JPH1093979A - Image communication system and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image communication system which prevents a code amount from being increased by maintaining a reference image in memory even if there are a signal error from a receiving side to a sending side and the delay of signal arrival. SOLUTION: An image signal receiving part 608 on an image receiving side detects the existence of an error of received image data and notifies the result to a signal receiving part 602 on an image sending side through a signal sending part 609. The part 602 notifies the existence or nonexistence of an error that is notified to a frame memory changing part 605. The part 605 performs write control so that one reference image sent from an encoding part 601 may surely remain in a frame memory part 603 when image data is correctly received according to the content of a signal from the part 602, and a reference image deciding part 604 selects an reference image in the part 603 and sends it to the part 601. The reference image number that is selected at the time is sent to the image receiving side through a reference image notifying part 606 for deciding a reference image at the time of decoding.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a radio transmission line
TECHNICAL FIELD The present invention relates to an image communication system and method for transmitting an image using a transmission path, such as N, in which a transmission error may significantly occur.

[0002]

2. Description of the Related Art In a general-purpose image encoding method represented by MPEG or the like, a technique for compressing the amount of information of a moving image is as follows.
A method of taking a difference between frames is general. In this inter-frame prediction method (hereinafter referred to as inter-frame coding), a current frame is predicted from a previous frame, and the prediction difference is transmitted. However, if an error is superimposed on one frame on the transmission line and data is erroneous, a frame is created on the receiving side using erroneous data, so that a frame containing an error is generated. Further, since the next frame is predicted based on the frame containing the error, there is a problem that the error propagates to subsequent frames.

[0003] A situation in which an error is superimposed on image data occurs when there is a reading error from a storage medium such as a CD-ROM, or when there is a transmission error in the case of passing through a communication path. In particular, transmission errors are remarkably large through a wireless transmission path. As a first conventional example of the image communication method on such an erroneous transmission path, when an error is detected on the receiving side, the error is notified to the image transmitting side, and the image transmitting side receives the error and performs inter-frame prediction. An intra-frame encoding method (generally, also referred to as INTRA encoding), which performs encoding without using, will be described.

FIG. 18 shows a general image coding method combining motion compensation and discrete cosine transform (DCT).
An example of the configuration when the first conventional example is combined is shown.
The difference between the input image and the reference image is calculated by a difference unit 101, and DCT is performed by a DCT unit 102. The DCT coefficient of the processing result is quantized by a quantizer (Q) of 103, and 1
09 is temporarily stored in the buffer (buff.). The stored data is stored in the 110 error control unit (error co.
nt. ) And transmitted via the transmission line 120. The signal quantized by the quantizer 103 is inversely quantized by the inverse quantizer (Q-1) 104, and then
Inverse DCT is performed in an inverse DCT unit (IDCT) of 105,
Further, the same reference image signal as the signal subtracted by the difference unit 101 is added by the addition unit 106 and stored in the frame memory (FM) 107. The frame difference control unit 108 reads out the encoded image of the previous frame stored in the frame memory 107, and sets 1 as a reference image signal.
01 to the difference section. When the error control unit 110 is notified of the error detection from the receiving side, the frame difference control unit 10
8, the input of the reference image signal to the difference unit 101 is canceled, and the mode is switched to the intra-frame encoding method.

[0005] The information transmitted via the transmission line 120 is
The error detection unit (error det) 111 of the image receiving side
(Elector), it is determined whether there is a reception error, and if there is no reception error, it is inversely quantized by the inverse quantization unit (Q ⁻¹ ) of 112. Then, the inverse DCT unit 113 (IDC
T), an inverse DCT is performed.
5 is added as a reference image signal and output to a monitor or the like, and is also stored in the frame memory 115. If a reception error is detected by the error detection unit 111, the image transmission side is notified of the detection of the error.

[0006] As a second conventional example of an image communication method on an erroneous transmission path, a method for preventing the propagation of an error by changing a reference image when calculating an inter-frame difference during encoding will be described. That is, if an error is detected in a frame received on the decoding side, the error is detected and the frame number or the latest frame number correctly received / decoded is sent to the encoding side. Then, the reference image of the next frame to be encoded is changed not to the frame in which the error was detected but to the last correctly received frame.

FIG. 19 shows a general image coding method combining motion compensation and discrete cosine transform (DCT).
An example in which the second conventional example is combined will be described. The elements 201 to 215 and 220 in FIG. 19 correspond to the elements 101 to 115 and 120 in FIG. The difference from the first conventional example is that reference numerals 207 and 215
As shown in FIG.
And 218, and the presence of frame memory selectors 217 and 219.

First, the configuration and operation of the image transmitting side will be described. The difference between the input image and the reference image is calculated in a difference unit 201, and DCT is performed in a DCT unit 202. The DCT coefficient of the processing result is quantized by the quantizer 203, and 209
Is temporarily stored in the buffer. The stored data is 21
0 under the control of the error control unit, and
20. At this time, the error control unit 210
Also transmits the coded frame number and the number of the frame used as the reference image. The signal quantized by the quantizer 203 is inversely quantized by the inverse quantizer 204,
Inverse DCT is performed in the inverse DCT unit 205. And 2
In the adding unit 06, the same reference image signal as the signal subtracted by the difference unit 201 is added to the signal subjected to the inverse DCT, and the added signal is sent to the frame memory writing unit 216.

[0009] The frame memory writing unit 216 converts the transmitted data (frame) into the FM1 →
.., FMn → FM1 →... In the frame memory 207, and the frame memory selection unit 2 determines which frame memory has been written and in what frame.
Notify 17. The frame memory selection unit 217 stores the correspondence between the frame memory and the frame number notified from the frame memory writing unit 216, and also outputs a signal from the FM1 to F
One is selected from the frame memories 207 up to Mn, the frames stored therein are read, and sent to the frame difference control unit 208. The frame difference control unit 208 sends the read contents of the frame memory to the difference unit 201 as a reference image signal.

In the error control unit 210, when an error is detected from the error detection unit 211 on the image receiving side via the transmission path 220 and the frame number in which the error is detected is notified, the frame on which the error is detected on the image receiving side is sent. The number is notified to the frame memory selection unit 217. Frame memory selection unit 21
7 reads the frame with the newest number before the notified frame number from the frame memory 207 and sends it to the frame difference control unit 208. Further, the read frame number is notified to the error control unit 210 on the image transmission side. The error control unit 210 notifies the image receiving side of the notified frame number as the frame number of the reference image together with the frame number being encoded.

In the frame memory selecting section 217, if a frame with a number earlier than the frame number notified from the error control section 210 does not exist in the frame memory 207, the difference section 201 in the frame difference control section 208
Cancels the input of the reference image signal to, and switches to intra-frame encoding. In addition, the error control unit 210 repeats the signal indicating the frame number in which the error has occurred, from the error detection unit 211 on the receiving side (until the image receiving unit changes the reference image and receives the encoded image). , Signals that are repeatedly transmitted).

Next, the configuration and operation of the image receiving side will be described. Information (data) transmitted via the transmission path 220
In the error detection unit 211, it is determined whether there is no reception error. If there is no reception error, the signal is inversely quantized by the inverse quantization unit 212 and then inverse DCT is performed by the inverse DCT unit 213. In addition, the error detection unit 211 includes an error control unit 210
Notifies the frame memory selection unit 219 of the frame number used as the reference image signal by the current coded image notified from the frame memory selection unit 219, reads out the frame of the frame number from the frame memory 215, and sends it to the addition unit 214. The adding unit 214 adds the sent reference image signal to the received signal,
The data is output to a monitor or the like, and sent to a frame memory writing unit 218.

The frame memory writing section 218 operates in exactly the same manner as the frame memory writing section 216 on the image transmission side, that is, transmits the transmitted data (frame) to the FM1.
.., FMn → FM1 →... Are stored in the frame memory 215 in this order, and the frame memory selection unit 219 is notified of which frame memory was written with which frame. 219 is a frame memory selection unit,
The correspondence between the frame memory and the frame number notified from the frame memory writing unit 218 is stored, and one of the frame memories from FM1 to FMn is selected and accumulated by a signal from the error detection unit 211. The frame is read and sent to the adder 214.

When a reception error is detected, the error detection section 211 informs the image transmission side that the error has been detected,
The frame number in which an error is detected or the latest frame number correctly received / decoded is notified. Further, the error detection unit 211 stores the frame number in which the error is detected, and encodes the data corresponding to the number preceding the frame number as a reference image, or the image data encoded in the frame. Until the data is received, the stored frame number is continuously notified to the frame memory selection unit 219.

