screen.

(Means for Solving the Problems) In order to achieve the above object, the two-screen television signal transmission system of the present invention is a television signal transmission system having a data channel in which digital data is multiplexed and transmitted on the main television signal. , digital data of the still image sub-screen is compressed and encoded, packetized, multiplexed onto the data channel of the main television signal and transmitted, and the receiving side converts the digital data of the still image sub-screen from the multiplexed and transmitted signal. The feature is that the screen is played back.

Further, the receiving device of the present invention includes a data channel decoder for extracting packets of the still image sub-screen from the PCM audio of the main television signal, and a buffer for receiving the transmitted two-screen television signal. a still image decoder for extracting data from the packet via a memory, performing decoding calculation processing, sequentially writing the obtained image information to a frame memory, and switching the sub-screen in accordance with the main program. It is characterized by this.

(Example) The signal format of the PCM audio transmission system of current television satellite broadcasting (Figures 2 (a) and (b)) includes an area for multiplexing data called a data channel with a capacity of at least 224 ps/sec. 5. Various data broadcasting services can be provided by packetizing (see Figure 3) and multiplexing digital data such as information services that supplement the content of television broadcast programs and independent information services. I can do it. The transmission system of the present invention uses this data channel to transmit a still image sub-screen signal that complements the content of a television broadcast program (hereinafter referred to as a main program).

Hereinafter, the present invention will be described in detail by way of examples with reference to the accompanying drawings.

FIG. 1 shows a transmission/reception system according to an embodiment of the transmission method according to the present invention.

In the transmission system of this device, an original image 1 is imaged by a television camera 2, and the camera output is transmitted at 13.5MHz or 14.5MHz.
It is sampled with the clock of 32 Mllz, AD converted, and input. After this is encoded and packetized by a still image encoder 3, it is multiplexed onto a data channel by a multiplexer (MPX) 4, and transmitted along with regular television programs via @(TX) 5 and a broadcasting satellite 6. .

In the reception system, the satellite broadcast receiver (TUNER) is used as usual.
7. Normal television broadcasting can be received and viewed using a TV receiver 8 or the like. On the other hand, a data channel decoder 9 extracts still image packets from the PCM audio. The still image decoder 10 extracts data from the packet via the main program, performs decoding calculation processing, sequentially writes the obtained image information into the frame memory, and switches the sub-screen 11 in accordance with the main program. For example, three frame memories are prepared, and it is possible to select and output video signals from any memory, such as going back to past screens or extending the display time of the current screen.

This service is assumed to use approximately 100 Kbps of the data channel's transmission capacity (minimum 224 Kbps) and to transmit one screen in 15 seconds. Therefore, the amount of data per still image is I Mbit (1
00KtlX 15 X 190/288″-71Mb
) must be compressed to: Natural images have a much larger amount of information than text, line drawings, etc., so highly efficient compression encoding is essential to realizing this service. Encoding is enabled Screen sample points (720 points in the horizontal direction x 48 points in the vertical direction)
0 points), this is 3 bits/ρ
C1 (3 bits/pixel) or less.

In addition, in order to perform the encoding and decoding processes in a short time, each within 15 seconds, and to keep the cost of the receiving device low, a relatively simple compression/expansion encoding method should be used.

Furthermore, since the data is packetized and multiplexed onto the data channel, compatibility with the packet format is also an important factor in determining the encoding method. This device uses DPCM (Diff
erential Pulse Code Module
ation) and BTC (Bit Truncation)
Two types of compression encoding methods (Coding) and packetization can be performed.

Each method will be described below.

(a) DPCM Assume that the human signals to be compressed include a luminance signal Y of 8 bits, and color difference signals RY and BY of 6 bits each. First, for the color difference signal, the number of sample points for the luminance signal is set to 1/2 in the horizontal direction and 1/2 in the vertical direction, 174 in total. Next, after field offset and soto subsampling both the luminance signal and the color difference signal (see Figure 4), the sample pattern shown in Figure 4 is created in two dimensions based on the true values of the first row and first column of the sample points. Perform predictive DPCM.

In other words, based on the true values of three points A, B, and C', D
Predict the value of the point, ZX = (3/8)Z, + (3/8)ZR + (1, /
4) ZA-9= Calculate the prediction error Zo Zx between this and the true value of point D, and display the value of point D using the difference value of this prediction error.

The difference value obtained at each sample point is then compressed and encoded into IY of 4 bits, A (RY), A (B
-Y) is quantized to 3b1t. Table 1 shows the quantization characteristics for compression encoding. In Table 1, the prediction error input is compressed at its output, as is the difference value output. This is based on the idea that it is extremely rare for prediction errors to be large between adjacent sample values. Since the difference value output can be positive or negative, the luminance signal is compressed to 15 levels (4 bits), including zero, and the color difference signal is compressed to 7 levels (3 bits).

As a result, the amount of data can be compressed to 2.77 bits/pel.

=10- Table 1 Quantization characteristics Packetization is first performed for true values. 72 points and (RY
) 1 point and (B-Y) 1 point make 1 block (8x2
+6x2=28 bits), and 6 blocks and control code C (6 bits).
(See Figure 5). The control code is information that allows the still image decoder to identify the encoding method and the different packet types depending on the encoding method. The true value of the first row of sample points is 180 (720-2÷2) blocks, and the first column is 240
(480-; Since 2 > block, the number of true value packets is 70.

Next, the difference value is packetized. AY 4 points and /I (
RY) 1 point, A (B-Y) 1 point is 1 block (4 x 4 + 3 x 2 = 22 bits), and 8 broncs and C are 1 packet (see Fig. 6). Since there are 5400 difference value packets, one screen includes 5470 packets including true value packets.

