JPH1188909A - Image compression transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To transmit a compressed image by separating an image into required luminance information of a screen and other data depending on maximum/ minimum luminance in the image and giving the luminance signal and the color difference signals to respective coding decoding circuits. SOLUTION: A maximum luminance calculation circuit 64 and a minimum luminance calculation circuit 65 compare luminance values of all pixels in one frame of a multi-bit digital video signal 63 and output a maximum luminance value 67 and a minimum luminance value 68 respectively. A bit decomposition circuit 70 receives a multi-bit digital video signal 69, the maximum luminance value 67 and the minimum luminance value 68 after the lapse of one frame, decomposes them into digital video signals in 8-bit or lower and provides an output of a luminance signal (Y) 16 to an MPEG coder 19 and an output of a color difference signal (C) 71 to a color difference signal distribution circuit 72. Then major luminance information of the image as 8-bit data is converted into the luminance signal (Y) and a difference between the multi-bit digital video signal and the video signal resulting from decoding the scale of the luminance signal (Y) is converted into the color difference signal (C).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image compression transmission apparatus for digitally compressing and transmitting an image taken by a surveillance camera installed on an aircraft or on the ground to a remote monitoring station or the like.

[0002]

2. Description of the Related Art In a monitoring system using a camera, a captured image is sent to a monitoring station, monitored by a monitor, recorded in a storage device, and an image when an abnormality occurs is used for later analysis. FIG. 7 is a schematic diagram showing various operation states of the monitoring system. 1 is an aircraft equipped with an imaging device for aerial photographing on the ground, 2 is an antenna for receiving image data transmitted from the aircraft 1 by radio, and 3 is a ground. Imaging device installed in the
4 is a fire situation, 5 is an intruder situation, 6 is a plant situation, 7 is a monitoring station which collects and collectively monitors images from the respective imaging devices, and 8 is a video station installed in the monitoring station 7. The receiving device 9 is a console installed in the monitoring station and provided with a monitoring monitor. As shown in the figure, in a system to which the present invention is applied, for example, an aerial image of the ground with an imaging device,
It captures the situation of the fire, the situation of the intruder, the situation of the plant, and the like, and transmits the image to the monitoring station 7 via a wireless or wired transmission path. Since the information amount of the image data is much larger than the voice data of a telephone or the like, data compression using some method is indispensable for transmitting moving image data.
For a method of compressing moving image data, for example, MPEG (M
oving Picture Experts Gro
up: ISO group), standardization work is carried out, and satellite broadcasting and DVD (Digital Versat)
ile Disc). A digital image communication / recording apparatus using the MPEG has been proposed for a monitoring system (Japanese Patent Laid-Open No. 8-329).
No. 71).

FIG. 8 is a diagram showing an example of a conventional image compression transmission apparatus using the MPEG, in which 10 is input light from the outside, 11 is an imaging device for photoelectrically converting the input light 10, and 12 is an imaging device. An analog composite video signal 13 converted into an electric signal by the device 11 is an analog composite video signal 12.
A / D conversion circuit for digitally converting the digital composite video signal 14, a digital composite video signal 1
4, a Y / C separation circuit for separating into luminance information and color information;
16 is a luminance signal (Y), 17 is a color difference signal (Cr), 18
Is a color difference signal (Cb), 19 is a compression / compression of the luminance signal (Y) 16, the color difference signal (Cr) 17, and the color difference signal (Cb) 18.
MPEG encoder for generating encoded data, 20 is compressed / encoded data, 21 is a modulator for modulating compressed / encoded data 20, 22 is compressed / encoded data after modulation, 23
Denotes a transmission path, 24 denotes a demodulator for demodulating the modulated compressed / coded data 22 sent via the transmission path 23, 25 denotes demodulated compressed / coded data, and 26 denotes demodulated compressed / coded data. MPEG decoder for decoding the decoded data 25, 27 is a decoded luminance signal (Y), and 28 is a decoded chrominance signal (C
r) and 29 are decoded chrominance signals (Cb), and 30 is a decoded luminance signal (Y) 27 and chrominance signals (Cr), respectively.
28, an encoder that converts a color difference signal (Cb) 29 into a digital composite video signal, 31 is a converted digital composite video signal, 32 is a D / A converter that converts the digital composite video signal 31 into an analog composite video signal, 33 Is an converted analog composite video signal, and 34 is an image output device for displaying the analog composite video signal.

