JP2959178B2 - Video signal transmission device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for transmitting a digital video signal.

[0002]

2. Description of the Related Art A conventional video signal transmission system is proposed in the literature (Takahiko Fukinuki: "A Consideration on Packet Video Coding", IEICE Transactions on Information and Systems, Vol.J73-B-INo.4, 1990). As described above, there is a method in which only the moving region is encoded and transmitted. One example will be described below with reference to the drawings.

FIG. 6 shows a transmission circuit of a conventional moving picture signal transmission device. In this figure, 600 is an intra-frame encoding unit, 601 is a frame memory, 602 is a moving image detection unit, and 6
03 is a difference block configuration unit, 604 is a difference value calculation unit, 6
05 is a determination unit, 606 is a pixel block transfer unit, and 607 is a determination result transfer unit. The operation of the moving picture signal transmission circuit configured as described above will be described below. An image signal to be handled is input in units of a pixel block composed of eight pixels in the horizontal direction and eight lines in the vertical direction. This pixel block is highly efficiently coded by the intra-frame coding unit 600. The difference block forming unit 603 forms a block (difference block) including a difference for each corresponding pixel between the input pixel block and the image signal at the same position in the frame memory 401. Difference value calculation unit 60
4 calculates the amplitude (difference value) Ea of this difference block. As a general method of calculating Ea, there is a mean square difference shown in (Equation 1) (see FIG. 8).

[0004]

## EQU1 ## As shown in FIG. 6, the determination unit 605 compares the difference value Ea calculated for each pixel block with a preset threshold value Vth, and determines a pixel block satisfying Ea ≧ Vth as a moving image block and a moving image block Ea. The pixel block of <Vth is determined as a still image block. At the start of operation of this circuit,
All pixel blocks in the first frame are determined to be moving image blocks. The pixel block transfer unit 606 transfers the pixel block signal only for the moving image block according to the determination result. Information transfer is not performed for still image blocks. The frame memory 601 records the transferred pixel block signal of the current frame, and forms a frame image signal. The determination result is information indicating which block on the frame screen corresponds to the pixel block signal to be transferred, and is required for image decoding in the receiving circuit. Therefore, this determination result is also transferred from the determination result transfer unit 607.

FIG. 7 shows a receiving circuit of a conventional moving picture signal transmitting apparatus. In the figure, reference numeral 700 denotes an image decoding unit;
Denotes a frame memory, 702 denotes a determination table, and 703 denotes a combining unit. The operation of the moving picture signal receiving circuit configured as described above will be described below. Image decoding unit 7
00 decodes the pixel block signal. The frame memory 701 records the decoded pixel block signal and forms a frame image signal. The determination table 702 holds the received determination result. The synthesizing unit 703 reproduces the moving image block with the pixel block signal and reproduces the still image block with the image signal at the same position in the frame memory according to the determination result.

As described above, the conventional image signal transmission apparatus encodes only a pixel block signal of the current frame which has a large change with respect to a signal already transmitted, with respect to a pixel block signal located at a certain position on the frame. To send. The received pixel block signal is recorded in a frame memory and forms a frame image signal. For the pixel blocks for which no information has been transferred, the current frame image signal is completed by supplementing with the image signal at the same position recorded in the frame memory. Therefore, the threshold value needs to be set optimally so that a moving image block and a still image block can be accurately determined.

[0007]

However, it is very difficult to determine an optimum threshold value for a general image signal. If the threshold value is increased, the reproduced image cannot follow the input image even if the input image slightly moves, resulting in an extremely unsightly image. Therefore, if the threshold value is reduced, the determination of a moving image block and a still image block is accurately performed, and a high-quality image can be reproduced. However, when the noise level of the input image is high, the difference value increases due to noise even though the image is originally a complete still image, and a situation occurs in which the image is erroneously determined to be a moving image block. In this case, unnecessary information is transmitted as a moving image block signal.

