JPH0583704A - Picture transmitter - Google Patents

Abstract

PURPOSE:To send picture information desired to be sent with relatively more excellent picture quality than other part with emphasis when a transmission rate is especially low. CONSTITUTION:An input picture signal is quantized by a quantizer 26 via an A/D converter section 22 and the result is sent and a desired range of the picture is pointed out by a mouse 41 or the like and the quantization width by the quantizer 26 is controlled based on the designated range 62.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image transmission apparatus for compressing and transmitting an image signal, and is suitable for application to, for example, a so-called video conference or video telephone system.

[0002]

2. Description of the Related Art As an image transmission device for compressing and transmitting an image signal, for example, a so-called video conference or a video telephone system, for example, H.264 in the so-called CCITT (International Telegraph and Telephone Consultative Committee) recommendation is used. There is a H.261 standard system.

This H.264 In the C.261 standard, the CIF format (intermediate signal format) has a luminance signal of 36
0 pixel x 288 lines 29.97Hz, color difference signal is 1
80 pixels x 144 lines, non-interlaced system. In addition, the encoding method has a basic algorithm of motion compensation prediction + orthogonal transformation. Here, in the motion compensation, the search range is ± 15 pixels × ± 15 lines, the color signal has no motion compensation, and the transform coding is the block size 8 × 8.
DCT (discrete cosine transform) of (pixels), applied quantization is selected from a maximum of eight types of scans, and a quantizer is a maximum of 32.
As for the in-loop filter, the filter is inserted in the frame memory output section in the inter-coding loop. Further, the transmission format is H.264. According to the 221 standard, the transmission rate is n × 384 kbit / sec (n = 1
5), the interface is I.V. It is 451 standard.

By the way, in the above-mentioned video conference system and the like, the transmission rate is defined as described above, but a signal is transmitted at a lower transmission rate (eg, 64 kbit / sec) among the defined transmission rates. In such a case, it becomes impossible to transmit all the image information. Therefore, in such a case, for example, the weighting of the information amount is changed in the image signals forming the screen so that only an image in a certain range is made clear and transmitted. That is, as a method of changing the weighting of the amount of information in this screen, for example, a method of recognizing a boundary of a person or the like and sending that part with priority, or a method of detecting a motion vector and giving priority to a moving part There are methods such as weighting a fixed position (for example, the central portion) of the screen.

[0005]

However, in each of the methods for changing the weighting of the information amount in the above-mentioned screen, in the method of recognizing the above-mentioned boundary and sending that part in an intensive manner,
For example, when a person or the like is a subject, it is difficult to detect a boundary between a face portion and a less important portion from the neck, for example, and this detection error may occur. Also,
For example, in the method of detecting the motion vector and placing importance on a moving portion, there may be a portion of the subject to which the information of the image is to be sent, even if there is not much movement. In this case, if there are many parts that are moving to other parts in contrast to the part to which the information is preferentially sent, the amount of transmission information will be occupied by the other part having the motion, and a good image will be displayed. May not be transmitted. Also, when weighting only the fixed position on the screen, it is sometimes desired to send the image information of the portion other than the fixed position in a focused manner.

Therefore, the present invention has been proposed in view of the above-mentioned circumstances, and when a transmission rate is particularly low, an arbitrary portion to which image information is preferentially sent is sent to other portions. An object of the present invention is to provide an image transmission device capable of transmitting with a relatively good image quality.

[0007]

An image transmitting apparatus of the present invention is proposed to achieve the above-mentioned object, and is an image transmitting apparatus for compressing and transmitting an image signal, which is an input image signal. Sampling means for sampling, a quantizing means for quantizing the output signal of the sampling means, a transmitting means for transmitting the output signal of the quantizing means, and a designation input means for designating a desired range of the image. And the quantizing means is such that the quantizing width is controlled based on the output signal of the designated input means.

Here, the range designated by the designation input means is not limited to the designation of the image of the image signal sent from the image transmission device on the transmission side (self side) to the image transmission device on the reception side (partner side). It is also possible to specify for the image sent from the other party to the own party. That is, when bidirectional communication is performed between the self-side device and the other-side device, an image sent from the other-side device to the own-side device is desired by the self-side specified input means. By designating the range and sending the output signal of the designation input means on the self side to the device on the partner side, the quantization width in the quantizing means on the partner side can be controlled. As a result, the image in the desired range of the image sent from the other party can be made clear.