In FIG. 8, an input light 10 is transmitted to an image pickup device 11.
And the analog composite video signal 12 is output. The analog composite video signal 12 is a signal obtained by frequency-multiplexing a luminance signal of a video and a chrominance signal into a single signal.
The combined system is NTSC (Nati
onal Television System Co
(mmite method) is generally used. According to this method, both a color image and a monochrome image can be compatible. The output composite video signal 12 is supplied to an A / D conversion circuit 13.
And output as a digital composite video signal 14. The Y / C separation circuit 15 separates the digital composite video signal 14 into luminance information and color information, and outputs a luminance signal (Y) 16, a color difference signal (Cr) 17, and a color difference signal (Cb).
18 is output. These signals usually use 8 bits / pixel. The configuration is defined in CCIR (International Radio Communication Advisory Committee) recommendation 601 and the color difference signal (C
r), the number of pixels in the horizontal direction of the color difference signal (Cb) is の of the luminance signal (Y). If the red component of the input light is R, the green component is G, and the blue component is B, the luminance signal (Y ), The color difference signal (Cr), and the color difference signal (Cb) are represented by “Equation 1”.

[0005]

(Equation 1)

The MPEG encoder 19 outputs a luminance signal (Y) 1
6. Receiving the color difference signal (Cr) 17 and the color difference signal (Cb) 18, motion compensation, DCT (discrete cosine transform), quantization,
And variable-length coding, and outputs compressed / coded data 20. The compressed / encoded data 20 is modulated by a modulator 21, and the modulated compressed / encoded data 22 is transmitted through a transmission line 23.
Sent to On the receiving side, the demodulator 24 demodulates the compressed / coded data 22 after modulation from the transmission path 23, and outputs the compressed / coded data 25 after demodulation. The MPEG decoder 26 receives the demodulated compressed / encoded data 25, performs variable length decoding, motion compensation, inverse quantization, and inverse DCT, and decodes the decoded luminance signal (Y) 27 and chrominance signal ( C
r) 28 and a color difference signal (Cb) 29 are output. The encoder 30 receives the three signals and receives a digital composite video signal 3
Convert to 1. The D / A converter 32 converts the digital composite video signal 31 into an analog composite video signal 33 and outputs the same to an image output device 34.

FIG. 9 is a block diagram showing the detailed configuration of the MPEG encoder 19 shown in FIG. 8. 35 is an image format conversion circuit, 36 is image data after format conversion, 37 is a motion compensation prediction circuit, and 38 is a reference image. Data, 39 is DC
T circuit, 40 is a quantization circuit, 41 is quantized data, 42
Is motion vector information, 43 is coding mode information, 44 is a variable length coding circuit, 45 is a transmission buffer, 46 is an inverse quantization circuit, 47 is an inverse DCT circuit, and 48 is a frame memory.

In FIG. 9, a luminance signal (Y) 16, a chrominance signal (Cr) 17, and a chrominance signal (Cb) 18 are converted into a spatial resolution used for encoding by an image format conversion circuit 35, and the image data after the format conversion is converted. 36 is output. Next, when the coding mode is a motion compensation prediction mode in which high coding efficiency is obtained when the correlation between frames is high, the motion compensation prediction circuit 37 detects a motion vector from a screen located in the past or future in time. , Performs motion compensation prediction and outputs reference image data 38. This motion vector detection is performed using the luminance signal (Y) 16 and is commonly used for the color difference signal (Cr) 17 and the color difference signal (Cb) 18. Next, the difference between the reference image data 38 output from the motion compensation prediction circuit 37 and the image data 36 after the format conversion is obtained, and the DCT circuit 39
The conversion and quantization circuit 40 performs quantization and outputs the result as quantized data 41. On the other hand, when the coding mode is an intra coding mode that does not use the correlation between frames (intra-frame predictive coding), the DCT is performed without performing motion compensation prediction. The quantized data 41 is encoded by the variable length encoding circuit 44 together with the motion vector information 42 and the encoding mode information 43 output from the motion compensation prediction circuit 37, and is stored in the transmission buffer 45. Is output. The quantized data 41 is
Since it needs to be used later as the reference image data 38 for motion compensation prediction, the inverse quantization circuit 46 performs inverse quantization and inverse D
The image data is subjected to inverse DCT conversion by the CT circuit 47, added to the reference image data 38, restored to image data in an image format converted state, and stored in the frame memory 48.