FIG. 20 is a diagram for explaining an operation example of the second conventional example. In particular, FIG. 20 is a diagram showing an operation example in the case where the number of frame memories 207 and 215 is 4, in a time series. In the figure, reference numeral 301 denotes the number of a frame that is being encoded on the image transmission side, and 303 denotes the number at the time when the encoding of one frame ends and the encoding of the next frame starts. Frame memory (FM1 to FM4) 2
07 is indicated by a frame number. Also, 30
Reference numeral 2 denotes a frame number for which decoding is being performed on the image receiving side, and reference numeral 304 denotes the contents of the frame memory 215 at the time when decoding of one frame ends and decoding of the next frame starts. Are similarly indicated by frame numbers. The reason why the processing frame number 301 on the encoding side and the processing frame number 302 on the decoding side are different is that there is a time required for transmission. In addition, as for the numbers attached to the arrows (solid lines) indicating the image data in the figure, for example, “9/8” indicates that the frame number 9 has been encoded using the frame of the frame number 8 as a reference image (image) data. Is represented. Actually, the image data has a large data amount and flows continuously from the transmission side to the reception side. However, only the last part of the image data is represented by an arrow (solid line) for easy understanding of the drawing.

The operation example shown in FIG. 20 shows a case where an error occurs in the data of frame number 10. When detecting the error, the error detection unit 211 sends a Nack signal (see 305 in the figure) including the frame number in which the error is detected. Further, the error detection unit 211 stores the frame number 10 in which the error has occurred. The Nack signal (10N) is received by the error control unit 210 while the image transmission side is processing the frame number 12, and the error control unit 210 sends a frame number 10 The newest number 9 before is selected, and control is performed so that the next frame number 13 is encoded using the corresponding frame as a reference image. At the same time, the image receiving side is notified that the frame 9 has been used as the reference image (see 306 in the figure). Upon receiving this signal, the error detection unit 211 instructs the frame memory selection unit 219 to select and read the frame number 9 as a reference image. In addition, the error detection unit 211 can determine whether the image data of the frame numbers 11 and 12 contains an error even if the image data itself does not include an error.
Since the reference image is a frame having a number larger than 10, the Nack signal (10N) including the frame number 10 is continuously transmitted.

In the case of this operation example, the error 10
The error propagates to the eleventh frame, the eleventh frame that uses it as a reference image, and the twelfth frame that uses the eleventh frame as a reference image, but the thirteenth frame that changes the reference image Does not propagate the error. As described above, the second conventional example has an advantage that even if an error occurs, the propagation of the error can be stopped without switching to the intra-frame coding.

[0018]

In the first prior art, the amount of data required for transmission of one frame is significantly increased by performing intra-frame encoding as compared with the case where there is no error. As a result, there is a problem that the number of transmission frames decreases as well as the quality of the decoded image deteriorates due to the increase in the number of quantization steps. In addition, since the amount of data is large, the probability that the intra-frame encoded data contains an error again increases, and there is a problem that a vicious cycle of repeatedly performing intra-frame encoding is required.

In the second conventional example, if the Nack signal sent from the image receiving side to the image transmitting side is delayed for some reason, it takes time until the image transmitting side changes the reference image. Therefore, when an attempt is made to change, a situation occurs in which an appropriate reference image does not already exist in the frame memory. In such a situation, when the Nack signal includes an error in the middle and cannot be recognized on the image transmitting side, when the time required for transmission is long, when the time required for transmission fluctuates, and the amount of data after encoding is further reduced. Occurs when not constant. In such a case, even in the second conventional example, the propagation of the error can be stopped only by performing the intra-frame coding, and the same problem as the first conventional example has occurred.

FIG. 21 is a diagram showing an operation example when an error occurs in a signal from the image receiving side to the image transmitting side and the image transmitting side cannot recognize the signal under the same conditions as the case shown in FIG. is there. In this operation example, reference numeral 401 denotes the number of a frame that is being encoded on the image transmitting side, and 403 denotes a point in time when encoding of one frame ends and encoding of the next frame starts. Of the frame memory 207 are indicated by frame numbers. Also, 40
2 indicates the number of the frame being decoded on the receiving side, 404 indicates that the decoding of one frame has been completed,
The contents of the frame memory 215 at the time when the decoding of the next frame is started are similarly indicated by frame numbers.
The difference between the processing frame number 401 on the encoding side and the processing frame number 402 on the decoding side is because there is a time required for transmission.

This operation example shows a case where an error has occurred in the data of the same frame number 10 as in the case of FIG. When detecting the error, the error detection unit 211 sends a Nack signal including the frame number in which the error is detected (see 405 in the figure). Here, an error occurred in the Nack signal, and the error control unit 210 could not recognize the error.
The image transmitting side encodes the frame number 13 using the frame of the number 12 as a reference image. On the image receiving side, next, the data of frame number 11 is received. Since this is encoded using the frame number 10 in which the error is detected as the reference image, a Nack signal including the frame number 10 is transmitted ( 406 in the figure). This Nack signal (10
N) is received by the error control unit 210 while the transmission side is processing the frame number 13, and the error control unit 210
Attempts to encode the frame number 14 by causing the frame memory selection unit 217 to select the newest number before the frame number 10 in which the error is detected. At this point,
Frames prior to frame number 10 are stored in frame memory 2
07 does not exist. Therefore, the intra-frame encoding has to be performed for the frame with the frame number 14 (see 407 in the figure).

Next, FIG. 22 is a diagram showing an operation example when the time required for transmission is long under the same conditions as the case shown in FIG. As in the case of FIG. 20, an error occurs in the image data of frame number 10 and N
The ack signal (10N) is received by the error control unit 210, but since the arrival of the signal is delayed (see 505 in the figure), the next frame to be coded on the image transmitting side is shifted to frame number 15. When the frame number 15 is encoded, the frames before the frame number 10 do not exist in the frame memory 207. Therefore, the intra-frame encoding has to be performed for the frame of frame number 15.

The present invention has been made in view of the above problems, and eliminates the disadvantages of the second conventional example.
The reference image to be changed is stored in the frame memory even if an error occurs in the signal notifying the reception error from the image receiving side to the image transmitting side, or when the arrival of the signal from the image receiving side to the image transmitting side is delayed. It is possible to prevent the situation that it does not exist in the frame, and to switch to intra-frame coding to degrade the image quality, or to switch to intra-frame coding, the data amount increases, and errors are included again. It is an object of the present invention to provide an image communication system and a method that do not repeat the above.

[0024]

In order to solve the above-mentioned problems, the present invention provides an image transmitting apparatus comprising the steps of: encoding an input image by an inter-frame encoding method in which compression is performed using a difference between frames; An encoding unit that outputs encoded image data, a signal receiving unit that receives, from the image receiving side, a signal that notifies the presence or absence of an error of the encoded image data received at the image receiving side and the image number thereof, A memory unit having a buffer for holding a plurality of encoded image data output from the encoding unit as reference images used for encoding by the inter-frame encoding method; and at least one image in the memory unit Is stored, based on the content indicated by the signal received by the signal receiving unit, a reference image for selecting a reference image to be used by the encoding unit from among the images stored in the memory unit. An image determining unit; a reference image notifying unit that notifies the image receiving side of the number of the reference image used by the encoding unit; and an image that notifies the image number of encoded image data output by the encoding unit. An image receiving side, on the other hand, on the image receiving side, an image which receives the encoded image data output by the encoding section on the image transmitting side, detects whether there is an error in the image data, and outputs the image data A data receiving unit, an image number receiving unit that receives an image number of the encoded image data notified from the image number notifying unit on the image transmitting side, and an image number receiving unit that receives the encoded image data received by the image number receiving unit. A signal transmitting unit that transmits to the image transmitting side a signal that notifies the image number and an error regarding the image data detected by the image data receiving unit; and an encoded image received by the image data receiving unit. Day And a memory unit having a buffer for holding a plurality of decoded image data output from the decoding unit as reference images used for the decoding. A reference image number receiving unit that receives a reference image number at the time of encoding notified from the reference image notifying unit on the image transmitting side; andwhere at least one image is stored in the memory unit, According to the reference image number received by the reference image number receiving unit, from among the images stored in the memory unit,
An image communication system having a reference image determination unit that selects a reference image used by the decoding unit, based on the content indicated by the signal received by the signal reception unit on the image transmission side,
The image processing apparatus further includes a memory changing unit configured to control writing of the encoded image data output from the encoding unit to the memory unit,
The control provides an image communication system including determining whether to write new data, determining a write position in the memory unit, and erasing data already written in the memory unit.

