JP2832015B2 - Image transmission device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an image transmission device for transmitting an image signal.

[Conventional technology]

When an image signal is digitized, the amount of data generally becomes very large, and when it is transmitted, the data rate becomes very high. For example, when the NTSS signal is sampled at 4 fsc (fsc is the color subcarrier frequency) and quantized at 9 bits per pixel, the data rate is about 118 Mbps. The data rate when the three primary color signals are sampled at 3 fsc and quantized similarly at 8 bits is 258 Mbp.
s. In recent years, a system using a high-definition television (HD-TV) signal with twice the number of scanning lines as the conventional one has been actively developed. However, the three primary colors of the HD-TV signal are converted to a sampling frequency of 64 MHz. And the data rate when quantized at 8 bits is
It will be about 1.5Gbps. Furthermore, after converting the HD-TV signal to TCI, 64
The data rate when sampling at MHz and quantizing at 8 bits is also as high as 518 Mbps.

When an image is digitized in this way, the bit rate becomes high, but when this digital signal is transmitted using a communication system, the capacity of the line becomes insufficient and the transmission cost becomes expensive. In order to reduce the amount of information of such a high bit rate signal as much as possible, various band compression methods have been proposed, but offset subsampling is effective as one of them.

[Problems to be solved by the invention]

However, offset sub-sampling does not pose any problem if some degradation in image quality can be tolerated during image transmission, but may be unsatisfactory when high-quality images are required. For example, in the line offset subsample, the deterioration of the vertical resolution is conspicuous, and in the field offset subsample, aliasing noise is conspicuous near the edge of a moving object.

Under such a background, the present invention can be applied to both a case where it is necessary to transmit one image signal of high quality and a case where two image signals are transmitted. It is an object of the present invention to provide an image transmission device that can be used effectively.

[Means for solving the problem]

For this purpose, according to the present invention, one system image signal and two system image signals can be input.
Input means for selectively supplying two types of image signals generated from two types of input image signals and two types of image signals generated from the two types of input image signals, and two types of signals supplied from the input means Of the first and second pixel groups spatially different from each other by sampling the image signal of
Generating means for generating image signals of the first and second types; encoding means for obtaining first and second codes by performing high-efficiency coding on the first and second image signals generated by the generating means, respectively; There is provided an image transmission apparatus including a transmission unit that transmits the first and second codes obtained by the second encoding unit.

[Action]

As described above, according to the present invention, one image signal and two image signals are transmitted by a common configuration.

〔Example〕

 Hereinafter, examples of the present invention will be described.

FIG. 1 is a block diagram showing the configuration of a transmission system as one embodiment of the present invention. In the figure, 1a and 1b are image signal input terminals, 2a and 2b are A / D converters for performing A / D conversion and filtering of input image signals from terminals 1a and 1b, and 3a and 3b are field offset subsampling. Circuit, 4 is a mode setting circuit for setting one of the high image quality transmission mode and the normal transmission mode, 5 is a data selector, 6a and 6b are high efficiency encoding circuits for band compression, 7a and 7b are claim numbers, Data addition circuit for adding sub data such as line numbers, 8a, 8
bE is an error correction code (ECC) encoder, and 9a and 9b are transmission paths. The timing circuit 10 is a timing circuit for controlling the processing timing of the circuits in the dashed lines A and B.

On the receiving side, 11a and 11b are ECC decoders that perform error correction and correction using ECC, 12a and 12b are the above-described sub-data extraction circuits, 13a and 13b are memories, and 14a and 14b are the above-described encoding circuits. 6
a, a decoding circuit that performs the reverse processing of 6b, 15 is a timing circuit that controls the processing timing of the circuits in the dashed lines C and D, 16 is a combining circuit that combines the outputs of the decoding circuits 14a and 14b, and 17a and 17b are An interpolation circuit for interpolating the pixels thinned out by sub-sampling, 18 is a control circuit for controlling the output mode, 19 is a mode setting circuit for setting one of the high image quality output mode and the normal output mode, 20 is a data selector, 21a , 21b are D / A converters, and 22a, 22b are output terminals for analog image signals.

 Hereinafter, the operation of the embodiment of FIG. 1 will be described.

