JP2003284064A - Image receiving equipment and image display control method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To display an image easy to see by autonomous control on a reception side when error is detected in image data. <P>SOLUTION: A variable-length decoding part 104 decodes a frame encoding mode. An error detecting part 111 detects the error of the image data during decoding by the decoding part 104. A receiving interval measuring part 110 measures a receiving interval (random access interval) of a key frame on the basis of the frame encoding mode. On the basis of existence of error, the frame encoding mode and the random access interval, a switching control part 109 controls the connection and disconnection of a switch 114, thereby switching over an image displayed in a display part 116. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image receiving device and an image display control method.

[0002]

2. Description of the Related Art Image encoding technology focuses on temporal / spatial redundancy and statistical redundancy of images, and is a technology that reduces the amount of data without degrading the original image quality as much as possible. is there. This image coding technology includes MPEG2, which is a compression technology standardized by the International Standards Organization / International Electrotechnical Commission (ISO / IEC), and the telecommunications standardization unit (ITU).
-T) standardized by H.263 for video conferencing. MPEG-2 is currently moving to MPEG-4 for purposes of multimedia communication applications.

Due to the rapid development of mobile wireless communication in recent years, image communication by a communication terminal such as a mobile phone is in the limelight, and studies are being made on the application of MPEG-4 to mobile wireless communication. However, wireless communication has a higher transmission error rate than wired communication. Therefore, one of the functions of MPEG-4 is error resistance assuming image communication under a severe error environment in mobile radio communication. The error resistance refers to a function of encoding coded data including an error so that the decoded image can be prevented from being deteriorated in image quality. In MPEG-4, the image encoding on the transmitting side has an error resistance so that the receiving side can detect and correct the error. Error resilience technologies include video packets that spatially localize errors, variable-length coding, concealment that conceals a portion that could not be decoded correctly using information that could be decoded correctly, and temporal error correction. There are refreshes that are localized in.

[0004]

However, the operation on the receiving side when an error is detected is not specified by the communication standard, and depends on the equipment on the receiving side. That is, the receiving side is free to choose what kind of image to display when an error is detected in the image data. At this time, the receiving side needs to display an easy-to-see image with little deterioration in image quality. In particular, in wireless communication in which the transmission error rate is much higher than in wired communication, what kind of image is displayed when a transmission error occurs is important.

On the other hand, in the image transmission apparatus described in Japanese Patent Laid-Open No. 4-334189, the display is stopped when an error is detected,
A demand refresh request is sent to the sender of the image data. However, if the display is uniformly stopped when an error is detected, the image may be harder to see than the display as it is. And this way,
Since it is necessary to exchange signals between the receiving side and the transmitting side, it is necessary to make an agreement on the procedure of signal transmission / reception between the receiving side and the transmitting side, which allows flexible system design and receiver design. It will be a hindrance to you.

The present invention has been made in view of the above point, and when an error is detected in image data, an image receiving apparatus and an image which can display an easy-to-see image by autonomous control on the receiving side. It is an object to provide a display control method.

[0007]

An image receiving apparatus according to the present invention includes a receiving means for receiving encoded image data, a reproducing means for reproducing the received image data, and an image obtained by the reproducing means. Display means for displaying, a detecting means for detecting an error in the received image data, a measuring means for measuring an error resistance strength of the received image data, and an error in the received image data And a switching unit that switches the image displayed on the display unit according to the measured error resistance strength.

In the image receiving apparatus of the present invention having the above-mentioned structure, when the switching means detects an error in the received image data, the switching means displays on the display means according to the strength of the measured error resistance. The image to be reproduced is switched between the image previously obtained by the reproducing means and the image obtained this time by the reproducing means.

With these configurations, when a transmission error occurs, the receiving device can autonomously control the switching of the display image according to the strength of the error tolerance.
Even if a transmission error occurs, it is possible to display an easy-to-see image without depending on the function of the transmitting side and only the function of the receiving side. Particularly, in wireless communication in which the transmission error rate is much higher than that in wired communication, it is possible to perform an optimal display that is easy to see. Further, it is not necessary to make an agreement regarding the procedure of signal transmission / reception between the receiving side and the transmitting side when a transmission error occurs, and it is possible to flexibly design the system and the receiving device. In addition, this configuration provides real-time communication (eg,
This is particularly effective in the case of performing display control when an error occurs in a receiving device capable of both receiving video streaming (videophone) and video streaming in which a key frame exists.

