JPH1066074A - Image transmitter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To send a moving image or a still image within a limited transmission capacity. SOLUTION: An image pickup element 12 converts an optical image by an image pickup lens 10 into an electric signal and its output is fed to a digital signal processing circuit 18 via a double correlation sampling(CDS)/automatic gain control(AGC) circuit 14 and an A/D converter 16 and the signal is subject to camera signal processing. A motion detection circuit 20 detects whether a current video image is a moving image or a still image. A picture element thinning circuit 22 thinnes picture elements in an image from output video data of the circuit 18 according to a detection output of the circuit 20. In the case of a moving image, much more picture elements are thinned than the still image, output data from the picture element thinned-out circuit 22 are given to a de-framing control circuit 26 via a memory 24 and the circuit 26 thinnes the image data in the unit of frames so that the still image has much more frames than the case with the motion image according to a detection output of the circuit 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an image transmitting apparatus.

[0002]

2. Description of the Related Art FIG. 6 is a schematic block diagram of a transmitting side of an image transmission system using a spread spectrum system. The image sensor 112 converts an optical image obtained by the photographing lens 110 into an electric signal. The CDS / AGC circuit 114 performs double correlation sampling (CD) on the output signal of the image sensor 112.
S) and automatic gain adjustment (AGC), and the A / D converter 11
6 converts the analog output signal of the CDS / AGC circuit 114 into a digital value. Digital signal processing circuit 118
Performs various camera signal processing (gamma processing, white balance adjustment, etc.) on the digital video signal output from the A / D converter 116 and temporarily stores the digital video signal in the memory 120. The frame drop control circuit 122 thins out the video data stored in the memory 120 on a frame (frame) basis,
The signal is supplied to the spread spectrum transmitting circuit 124. The spread spectrum transmitting circuit 124 transmits the video data to be transmitted from the antenna 126 by the spread spectrum method.

In the conventional example, when the communication capacity of the transmission medium is small, the number of frames per second (the number of frames) is reduced by the frame drop control circuit 122 to reduce the amount of data to be transmitted.

[0004] Image transmission by the spread spectrum method will be briefly described. In general, in a spread spectrum system using a direct spread system, a transmitting side converts a baseband signal of a digital signal to be transmitted into a pseudo noise code (P
(N code) or the like, and spread to a baseband signal having a much wider bandwidth than the original data.
And PSK (phase shift keying) and FSK
(Frequency shift keying) or the like, and convert to an RF (radio frequency) signal for transmission.

[0005] On the receiving side, processing opposite to that on the transmitting side is performed. That is, after demodulation, despreading is performed to obtain a correlation with the received signal using the same spreading code as that on the transmitting side, and the received signal is converted into a narrow band signal having a bandwidth corresponding to the original data.
Subsequently, normal data demodulation is performed to reproduce the original data.

In the spread spectrum communication system, the transmission bandwidth is extremely wide with respect to the information bandwidth, so that the transmission rate is not fast enough to transmit a moving image sufficiently under the condition that the transmission bandwidth is fixed. Accordingly, in the conventional example, only about one frame (frame) of a still image can be transmitted per second.

[0007]

In the prior art, when transmitting image data with a large amount of information, especially moving image data, there is no problem in a wireless transmission system with a wide transmission bandwidth, but in a transmission system with a small transmission bandwidth. In order to reduce the amount of data to be transmitted, a frame drop image is transmitted, or
An image in which the number of pixels of the frame is reduced (ie, thinned out) is transmitted.

The amount of information of a video signal per unit time (1 second) will be described. A general NTSC TV signal is 3
0 frames / sec. One frame screen is horizontal 72
It is composed of pixel data of 0 pixels and 480 vertical pixels, and one pixel is composed of a total of 16 bits of data of 8 bits of luminance signal and 8 bits of color signal. That is, the total amount of video signal data for one second is 30 (frames) × 720 (horizontal) × 480 (vertical) ×
16 bits (1 pixel) = about 160 Mbit.