First, the operation in the high image quality transmission mode and the high image quality output mode will be described. FIG. 2 is a diagram showing a sampling pattern of the sub-sampling circuits 3a and 3b in FIG. 1. In FIG. Indicates a pixel. In the drawing, ○ indicates a pixel sampled by the sub-sampling circuit 3a, and X indicates a pixel sampled by the sub-sampling circuit 3b. When the high image quality transmission mode is set by the mode setting circuit 4, the selector 5 outputs an H-side input signal, and the sub-sampling circuits 3a and 3b perform sampling in accordance with the timing chart of FIG. In FIG.
D0, D1,..., D6 indicate data of each pixel, (a) indicates the output timing of the A / D converter 2a, and (b) indicates the sub-sampling circuit.
3c, the control clock of the sub-sampling circuit 3b, (c) the output timing of the circuit 3a, (d) the control clock of the sub-sampling circuit 3b,
(E) shows the output timing of the circuit 3b. The control clocks shown in (b) and (d) are timing circuits.
Given by 10. Thus the sub-sampling circuit
The bit rate of the output data of 3a, 3b is set to 1/2 of that of the output data of A / D converters 2a, 2b.

The A / D converters 2a and 2b have a space filter inside,
The band is limited so that aliasing noise does not occur. FIG. 4 shows the characteristics of this spatial filter. In the case where the carrier arrangement when sub-sampling is not performed is as shown in FIG. 4A, the carrier arrangement when sub-sampling is performed is as shown in FIG. 4B. The hatched area in the figure shows the ideal pass band in each carrier arrangement. In FIG. 4, the h-axis indicates the frequency in the horizontal direction, and the v-axis indicates the frequency in the vertical direction. The frequency in the time direction is omitted.

In the case of the high image quality transmission mode, the same pixels as those in the case where no sub-sampling is performed are transmitted, so that the pass band of the spatial filter inside the A / D converter 2a is indicated by the hatched area in FIG. Becomes

The data sub-sampled by the sub-sampling circuits 3a and 3b are supplied to coding circuits 6a and 6b, respectively, and band-compressed by a well-known coding method such as DPCM and block coding.

The encoded data is supplied to the sub-code adding circuit 7 at the next stage, respectively.
After being input to a and 7b and adding codes indicating frame numbers and line numbers, they are input to ECC encoders 8a and 8b.
In the ECC encoders 8a and 8b, a known ECC is added after interleave processing according to the characteristics of the transmission path, and after adding synchronization data, predetermined digital modulation is performed and transmitted to the transmission paths 9a and 9b.

Next, the receiving side will be described. The transmitted data is supplied to ECC decoders 11a and 11b, subjected to demodulation, error correction and correction, deinterleaving, and the like, and supplied to sub-data extraction circuits 12a and 12b. In addition, ECC decoders 11a, 11
b generates a flag when error correction (interpolation) cannot be performed, for example, when a code error occurs continuously for one or more lines, and supplies the flag to the control circuit 18. The sub data extraction circuits 12a and 12b extract data indicating the frame number and the line number, and store the data on the addresses of the memories 13a and 13b according to the extracted data. Reading of data from the memories 13a and 13b is performed synchronously, whereby data having the same frame number and line number is simultaneously read from the memories 13a and 13b.

These synchronized image data are subjected to the reverse processing of the encoding circuits 6a and 6b in the decoding circuits 14a and 14b, and the output data of the decoding circuit 14a is sent to the interpolation circuit 17a and the synthesis circuit 16 and the decoding circuit 14b.
Are supplied to the interpolation circuit 17b and the synthesis circuit 16, respectively.

The synthesis circuit 16 outputs the output of each of the decoding circuits 14a and 14b to the A / D converter 2a.
The operation data is read alternately with the clock having the same frequency as that of the operation clock to obtain output data as shown in FIG. On the other hand,
The interpolation circuits 17a and 17b insert the same number of 0 samples into the output data of the decoding circuits 14a and 14b, and perform data interpolation by passing the data through a filter having a pass band indicated by hatching in FIG. 4 (b).
The data having the same bit rate as the output data of the synthesis circuit 16 is output.

When the high image quality output mode is set by the mode setting circuit 19, the control circuit 18 normally controls the selector 20 to output the input data to the H terminal. However, transmission line 9a
When data that cannot be corrected is generated in the data from, the selector 20 controls the selector 20 to output the input data to the terminal B, that is, the output data of the interpolation circuit 17b, in response to the flag. When data from the transmission path 9b that cannot be corrected is generated, the selector 20 similarly controls the input data to the terminal A, that is, the output data of the interpolation circuit 17a. When any of the data from the transmission lines 9a and 9b includes data that cannot be corrected, the selector 20 outputs the input data of the A or B terminal.

In this way, the selector 20 normally outputs high-quality image data from the synthesizing circuit 16, and when one of the transmission lines 9a and 9b fails, data is obtained from the other transmission line. Interpolates and outputs image data. The output of this selector 20 is converted into an analog signal by a D / A converter 21a,
Output to a.