As described above, the conventional moving picture signal transmission apparatus has a problem that the amount of unnecessary transmission information is increased depending on the type of input image. Also, ATM
In the case of performing moving image transfer using a packet such as (asynchronous transfer mode), an increase in the amount of unnecessary information causes an increase in transfer cells, and increases the possibility of causing ATM network congestion. Cell discarding that occurs at the time of congestion causes a large deterioration in image quality in image transmission.

The present invention solves the above-mentioned conventional problems, and provides a moving picture signal transmission apparatus for minimizing an increase in the amount of unnecessary transmission information due to a noise component of an input image. It is another object of the present invention to provide a moving picture signal transmission apparatus that minimizes unnecessary information generation in image transmission by ATM and minimizes image quality degradation when cells are discarded.

[0010]

In order to achieve this object, a moving picture signal transmitting apparatus according to the present invention sets a first threshold value and a second threshold value larger than the first threshold value in determining a pixel block. I do. For each pixel block, the difference value is the second
The pixel block signal is transferred for those that are greater than or equal to the threshold, the difference block signal is transferred for those that are smaller than the second threshold and greater than or equal to the first threshold, and information transfer is not performed for those that are smaller than the first threshold. It has a configuration. The received pixel block signal is reproduced as an output image and recorded in the frame memory. The received difference block signal forms a block (addition block) including an addition value for each corresponding pixel with the image signal at the same position in the frame memory, and reproduces this as an output image. For pixel blocks that did not transfer information,
An image signal at the same position in the frame memory is reproduced.

In image transmission by ATM,
A packet is formed from each of the pixel block signal, the difference block signal, and the determination result and transferred. In this case, the priority of the transfer of the differential block signal, which is small enough to deteriorate the image even if it is lost, is set to a low priority regarding the transfer at the time of network congestion, and the packet is discarded first at the time of congestion. When the packet is discarded, the receiving device compensates for the discard with an image signal at the same position in the frame memory as in the case of a pixel block without information transfer.

[0012]

With this configuration, even when the input image contains a noise component, the increase in the amount of unnecessary transmission information can be minimized.

[0013] In addition, in moving image transmission by ATM, generation of unnecessary cells can be suppressed, and image quality degradation at the time of cell discard can be minimized.

[0014]

【Example】

(Embodiment 1) A first embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows the configuration of the transmission circuit. In the figure, 100 is an intra-frame encoding unit, 101 is a frame memory, 102 is a moving image detection unit, 103 is a difference block configuration unit, 104 is a difference value calculation unit, 105 is a determination unit, 106 is a difference encoding unit, 107 Denotes a pixel block transfer unit, 108 denotes a difference block transfer unit, and 109 denotes a determination result transfer unit.
The operation of the moving picture signal transmission circuit configured as described above will be described below. The image signal has a horizontal direction of 8
Pixels are input in units of a pixel block composed of eight lines in the vertical direction. This pixel block is highly efficiently coded by the intra-frame coding unit 100. The difference block forming unit 103 calculates the difference between the input pixel block and the image signal at the same position of the image signal in the frame memory 101.
A difference block composed of the difference for each corresponding pixel is configured. The difference value calculator 104 calculates a difference value Ea. As shown in FIG. 3, the determination unit 105 compares Ea with a preset first threshold Vth1 and second threshold Vth2 (here, Vth1 <Vth2), and determines a pixel block in which Ea ≧ Vth2. A moving image block, a pixel block satisfying Vth2> Ea ≧ Vth1 is determined to be a pixel block to which a difference block signal is to be transferred (hereinafter referred to as a moving image block with a difference), and a pixel block satisfying Ea <Vth1 is a still image block. At the start of the operation of this circuit, all the pixel blocks in the first frame are determined as moving image blocks. Differential encoding unit 1
06 encodes the difference block signal. The pixel block transfer unit 107 transfers a pixel block signal for a moving image block according to the determination result. Difference block transfer unit 1
08 transfers a difference block signal for the difference-added moving image block according to the determination result. Information transfer is not performed for still image blocks. The frame memory 101 records the transferred pixel block signal of the current frame, and forms a frame image signal. The determination result is also transmitted to the determination result transfer unit 1.
09 is transferred.