In the image receiving apparatus of the present invention having the above-mentioned structure, the measuring means intraframe-codes all the coding units included in one frame among the frames forming the received image data. The frame reception interval is measured as the strength of error tolerance, and when the switching unit detects an error in the received image data, an image displayed on the display unit is displayed according to the measured reception interval. Take the configuration to switch.

In the image receiving apparatus of the present invention having the above-mentioned structure, the measuring means measures the number of coding units coded in the frame as a strength of error tolerance in the frames forming the received image data. However, the switching unit employs a configuration in which, when an error is detected in the received image data, the image displayed on the display unit is switched according to the number of measured coding units.

In the image receiving apparatus of the present invention, in the above structure, the measuring means is a video which is composed of a sync word and a plurality of coding units following the sync word in a frame which constitutes the received image data. The number of packets is measured as the strength of error resistance, and when the switching unit detects an error in the received image data, an image displayed on the display unit according to the measured number of video packets. Take the configuration to switch.

According to these configurations, an appropriate image can be displayed according to the strength of the error resistance.

The image receiving apparatus of the present invention comprises a receiving means for receiving the encoded image data, a reproducing means for reproducing the received image data, and a display means for displaying the image obtained by the reproducing means. , A detecting means for detecting an error in the received image data, a measuring means for measuring the receiving quality of the received image data, and a receiving quality measured when an error is detected in the received image data. Accordingly, a configuration is provided that includes a switching unit that switches the image displayed on the display unit.

According to this structure, when a transmission error occurs, the receiving device can autonomously control the switching of the display image according to the reception quality, so that the receiving side does not depend on the function of the transmitting side. Even if a transmission error occurs, it is possible to display an easy-to-see image only with the function on the side. Particularly, in wireless communication in which the transmission error rate is much higher than that in wired communication, it is possible to perform an optimal display that is easy to see. Further, it is not necessary to make an agreement regarding the procedure of signal transmission / reception between the receiving side and the transmitting side when a transmission error occurs, and it is possible to flexibly design the system and the receiving device. Further, this configuration is particularly suitable for performing display control when an error occurs in a receiving device capable of both real-time communication (for example, a videophone) in which no key frame exists and video streaming in which a key frame exists. It is valid.

In the image receiving apparatus of the present invention, in the above-mentioned configuration, when the switching means detects an error in the received image data and the measured reception quality is equal to or higher than a predetermined value, the reproduction is performed. The image obtained this time by the means is used as the image displayed on the display means.

According to this structure, when the reception quality is relatively high, it is determined that the image quality deterioration is small, and the image obtained this time is displayed even if an error is detected, so that an easy-to-see image is continuously displayed. be able to.

In the image receiving apparatus of the present invention, in the above configuration, when the switching means detects an error in the received image data and the measured reception quality is less than a predetermined value, the reproduction is performed. The image obtained previously by the means is used as the image displayed on the display means.

According to this structure, when the reception quality is relatively low, it is determined that the image quality is large, and when an error is detected, the still image is temporarily displayed, so that the disordered image is displayed. Will disappear.

In the image receiving apparatus of the present invention having the above-mentioned structure, the measuring means measures the error rate of the received image data as the reception quality, and the switching means detects an error in the received image data. In this case, the image displayed on the display unit is switched according to the measured error rate.

According to this structure, an appropriate image can be displayed according to the reception quality.

The communication terminal device of the present invention has a configuration including any one of the above image receiving devices.

According to this structure, it is possible to provide a communication terminal device having the same operations and effects as above.

The image display control method of the present invention comprises a receiving step of receiving encoded image data, a reproducing step of reproducing the received image data, and a displaying step of displaying the image obtained in the reproducing step. A detection step of detecting an error in the received image data, a measurement step of measuring an error resistance strength of the received image data, and a detection step according to the measured error resistance strength when an error is detected in the received image data. And a switching step of switching the image displayed in the display step.