Further, according to the present invention, there is provided an image transmitting side comprising: a step of encoding an input image by an inter-frame encoding method for performing compression using a difference between frames, and outputting encoded image data; Receiving, from the image receiving side, a signal notifying the presence or absence of an error in the encoded image data received on the side, and the image number thereof; and the outputting the encoded image data by the inter-frame encoding method. When at least one image is stored in the memory unit having a buffer for holding a plurality of reference images used for encoding, the image is stored in the memory unit based on the content indicated by the signal received from the image receiving side. Selecting a reference image to be used in the encoding from among the images, and notifying the image receiving side of the number of the reference image used in the encoding, Notifying the image number of the output encoded image data, while the image receiving side receives the encoded image data output from the image transmitting side, and if there is an error in the image data Detecting and outputting; the step of receiving the image number of the encoded image data notified from the image transmitting side; the image number of the received encoded image data;
Transmitting a signal notifying the presence or absence of the detected error with respect to the image data to the image transmitting side; Decoding the received encoded image data, and outputting decoded image data; A step of receiving a reference image number at the time of encoding notified from the image transmitting side; and a memory unit having a buffer for holding a plurality of the output decoded image data as reference images used for the decoding. Selecting at least one reference image to be used in the decoding from among the images stored in the memory unit in accordance with the received reference image number. Controlling the writing of the output encoded image data to the memory unit based on the content indicated by the signal received by the image transmitting side. Further comprising, said control provides determination of whether new data is written, the determination of the writing position in the memory unit, an image communication method is intended to include already erased the written data in the memory unit.

According to these systems and methods, the memory unit on the transmitting side always stores one reference image at the time of encoding that was correctly received last on the image receiving side. Is notified, the situation where the correct reference image is lost can be avoided.

Here, due to the writing control performed by the memory changing means, a reference image older than the reference image corresponding to the encoded image data that was last correctly received on the image receiving side, or a reception error was notified from the image receiving side. It is preferable to delete the reference image corresponding to the encoded image data from the memory unit in order to reduce the buffer area (the number of frame memories, etc.) of the memory unit. Note that the image processing unit in the present invention is typically a frame unit, but in addition, a processing unit is a unit of a small area of an image forming a frame or a group of pixels forming the small area. You can also.

The following is an embodiment of the present invention. The image transmitting side determines whether or not the signal receiving unit has received a signal from the image receiving side within a preset time, and when it is determined that the signal has not been received, the memory changing unit determines whether the signal has been received. If the timer control means further includes a timer means for notifying that a signal from the image receiving side to the image transmitting side, particularly a signal for notifying a reception error, cannot be received due to the writing control of the memory changing means. Alternatively, even when the arrival of a signal is delayed due to an increase in transmission delay, processing delay on the image receiving side, or the like, the reference image is quickly changed.

The image transmitting side determines whether or not the signal receiving section has received a signal from the image receiving side while the encoding section encodes a predetermined amount of images. However, if it is determined that it has not been received, if it further has an image counting means for notifying the memory changing means to that effect, by the writing control of the memory changing means, there is a variation in the coding amount of the image, In addition, when the signal from the image receiving side, especially the signal notifying the receiving error to the image transmitting side cannot be received due to an error, or the arrival of the signal is delayed due to an increase in transmission delay, a processing delay on the image receiving side, or the like. In such a case, the reference image is immediately changed.

Further, the image transmitting side monitors the contents of the memory section of the transmitting side, and when no reference image usable for the inter-frame encoding is stored in the memory section, the encoding section Further includes a memory holding status notifying unit for notifying the fact, and when the coding unit receives the notification from the memory holding status notifying unit, performs the coding of the next image by the intra-frame coding method. You may do it.

Further, when the encoding unit performs the encoding by using either the inter-frame encoding method or the intra-frame encoding method and performs the encoding by any one of the encoding methods, When the unit has performed intra-frame encoding, it further includes an encoding status notifying unit that notifies the memory changing unit of the fact, and the intra-frame encoding is performed by the write control of the memory changing unit. In this case, unnecessary data in the memory may be deleted in consideration of the effect of preventing the error from being propagated by the encoding.

Further, the image receiving side further includes a memory information notifying unit for notifying the image transmitting side of information of the image stored in the memory unit of the receiving side, and the image transmitting side includes:
Further provided is a memory information receiving unit for receiving the image information notified from the memory information notifying unit and notifying the content to a reference image determining unit on the transmitting side, wherein the reference image determining unit on the image transmitting side includes the reference image determining unit. The selection of the image may be performed based on the content indicated by the signal received by the signal receiving unit and the information notified from the memory information receiving unit. This prevents the reference image determination unit on the image transmission side from selecting an image that does not exist in the memory unit on the image reception side as a reference image.

The image receiving side receives information on the presence / absence of an error detected by the image data receiving unit. If there is an error, the output from the decoding unit is sent to the memory unit on the receiving side. Alternatively, a switching unit may be further provided for controlling the output from the decoding unit to be sent to the memory unit when there is no error. This makes it possible to realize a system that intentionally uses an error image while retaining only error-free image data inside the system.

The effects obtained by these application examples are as follows.
The same can be obtained by executing the method corresponding to the operation of each mode. In addition, the present invention provides a transmitting device having each component on the image transmitting side, a receiving device having each component on the image receiving side, and a method corresponding to each of the devices in the above-described system. A storage medium storing a computer program to be executed is provided.

[0035]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a block diagram showing the overall configuration of the first embodiment according to the present invention. First, the configuration and operation of the image transmitting side 1101 will be described. An image input from a camera or the like is encoded by an encoding unit 601 using an image encoding method for performing compression using a difference between frames, and is transmitted from the encoding unit 601 to a frame memory changing unit 605. Frame memory change unit 6
05 indicates whether or not the reference image data from the encoding unit 601 is to be written into the frame memory unit 603 according to a signal from the signal receiving unit 602 that receives Ack and Nack signals from the image receiving side described later. Then, where to write in a buffer (frame memory) that can hold a plurality of pieces, or when erasing, which part or all of the frame memory is to be erased is determined. Further, the frame number notified from the frame number notification unit 607 is made to correspond to the reference image data from the encoding unit 601 (where the writing is performed). An example of a specific determination method will be described later.

The reference image determining unit 604 determines what the reference image of the next frame to be encoded is based on the signal from the frame memory changing unit 605, reads out the frame from the frame memory unit 603, and sends it to the encoding unit 601. send. An example of a specific determination method will be described later. Also, the reference image notification unit 606
, The number of the reference image used for encoding is notified to the image receiving side. Further, the image receiving side is notified of the coded frame number via the frame number notifying unit 607.

Next, the configuration and operation of the image receiving side 1201 will be described. The image signal receiving unit 608 receives the encoded data from the image transmitting side, detects the presence or absence of an error in the encoded data, and if an error is detected, the signal transmitting unit 6
09 is notified. The signal transmitting unit 609 reads the frame number of the frame in which the error has occurred from the frame number receiving unit 610 that receives the frame number notified from the frame number notifying unit 607 on the image transmitting side, and outputs a Nack signal indicating that an error has been detected. To the image transmitting side together with the frame number.

If no error is detected, the image signal receiving section 608 notifies the signal transmitting section 609 of the error. The signal transmitting unit 609 reads the frame number at that time from the frame number receiving unit 610, and notifies the image transmitting side of an Ack signal indicating that no error has been detected, together with the frame number. Otherwise,
The image sending side is notified that the error continues.

The encoded data received by the image signal receiving unit 608 is decoded by the decoding unit 613. If decoding is possible without error, the reference image determination unit 611 determines, via the reference image number reception unit 612, what the reference image number of the encoded data notified from the reference image notification unit 606 on the image transmission side is. The data corresponding to the number is read from the frame memory unit 614 and sent to the decoding unit 613.

The decoding unit 613 decodes the image data without error, outputs the image data to a monitor or the like, and writes the image data in the frame memory unit 614. If no error-free image data is obtained, the output to a monitor or the like or the frame memory 61
4 is not written. Frame memory unit 614
Reads the frame number from the frame number receiving unit,
A correspondence with the decoded image written by the decoding unit is given. Further, the frame memory unit 614 includes a reference image determination unit 611.
, The newly written frame number and its position (in the memory) are notified.

The details of each unit in this embodiment are the same as the configuration of FIG. 19 used in the description of the second conventional example, except for the frame memory change unit 605 on the image transmission side. However, the operation of a portion corresponding to the error control unit 210 and the error detection unit 211 in FIG. 19 is different from the second conventional example. The error detection unit 211 described in the second conventional example notifies the error control unit 210 only when an error is detected, but the image signal reception unit 60 on the image reception side according to the present embodiment.
8 notifies the signal receiving unit 602 of the image transmitting side of the Ack signal including the correctly received frame number even when there is no error. Similarly, the error control unit 210 controls the error detection unit 21
1 is notified to the frame memory selecting unit 219 only when an error is notified, but the signal receiving unit 602 of the present invention can also perform the frame memory changing unit even when notified of reception without error. 605 is notified.