[0009]

According to the present invention, the specified input portion is used to specify an arbitrary portion of interest, and the quantization width of the portion specified by the designated input means is made fine, for example, to thereby determine a predetermined transmission rate. Within that, the image quality of the designated portion is made good.

[0010]

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

As shown in FIG. 1, the image transmitting apparatus according to the embodiment of the present invention compresses the image signal supplied to the input terminal 10 and outputs the compressed image signal from the output terminal 11 so that the image transmitting apparatus on the other side (reception side) is transmitted. Image transmission device for transmitting to an analog / digital converter which is a sampling means for sampling an input image signal.
A digital (A / D) converter 22, a quantizer 26 for quantizing the output signal of the A / D converter 22, and a transmission means for transmitting the output signal of the quantizer 26, for example, a transmission buffer 29. And a line interface circuit 30,
For example, the mouse 4 which is a designation input unit for designating a desired range of the image (the image on the self side or the image on the partner side)
1, a pointing device such as a keyboard 42 (so-called trackball or touch screen not shown), and the quantizer 26, based on the output signal of the designated input means, the quantization width (quantization step size). Is controlled. The quantization step size in the quantizer 26 is specifically controlled based on the output of the quantization control circuit 33 described later.

That is, in FIG. 1, the input terminal 10
For example, the above-mentioned input image signal obtained from an image signal from a video tape recorder (VTR), a video camera, a video scanner or the like via the switcher 51 is supplied. The input image signal is output from the output terminal 1
It is displayed on the screen 61 of the preview monitor 60 via the screen 2. In this embodiment, for example, an image of a person 63 is displayed on the screen 61 of the preview monitor 60.

Further, the input image signal is output from the output terminal 11 to the communication line as a transmission signal via each component from an image codec 21 to a line interface circuit 30 which will be described later.

Here, when performing this signal transmission, as described above, for example, H.264. Signals are transmitted at a transmission rate according to the H.261 standard. In the present embodiment, when the transmission rate is determined in this way, and particularly when the transmission rate is low, the desired range (part of interest) to which image information is to be sent is focused on another range (part). In contrast, it is possible to transmit with a relatively good image quality.

That is, in this embodiment, specifically, the image of the portion of interest is transmitted with high image quality as described below.

In this embodiment, the person 63 on the screen 61 is
On the other hand, a case where an image of a face portion is sent with high image quality will be described as an example. That is, for example, it is assumed that the image of the designated range (focused portion) 62 indicated by the dotted line in the figure on the screen 61 is sent with high image quality. In this case, first, by inputting from the mouse 41 or the keyboard 42, the instruction range 6
Specify 2. For example, the pointing range 62 with the mouse 41
When designating, the instruction frame is first displayed on the screen 61 of the monitor 60 in a composite manner, and the combined display instruction frame (designated range) is moved to the desired position by the mouse 41. At this time, the size of the designated range 62 can be freely expanded or reduced. Of course, the display of the instruction frame and movement, enlargement, reduction, etc. of the instruction range 62 can also be performed by inputting from the keyboard 42.

Signals from the mouse 41 and the keyboard 42 are sent via an input interface circuit 43 to a microcomputer 45 that controls the entire image transmission apparatus. The microcomputer 45
Generates an image signal of the instruction range 62 to be displayed on the screen 61 of the monitor 60 based on the input information from the mouse 41 or the keyboard 42 supplied via the input interface circuit 43, and outputs this instruction. Processing such as movement, enlargement, and reduction is performed on the image signal in the range 62. For example, when moving the designated range 62, the coordinates designated by the mouse 41 or the keyboard 42 are calculated, and the image signal of the designated range 62 moved based on the calculated coordinate information is calculated. I am trying to form.

The image signal of the instruction range 62 formed by the microcomputer 45 is sent to the superimposing circuit 44. This superimposing circuit 44
As a result, the image signal in the designated range 62 is superimposed on the input image signal via the input terminal 10. In this way, the image signal obtained by superimposing the image signal of the instruction range 62 is sent to the monitor 60, so that the instruction range 62 is displayed on the screen 61 of the monitor 62 together with the image of the person 63 or the like. Will be displayed.