FIG. 10 is a block diagram showing a detailed configuration of the MPEG decoder 26 shown in FIG.
Is encoded image data, 51 is a variable length decoding circuit, 52 is quantized data, 53 is encoding mode information, 54 is motion vector information, 55 is an inverse quantization circuit, 56 is an inverse DCT circuit, and 57 is image data. , 58 is an image format conversion circuit, 59 is a motion compensation prediction circuit, 60 is reference image data,
61 is an addition output, and 62 is a frame memory.

In FIG. 10, coded image data 50 received by a reception buffer 49 is first decoded by a variable length decoding circuit 51, and is separated into quantized data 52, coding mode information 53, and motion vector information 54. You. The quantized data 52 is inversely quantized by an inverse quantization circuit 55 and inverse DCT-transformed by an inverse DCT circuit 56 to be converted into image data 57. In the case of the intra-encoding mode, the image data is directly outputted as a luminance signal (Y) 27, a color difference signal (Cr) 28, and a color difference signal (Cb) 29 via the image format conversion circuit 58. In the motion compensation prediction mode, the motion vector information 54 extracted by the variable length decoding circuit 51 is input to the motion compensation prediction circuit 59, and the reference image data 60 subjected to motion compensation prediction and the output of the inverse DCT circuit 56 are output. And the added image data 57 is output, and the added output 61 is output via the image format conversion circuit 58. The addition output 61 is stored in the frame memory 62 because it needs to be used later as the reference image data 60.

[0011] As described above, MPEG is characterized by utilizing the correlation existing between consecutive frames and reducing the amount of encoded information by motion compensation. Details of these are, for example, "Comprehensive Multimedia Selection MPEG"
(1st edition, 2nd printing, published on December 20, 1996 by Ohmsha)
Is described in detail.

[0012]

The conventional apparatus is constructed as described above, and the image pickup apparatus generally uses a visible color camera or a black and white camera, and MPEG encoding for image compression encoding is performed. Since the number of gradations of the luminance signal handled by the imager and the MPEG decoder that performs image compression / decoding is 8 bits, if an infrared camera or the like having a wide dynamic range of luminance (for example, 12-bit gradation) is used for the imaging device, However, there has been a problem that a desired video signal cannot be reproduced on the receiving side. Further, if an MPEG encoder and an MPEG decoder capable of handling a luminance signal having 12-bit gradations for an infrared camera are to be realized, a commercially available LSI or the like cannot be used, and there is a problem that the apparatus cost increases.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and a monochrome image signal in which the number of gradations of a luminance signal exceeds 8 bits is decomposed into a plurality of data to encode and decode the luminance signal. By using means for assigning to the encoding circuit and the encoding / decoding circuit for the color difference signal, the conventional encoding /
It is an object of the present invention to provide an image compression transmission apparatus capable of compressing and transmitting a monochrome image in which the number of gradations of a luminance signal exceeds 8 bits using a decoding circuit.

[0014]

According to a first aspect of the present invention, there is provided an image compression and transmission apparatus for calculating a maximum luminance value from a digital video signal, and a minimum luminance for calculating a minimum luminance value from the digital video signal. A value calculation circuit, an image memory for storing the digital video signal for one screen, and a bit separation for decomposing main luminance information of the screen into a luminance signal according to the maximum luminance value and the minimum luminance value, and decomposing other data into a color difference signal. Circuit, a color difference signal distribution circuit for distributing the bit-separated data into two types of color difference signals, a multiplexer for multiplexing the maximum luminance value and the minimum luminance value to the compressed / encoded data, and the compressed / encoded data after transmission A demultiplexer for separating a maximum luminance value and a minimum luminance value from the image signal, a color difference signal combining circuit for combining two types of color difference signals decoded by the MPEG decoder into one color difference signal, A bit synthesizing circuit for synthesizing a digital video signal from the luminance signal and the synthesized color difference signal; even when the input image is a monochrome image exceeding 8 bits, the main luminance information of the screen according to the maximum luminance and the minimum luminance in the screen And means for assigning the decomposed data to a luminance signal encoding / decoding circuit and a chrominance signal encoding / decoding circuit, respectively.