Next, the operation of the frame memory changing unit 605 which is a feature of the present invention will be described in more detail. 2 and 3 are flowcharts showing the operation flow of the frame memory changing unit 605. Frame memory change unit 605
Monitors the input from the signal receiving unit 602 and the input from the encoding unit 601 (701, 702), and operates according to each input. The specific operation will be described below together with an operation example of the system. Note that FIG. 2 shows that the processing flow continues in FIG. 3 and FIG. 3 shows that the processing flow continues in FIG.

FIG. 4 is a diagram showing an operation example of this embodiment in chronological order. The format of the figure and the meaning of each code are shown in FIG.
It is the same as 0, and the operation example in the case where the number of internal frame memories (buffers) of the frame memory units 603 and 614 is 4 is shown in time series. Reference numeral 801 denotes the number of a frame that is being encoded on the image transmission side.
The frame memory unit 603 at the time when encoding of one frame ends and encoding of the next frame starts.
Reference buffer (frame memory (FM1 to FM4))
Are indicated by frame numbers. 802 is
Reference numeral 804 denotes a frame number of a frame being decoded on the image receiving side. Reference numeral 804 denotes a reference buffer of the frame memory 614 at the time when decoding of one frame ends and decoding of the next frame starts. (Frame memory (FM1
The contents of FM4)) are similarly indicated by frame numbers. The difference between the processing frame number 801 on the encoding side and the processing frame number 802 on the decoding side is because there is a time required for transmission.

As for the numeral attached to the arrow (solid line) indicating the image data in the figure, for example, “9/8” is obtained by encoding the frame number 9 using the frame of the frame number 8 as a reference image ( Image) data. However, the notation of the reference buffer is a stack type memory in which the latest frame exists in the FM4 instead of overwriting an old frame as shown in FIG. Described assuming management.

Ac including frame number 9 from the image receiving side
The signal receiving unit 60 on the image transmitting side that has received the k signal (9A)
2 notifies this to the frame memory change unit 605.
The frame memory change unit 605 determines in step 703 of FIG.
According to the processing of No. 7, a frame older than No. 9
Eight frames are deleted from the frame memory unit 603.
As a result, the contents of the frame memory 603 are numbered 9 and 1,
0 frame. Next, in accordance with the process of step 704 in FIG. 3, the reference image determination unit 604 is instructed to use the latest frame in the frame memory unit 603 as a reference image.

Next, when the encoding of the frame of the number 11 is completed, the image data of the frame of the number 11 is encoded.
01 to the frame memory changing unit 605. The frame memory changing unit 605 writes the image data of the frame of the number 11 into the frame memory unit 603 according to the process of step 705 in FIG. Thereafter, the encoding unit starts encoding the frame of the number 12, and the contents of the frame memory unit 603 at that time are indicated by reference numeral 805 in FIG.
"9, 10, 11" as shown by. Also,
The reference image determination unit 604 instructed to use the latest frame in the frame memory unit 603 as the reference image as the reference image replaces the frame 11, which is the latest frame at this time, with the encoding of the frame 12. Works to be used as a reference image.

Next, it is assumed that the Nack signal (10N) of the frame of the number 10 is received during the encoding of the frame of the number 12. The signal receiving unit 602 notifies the frame memory changing unit 605 of this. Frame memory change unit 60
5 searches for a frame using a frame other than the immediately preceding frame as a reference image in accordance with the process of step 706 in FIG. 3, but also uses the immediately preceding frame as a reference image for each of the frames 9, 10, and 11 in the frame memory. Therefore, according to the processing of step 707, the frames 10 and 11 following the number 10 written in the Nack signal are used.
Erase from frame memory.

Further, by the processing of step 708, the frame of the number 12 currently being encoded is stored in the frame memory unit 60.
Do not write to 3. As shown by reference numeral 806, the inside of the frame memory at the end of the encoding of the frame of the number 12 is only “9”. Next, frame 1
3 is started. At that time, the frame 9 which is the only latest frame in the frame memory is used as the reference image by the processing in step 704.

Next, the signal receiving unit 602, which has received the Nack signal (10N) of the frame 10 again during the encoding of the frame 13, notifies the frame memory changing unit 605 of the reception. The frame memory changing unit 605 searches for a frame that uses a frame other than the immediately preceding frame as a reference image according to the process of step 706 in FIG. In this case, since the frame 13 uses the frame 9 as a reference image instead of the immediately preceding frame, the frame 13 is used in accordance with the processing of the step 709 in FIG. The frame 14 is encoded using the reference image 13 as a reference image.

During encoding of the next frame 14, frame 1
The operation when a Nack signal (10N) of 0 is received is as follows.
Same as above. Finally, the signal receiving unit 602, which has received the Ack signal (13A) of the frame 13 during the encoding of the frame 15, notifies the frame memory changing unit 605 of the reception. The frame memory change unit 605 determines in step 703
, The frame number 13 written in the Ack signal
The older frame 9 is deleted from the frame memory. Encoding of the frame 16 is performed using the frame 15 as a reference image in accordance with the process of step 704.

FIG. 5 shows motion compensation and discrete cosine transform (D
This is a modified embodiment example in which a general image coding method combined with CT) is combined with the above embodiment example. In the above-described embodiment, an example in which an image is processed in a frame unit has been described. However, the image processing unit is not limited to the frame unit, but may be a GOB (Group of Block: a small area of an image forming a frame) or an MB (Macro). Blo
It is also possible to use ck: a unit of a group of pixels (Cr, Cb, Y) constituting the GOB.

Therefore, in this modified embodiment, regarding the names of the respective parts in FIG. 1, "image numbers" are employed in place of "frame numbers", and a plurality of image memories (M1, M2) are employed in place of "frame memories". ,... M3), and a “memory changing unit” is used instead of the “frame memory changing unit”. However, in the modified embodiment of FIG. 5, the same components as those in FIG. 1 are denoted by the same reference numerals as those in FIG. It should be noted that a difference unit, a discrete cosine transform unit (DCT), a quantizer (Q),
The parts corresponding to the inverse quantizer (Q ^-1 ), the inverse DCT unit (IDCT), the adder, and the frame difference controller are shown in FIG.
Is described as an encoding unit 601. In addition, the inverse quantizer (Q ^-1 ) and the inverse DCT unit (I
DCT) and a portion corresponding to the addition unit are described as a decoding unit 613 in FIG. In FIG. 5, the image memory (M1, M2,... M3) and the memory writing unit (614a) are described together as a memory 614.

When the processing unit of an image is not a frame but a smaller unit, it is necessary to close the motion compensation range within the small unit.

According to the above-described first embodiment, the reference image is changed in the frame memory in contrast to the conventional technology in which the inter-frame coding is continued to prevent error propagation by changing the reference image. Even in the case where it does not exist and the intra-frame encoding is forced, the reference image of the last correctly received frame can be held in the frame memory with the same number of frame memories, thereby preventing image quality deterioration. be able to. Therefore, even if the conventional technology does not work well, it can be operated without any problem.

Next, a second embodiment according to the present invention will be described. FIG. 6 is a block diagram showing the overall configuration of the second embodiment. In this figure, a timer unit 615 having a built-in timer is added as compared with FIG. 1 which is a block diagram showing the entire configuration of the first embodiment. The other components have the same configuration as in the first embodiment, and thus the same components as those in FIG. 1 are denoted by the same reference numerals.

FIG. 7 is an operation flow showing the operation of the timer unit 615. In the operation according to the present embodiment, in addition to the above-described operations performed by the respective units in FIG.
Ack, Nack from the signal transmission unit 609 on the image receiving side
When the signal is received, it notifies the timer unit 615 of the signal. The timer section 615 resets the timer with this signal and repeats restarting. When this signal is not notified and the timer expires, the timer section 615 notifies the frame memory change section 605 of the expiration.

FIGS. 8 and 9 show an operation flow of the frame memory changing unit 605 in the second embodiment. As shown in the flow, in addition to the operation shown in the first embodiment, an operation of changing the reference image is also performed by a signal from the timer unit 615 (step C01). FIG.
9 shows that the processing flow continues in FIG. 9, FIG. 9 shows in FIG. 8, and FIG. 8 shows in FIG. 9. FIG. 10 is a diagram showing an operation example of the second embodiment in chronological order. The meanings of the reference numerals are the same as those in FIG.

The timer section 615 receives the Ack signal or N
reset the built-in timer by receiving the ack signal,
Repeat the restart. In this operation example, as in FIG.
An example in which an error has occurred in the image data of the frame is shown. Furthermore, an error occurs in the Nack signal corresponding to the Nack signal, and the signal is lost (it cannot be recognized by the signal receiving unit 602 on the image transmission side). In this case, in the timer unit 615, the timer started after receiving the Ack signal of the frame 9 expires, so that the timer expiration is notified to the frame memory changing unit 605. In response to this, the frame memory changing unit 605 changes the reference image for the thirteenth frame to the image of the ninth frame receiving the Ack signal. The timer value set in the timer unit 615 may be set based on the round-trip delay time of the signal.