[0009] Such image data is transmitted with a transmission capacity of 16
When transmitting in a communication system of 0 Mbit / sec or more, a clear TV video can be transmitted without any problem. However, in a communication system with a transmission capacity of less than that, the only option is to drop frames or reduce the number of pixels in one frame. However, in the conventional example, the smoothness of the motion is deteriorated when the frame is dropped, and the resolution is deteriorated when the number of pixels in one frame is reduced.

An object of the present invention is to solve such a problem and to provide an image transmitting apparatus capable of transmitting an image with good image quality even in a transmission system with a small transmission capacity.

[0011]

SUMMARY OF THE INVENTION An image transmitting apparatus according to the present invention controls pixel thinning means for thinning out pixels of image information to be transmitted in a screen, and controls the number of frames of image information to be transmitted per unit time. In the case of a moving image, the frame number control means and the motion detection means for detecting the motion amount between the screens of the image information to be transmitted, and controlling the pixel thinning means and the frame number control means according to the detection result. Is characterized in that the number of pixels per screen is reduced to increase the number of frames per unit time, and in the case of a still image, the number of pixels per screen is increased to reduce the number of frames per unit time.

Thus, the image information can be transmitted by appropriately controlling the resolution and the smoothness of the motion within the limited transmission capacity according to the content of the image information to be transmitted (the amount of motion between the screens).

By weighting the amount of movement between screens on the screen, it is possible to appropriately select and control the resolution and the smoothness of the movement for the portion of interest.

[0014]

Embodiments of the present invention will be described below in detail with reference to the drawings.

FIG. 1 is a schematic block diagram of a transmitting side according to an embodiment of the present invention. Reference numeral 10 denotes a photographing lens, 12 denotes an image pickup device for photoelectrically converting an optical image of a subject by the photographing lens 10, and 14 denotes a CD for performing double correlation sampling (CDS) and automatic gain adjustment (AGC) of an output signal of the image pickup device 12.
An S / AGC circuit 16, an A / D converter for converting an analog output signal of the CDS / AGC circuit 14 into a digital value;
Reference numeral 18 denotes a digital signal processing circuit for performing various camera signal processing (gamma processing, white balance adjustment, etc.) on the digital video signal output from the A / D converter 16;
0 is a motion detection circuit that detects the presence or absence of motion from the digital video signal from the digital signal processing circuit 18, that is, whether it is a moving image or a still image, and 22 is an output of the digital signal processing circuit 18 in accordance with the detection result of the motion detection circuit 20. A pixel thinning circuit for thinning out pixels in a screen from video data; 24, a memory for temporarily storing output data of the pixel thinning circuit 22;
Is stored in the memory 24 according to the motion detection result of the motion detection circuit 20.
A frame-drop control circuit 28 controls the number of frames (number of frames) of video data from the CPU, a spread-spectrum transmission circuit 28 transmits data from the frame-drop control circuit 26 by a spread-spectrum method, and a transmission antenna 30.

FIG. 2 is a block diagram showing a schematic configuration of the motion detecting circuit 20. Digital video data is input to the input terminal 32 from the digital signal processing circuit 18. The digital video data input to the input terminal 32 is divided by the block dividing circuit 34 into a plurality of blocks in the screen. The digital video data input to the input terminal 32 is also delayed by one field by a one-field delay circuit 36, and then divided into a plurality of blocks in a screen by a block dividing circuit 38 similar to the block dividing circuit 34.

The matching circuit 40 matches the outputs of the block dividing circuits 34 and 38 for each block and calculates a correlation distribution. Motion vector detection circuit 42 for each block
Calculates a motion vector for each block from the correlation distribution calculated by the matching circuit 42. The moving image / still image detection circuit 44 calculates the current motion vector from the magnitude of the motion vector of each block calculated by the motion vector detection circuit 42. Is detected as a moving image or a still image. Video / still image detection circuit 4
4 is output from the output terminal 46 to the pixel thinning circuit 22.
And is applied to the control terminal of the frame drop control circuit 26.