According to a second aspect of the present invention, there is provided an image compression transmission apparatus according to the first aspect, further comprising: a first luminance range determination for determining a luminance range from a maximum luminance value and a minimum luminance value in a screen. And a second luminance range determination circuit that determines a luminance range from the maximum luminance value and the minimum luminance value separated by the demultiplexer on the receiving side, and detects a difference between the maximum luminance and the minimum luminance by detecting a difference between the maximum luminance and the minimum luminance. This uses a means for preventing the tone from being converted.

According to a third aspect of the present invention, there is provided an image compression transmission apparatus according to the second aspect, further comprising a minimum luminance value storage circuit for storing a minimum luminance value in a screen and a minimum luminance value on a time axis. And a means for decomposing into the main luminance information of the screen and other data using, for example, the average value of the minimum luminance values.

According to a fourth aspect of the present invention, there is provided an image compression transmission apparatus according to the second aspect, further comprising a minimum luminance value storage circuit for storing a minimum luminance value in a screen, and a change rate of the minimum luminance value. And a change rate determination circuit for switching a minimum luminance value to be output according to the following formula. If the change rate is large, a means for decomposing the main luminance information on the screen and other data using the minimum luminance value of the previous frame is used. is there.

An image compression transmission apparatus according to a fifth aspect of the present invention includes, in addition to the image compression transmission apparatus according to the second aspect, a minimum luminance value storage circuit for storing a minimum luminance value in a screen, and an MPE.
A coding mode determination circuit for switching the minimum brightness value to be output according to the coding mode of the G encoder, wherein the minimum brightness in the previous intra coding mode is used in the motion compensation prediction mode using the correlation between frames. This uses a means for decomposing into main luminance information of the screen and other data using the values.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. FIG. 1 is a block diagram showing a first embodiment of the present invention. In FIG.
65 is a minimum luminance value calculation circuit, 66 is an image memory for storing a digital video signal for one screen, 67 is a maximum luminance value, 68
Is a minimum luminance value, 69 is a multi-bit digital video signal after one frame has elapsed, 70 is a bit separation circuit, 71 is a color difference signal (C), 72 is a color difference signal distribution circuit, 73 is a multiplexer, 74 is compression / compression after multiplexing. Encoded data, 75 is a demultiplexer, 76 is a bit combining circuit, 77 is decompressed / encoded data after demultiplexing, 78 is a color difference signal combining circuit, 79
Is a synthesized color difference signal (C), and 80 is a reproduced multi-bit digital video signal. 10 to 34 are equivalent to those in FIG.

In the configuration shown in FIG. 1, when an infrared camera or the like having a wide dynamic range of luminance is used as the imaging device 11, the A / D converter 13 outputs a multi-bit digital video signal 63 of, for example, 12 bits. The multi-bit digital video signal 63 is supplied to a maximum brightness value calculation circuit 64, a minimum brightness value calculation circuit 65, and an image memory 66, and the maximum brightness value calculation circuit 65 outputs all the pixels in one frame of the multi-bit digital video signal 63. The luminance values are compared, and the maximum luminance value 67 is
The minimum luminance value calculation circuit 65 similarly compares the luminance values of all the pixels in one frame of the multi-bit digital video signal 63, and outputs a minimum luminance value 68. The image memory 66 stores the multi-bit digital video signal 63 for one frame in order to synchronize while the calculation of the maximum luminance value 67 and the minimum luminance value 68 is completed, and the multi-bit digital video signal 69 after the lapse of one frame. Is output. The bit decomposition circuit 70 receives the multi-bit digital video signal 69 after one frame has elapsed, the maximum luminance value 67 and the minimum luminance value 68, and decomposes the digital video signal into 8-bit or less digital signals.
The signal is output to the EG encoder 19 and output to the color difference signal distribution circuit 72 as a color difference signal (C) 71. Bit decomposition circuit 70
Let M be the multi-bit digital video signal, max be the maximum luminance value, min be the minimum luminance value, and int () be an integer operation of rounding down decimal places, the luminance signal (Y),
The color difference signal (C) is represented by “Equation 2”.