FIG. 11 shows a modified embodiment in which a general image coding method combining motion compensation and discrete cosine transform (DCT) is combined with the second embodiment. This figure is a modified example of the second embodiment corresponding to the modified example of the first embodiment shown in FIG. 5, and a timer unit 615 is added as compared with FIG. The other components have the same configuration as the modified configuration example (of the first embodiment) in FIG. 5, and therefore, the respective components are denoted by the same reference numerals as in FIG. 5.

According to the second modified embodiment, by adding a timer unit, a signal from the image receiving side, particularly a Nack signal, is not received by the image transmitting side due to an error or the like, When reception on the image transmission side is delayed due to an increase in delay, processing delay on the reception side, or the like, the reference image can be quickly changed, and recovery from the error image on the image reception side can be expedited. More specifically, in FIG. 10, in the configuration of the first embodiment, the Nack signal (1
0N) is received on the image transmitting side, the reference image for the frame 14 is changed. In the configuration of the second embodiment, the reference image for the frame 13 can be changed.

Next, a third embodiment according to the present invention will be described. FIG. 12 is a block diagram showing the overall configuration of the third embodiment. In this figure, a frame counting unit 616 is added as compared with FIG. 1 which is a block diagram showing the entire configuration of the first embodiment. FIG. 13 is an operation flow showing the operation of the frame counting unit 616. The operation according to the present embodiment is similar to the above-described operation by each unit in FIG.
When an ack signal is received, it is
Notify 6. Further, the frame number notifying unit 607 sends the frame number of the encoded image to the frame number receiving unit 61.
0, and also notifies the frame counting unit 616.
The frame counting unit 616 counts the number of frames notified from the frame number notifying unit 607 and repeats resetting the count value when receiving the signal, but the count value is not reset because the signal is not notified. If the number exceeds the specified number, the frame memory changing unit 605 is notified of the fact.

FIGS. 14 and 15 show the operation flow of the frame memory changing unit 605 in the third embodiment. As shown in the flow, in addition to the operation in the first embodiment, an operation of changing the reference image is also performed by a signal from the frame counting unit 616 (step H0).
1). It is to be noted that FIG. 14 shows that the processing flow continues in FIG. 15, FIG. 15 shows in FIG. 14, and FIG. 14 shows in FIG. 15.

FIG. 16 is a diagram showing an operation example of the third embodiment in chronological order. The meanings of the reference numerals are the same as those in FIG. In this operation example, when the counted value reaches 3, the frame counting unit 616 is notified to the frame memory changing unit 605.
The frame counting unit 616 counts the number of encoded frames as the encoding progresses. However, Ack
When a signal or Nack signal is received, the count value is reset.

This operation example shows an example in which an error has occurred in the image data of the eleventh frame. In addition, an error occurs in the Nack signal (11N) corresponding thereto, and a case where the signal is lost (cannot be recognized on the image transmitting side) continues twice. In this case, the frame counting unit 616 notifies the frame memory changing unit 605 of the counted value that has been counted from the end of the encoding of the frame 12 to 3 due to the end of the encoding of the frame 14, and notifies the frame memory changing unit 605 of the counted value. The changing unit 605 changes the fifteenth frame reference image to the tenth frame image receiving the Ack signal. The setting value set in the frame counting unit 616 may be set based on the round-trip delay time of a signal and the amount of image data to be encoded.

FIG. 17 shows a general image coding method combining motion compensation and discrete cosine transform (DCT).
This is a modified embodiment example in which the third embodiment example is combined. This figure shows a third modified embodiment corresponding to the first modified embodiment shown in FIG.
An image signal counting unit 616 corresponding to the frame counting unit is added as compared with FIG. The other components have the same configuration as that of the first modified embodiment of FIG. 5, and thus the same reference numerals are given to those components.

According to the third embodiment, by providing the image signal counting unit, the amount of image data of the encoded frame varies, and the signal from the image receiving side, especially the Nack signal, is output by an error or the like. If the image is not received on the image transmission side, or if the reception on the image transmission side is delayed due to an increase in transmission delay, processing delay on the reception side, etc., the reference image can be changed promptly and an error on the image reception side Recovery from an image can be hastened. In particular, in the case of an image encoding method that takes an inter-frame difference, the data amount after encoding is usually not constant depending on the content of the image unless the resolution is adjusted to control the data amount to be constant. Therefore, it is effective to apply to such a case.

More specifically, referring to FIG. 16, in the case of the second embodiment, the Ack signal (9
A) The Ack signal (10
A) It is appropriate to make the timer value larger than the time until reception, but in such a case, the timer started by the reception of 10A expires after the encoding of the frame 15 is completed, It is becoming. Therefore, the reference image is changed from the frame 17.
However, according to the third embodiment, the reference image of the frame 15 can be changed.

Next, a fourth embodiment according to the present invention will be described. FIG. 23 is a block diagram showing the overall configuration of the fourth embodiment. In this figure, a memory holding status notifying unit 621 is added as compared with FIG. 1 which is a block diagram showing the entire configuration of the first embodiment. In the operation of the first embodiment, the frame memory unit 60 on the image transmission side is used.
In some cases, the data stored in the frame memory unit 603 may be erased and the contents of the frame memory unit 603 may be emptied due to a special case, such as no reference image of a correctly received frame. It may be. In such a case, it is impossible to perform an inter-frame encoding method that takes an inter-frame difference, so the fourth embodiment is configured to switch to intra-frame encoding.

That is, information on the contents stored in the frame memory unit 603 is notified to the memory holding status notifying unit 621 via the frame memory changing unit 605.
The memory holding status notifying unit 621 is a
In the case where no reference image is stored in 3, the encoding unit 601 is notified of that fact. The encoding unit 601 having received the notification encodes the input image by intra-frame encoding. This can prevent a special situation where an input image is inter-frame coded when there is no reference image.

Next, a fifth embodiment according to the present invention will be described. FIG. 24 is a block diagram showing the overall configuration of the fifth embodiment. In this figure, an encoding status notifying unit 623 is added as compared with FIG. 1 which is a block diagram showing the entire configuration of the first embodiment. In the fifth embodiment, the encoding unit 601 performs intra-frame encoding according to conditions in addition to inter-frame encoding. Encoding status notification unit 6
23 detects, when the encoding unit 601 has performed the intra-frame encoding, based on the information on the encoding transmitted from the encoding unit 601,
To that effect.

The frame memory changing unit 605 determines the contents of the frame memory unit 603 based on the contents of the signal from the image receiving side obtained via the signal receiving unit 602 and the contents of the notification from the encoding status notifying unit 623. Is rewritten. FIG. 25 shows a partial flow of an operation example of the frame memory changing unit 605 in this case. This figure corresponds to the operation of the first embodiment shown in FIG.
25 is the same as the first embodiment except that 1 and D02 are added. That is, the flow chart combining FIG. 25 and FIG. 3 is the flow chart of the frame memory changing unit 605 in the fifth embodiment. FIG. 4 is an overall flowchart of an operation example. That is, according to the present embodiment, when intra-frame encoding is performed, the next encoding is performed by erasing unnecessary data in the memory in consideration of the error propagation prevention effect of the encoding. It is possible to rewrite the memory so that the contents can be performed more appropriately.

Next, a sixth embodiment according to the present invention will be described. FIG. 26 is a block diagram showing the overall configuration of the sixth embodiment. In the figure, a memory information notifying unit 625 and a memory information receiving unit 626 are added as compared with FIG. 1 which is a block diagram showing the entire configuration of the first embodiment. In the first embodiment, the reference image determination unit 60 determines the operation timing of the transmission side and the reception side and the occurrence of an error.
4 may select an image that does not exist in the frame memory unit 614 on the image receiving side as a reference image.

In the sixth embodiment, the memory information notifying section 625 on the image receiving side includes the frame memory section 614.
Is notified to the memory information receiving unit 626 on the image transmitting side of all the contents held in the image transmitting unit or information on the oldest or latest contents. Memory information receiving unit 6 that has been notified
26 transmits the information to the reference image determination unit 604. The reference image determining unit 604 determines what the reference image of the next frame to be encoded is based on the signal from the frame memory changing unit 605 and the information from the memory information receiving unit 626.