Next, operations in the normal transmission mode and the normal output mode will be described. Now, it is assumed that an image signal is input only from the terminal 1a. A / D converter 2a even in normal transmission mode
The difference is that the normal band of the filter inside is set as shown by the hatched portion in FIG. 4 (b), but the processing reaching the transmission line 9a is the same as in the high image quality transmission mode. Further, the processing of the data transmitted via the transmission path 9a to the interpolation circuit 17a on the receiving side is the same as that in the high image quality output mode. However, in this case,
The data selector 20 always outputs the output data of the interpolation circuit 17a, and the output terminal 22a outputs an analog image signal restored by the sub-sampled data.

In the system of the present embodiment, it is possible to transmit two completely different image signals using the normal transmission mode and the normal output mode. In this case, the selector 5 outputs the N-side input data to the subsequent stage. Since the pass band of the filter in the A / D converter 2b is set as shown by the hatched portion in FIG. 4 (b), the processing from the terminal 1b to the transmission line 9b is performed from the terminal 1a in the normal transmission mode. This is the same as the process leading to the road 9a.

Also on the receiving side, the processing from the transmission path 9b to the output terminal 22b is the same as the processing from the transmission path 9a to the output terminal 22a in the normal output mode, and two systems of image signals are output simultaneously. Will be.

In the system of the embodiment as described above, two transmission paths are used when transmitting high-quality images, and one transmission path is used when transmitting normal-quality images.
It can be used according to the purpose and the transmission path can be used efficiently. Further, when transmitting a high-quality image, even if a failure occurs in one of the transmission paths, the image information can be reliably transmitted if the other transmission path is normal. Furthermore, when transmitting images of normal quality, two different types of images can be transmitted at the same time.
It can be used effectively as a whole system.

In the system of the above-described embodiment, the case where two transmission paths are used has been described. However, sampling is performed by using three or more transmission paths and sampling with three or more types of subsampling patterns that are spatially different from each other. The same effect can be obtained even when the digital information of three or more systems is transmitted through each transmission path, and a higher quality image can be transmitted.

〔The invention's effect〕

As described above, according to the present invention, one image signal and two image signals are transmitted by a common configuration.

Therefore, the configuration of the apparatus can be effectively used in the case where a high-quality image signal is transmitted as a single system image signal and in the case where a two-system image signal is transmitted.

[Brief description of the drawings]

FIG. 1 is a block diagram showing the configuration of an image transmission system as one embodiment of the present invention, FIG. 2 is a diagram showing a sampling pattern in the system of FIG. 1, and FIG. 3 is a diagram of the system of FIG. 4 (a) and 4 (b) are diagrams for explaining the characteristics of a carrier and a filter of a transmission signal in the high image quality mode and the normal mode by the system of FIG. 1, respectively. 1a and 1b are image input terminals, 2a and 2b are A / D converters, 3a and 3b are sub-sampling circuits, 5 is a data selector, 6a and 6b are encoding circuits, 9a and 9b are transmission lines, and 14a and 14b are A decoding circuit, 16 is a synthesis circuit, 17a and 17b are interpolation circuits, and 20 is a data selector.

Claims (3)

(57) [Claims] 1. An image signal of one system and an image signal of two systems can be inputted, and two image signals generated from the input image signal of one system and two image signals generated from the input image signal of the two systems. An input unit that can selectively supply a system image signal; and a first unit that samples first and second pixel groups spatially different from each other by sampling the two system image signals supplied from the input unit. Generating means for generating the first and second image signals, and first and second codes for obtaining the first and second codes by performing high-efficiency coding on the first and second image signals generated by the generating means, respectively. Encoding means; and the first and second encoding means obtained by the first and second encoding means.
An image transmission apparatus comprising: a transmission unit that transmits a second code. 2. The apparatus according to claim 1, wherein said generating means includes first and second sub-sampling means for sub-sampling two systems of image signals supplied from said input means in spatially different patterns. The image transmission device according to item (1). 3. The input means includes first and second image input means for inputting different image signals, respectively, and the first and second image input means.
And first and second A / D converters for respectively converting image signals input from the image input unit into digital signals. The first sub-sampling unit includes the first A / D converter.
An image signal from the D / A converter is supplied, and an image signal from the first A / D converter and an image signal from the second A / D converter are selected for the second sub-sampling unit. Claims (2) characterized in that they are supplied uniformly.
An image transmission device according to any one of the preceding claims.