The input image signal is demodulated by an image codec (modulator / demodulator) 21 and then sampled by the A / D converter 22 into a digital signal. This digital signal is sent to the motion compensation circuit 24 via a standard conversion circuit 23 for converting it into a standard. In the motion compensation circuit 24, the above-mentioned H.264. Motion compensation processing defined by H.261 is performed (search range is ± 15 pixels × ± 15 lines, no motion compensation for color signals). The output of this motion compensation circuit 24 is the DCT
The (discrete cosine transform) circuit 25 performs DCT processing with a block size of 8 × 8 pixels, for example.

The signal on the frequency axis obtained from the DCT circuit 25 is sent to the quantizer 26 and adaptively quantized by the quantizer 26. At this time, the quantizer 26 controls the quantization step size based on the signal from the quantization control circuit 33. That is, the quantization control circuit 33 has
Data (for example, coordinate information) indicating the instruction range 62 is supplied from the microcomputer 45, and the quantization control circuit 33 is based on the output from the microcomputer 45, for example, the monitor 60. A quantizing control signal for making the quantizing step size finer is sent to the quantizer 26 only for the output of the DCT circuit 25 corresponding to the image in the designated range 62 on the screen 61. In this way, the quantizer 26 performs quantization with a fine quantization step size only on the image information of the portion specified by the instruction range 62, and thus the resulting image (that is, described later). The image within the designated range 62 of the image displayed on the monitor of the receiving unit after being transmitted to the receiving unit has an excellent image quality.

The output of the quantizer 26 is subjected to a variable length coding process by a variable length coding circuit 27 which performs, for example, Huffman coding which adaptively uses so-called run length coding, and then a multiplexer 28. Sent to. The multiplexer 28 includes the output from the variable length encoding circuit 27, the voice data from the voice codec 31, and the receiving side, that is, the other party when the configuration of FIG. 1 is set to the transmitting side (self side) as described later. An instruction range transmission data generation circuit 32 that generates transmission data indicating the instruction range when the transmission side (self side) sets any of the instruction ranges as needed for the image sent from the side. And output from.

That is, in the present embodiment, as will be described later, since bidirectional communication is performed between the other side and the self side, both have a transmitting section and a receiving section. By setting the above-mentioned instruction range as necessary for the image of the other party received by the receiving section on the other side, the image quality of the portion of the image of the other side that is sent from the other party is made good. You can receive it.

In the multiplexer 28, the voice data and the instruction range transmission data for the image from the other party are multiplexed with the output of the variable length coding circuit 27. The instruction range transmission data generation circuit 32 is used.
Is supplied with an image signal from the receiving unit on the self side via the terminal 34. The output of the multiplexer 28 is
It is sent to the transmission buffer 29.

The transmission buffer 29 temporarily stores the output of the multiplexer 28 in order to match the output signal of the multiplexer 28 with the transmission rate defined according to the transmission in the communication line after the line interface circuit 30 in the subsequent stage. It is output after doing. By the way, since the transmission rate differs between the input and the output of the transmission buffer 29, the transmission buffer 29 may be overflowed. Therefore, the data indicating the storage amount of the transmission buffer 29 is sent to the quantization control circuit 33. That is, the quantization control circuit 33 also controls the quantization of the quantizer 26 based on the accumulated amount data. For example, the quantization control circuit 33, when the transmission buffer 29 overflows,
Control is performed to reduce the amount of output data from the quantizer 26.

The output from the transmission buffer 29 is transmitted through the line interface circuit 30 and further to the output terminal 1
Sent via 1.

FIG. 2 shows a flowchart of processing such as detection of the designated range in the microcomputer 45 and the quantization control circuit 33 of the apparatus of this embodiment. That is, in the flowchart of FIG. 2, in step S1, the screen 61 is displayed by the mouse 41 or the keyboard 42.
The start point (for example, pixel) of the designated range 62 specified above is detected, and the total point (for example, pixel) of the designated range 62 is detected in step S2. After step S2, in step S3, the coordinate value on the screen 61 (that is, the range calculation) is calculated based on the information of the start point and / or the total point of the designated range 62. Then, in step S4, the quantizer 2 is operated based on the coordinate values obtained in step S3.
The control information (quantization control signal) of the quantization step size to 6 is output.