That is, the reference image determining unit 604 determines what the reference image of the next frame to be encoded is based on the signal from the frame memory changing unit 605. Here, the memory information on the image receiving side is determined. It is assumed that the notification unit 625 is set to notify the memory information reception unit 626 on the image transmission side of information about all contents held in the frame memory unit 614. In this case, for example, when the reference image determination unit 604 is instructed to use the latest frame in the frame memory unit 603 as the reference image according to the process of step 704 in FIG. If the image does not exist in the frame memory unit 614, the image is not selected as a reference image and the first image is not selected.
The frame memory unit 60 using the immediately preceding frame as a reference image
3 to be sent to the encoding unit 601. By such processing, the reference image determination unit 60
4 is prevented from selecting an image that does not exist in the frame memory unit 614 on the image receiving side as a reference image.

Next, a seventh embodiment according to the present invention will be described. FIG. 27 is a block diagram showing the overall configuration of the seventh embodiment. In this figure, compared with FIG. 1 which is a block diagram showing the entire configuration of the first embodiment, the switching unit 62
8 is added. In the above-described first embodiment, when no error-free image data is obtained, output of image data from the decoding unit 613 to a monitor or the like, and writing of data to the frame memory unit 614 are not performed. . However, in a practical mode, even in such a case, outputting image data to a monitor or the like often makes the system easier to use for a user observing the monitor. However, in this case, it is not preferable that an image including an error is written to the frame memory unit 614.

In the seventh embodiment, the image signal receiving unit 608 notifies the switching unit 628 of the presence / absence of an error, and even if there is an error in the image data, the encoding unit 613 sends it to the switching unit 628. Data is sent. When the content notified from the image signal receiving unit 608 is “no error”, the switching unit 628 outputs the output from the decoding unit 613 to both an external device such as a monitor and the frame memory unit 614. In the case of "with error", it works so as to output the output from the decoding unit 613 only to the outside such as a monitor. As a result, it is possible to realize a system that is more user-friendly and uses the error image while keeping only the error-free image data inside the system.

[0077]

According to the image communication system and method according to the present invention, since at least one reference image at the time of encoding that was correctly received last by the image receiving side is always held in the memory unit on the transmitting side, When a receiving error is notified from the image receiving side, it is possible to avoid a situation in which a correct reference image is lost. That is, in the conventional technique of preventing error propagation while continuing inter-frame coding, even in the case where the reference image does not exist in the memory unit and the intra-frame coding has to be performed, the last correctly received data is received with the same memory scale. The reference image thus obtained can be stored in the memory unit, and deterioration of image quality can be prevented.

Further, by adding the timer means and the image counting means to the image transmitting side, a signal from the image receiving side to the image transmitting side, in particular, a reception error is notified by the writing control of the memory changing means. Even when the signal cannot be received due to an error, or when the signal arrives late due to an increase in transmission delay, processing delay on the image receiving side, etc., the reference image is immediately changed and the error on the image receiving side is changed. It is possible to hasten recovery from the image.

Further, by adding the memory holding status notifying means to the image transmitting side, it is possible to prevent a special situation in which an input image is inter-frame coded when there is no reference image in the memory unit.

Also, by adding the above-mentioned encoding status notifying means to the image transmitting side, when intra-frame encoding is performed, the effect of preventing error propagation by the encoding is considered.
It is possible to rewrite the memory so that the next encoding is performed more appropriately, such as by deleting unnecessary data in the memory.

Further, by adding the above-mentioned memory information notifying means to the image receiving side and adding the above-mentioned memory information receiving means to the image transmitting side, the reference image determining section on the image transmitting side can store in the memory section on the image receiving side. It is possible to prevent an image that does not exist from being selected as a reference image.

Further, by adding the above-mentioned switching means to the image receiving side, it is possible to realize an easy-to-use system for the user who intentionally uses the error image while keeping only the image data without error inside the system. Becomes possible. Note that the effects obtained by the additional embodiments can be similarly obtained by executing a method corresponding to the operation of each embodiment.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an overall configuration of a first embodiment of the present invention.

FIG. 2 is an operation flowchart (1) of a frame memory changing unit in FIG. 1;

FIG. 3 is an operation flowchart (part 2) of the frame memory changing unit in FIG. 1;

FIG. 4 is an explanatory diagram of an operation example of the first embodiment.

FIG. 5 is a configuration diagram of a modified embodiment in which a general image encoding method and the first embodiment are combined.

FIG. 6 is a block diagram showing an overall configuration of a second embodiment of the present invention.

FIG. 7 is an operation flowchart of the timer unit of FIG. 6;

FIG. 8 is an operation flowchart (1) of the frame memory changing unit in FIG. 6;

9 is an operation flowchart (part 2) of the frame memory changing unit in FIG. 6;

FIG. 10 is an explanatory diagram of an operation example of the second embodiment.

FIG. 11 is a configuration diagram of a modified embodiment in which a general image encoding method and the second embodiment are combined.

FIG. 12 is a block diagram showing an overall configuration of a third embodiment of the present invention.

FIG. 13 is an operation flowchart of the frame counting unit in FIG. 12;

14 is an operation flowchart (part 1) of the frame memory changing unit in FIG. 12;

FIG. 15 is an operation flowchart (part 2) of the frame memory changing unit in FIG. 12;

FIG. 16 is an explanatory diagram of an operation example of the third embodiment.

FIG. 17 is a configuration diagram of a modified embodiment in which a general image encoding method and the third embodiment are combined.

FIG. 18 is a configuration diagram in a case where a general image encoding method and the first conventional example are combined.

FIG. 19 is a configuration diagram in a case where a general image encoding method and a second conventional example are combined.

FIG. 20 is an explanatory diagram of an operation example of the second conventional example.

FIG. 21 is an explanatory diagram of another operation example of the second conventional example.

FIG. 22 is an explanatory diagram of still another operation example of the second conventional example.

FIG. 23 is a block diagram showing an overall configuration of a fourth embodiment of the present invention.

FIG. 24 is a block diagram showing an overall configuration of a fifth embodiment of the present invention.

FIG. 25 is a partial flowchart of the operation of the frame memory changing unit in FIG. 24;

FIG. 26 is a block diagram showing an overall configuration of a sixth embodiment of the present invention.

FIG. 27 is a block diagram showing an overall configuration of a seventh embodiment of the present invention.

[Explanation of symbols]

 Reference numeral 601: coding unit 602: signal receiving unit 603: (frame) memory unit 604: reference image determination unit 605: (frame) memory change unit 606: reference image notification unit 607: frame number notification unit (image number notification unit) 608 ... Image signal receiving unit 609 ... Signal sending unit 610 ... Frame number receiving unit (image number receiving unit) 611 ... Reference image determining unit 612 ... Reference image number receiving unit 613 ... Decoding unit 614 ... (Frame) memory unit 615 ... Timer Unit 616: Frame counting unit (image signal counting unit) 621: Memory holding status notifying unit 623 ... Encoding status notifying unit 625 ... Memory information notifying unit 626 ... Memory information receiving unit 628 ... Switching unit

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Hideaki Kizen 3-19-2 Nishi-Shinjuku, Shinjuku-ku, Tokyo Nippon Telegraph and Telephone Corporation (72) Inventor Ryota Suzuki 3-19, Nishishinjuku, Shinjuku-ku, Tokyo 2 Nippon Telegraph and Telephone Corporation (72) Inventor Akimoto ▲ Taka ▼ Akira Nippon Telegraph and Telephone Corporation 3-19-2 Nishishinjuku, Shinjuku-ku, Tokyo

Claims (44)