According to this method, when the transmission error occurs, the receiving device can autonomously control the switching of the display image according to the strength of the error tolerance, and therefore the function of the transmitting side does not depend. Instead, it is possible to display an easy-to-see image even if a transmission error occurs, using only the function of the receiving side. Particularly, in wireless communication in which the transmission error rate is much higher than that in wired communication, it is possible to perform an optimal display that is easy to see. Further, it is not necessary to make an agreement regarding the procedure of signal transmission / reception between the receiving side and the transmitting side when a transmission error occurs, and it is possible to flexibly design the system and the receiving device. Furthermore, this method is particularly suitable for performing display control when an error occurs in a receiving device capable of both real-time communication (for example, a videophone) in which a key frame does not exist and video streaming in which a key frame exists. It is valid.

The image display control method of the present invention comprises a receiving step of receiving encoded image data, a reproducing step of reproducing the received image data, and a displaying step of displaying the image obtained in the reproducing step. A detecting step of detecting an error in the received image data, a measuring step of measuring the receiving quality of the received image data, and a displaying step according to the measured receiving quality when an error is detected in the received image data. And a switching step of switching the image displayed by.

According to this method, when a transmission error occurs, the receiving device can autonomously control the switching of the display image according to the reception quality, so that the receiving device does not depend on the function of the transmitting side. Even if a transmission error occurs, it is possible to display an easy-to-see image only with the function on the side. Particularly, in wireless communication in which the transmission error rate is much higher than that in wired communication, it is possible to perform an optimal display that is easy to see. Further, it is not necessary to make an agreement regarding the procedure of signal transmission / reception between the receiving side and the transmitting side when a transmission error occurs, and it is possible to flexibly design the system and the receiving device. Furthermore, this method is particularly suitable for performing display control when an error occurs in a receiving device capable of both real-time communication (for example, a videophone) in which a key frame does not exist and video streaming in which a key frame exists. It is valid.

The image display control program of the present invention comprises a receiving step of receiving the encoded image data, a reproducing step of reproducing the received image data, and a displaying step of displaying the image obtained in the reproducing step. A detection step for detecting an error in the received image data, a measurement step for measuring the error resistance strength of the received image data, and a detection step depending on the measured error resistance strength when an error is detected in the received image data. The computer is made to execute the switching step of switching the image displayed in the display step.

According to this program, when a transmission error occurs, the receiving device can autonomously control the switching of the display image according to the strength of the error resistance, so that it does not depend on the function of the transmitting side. Instead, it is possible to display an easy-to-see image even if a transmission error occurs, using only the function of the receiving side. Particularly, in wireless communication in which the transmission error rate is much higher than that in wired communication, it is possible to perform an optimal display that is easy to see. Further, it is not necessary to make an agreement regarding the procedure of signal transmission / reception between the receiving side and the transmitting side when a transmission error occurs, and it is possible to flexibly design the system and the receiving device. Furthermore, this program is particularly suitable for performing display control when an error occurs in a receiving device capable of both real-time communication (for example, a videophone) in which no key frame exists and video streaming in which a key frame exists. It is valid.

The image display control program of the present invention includes a receiving step of receiving the encoded image data, a reproducing step of reproducing the received image data, and a displaying step of displaying the image obtained in the reproducing step. A detecting step for detecting an error in the received image data, a measuring step for measuring the receiving quality of the received image data, and a displaying step according to the measured receiving quality when an error is detected in the received image data. The computer is made to perform the switching step of switching the image displayed by.

According to this program, when a transmission error occurs, the receiving device can autonomously control the switching of the display image in accordance with the reception quality, so that the receiving side does not depend on the function of the transmitting side. Even if a transmission error occurs, it is possible to display an easy-to-see image only with the function on the side. Particularly, in wireless communication in which the transmission error rate is much higher than that in wired communication, it is possible to perform an optimal display that is easy to see. Further, it is not necessary to make an agreement regarding the procedure of signal transmission / reception between the receiving side and the transmitting side when a transmission error occurs, and it is possible to flexibly design the system and the receiving device. In addition, this program
This is particularly effective when performing display control when an error occurs in a receiving device that can perform both real-time communication (for example, a videophone) where key frames do not exist and video streaming where key frames exist.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION The essence of the present invention is that, when an error occurs in image data, the receiving side of the image data autonomously performs display control according to the strength of error tolerance and the reception quality. .