FIG. 3 is a block diagram showing another schematic configuration of the motion vector detecting circuit 20. Until the motion vector detection circuit 42 detects a motion vector for each block, FIG.
Is the same as In FIG. 3, the weighting circuit 48 assigns a predetermined weight to the motion vector for each block detected by the motion vector detection circuit 42. For example, a large weight is assigned to the center of the screen, and the weight around the screen is reduced. That is, the center of the screen is emphasized. The moving image / still image detection circuit 50 detects whether the current video is a moving image or a still image according to the output of the circuit 48. The detection result of the moving image / still image detecting circuit 50 is applied from the output terminal 52 to the control terminals of the pixel thinning circuit 22 and the frame dropping control circuit 26.

The operation of the embodiment shown in FIG. 1 will be described. The image sensor 12 converts an optical image from the photographing lens 10 into an electric signal. The CDS / AGC circuit 14 performs double correlation sampling (CDS) and automatic gain adjustment (AGC) on the output signal of the image sensor 12, and the A / D converter 16 performs CDS / AGC
The analog output signal of the circuit 14 is converted into a digital value. The digital signal processing circuit 18 includes the A / D converter 16
Performs various camera signal processing (gamma processing, white balance adjustment, and the like) on the digital video signal output from. The motion detection circuit 20 detects from the digital video data from the digital signal processing circuit 18 whether the current video is a moving image or a still image.

The pixel thinning circuit 22 includes a motion detection circuit 20
Of the digital video data output from the digital signal processing circuit 18 in accordance with the detection output of, the pixels in the screen are thinned out. In the case of a moving image, many pixels are thinned out, and in the case of a still image, fewer pixels are thinned out or pixels are not thinned out.

The output data of the pixel thinning circuit 22 is temporarily stored in the memory 24, and the frame drop control circuit 26 converts the video data stored in the memory 24 into frames according to the detection output of the motion detection circuit 20. Thin out in frames). In the case of a still image, the number of frames per second is reduced, and in the case of a moving image, the number of frames per second is kept at 30.

The spread spectrum transmitting circuit 28 spreads the video data from the frame dropping control circuit 26 by a spread spectrum method, and outputs PSK (phase shift keying) or FSK.
The signal is modulated by SK (frequency shift keying) or the like, converted into an RF (radio frequency) signal, supplied to the antenna 30, and transmitted by radio.

FIG. 4 is a schematic block diagram of the receiving side of this embodiment. The radio signal transmitted from the antenna 30 in FIG. 1 is received by the antenna 60 and supplied to the spread spectrum receiving circuit 62. Spread spectrum receiving circuit 62
Performs spread spectrum despreading that correlates with the received signal using the same spreading code as the transmitting side, converts the received signal into a narrowband signal with the bandwidth corresponding to the original data, and then performs normal data demodulation And reproduce the original data. After the image data reproduced by the receiving circuit 62 is subjected to rate adjustment by the input buffer 64, the image data is stored in a frame memory 66 capable of storing one frame of image data.

The image data read from the frame memory 66 is transmitted via the recording / reproducing device 68 or directly.
The signal is applied to the synchronization signal adding circuit 70. The synchronization signal adding circuit 70 adds the synchronization signal from the synchronization signal generation circuit 72 to the image data from the memory 66 or the recording / reproducing device 68. The D / A converter 74 converts the image data with the synchronization signal output from the synchronization signal adding circuit 70 into an analog signal, and applies the analog signal to a liquid crystal display (LCD) monitor 76. LCD
The monitor 76 displays the received image as an image.

The reception frame control circuit 78 receives the input buffer 64 according to the synchronization signal from the synchronization signal generation circuit 72.
And the writing and reading of the frame memory 66 are controlled, and the image data for one frame is stored in the frame memory 6.
6, the image data is sequentially read from the memory 66 at a predetermined rate.