FIG. 2 shows the configuration of the receiving circuit. In the figure, reference numeral 200 denotes an image decoding unit; 201, a frame memory;
02 is a difference decoding unit, 203 is an addition unit, 204 is a determination table, and 205 is a combining unit. The operation of the moving picture signal receiving circuit configured as described above will be described below. The image decoding unit 200 decodes a pixel block signal. The frame memory 201 records the decoded pixel block signal and forms a frame image signal. The difference decoding unit 202 decodes the difference block signal. Adder 20
Reference numeral 3 denotes a block (addition block) composed of the added value for each corresponding pixel between the decoded difference block signal and the image signal at the same position in the frame memory. The determination table 204 holds the received determination result. The synthesizing unit 205 reproduces a moving image block with a pixel block signal, reproduces a moving image block with a difference with an addition block signal, and converts a still image block into a frame memory 201 according to the determination result.
Is reproduced with the image signal at the same position in the image.

As described above, according to the present embodiment, the judgment is made based on two threshold values for each pixel block. here,
By setting the first threshold value to a small value, it is possible to accurately extract a still image block from an image having less noise. In the case of an image with large noise, the number of images whose difference value exceeds the first threshold value increases even though the image is originally a still image. The second threshold value is set to be slightly larger than the difference value due to the noise, and for a pixel block having a difference value equal to or greater than the second threshold value,
Transfer the pixel block signal. For a pixel block having a difference value smaller than the second threshold value and equal to or larger than the first threshold value, the difference block signal is transferred without transferring the pixel block signal. Since the dynamic range of the difference block signal is smaller than the dynamic range of the moving image block signal, the amount of encoded information is small, and an increase in unnecessary information amount can be minimized.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings.

FIG. 4 shows the configuration of the transmitting apparatus. In the figure, 100 is an intra-frame encoding unit, 101 is a frame memory, 102 is a moving image detection unit, 103 is a difference block configuration unit, 104 is a difference value calculation unit, 105 is a determination unit, 106 is a difference encoding unit, 107 Is a pixel block transfer unit, 108 is a difference block transfer unit, 109 is a determination result transfer unit, and the above is the same as FIG. In the figure, a packet configuration unit 400 is added to this. The operation of the moving picture signal transmitting apparatus configured as described above will be described below. The packet configuration unit 400 configures a first group of packets from the moving image block signal, a second group of packets from the difference block signal, and a third group of packets from the determination result. Each packet is provided with an area indicating priority in preparation for discarding a packet which occurs at the time of network congestion, and at the time of congestion, a packet having a lower priority is discarded. When the difference block signal is lost, the degree of image deterioration is small compared to the pixel block signal and the determination result. Therefore, packets of the first group and packets of the third group are given high priority to be priority packets, and packets of the second group are given low priority to be non-priority packets and then transferred. Further, as described above, the determination on the pixel block is not made with the image signal at the same position in the previous frame, but with the signal in the frame to which the pixel block signal was transferred in the past. For this reason, even if the difference block signal is lost due to the packet discard and the added block of the current frame cannot be restored, the effect does not reach the next frame and thereafter.

FIG. 5 shows the configuration of the receiving apparatus. In the figure, reference numeral 200 denotes an image decoding unit; 201, a frame memory;
02 is a difference decoding unit, 203 is an addition unit, 204 is a determination table, and 205 is a synthesis unit, which is the same as that in FIG. In the figure, a packet classification unit 500 and a packet discard detection unit 501 are added to this. The operation of the moving picture signal receiving apparatus configured as described above will be described below.
The packet classifying unit 500 classifies the arriving packets into a first group,
The packets are classified into a second group and a third group. When detecting the discard of the second group of packets, the packet discard detection unit 501 replaces the discarded difference block signal with “0” and outputs it. In this case, like the pixel block without information transfer, the difference-added moving image block is supplemented with the image signal at the same position in the frame memory as described above. A signal constitutes a non-priority packet, and when the non-priority packet is discarded, it is reproduced in the same manner as a still image block, so that deterioration can be kept to a minimum.

[0021]

As described above, the present invention can minimize an unnecessary increase in the amount of transmission information for a moving image signal having a lot of noise.