(b) BTC human power is Y (3 bits), R-Y (7 bits), B-Y
(7 bits), and encode each block with 4 sample points x 4 points as one block. One screen is 180x120
=21600 blocks. First, Y in the block
, R-Y, B-Y each average value ¥Y (8bit)
, ¥CR (7 bits), ¥CB (7 bits). Next, find the average value (absolute deviation $Y) of the absolute difference between each pixel of Y and ¥Y, and if it exceeds the threshold, determine whether each pixel of Y is larger or smaller than ¥Y. (1 if Y≧¥Y, 0 if Y<¥Y) bit plane BP (1
6 bits). Mode information M (1 bit) indicating whether $Y exceeds the threshold and ¥¥1¥CR
, ¥CB are transmitted for all blocks as basic information K (23 bits). If eight K and control code C (6 bits) are combined into one packet, the number of packets for one screen is 2700 (see FIG. 7).

For blocks in which $Y exceeds the threshold, $Y and BP are also transmitted as additional information T (23 bits). 8
T and C are combined into one packet (see Figure 8).
-The total number of packets per screen varies depending on the original image: 270
The number is between 0 and 5400. (1,44~2.88
bit/pel).

To decode this, first create a screen with only basic information (each pixel in a block is equal to the average value), and perform two-dimensional LPF processing on each of YXR-Y and B-Y to reduce block distortion. . Next, for blocks with additional information, calculate the sum Q of the number of 1s in BP, and for pixels with BP of 1, ¥-¥Y+$Yx8/Q, and for pixels with BP of O, calculate Y-¥Y-$ Substitute YX8/ (16-Q).

This device is compatible with two types of encoding methods: DPCM and BTC, but both still image encoder and decoder encode
Since decoding is performed by the CPU, encoding methods other than these can be easily accommodated by changing the software.

The still image decoder of this device has the function of automatically identifying and decoding two types of encoding methods using a control code. Furthermore, the encoding method suitable for each human-generated image differs. Therefore, we perform multiple encodings for each image,
By selecting the most suitable encoding method for the image depending on the data compression rate and encoding error, data transmission efficiency and received image quality can be improved compared to when the encoding method is fixed to one. . According to experiments conducted by the inventors, it has been revealed that the BTC method is superior when the scene to be captured is only landscapes, and the DPCM method is suitable when the subject is a person.

Furthermore, in order to enhance the effect of the main program with still images, it is necessary to be able to accurately specify the timing of screen presentation. Information about the time when the screen becomes valid can be multiplexed into the still image packet. On the other hand, since one of the services that uses a data channel is time broadcasting that indicates the current time (see, for example, Japanese Patent Application No. 61137655, ``Time Information Transmission System, Transmitting Device, and Receiving Device''), using that time as a reference, It is also possible to easily synchronize the main program and the still image sub-screen.

(Effects of the Invention) According to the present invention, it is possible to transmit multiple still images of not only characters and graphics but also natural images, which was not available in conventional broadcasting services, and the main program can be supplemented with a sub-screen. This is considered to be a particularly useful service for educational and cultural programs. It can also be used as an independent service, separated from the main program. For example, it is conceivable to perform BGV (background video) broadcasting, catalog broadcasting, etc. by multiplexing packetized PCM audio onto a data channel and combining it with still images that are updated every 15 seconds.

[Brief explanation of the drawing]

Figure 1 shows the transmission and reception system of the transmission system of the present invention, Figures 2 (a) and (b) respectively show two examples of the PCM audio transmission signal format, and Figure 3 shows the structure of the packet. , FIG. 4 shows a sample pattern for explaining the two-dimensional DPCM applied to the present invention. 6. 7.
FIG. 8 shows a true value packet format, a difference value packet format, a basic information packet format, and an additional information packet format in the present invention, respectively. 1... Original image 2... Television camera 3... Still image encoder 4... Multiplexing device 5.
・Transmitter 6...Broadcast satellite 7...Satellite broadcast receiver 8...TV receiver 9...Data channel decoder

Claims (1)

[Claims] 1. In a television signal transmission system having a data channel in which digital data is multiplexed and transmitted on a main television signal, the digital data of a still image sub-screen is compressed and encoded and packetized. A two-screen television signal transmission system characterized in that the still image sub-screen is multiplexed onto a data channel of a main television signal and transmitted, and the receiving side reproduces the still image sub-screen from the multiplexed and transmitted signal. 2. The two-screen television signal transmission system according to claim 1, wherein the compression encoding system is a two-dimensional differential encoding system. 3. The two-screen television signal transmission system according to claim 1, wherein the compression encoding system is a bit truncation encoding system. 4. In the transmission method according to claim 1, in which a plurality of compression encoding methods are switched and used, one of the plurality of compression encoding methods is adaptively selected according to a picture of the still image sub-screen. A two-screen television signal transmission system featuring: 5. According to any one of claims 1 to 4, control time data capable of instructing the presentation timing of the still image sub-screen transmitted in packets in synchronization with the main program is transmitted at the same time. 2-screen television signal transmission system. 6. In a receiving device that receives a two-screen television signal transmitted by the transmission method according to any one of claims 1 to 5, extracting the packet of the still image sub-screen from the PCM audio of the main television signal. a data channel decoder for extracting data from the packets via a buffer memory, performing decoding calculation processing, and sequentially writing the obtained image information to a frame memory to switch sub-screens in accordance with the main program. A two-screen television signal receiving device comprising: a still image decoder; and a still image decoder.