FIG. 5 is a diagram symbolically showing the operation of the image thinning circuit 22 and the frame dropping control circuit 26. If the maximum transmission rate is 40 Mbit / sec, the amount of video data of a normal TV signal is 160 Mbit / sec.
It cannot be transmitted as it is. Therefore, in the present embodiment, the motion detection circuit 20 detects whether the captured video is a moving image or a still image, and in the case of a moving image, controls the frame dropping control circuit 26 so as to increase the number of frames as much as possible. The thinning circuit 22 is controlled so that the number decreases, that is, the pixel thinning number increases. In the case of a still image, contrary to the case of a moving image, image quality is prioritized over smoothness of motion, the number of frames is reduced by the frame skipping control circuit 26, and the number of pixel thinnings of the pixel thinning circuit 22 is reduced.

In the present embodiment, when the transmission capacity is limited or when there is a shortage, the smoothness of the movement is given priority in the case of a moving image, and the resolution is given priority in the case of a still image. Image information can be appropriately transmitted under the restriction of capacity. By assigning a large weight to the center of the screen in detecting a moving image / still image, a satisfactory image quality can be provided to the photographer.

[0028]

As can be easily understood from the above description, according to the present invention, priority is given to smoothness of motion in the case of a moving image according to the content of the image (moving image or still image), and In the case of an image, the resolution is prioritized, so that image information can be efficiently transmitted within the limited transmission capacity.

[Brief description of the drawings]

FIG. 1 is a schematic block diagram of a transmitting side according to an embodiment of the present invention.

FIG. 2 is a schematic block diagram of a configuration of a motion detection circuit 20.

FIG. 3 is another schematic configuration block diagram of the motion detection circuit 20.

FIG. 4 is a schematic configuration block diagram of a receiving side of the present embodiment.

FIG. 5 is an image thinning circuit 22 and a frame drop control circuit 2
It is a schematic diagram which shows the effect | action of No.6.

FIG. 6 is a schematic block diagram of a transmission side of a conventional example.

[Explanation of symbols]

 10: Photographing lens 12: Image sensor 14: CDS / AGC circuit 16: A / D converter 18: Digital signal processing circuit 20: Motion detection circuit 22: Pixel thinning circuit 24: Memory 26: Frame dropping control circuit 28: Spectrum spread Transmission circuit 30: Transmission antenna 32: Input terminal 34: Block division circuit 36: 1 field delay circuit 38: Block division circuit 40: Matching circuit 42: Motion vector detection circuit 44: Moving image / still image detection circuit 46: Output terminal 48: Weighting circuit 50: Moving picture / still picture detecting circuit 52: Output terminal 60: Antenna 62: Spread spectrum receiving circuit 64: Input buffer 66: Frame memory 68: Recording / playback device 70: Synchronous signal adding circuit 72: Synchronous signal generating circuit 74: D / A converter 76: Liquid crystal display (LCD) monitor 78: Receive frame control circuit 110: Photographing lens 112: Image sensor 114: CDS / AGC circuit 116: A / D converter 118: Digital signal processing circuit 120: Memory 122: Frame drop control circuit 124: Spread spectrum transmission circuit 126: antenna

Claims (4)

[Claims] 1. A pixel thinning unit for thinning out pixels of image information to be transmitted in a screen, a frame number control unit for controlling the number of frames per unit time of image information to be transmitted,
It comprises a motion detection means for detecting the amount of motion between screens of image information to be transmitted and controlling the pixel thinning means and the frame number control means in accordance with the detection result. An image transmitting apparatus characterized in that the number of frames per unit time is increased by reducing the number of pixels, and in the case of a still image, the number of pixels per screen is increased to reduce the number of frames per unit time. 2. The image processing apparatus according to claim 1, wherein said motion detecting means includes a moving image / still image detecting means for detecting whether the image information to be transmitted is a moving image or a still image based on the amount of movement between screens of the image information to be transmitted. 2. The image transmission device according to 1. 3. The image transmission according to claim 1, wherein said motion detection means detects a moving image or a still image by assigning a weight on a screen to a motion amount between screens of image information to be transmitted. apparatus. 4. The image transmitting apparatus according to claim 1, wherein said frame number control means controls the number of frames per unit time of an output image of said pixel thinning means.