Further, in the moving image transmission by the ATM, the generation of unnecessary cells can be suppressed, and the deterioration of the image quality when the cells are discarded can be minimized.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a moving image signal transmission circuit according to a first embodiment of the present invention;

FIG. 2 is a configuration diagram of a moving image signal receiving circuit according to a first embodiment of the present invention;

FIG. 3 is an explanatory diagram of a determination method for a pixel block according to the present invention.

FIG. 4 is a configuration diagram of a moving image signal transmitting apparatus according to a second embodiment of the present invention;

FIG. 5 is a configuration diagram of a moving image signal receiving apparatus according to a second embodiment of the present invention;

FIG. 6 is a configuration diagram of a transmission circuit of a conventional moving image signal transmission device.

FIG. 7 is a configuration diagram of a receiving circuit of a conventional moving image signal transmission device.

FIG. 8 is an explanatory diagram when calculating a difference value of a pixel block;

FIG. 9 is an explanatory diagram of a conventional determination method for a pixel block.

[Explanation of symbols]

 REFERENCE SIGNS LIST 100 intra-frame encoding unit 101 frame memory 102 moving image detection unit 103 difference block configuration unit 104 difference value calculation unit 105 determination unit 106 difference encoding unit 107 pixel block transfer unit 108 difference block transfer unit 109 determination result transfer unit 200 image decoding unit Reference Signs List 201 Frame memory 202 Difference decoding unit 203 Addition unit 204 Decision table 205 Combining unit 400 Packet configuration unit 500 Packet classification unit 501 Packet discard detection unit 600 Intra-frame encoding unit 601 Frame memory 602 Moving image detection unit 603 Difference block configuration unit 604 Difference value Calculation unit 605 Judgment unit 606 Pixel block transfer unit 607 Judgment result transfer unit 700 Image decoding unit 701 Frame memory 702 Judgment table 703 Synthesis unit

Claims (4)

(57) [Claims] An intra-frame encoding unit for intra-frame encoding a pixel block including a plurality of pixels of a current frame, a frame memory for recording only a pixel block signal transferred up to a previous frame, the pixel block and the frame A difference block forming unit that forms a block (hereinafter, referred to as a difference block) including a difference between pixels corresponding to an image signal at the same position in the memory, and an amplitude of the difference block (hereinafter, referred to as a difference value) ) For calculating a difference value,
A predetermined first threshold and a second greater than said first threshold
A determination unit that outputs a comparison result between the threshold value and the difference value,
A difference encoding unit that encodes the difference block, a pixel block transfer unit that transfers a pixel block signal of a current frame having a difference value equal to or greater than the second threshold value according to a result of the determination by the determination unit, A moving image, comprising: a difference block transfer unit that transfers a difference block signal having a difference value smaller than the second threshold value and equal to or greater than the first threshold value; and a determination result transfer unit that transfers the determination result. Image signal transmission circuit. 2. An image decoding unit for decoding a received pixel block signal, a frame memory for recording the pixel block signal, a difference decoding unit for decoding a received difference block signal, the difference block signal and the frame memory And a block to which a pixel block signal is transferred in accordance with a received determination result. A synthesizing unit for displaying a pixel block signal, displaying the addition block signal for a block to which a difference block signal has been transferred, and displaying an image signal at the same position in the frame memory for a block without information transfer. A moving picture signal receiving circuit characterized by the above-mentioned. 3. The transmission circuit according to claim 1, wherein a first group of packets is formed from the pixel block signals, a second group of packets is formed from the differential block signals, and a third group is formed from the determination result. A packet forming unit which configures a packet of the second group and gives a low priority to the transfer of the second group of packets whose loss is low when the network is congested by a packet priority display area. A transmitting apparatus for a moving image signal, comprising: 4. A receiving circuit according to claim 2, a packet classifying unit for classifying the packet according to the type of the received packet, and monitoring a loss of the packet and a predetermined value when the packet of the second group is lost. A moving image signal receiving apparatus, comprising: a packet discard detection unit that outputs a differential block signal.