[0021]

(Equation 2)

FIG. 2 shows a luminance signal (Y) represented by "Equation 2".
In the figure, the horizontal axis of the graph indicates the luminance of the pixels in the screen, and the vertical axis indicates the frequency of appearance of the pixels in one screen. As described above, since the motion compensation prediction performed by the MPEG encoder 19 is performed using the luminance signal (Y), the luminance signal (Y) after the bit decomposition needs to hold the main luminance information of the screen. . Therefore, first, the minimum luminance value is subtracted from the luminance value of each pixel of the multi-bit digital video signal to obtain a video signal from a luminance value of 0, and further, scale conversion is performed so that the maximum luminance value falls within an 8-bit full scale. The luminance information is converted into a luminance signal (Y) as 8-bit data. Further, the difference between the multi-bit digital video signal and the video signal obtained by scale-reconstructing the luminance signal (Y) is converted into a color difference signal (C).

The color difference signal distribution circuit 72 has a color difference signal (C) 7.
1 is a color difference signal (Cr) 8 for every other pixel in the horizontal direction,
A color difference signal (Cb) 9 and an MPEG encoder 19
Output to This is because the color difference signal (Cr) 8 and the color difference signal (C
b) The number of pixels in the horizontal direction of 9 is の of the luminance signal (Y). The multiplexer 73 multiplexes the maximum luminance value 67 and the minimum luminance value 68 on the compressed / coded data 20,
The multiplexed compressed / encoded data 74 is output to the modulator 21. On the receiving side, the demultiplexer 75 separates the multiplexed maximum luminance value 67 and minimum luminance value 68 from the demodulated compressed / coded data 25 and outputs them to the bit synthesizing circuit 76. Encoded data 7
7 is output to the MPEG encoder 26. The chrominance signal synthesizing circuit 78 is a chrominance signal (Cr) 28 and a chrominance signal (Cb) 29 decoded by the reverse operation of the chrominance signal distribution circuit 72.
Are combined with the combined color difference signal (C) 79 and output to the bit combining circuit 76. The bit synthesizing circuit 76 receives the decoded luminance signal (Y) 27 and color difference signal (C) 78 and reproduces a multi-bit digital video signal 80. The luminance signal input to the bit synthesizing circuit 76 is Y, the color difference signal is C, the maximum luminance value is max, the minimum luminance value is min, and i
Assuming that nt () is an integer conversion operation with rounding down to the nearest whole number, the multi-bit digital video signal M to be reproduced is represented by “Equation 3”.

[0024]

(Equation 3)

The operations 10 to 34 in FIG.
It is equivalent to the one described in.

As described above, according to the above configuration, even when the input image is a monochrome image exceeding 8 bits, the input image is decomposed into main luminance information of the screen and other data according to the maximum luminance and the minimum luminance in the screen. By allocating to the luminance signal encoding / decoding circuit and the chrominance signal encoding / decoding circuit, the image can be compressed and transmitted using the conventional encoding / decoding circuit.

By the way, in a scene, there is a screen whose luminance distribution range does not exceed 8 bits, and when a scale conversion is performed so as to be within an 8-bit full scale, a pixel of a specific luminance does not exist and an image signal is not present. May be lost, leading to a decrease in coding efficiency.

Embodiment 2 FIG. 3 is a block diagram showing Embodiment 2 of the present invention. In FIG. 3, reference numeral 81 denotes a luminance range within one screen from a maximum luminance value 67 and a minimum luminance value 68 within one screen of an input image. 1 is a luminance range determination circuit, 82 is a gradation allocation prohibition command, and 83 is a second luminance for determining a luminance range in one screen from the maximum luminance value 67 and the minimum luminance value 68 extracted from the demultiplexer on the receiving side. A range determination circuit 82 is a tone assignment prohibition command.
11 to 80 are equivalent to those in FIG.