As described above, according to the image transmission apparatus of the present embodiment, the A / D converter 22 for sampling the input image signal and the quantizer for quantizing the output signal of the A / D converter 22. 26, a transmission buffer 29 for transmitting the output signal of the quantizer 26, and a line interface circuit 3
0, and, for example, a mouse 41 and a keyboard 42 for designating a desired range of the image (the image on the self side or the image on the partner side), the quantizer 26 is based on the output signal of the designation input means. Quantization control circuit 3 that operates
Since the quantization width (quantization step) is controlled by the output of 3, the portion (instruction range) in which the image information is to be preferentially sent to the other portion is particularly emphasized when the transmission rate is low. Therefore, it is possible to transmit with relatively good image quality.

FIG. 3 shows the configuration of the receiving section on the other side corresponding to the transmitting section of the image transmitting apparatus of this embodiment shown in FIG. The configuration of the receiving unit in FIG. 3 is also provided on the side of the image transmitting apparatus in FIG. 1 so that the self-side can receive the signal from the transmitting unit on the other side.

That is, in FIG. 3, the signal from the output terminal 11 of the transmitting section shown in FIG. 1 is supplied to the input terminal 70 of the receiving section through a communication line. The signal supplied to the input terminal 70 is passed through a line interface circuit 81 that interfaces with the communication line.
It is sent to the reception buffer 82. The receiving buffer 82
Is provided for adjusting the transmission rate between the input and the output of the receiving buffer 82, similarly to the transmitting buffer 29. The output of the reception buffer 82 is sent to the demultiplexer 83. The demultiplexer 83 includes an audio signal included in the received signal, an image signal, and instruction range transmission data from the instruction range transmission data generation circuit 32 on the transmission side (that is, the transmission unit having the configuration of FIG. 1). Are to be separated. The audio signal is sent to an audio generating unit 89 including, for example, a speaker and a driving circuit for the speaker, and the image signal is passed through a decoding circuit 84 which performs a process reverse to that of the variable length encoding circuit 27. ,
It is sent to the inverse quantizer 85. The designated range transmission data is sent to the quantization control circuit of the transmission unit provided in a pair with the reception unit of FIG. 3 via the terminal 90.

In the inverse quantizer 85, the above-mentioned FIG.
Quantization processing opposite to that of the quantizer 26 of is performed. The output of the inverse quantizer 85 is an IDCT circuit 86 that performs a process (inverse discrete cosine transform process) opposite to that of the DCT circuit 25.
Via the standard conversion circuit 87, and is sent to the monitor 88 on the receiving side. This monitor 8
At 8, an image having a good image quality in the designated range is displayed.

FIG. 4 shows a system configuration of an image transmission system (for example, a video conference system) which performs bidirectional communication between image transmission devices having the receiving unit and the transmitting unit of this embodiment.

Here, in the example of FIG. 4, it is assumed that two positions, point A and point B, are shown at the same time with the dotted line in the figure as a boundary. Further, the image transmission systems at the point A and the point B both have the same configuration (however, in the example of FIG. 4, only the encoding / decoding device 107 of the image transmission system is shown at the point B for simplification). .. Furthermore, the points A and B above
It is assumed that the point image transmission system is connected by a communication line.

That is, in FIG. 4, for example, the transmission monitor 100 (60) of the image transmission system at the point A is used.
The image sent to the image transmission system on the point B side is displayed on the screen, and the image of the image signal transmitted from the image transmission system on the point B is displayed on the reception monitor 101 (88). Here, as described above, the image transmission system includes the keyboard 108 (42).
It also has an instruction input means such as a mouse 109 (41) or a trackball or a touch screen, and a signal from this instruction input means is transmitted to the input control device 103.