[Claims] An encoding unit that encodes an input image using an inter-frame encoding method that performs compression using a difference between frames, and outputs encoded image data; A signal receiving unit that receives a signal notifying the presence or absence of an error of the encoded image data and the image number from the image receiving side, and encoding the encoded image data output from the encoding unit with the inter-frame code. Unit having a buffer for holding a plurality of reference images used for encoding by the encoding method, and when at least one image is stored in the memory unit, the content indicated by the signal received by the signal receiving unit A reference image determination unit that selects a reference image to be used by the encoding unit from among the images stored in the memory unit; and a reference image number used by the encoding unit. A reference image notifying unit for notifying a receiving side, and an image number notifying unit for notifying an image number of encoded image data output by the encoding unit, and an image receiving side encoding unit of the image transmitting side. Receiving the encoded image data to be output, an image data receiving unit for detecting and outputting an error in the image data, and outputting the encoded image data notified from the image number notifying unit on the image transmitting side. An image number receiving unit that receives an image number, a signal that notifies the image number of the encoded image data received by the image number receiving unit, and the presence or absence of an error detected by the image data receiving unit regarding the image data. A signal transmitting unit that transmits to the image transmitting side, a decoding unit that decodes the encoded image data received by the image data receiving unit, and outputs decoded image data, and a signal that is output from the decoding unit. And a memory unit having a buffer for holding a plurality of decoded image data as reference images used for the decoding, and a reference image number at the time of encoding notified from the reference image notifying unit on the image transmitting side. A reference image number receiving unit, and if at least one image is stored in the memory unit, from among the images stored in the memory unit according to the reference image number received by the reference image number receiving unit. An image communication system comprising: a reference image determining unit that selects a reference image used by the decoding unit; and A memory changing unit that controls writing of the encoded image data to be output to the memory unit; the control includes determining whether or not to write new data; Determining the viewing position, image communication system is intended to include erasure of already written data in the memory unit. 2. The writing control of the memory changing means,
2. The image according to claim 1, further comprising: erasing a reference image older than a reference image corresponding to encoded image data that was last correctly received on the image receiving side from the reference images stored in the memory unit. 3. Communications system. 3. The writing control of the memory changing means,
The image communication system according to claim 1, further comprising: erasing a reference image corresponding to encoded image data for which a reception error has been notified from the image receiving side, from the reference images stored in the memory unit. 4. The image communication system according to claim 1, wherein the processing unit of the input image is one of a frame unit, a small area of an image forming a frame, and a group of pixels forming the small area. . 5. The image transmitting side, wherein the signal receiving unit determines whether a signal from the image receiving side has been received within a preset time, and determines that the signal has not been received. A timer means for notifying the memory change means of the fact, wherein the memory change means, when receiving a notification from the timer means, controls writing to the memory unit based on the contents of the notification. 2. The image communication system according to 1. 6. The image transmission side, wherein the signal reception unit receives a signal from the image reception side while the encoding unit encodes a predetermined amount of images. Determining, and further comprising an image counting means for notifying the memory changing means when it is determined not to have been received, wherein the memory changing means receives the notification from the image counting means, The image communication system according to claim 1, wherein writing control to the memory unit is performed based on: 7. The image transmission side monitors the contents of a memory unit on the transmission side, and if no reference image usable for the inter-frame encoding is stored in the memory unit, the encoding is performed. A memory holding status notifying unit for notifying the unit of the fact, and the encoding unit, when receiving the notification from the memory holding status notifying unit, performs encoding of a next image by an intra-frame encoding method. The image communication system according to claim 1. 8. The encoding unit performs encoding by using one of the inter-frame encoding method and the intra-frame encoding method, and the encoding unit performs the encoding on the image transmission side. When the unit has performed intra-frame encoding, the unit further includes an encoding status notifying unit that notifies the memory changing unit of the fact, wherein the memory changing unit receives a notification from the encoding status notifying unit. 2. The image communication system according to claim 1, wherein writing control to the memory unit is performed based on the content of the notification. 9. The image receiving side further comprises: memory information notifying means for notifying the image transmitting side of information of an image stored in a memory unit of the receiving side. The image processing apparatus further includes a memory information receiving unit that receives the image information notified from the notifying unit and notifies a content of the image information to a reference image determining unit on the transmitting side, wherein the reference image determining unit on the image transmitting side includes the reference image. 2. The image communication system according to claim 1, wherein the selection is performed based on the content indicated by the signal received by the signal receiving unit and information notified from the memory information receiving unit. 10. The image receiving side receives information on the presence / absence of an error detected by the image data receiving unit, and when there is an error, an output from the decoding unit is sent to a memory unit on the receiving side. 2. The image communication system according to claim 1, further comprising a switching unit that controls output from the decoding unit to be sent to the memory unit when there is no error. 11. A process in which an image transmitting side encodes an input image by an inter-frame encoding method for performing compression using a difference between frames, and outputs encoded image data. Receiving a signal notifying the presence or absence of an error of the encoded image data and the image number from the image receiving side, and using the output encoded image data as a reference image used for encoding by the inter-frame encoding method. When at least one image is stored in the memory unit having a buffer for holding a plurality of images, the code is selected from the images stored in the memory unit based on the content indicated by the signal received from the image receiving side. Selecting a reference image to be used in the encoding, notifying the image receiving side of the number of the reference image used in the encoding, and outputting the encoded image. Notifying the image number of the image data, wherein the image receiving side receives the encoded image data output from the image transmitting side, and detects and outputs an error of the image data, and outputs the image data. Receiving the image number of the encoded image data notified from the image transmitting side; and notifying the image number of the received encoded image data and the presence or absence of the detected error regarding the image data. Transmitting a signal to the image transmitting side, decoding the received encoded image data, and outputting decoded image data, and encoding a reference image number notified from the image transmitting side. Receiving at least one image in a memory unit having a buffer for holding a plurality of the output decoded image data as reference images used for the decoding. If it is,
Selecting a reference image to be used in the decoding from among the images stored in the memory unit according to the received reference image number, wherein the image transmitting side receives the received image. Further comprising the step of performing a write control of the output coded image data to the memory unit based on the content indicated by the signal that has been output, the control comprising: determining whether to write new data; And an erasing of data already written in the memory unit. 12. The writing control to the memory unit, wherein the reference image older than the reference image corresponding to the coded image data last correctly received on the image receiving side is selected from the reference images stored in the memory unit. The image communication method according to claim 11, comprising erasing the image. 13. The writing control to the memory unit, wherein the reference image corresponding to the coded image data for which the reception error has been notified from the image receiving side is deleted from the reference images stored in the memory unit. The image communication method according to claim 11, comprising: 14. The processing unit of the input image is any one of a frame unit, a small area of an image forming a frame, and a group of pixels forming the small area.
The image communication method according to 1. 15. The image transmitting side determines whether or not a signal from the image receiving side has been received within a preset time, and outputs information indicating that when the signal has not been received. The image communication method according to claim 11, further comprising the step of: when the information is output, the step of performing a write control to the memory unit performs the control based on the information. 16. The image transmitting side determines whether or not a signal has been received from the image receiving side while encoding a predetermined amount of images, and determines that no signal has been received. The image communication according to claim 11, further comprising a step of outputting information indicating the fact, wherein, when the information is output, the step of performing a write control to the memory unit performs the control based on the information. Method. 17. Monitoring the contents of a memory unit on the image transmission side, and if no reference image usable for the inter-frame encoding is stored in the memory unit, outputs information indicating that. 12. The image communication method according to claim 11, further comprising the step of: when the information is output, the step of encoding the input image performs encoding of a next image by an intra-frame encoding method. 18. The process of encoding the input image, wherein the inter-frame encoding method and the intra-frame encoding method are used together, and encoding is performed by any one of the methods, and the intra-frame encoding is performed. Further comprising the step of outputting information indicating that, when the information is output, the step of controlling the writing to the memory unit performs the control based on the information. Image communication method as described. 19. The method according to claim 19, further comprising: notifying the image transmitting side of image information stored in the memory unit on the image receiving side; and receiving the information on the image transmitting side. The step of determining a reference image on the side includes the selection of the reference image, a signal notifying the presence or absence of an error of the received encoded image data and the image number thereof, and the signal is stored in the memory unit of the image reception side The image communication method according to claim 11, wherein the method is performed based on image information. 20. Receiving information on the presence / absence of an error detected on the image receiving side, if there is an error, the decoded output is not sent to the memory unit on the receiving side, and if there is no error, 12. The image communication method according to claim 11, further comprising controlling the decoded output to be sent to the memory unit. 21. An encoding unit for encoding an input image by an inter-frame encoding method for performing compression using a difference between frames and outputting encoded image data, and an encoded image received by an image receiving side. A signal receiving unit that receives a signal notifying the presence or absence of a data error and its image number from the image receiving side; and encoding the encoded image data output from the encoding unit by the inter-frame encoding method. A memory unit having a buffer for holding a plurality of reference images used in the memory unit, and when at least one image is stored in the memory unit, based on the content indicated by the signal received by the signal receiving unit, the memory unit A reference image determining unit for selecting a reference image to be used by the encoding unit from among the images stored in the encoding unit; and a reference image number used by the encoding unit to the image receiving side. A reference image notifying unit, and an image number notifying unit that notifies an image number of encoded image data output by the encoding unit, wherein the content indicated by the signal received by the signal receiving unit is A memory changing unit that controls writing of the encoded image data output by the encoding unit to the memory unit, the control includes determining whether to write new data, An image transmitting apparatus including determining a writing position and erasing data already written in the memory unit. 22. The writing control of the memory changing means, wherein, among the reference images stored in the memory unit, the reference image older than the reference image corresponding to the last coded image data correctly received on the image receiving side. 22. The image transmission device according to claim 21, comprising erasing an image. 23. The writing control of the memory changing means, wherein the reference image corresponding to the encoded image data for which a reception error has been notified from the image receiving side is deleted from the reference images stored in the memory unit. 22.