In the configuration of FIG. 3, the first luminance range determination circuit 81 calculates the difference between the maximum luminance value 67 output from the maximum luminance value calculation circuit 64 and the minimum luminance value 68 output from the minimum luminance value calculation circuit 65. If the luminance difference does not exceed 8 bits, the gradation disabling
Output to 0. The bit decomposition circuit 70 does not perform the process of allocating the gradation between the maximum luminance value 67 and the minimum luminance value 68 to 8 bits only when receiving the gradation allocation prohibition command 82. M for multi-bit digital video signal, m for maximum luminance value
Assuming that ax and the minimum luminance value are min, the luminance signal (Y) and the color difference signal (C) when receiving the gradation assignment prohibition command are represented by “Equation 4”.

[0030]

(Equation 4)

The second luminance range determination circuit 83 calculates the difference between the maximum luminance value 67 and the minimum luminance value 68 output from the demultiplexer 75, and if the luminance difference does not exceed 8 bits, the gradation An assignment prohibition command 84 is output to the bit synthesizing circuit 76. The bit synthesizing circuit 76 does not perform the process of allocating the decoded luminance signal (Y) 27 between the maximum luminance value 67 and the minimum luminance value 68 only when receiving the gradation allocation prohibition command 84. The luminance signal input to the bit synthesis circuit 76 is Y, the color difference signal is C, and the maximum luminance value is ma.
Assuming that x and the minimum luminance value are min, the multi-bit digital video signal reproduced when receiving the gradation assignment prohibition command is represented by “Equation 5”.

[0032]

(Equation 5)

In FIG. 3, the operations 11 to 80 are the same as those in FIG.
It is equivalent to the one described in.

As described above, according to the above-described configuration, even when a monochrome image exceeding 8 bits of the input image and the luminance distribution range of only a specific scene does not exceed 8 bits, the maximum luminance and the minimum luminance can be reduced. By detecting the difference between the two, it is possible to prevent the deterioration of the coding efficiency due to the lack of continuity of the image signal without performing the gradation conversion.

In the meantime, the MPEG encoder creates reference image data by motion compensation prediction from a screen located in the past or the future in time, and compresses and encodes difference data from the reference image data. Therefore, if the minimum luminance value, which is a reference at the time of the bit decomposition, changes suddenly, the level of the luminance signal after the bit decomposition changes, so that the difference data increases, which may lead to deterioration of the coding efficiency.

Embodiment 3 FIG. 4 is a block diagram showing a third embodiment of the present invention. In FIG. 4, reference numeral 85 denotes a minimum luminance value storage circuit for storing a minimum luminance value 68 in one screen of an input image, 86 denotes a smoothing circuit, and 87 denotes a smoothing circuit. Is the stored minimum luminance value, and 88 is the minimum luminance value after smoothing. 10-84
Is equivalent to that in FIG.

In the configuration of FIG. 4, the minimum luminance value storage circuit 85 stores the minimum luminance value 6 output from the minimum luminance value calculation circuit 65.
8 for the last few frames. The smoothing circuit 86 receives the minimum luminance value 68 and the stored minimum luminance value 87, and calculates, for example, an average from the minimum luminance values of recent several frames,
It outputs to the bit division circuit 70 and the multiplexer 73 as the smoothed minimum luminance value 87 smoothed on the time axis. The operation after the bit division circuit 70 is the same as that described with reference to FIG.

As described above, according to the above-described configuration, in the case where the input image is a monochrome image exceeding 8 bits, the minimum luminance value for the latest several frames is stored, and for example, the main luminance information of the screen is stored using the average value. By decomposing the data into other data, it is possible to prevent a decrease in coding efficiency due to a change in the minimum luminance value between frames.

Embodiment 4 FIG. 5 is a block diagram showing Embodiment 4 of the present invention. In FIG. 5, reference numeral 89 denotes a change rate judgment circuit, and 90 denotes the minimum luminance after the change rate judgment. 10
85 are equivalent to those in FIG.