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(Embodiment 1) When an image is encoded, an image for one frame is divided into a plurality of blocks and this is used as an encoding unit. This is called a macroblock. In addition, although not often used in real-time communication such as a videophone, in a service called streaming in which the receiving side plays while downloading the image data stored in the server, all macroblocks included in one frame are Intra-frame encoded frames are periodically inserted and transmitted. A frame in which all macroblocks included in one frame are intra-coded is called a random access point or a key frame. Conventionally, this key frame is inserted in order to realize special reproduction such as fast forward and rewind during reproduction of image data. However, the present inventor has found that this key frame can be used as a frame for recovering deteriorated image quality in wireless communication. When a key frame is used to recover degraded image quality in wireless communication, the shorter the key frame reception interval, the higher the error resilience and the faster the image quality recovery speed. Conversely, the longer the key frame reception interval, the more error The strength of resistance is low and the recovery speed of image quality is slow.

Therefore, the image receiving apparatus according to the first embodiment of the present invention measures the reception interval of key frames as the strength of error tolerance, and when an error is detected in the received image data, the key frame The display image is switched according to the reception interval. Specifically, if the key frame reception interval is equal to or greater than a predetermined value, the moving image is continuously displayed by sequentially displaying the images reproduced this time, and if the key frame reception interval is less than the predetermined value, Display a replayed image and display a still image until a keyframe is received.

FIG. 1 is a block diagram showing the configuration of the image receiving apparatus according to the first embodiment of the present invention. In the following description, the case where the image receiving device is installed in a communication terminal device such as a mobile phone used in mobile wireless communication will be described as an example. The same applies to the second and subsequent embodiments.

In the image receiving apparatus shown in FIG. 1, a signal wirelessly transmitted from the transmitting side is received by the wireless receiving section 102 via the antenna 101. This signal includes image data, and the image data is encoded. The wireless reception unit 102 demodulates the received signal. As a result, video packet format image data is obtained. The image data obtained by the wireless reception unit 102 is sequentially stored in the reception buffer 103.

The image data stored in the reception buffer 103 is decoded by the variable length decoding unit 104. That is, the quantized DCT coefficient is decoded from the image data and input to the inverse quantization unit 105. The quantized DCT coefficient becomes a DCT coefficient in the inverse quantization unit 105, and the prediction error signal is calculated from the DCT coefficient in the inverse IDCT unit 106.

The variable length decoding unit 104 decodes the motion vector and the macroblock address indicating the spatial position on the frame, the motion vector is input to the memory control unit 107, and the macroblock address is stored in the memory. It is input to the control unit 107 and the concealment range determination unit 108.

Further, the variable length decoding unit 104 decodes the frame coding mode and inputs it to the switching control unit 109 and the reception interval measuring unit 110. Here, the frame coding mode indicates whether or not each frame forming the received image data is a key frame, and is added to the header portion of each frame.

Further, the error detection unit 111 included in the variable length decoding unit 104 detects an error in the image data during the decoding by the variable length decoding unit 104. Specifically, the code word of the macro block decoded by the variable length decoding unit 104 and the code word on the variable length code word table are matched, and the code word of the decoded macro block is displayed on the variable length code word table. If there is no error, it is judged as'There is an error 'and if it is on the variable length codeword table, it is judged as'No error'. Then, the error detection unit 111 sends a signal indicating the presence or absence of an error to the concealment range determination unit 108 and the switching control unit 10.
Enter in 9.

The reception interval measuring unit 110 measures the reception interval of key frames based on the input frame coding mode. That is, the timer measures the interval at which the frame coding mode indicating the key frame is input. In this case, the measurement accuracy is improved by setting the average value of the intervals measured a plurality of times as the measurement value. In the following description, the key frame reception interval is also referred to as a random access interval as appropriate. The measured random access interval is input to the switching control unit 109.