An image transmitting device according to claim 1. 24. The processing unit of the input image is one of a frame unit, a small area of an image forming a frame, and a group of pixels forming the small area.
An image transmitting device according to claim 1. 25. The signal receiving unit determines whether or not a signal from the image receiving side has been received within a preset time, and when it determines that the signal has not been received, the memory changing unit sends the signal to the memory changing unit. 22. The image transmission apparatus according to claim 21, further comprising timer means for notifying that the memory has been changed, the memory change means, when receiving a notification from the timer means, controls writing to the memory unit based on the content of the notification. apparatus. 26. While the encoding unit encodes a predetermined amount of images, the signal receiving unit determines whether a signal from the image receiving side has been received, and determines whether or not the signal has been received. Further comprising image counting means for notifying the memory changing means when it has been determined that the memory changing means has received a notification from the image counting means, based on the contents of the notification. 22. The image transmission device according to claim 21, wherein the image transmission device performs writing control. 27. The contents of the memory unit are monitored, and one or more reference images usable for the inter-frame encoding are stored in the memory unit.
If none is stored, the memory unit further includes a memory holding status notifying unit that notifies the coding unit of the fact. 22. The image transmitting apparatus according to claim 21, wherein encoding is performed by an intra-frame encoding method. 28. The encoding section, wherein the encoding section performs encoding by using one of the inter-frame encoding scheme and the intra-frame encoding scheme, and the encoding section performs the intra-frame encoding. When performing the above, further comprises an encoding status notifying unit for notifying the memory changing unit of the fact, the memory changing unit, when receiving a notification from the encoding status notifying unit, the content of the notification 22. The image transmitting apparatus according to claim 21, wherein the image transmitting apparatus performs writing control to the memory unit based on the control. 29. A memory information receiving means for receiving information of an image stored in a memory unit of the receiving side, which is notified from the image receiving side, and notifying the content to the reference image determining unit. 22. The reference image determining unit selects the reference image based on the content indicated by the signal received by the signal receiving unit and information notified from the memory information receiving unit.
An image transmitting device according to claim 1. 30. Receiving image data output by an image transmitting side and encoded by an inter-frame encoding method for performing compression using a difference between frames, and detecting and outputting an error in the image data. An image data receiving unit, an image number receiving unit that receives an image number of the encoded image data notified from the image transmitting side, and the image number of the encoded image data received by the image number receiving unit. A signal transmitting unit that transmits a signal notifying the presence or absence of an error of the image data detected by the image data receiving unit to the image transmitting side; decoding and decoding the encoded image data received by the image data receiving unit A decoding unit that outputs image data, and a buffer that holds a plurality of decoded image data output from the decoding unit as reference images used for the decoding. A reference image number receiving unit that receives a reference image number at the time of encoding notified from the image transmitting side; and a reference image number when at least one image is stored in the memory unit. An image receiving apparatus having a reference image determining unit that selects a reference image to be used by the decoding unit, from among images stored in the memory unit, according to a reference image number received by a receiving unit, An image receiving apparatus further comprising a memory information notifying unit for notifying the image transmitting side of information of an image stored in the memory unit. 31. Receiving image data output by an image transmitting side and encoded by an inter-frame encoding method for performing compression using a difference between frames, detecting the presence or absence of an error in the image data, and outputting the detected data. An image data receiving unit, an image number receiving unit that receives an image number of the encoded image data notified from the image transmitting side, and the image number of the encoded image data received by the image number receiving unit. A signal transmitting unit that transmits a signal notifying the presence or absence of an error of the image data detected by the image data receiving unit to the image transmitting side; decoding and decoding the encoded image data received by the image data receiving unit A decoding unit that outputs image data, and a buffer that holds a plurality of decoded image data output from the decoding unit as reference images used for the decoding. A reference image number receiving unit that receives a reference image number at the time of encoding notified from the image transmitting side; and a reference image number when at least one image is stored in the memory unit. An image receiving apparatus having a reference image determining unit that selects a reference image to be used by the decoding unit, from among images stored in the memory unit, according to a reference image number received by a receiving unit, The image data receiving unit receives information on the presence / absence of an error detected.If there is an error, the output from the decoding unit is not sent to the memory unit. An image receiving apparatus further comprising switching means for controlling output to be sent to the memory unit. 32. A process of encoding an input image by an inter-frame encoding method for performing compression using a difference between frames, outputting encoded image data, and a process of encoding the encoded image data received by the image receiving side. A step of receiving a signal notifying the presence or absence of an error and the image number from the image receiving side, and holding the output encoded image data as a plurality of reference images used for encoding by the inter-frame encoding method. When at least one image is stored in the memory unit having the buffer of the above, it is used in the encoding from among the images stored in the memory unit based on the content indicated by the signal received from the image receiving side. A step of selecting a reference image, a step of notifying the image receiving side of a reference image number used in the encoding, and a step of notifying the image of the output encoded image data. Transmitting an encoded image data to the memory unit based on the content indicated by the signal received by the image transmitting side. The control includes determining whether to write new data, determining a write position in the memory unit, and erasing data already written in the memory unit. 33. The writing control to the memory unit is performed by, among reference images stored in the memory unit, a reference image older than a reference image corresponding to encoded image data last correctly received on the image receiving side. 33. The method of claim 32, comprising erasing the image. 34. The writing control to the memory unit, wherein the reference image corresponding to the coded image data for which the reception error has been notified from the image receiving side is erased from the reference images stored in the memory unit. 33. The image transmission method according to claim 32, comprising: 35. The processing unit of the input image is one of a frame unit, a small area of an image forming a frame, and a group of pixels forming the small area.
The image transmission method described in 1. 36. A process for judging whether or not a signal from the image receiving side has been received within a preset time, and outputting information indicating that when it has not been received. 33. The image transmission method according to claim 32, wherein when the information is output, the step of controlling the writing to the memory unit performs the control based on the information. 37. While encoding a predetermined amount of images, it is determined whether or not a signal has been received from the image receiving side. If it is determined that no signal has been received, information indicating that fact has been received. 33. The image transmission method according to claim 32, further comprising a step of outputting the information, wherein when the information is output, the step of controlling the writing to the memory unit performs the control based on the information. 38. The contents of the memory unit are monitored, and the memory unit stores one reference image usable for the inter-frame encoding.
If none is stored, the method further comprises the step of outputting information indicating that, and if the information is output, the step of encoding the input image includes encoding the next image with an intra-frame code. 33. The image transmission method according to claim 32, wherein the image transmission method is performed by a conversion method. 39. The step of encoding the input image, wherein the inter-frame encoding method and the intra-frame encoding method are used in combination, and encoding is performed by one of the methods, and the intra-frame encoding is performed. 33. The method according to claim 32, further comprising the step of, when the information is output, the step of controlling the writing to the memory unit to perform the control based on the information. The described image transmission method. 40. The method according to claim 40, further comprising: receiving information of the image stored in the memory unit on the image receiving side from the receiving side. The step of determining the reference image includes receiving the selection of the reference image. 33. The image transmission method according to claim 32, wherein the image transmission method is performed based on a signal notifying the presence / absence of an error of the encoded image data and the image number thereof and image information stored in a memory unit on the image receiving side. 41. A computer-readable recording medium on which a program for causing a computer to execute the method according to claim 32 is recorded. 42. Image data output by an image transmitting side and encoded by an inter-frame encoding method for performing compression using a difference between frames is received, and the presence or absence of an error in the image data is detected and output. Receiving an image number of the encoded image data notified from the image transmitting side; the image number of the received encoded image data; and the presence or absence of the detected error regarding the image data. Transmitting a signal notifying the above to the image transmitting side, decoding the received encoded image data, and outputting decoded image data, and at the time of encoding notified from the image transmitting side. A step of receiving a reference image number, and at least a memory unit having a buffer for holding a plurality of the output decoded image data as reference images used for the decoding. If one image is stored,
Selecting a reference image to be used in the decoding from among the images stored in the memory unit in accordance with the received reference image number. An image receiving method, further comprising a step of notifying the image transmitting side of the information of the performed image. 43. Receiving image data encoded by an inter-frame encoding method for performing compression using a difference between frames, which is output from an image transmission side, and detects and outputs an error in the image data. Receiving an image number of the encoded image data notified from the image transmitting side; the image number of the received encoded image data; and the presence or absence of the detected error regarding the image data. Transmitting a signal notifying the above to the image transmitting side, decoding the received encoded image data, and outputting decoded image data, and at the time of encoding notified from the image transmitting side. A step of receiving a reference image number, and at least a memory unit having a buffer for holding a plurality of the output decoded image data as reference images used for the decoding. If one image is stored,
Selecting a reference image to be used in the decoding from among the images stored in the memory unit in accordance with the received reference image number. In response to the presence / absence information, control is performed such that the decoded output is not sent to the memory unit when there is an error, and the decoded output is sent to the memory unit when there is no error. An image receiving method further comprising a step. 44. The computer according to claim 42 or 43.
A computer-readable recording medium recording a program for executing the method according to 1.