In the configuration of FIG. 5, the change rate judgment circuit 89
Calculates the rate of change of the minimum luminance value 68, and if the rate of change is greater than a preset value, the minimum luminance value of the previous frame stored in the minimum luminance value storage circuit 85 is calculated as the minimum The luminance value 90 is output to the bit division circuit 70 and the multiplexer 73. Bit dividing circuit 70
Subsequent operations are the same as those described with reference to FIG.

As described above, according to the above-described configuration, when the input image is a monochrome image exceeding 8 bits, the change rate of the minimum luminance value is monitored, and when the change rate is large, the minimum luminance value of the previous frame is used. By decomposing into the main luminance information of the screen and other data, it is possible to prevent the coding efficiency from deteriorating due to the fluctuation of the minimum luminance value between frames.

Embodiment 5 FIG. FIG. 6 is a block diagram showing a fifth embodiment of the present invention. In FIG. 6, reference numeral 91 denotes an encoding mode determination circuit, reference numeral 92 denotes encoding mode information, and reference numeral 93 denotes a minimum luminance value after the encoding mode determination. 10 to 85 are equivalent to those in FIG.

In the configuration shown in FIG. 6, a coding mode determining circuit 91 receives coding mode information 92 output from the MPEG encoder 19, and in the case of an intra coding mode in which correlation between frames is not used, the minimum of the current frame. The luminance value is stored in the minimum luminance value storage circuit 85 in the motion compensation prediction mode using the correlation between frames, and the minimum luminance value in the previous intra-encoding mode is the minimum luminance value after the encoding mode determination. The luminance value 93 is output to the bit division circuit 70 and the multiplexer 73. The operation after the bit division circuit 70 is the same as that described with reference to FIG.

As described above, according to the above configuration, when the input image is a monochrome image exceeding 8 bits, the MPE
The coding mode of the G encoder is monitored, and in the motion compensation prediction mode using the correlation between frames, the main brightness information of the screen and the other brightness information are used using the minimum brightness value in the previous intra coding mode. By decomposing the data, it is possible to prevent the coding efficiency from deteriorating due to the fluctuation of the minimum luminance value between frames.

[0045]

According to the first aspect of the present invention, even when the input image is a monochrome image exceeding 8 bits, the maximum luminance in the screen can be improved.
Decomposes into the main luminance information of the screen and other data according to the minimum luminance, and assigns it to the luminance signal encoding / decoding circuit and the chrominance signal encoding / decoding circuit. The image can be compressed and transmitted using the circuit.

According to the second aspect of the present invention, the 8
Even if the brightness distribution range of a specific scene does not exceed 8 bits in a monochrome image exceeding bits, even if the brightness distribution range does not exceed 8 bits, the image is not subjected to gradation conversion by detecting the difference between the maximum brightness and the minimum brightness. Deterioration of coding efficiency due to lack of signal continuity can be prevented.

According to the third aspect of the present invention, when the input image is 8
In the case of a monochrome image exceeding bits, the minimum luminance value for the latest several frames is stored, and for example, the average luminance value is used to decompose the main luminance information of the screen and other data, thereby obtaining the minimum luminance value between frames. It is possible to prevent the coding efficiency from deteriorating due to the fluctuation.

Further, according to the fourth aspect, when the input image is 8
In the case of a monochrome image exceeding bits, the change rate of the minimum luminance value is monitored, and if the change rate is large, the frame is decomposed into the main luminance information of the screen and other data using the minimum luminance value of the previous frame. It is possible to prevent the coding efficiency from deteriorating due to the fluctuation of the minimum luminance value during the period.

Further, according to the fifth aspect, the input image is 8
In the case of a monochrome image exceeding bits, the encoding mode of the MPEG encoder is monitored, and in the case of the motion compensation prediction mode using the correlation between frames, the screen is displayed using the minimum luminance value in the previous intra encoding mode. By decomposing into the main luminance information and other data, it is possible to prevent the coding efficiency from deteriorating due to the fluctuation of the minimum luminance value between frames.

[Brief description of the drawings]

FIG. 1 is a first embodiment of a target detecting apparatus according to the present invention;
FIG.

FIG. 2 is a diagram showing a procedure of bit decomposition according to the present invention.