The input control device 103 includes a video camera 104, a VTR 105, and a video scanner 106.
Etc. are also connected. The input control device 103 controls the instruction input means and performs a process of displaying the instruction range on the monitor 100. Further, the input control device 103 calculates the coordinates of the instruction range designated by the instruction input means, and outputs the coordinates to the encoding / decoding device 102. The input control device 103 of the example of FIG. 4 includes the switcher 51, the input interface circuit 43 of FIG.
A macro computer 45 and the like are included.

If the coordinate information is within the designated range for the image displayed on the transmission monitor 100, the encoding / decoding apparatus 102 is the encoding / decoding apparatus 1.
If the coordinate information controls the quantization step size of the quantizer in 02 and the coordinate information is within the designated range for the image displayed on the reception monitor 101, the coordinate data (that is, the designated range transmission data). Via the communication line to the encoding / decoding device 107 of the other party (for example, the image transmission system side of the point B). That is, in the image transmission system of the present embodiment, with respect to the image transmitted from the other side (the image on the reception monitor),
By setting an arbitrary instruction range for the received image from the other party on its own side and transmitting the data of the instruction range for this received image to the encoding / decoding device 107 of the other party, The image in the above-mentioned designated range of the received image can be improved. Therefore, according to the image transmission system of the present embodiment, it becomes possible for the transmission side and the reception side to transmit the respective points of interest (instruction range) with better images than in other areas. The encoding / decoding device 102 includes the superimposing circuit 44, the image codec 21 to the line interface circuit 33, the quantization control circuit 33, the audio codec 31, the instruction range transmission data generating circuit 32, etc. of FIG. It is included.

Further, the input control device 103 can send the data of the designated range to the other party as it is, or can further send the data with a wider range, and these operation modes can be set in advance. Is possible.

Further, it is possible to set the effective time of the portion designated as the designated range. For example, after the designated range is set, this valid time can be set from 1 second to infinity.

As described above, in the image transmission system according to the present embodiment, it is possible to directly designate the portion (designated range) that the transmitting side prefers to send or the portion that the receiving side clearly wants to see, and perform this designation. As a result, important information can be efficiently allocated within the limited transmission information amount. In particular, when the transmission rate is low, it becomes possible to transmit the designated range (the portion of interest) with relatively good image quality.

[0039]

As described above, in the image transmission apparatus of the present invention, the input image signal is sampled, the sampled signal is quantized and transmitted, and the desired range of the image is designated and quantized. The quantization width is controlled on the basis of this specified range during conversion, that is, for example, by specifying a portion of an image signal in a screen that is desired to have good image quality, the quantization of the specified portion By narrowing the conversion width (increasing the amount of information to be allocated), the image of the part (indicated range) where you want to send the image information with priority, relative to other parts, especially when the transmission rate is low. It becomes possible to transmit with a good image quality.

[Brief description of drawings]

FIG. 1 is a block circuit diagram illustrating a schematic configuration of a transmission unit of an image transmission device according to an embodiment.

FIG. 2 is a flowchart of processing such as designation of an instruction range in the image transmission apparatus of this embodiment.

FIG. 3 is a block circuit diagram showing a schematic configuration of a receiving unit of the image transmission apparatus of this embodiment.

FIG. 4 is a diagram for explaining the image transmission system of the present embodiment.

[Explanation of symbols]

 21 ... Image codec 22 ... A / D converter 24 ... Motion compensation circuit 25 ... DCT circuit 26 ... Quantizer 27 ... -Variable length coding circuit 28-Multiplexer 29-Transmission buffer 30-Line interface circuit 33-Quantization control circuit 41-Mouse 42-・ ・ ・ Keyboard 43 ・ ・ ・ ・ ・ Input interface circuit 44 ・ ・ ・ ・ ・ Superimpose circuit 45 ・ ・ ・ Microcomputer 60 ・ ・ ・ ・ ・ Preview monitor 61 ・ ・ ・ Screen 62 ・ ・ ・..Instruction range

Claims (1)

[Claims] 1. An image transmission apparatus for compressing and transmitting an image signal, sampling means for sampling an input image signal, quantizing means for quantizing an output signal of the sampling means, and output signal of the quantizing means. And a designation input means for designating a desired range of the image, wherein the quantization means controls a quantization width based on an output signal of the designation input means. Image transmission device.