FIG. 3 is a second embodiment of the target detecting apparatus according to the present invention;
FIG.

FIG. 4 is a third embodiment of the target detecting apparatus according to the present invention;
FIG.

FIG. 5 is a fourth embodiment of the target detecting apparatus according to the present invention;
FIG.

FIG. 6 is a fifth embodiment of the target detecting apparatus according to the present invention;
FIG.

FIG. 7 is a diagram showing an operation state of a system to which the present invention is applied.

FIG. 8 is a diagram illustrating an example of a conventional image compression transmission apparatus.

FIG. 9 is a diagram illustrating a detailed configuration of an MPEG encoder.

FIG. 10 is a diagram showing a detailed configuration of an MPEG decoder.

[Explanation of symbols]

11 imaging device, 13 A / D converter, 19 MPEG
Encoder, 21 modulator, 23 transmission line, 24 demodulator, 26 MPEG decoder, 32 D / A converter, 3
4 Image output device, 64 Maximum luminance value calculation circuit, 65
Minimum luminance value calculation circuit, 66 image memory, 70 bit separation circuit, 72 color difference signal distribution circuit, 73 multiplexer, 75 demultiplexer, 76 bit synthesis circuit,
78 color difference signal synthesis circuit, 81 first luminance range determination circuit, 83 second luminance range determination circuit, 85 minimum luminance value storage circuit, 86 smoothing circuit, 89 change rate determination circuit,
91 coding mode determination circuit.

Claims (5)

[Claims] 1. An imaging device for converting input light into an image and converting the image into an analog image signal, an A / D converter for converting an analog image signal into a digital image signal, and a digital image signal output from the A / D converter. A maximum brightness value calculation circuit for calculating a maximum brightness value; a minimum brightness value calculation circuit for calculating a minimum brightness value from the digital video signal; an image memory for storing the digital video signal for one screen; A bit separation circuit that separates the main luminance information of the screen into a luminance signal according to the luminance value and decomposes other data into a color difference signal,
A color difference signal distribution circuit for distributing the bit-separated data into two types of color difference signals; and an MPEG (Movi) for generating compressed / encoded data from the luminance signal and the two types of color difference signals.
ng Picture Experts Group)
An encoder, a multiplexer for multiplexing the maximum luminance value and the minimum luminance value to the compressed / encoded data, a modulator for modulating the compressed / encoded data, and a transmission for transmitting the modulated compressed / encoded data Channel, a demodulator for demodulating the transmitted compressed / encoded data, a demultiplexer for separating a maximum luminance value and a minimum luminance value from the demodulated compressed / encoded data, and a luminance signal for converting the compressed / encoded data to a luminance signal. An MPEG decoder for decoding the two types of color difference signals, a color difference signal synthesizing circuit for synthesizing the decoded two types of color difference signals into one color difference signal, and a digital image from the luminance signal and the synthesized color difference signals. A bit combining circuit for combining the signals, a D / A converter for converting a digital video signal from the bit combining circuit into an analog video signal, and an image output for displaying the analog video signal. Image compression transmission apparatus characterized by comprising a device. 2. A first brightness range determination circuit for determining a brightness range from a maximum brightness value and a minimum brightness value in a screen, and a brightness range from a maximum brightness value and a minimum brightness value separated by a demultiplexer on a receiving side. 2. The image compression transmission apparatus according to claim 1, further comprising a second luminance range determination circuit for determining, and a unit for preventing an expansion conversion of a gradation based on a difference between the maximum luminance value and the minimum luminance value. . 3. The image according to claim 2, further comprising a minimum luminance value storage circuit for storing a minimum luminance value in the screen, and a smoothing circuit for smoothing the minimum luminance value on a time axis. Compression transmission equipment. 4. A minimum luminance value storage circuit for storing a minimum luminance value in a screen, and a change rate judging circuit for switching a minimum luminance value to be output according to a change rate of the minimum luminance value. 3. The image compression transmission device according to 2. 5. A minimum luminance value storage circuit for storing a minimum luminance value in a screen, and an encoding mode determination circuit for switching a minimum luminance value to be output according to an encoding mode of an MPEG encoder. The image compression transmission apparatus according to claim 2.