Here, the random access interval measured by the reception interval measuring unit 110 corresponds to the strength of error tolerance. That is, it can be said that the shorter the random access interval, the faster the recovery speed of image quality, and thus the higher the error resilience strength, and conversely, the longer the random access interval, the slower the image recovery speed, and thus the lower the error resilience strength. In this way, the reception interval measuring unit 110 measures the random access interval as the strength of error tolerance.

The switching control unit 109 switches the image displayed on the display unit 116 by controlling connection / disconnection of the switch 114 based on the presence / absence of an error, the frame coding mode and the random access interval. Specifically, the switch 114 is controlled as shown in FIG.

That is, the switching control unit 109 controls the switch 114 based on the frame coding mode when the decoded image data has no error. If there is no error and it is a key frame, switch 1
14 are connected and the images obtained this time are sequentially displayed on the display unit 11.
6 to display. That is, when there is no error and the key frame is present, a moving image is displayed on the display unit 116. The specific operation is as follows.

The memory control unit 107 calculates an address for reading the data serving as the predicted reference image from the motion vector and the macroblock address. Then, referring to the frames stored in the frame memory 112,
The data corresponding to the calculated address is read and input to the adder 113. In addition, in the frame memory 112,
At least the previously reproduced image (frame) is stored. In the addition unit 113, the data to be the predicted reference image input from the frame memory 112 and the inverse IDCT
The prediction error signal input from the unit 106 is added.
A reproduced image is obtained by these processes. This reproduced image is stored in the display data memory 115 via the switch 114. Then, the image stored in the display data memory 115 is displayed on the display unit 116 such as a liquid crystal monitor. Note that the image stored in the display data memory 115 is updated every time a new image is input to the display data memory 115. Therefore, when the switch 114 is in the connected state, a moving image is displayed on the display unit 116. Is displayed.

If there is no error in the decoded image data and it is not a key frame, the switching control unit 1
09 maintains the current state of the switch 114. If the current state of the switch 114 is the connected state, the image stored in the display data memory 115 is updated with the image reproduced this time as in the above, and thus a moving image is displayed on the display unit 116. If the current state of the switch 114 is the disconnection state, the image stored in the display data memory 115 is not updated and remains the previously reproduced image, so that the previously reproduced image is continuously displayed on the display unit 116. To be done. That is, a still image is displayed.

On the other hand, when there is an error in the decoded image data, the switching control unit 109 controls the switch 114 based on the random access interval. If there is an error and the random access interval is equal to or greater than the predetermined value, the switch 114 is connected and the image obtained this time is
The images are sequentially displayed on the display unit 116. Therefore, when there is an error and the random access interval is equal to or greater than the predetermined value, the moving image is displayed on the display unit 116. This is for the following reason.

If the decoded image data has an error, it is possible to uniformly switch off the switch 114 so that the disturbed image reproduced this time is not displayed. That is, if there is an error in the decoded image data, it is possible to uniformly display the still image on the display unit 116. However, when the random access interval is equal to or greater than the predetermined value, it is predicted that no key frame will be received for a long time. Therefore, if the switch 114 is uniformly disconnected when there is an error, the switch 114 remains in the disconnected state for a long time, and the still image is continuously displayed for a long time. In this case, depending on the degree of error, the distorted image may be more difficult to see than the undisturbed display. Therefore, even if there is an error, if the random access interval is equal to or larger than the predetermined value, the image obtained this time is displayed to display the moving image.

As described above, when there is an error and the random access interval is equal to or larger than the predetermined value, there is no error and the switch 1 is the same as the case of the key frame.
14 is connected. However, the operation is different in the following points. That is, when there is an error and the random access interval is equal to or larger than a predetermined value, the concealment process (concealment) is performed on the reproduced image. In particular,
When the concealment range determination unit 108 receives the signal indicating “with error”, the concealment range determination unit 108 determines from which position on the frame to which data on the frame the data has been lost due to the error, based on the macroblock address. Then, in order to make the image quality deterioration in the range where the data is lost conspicuous, an address for reading the data from the same position of the previous frame stored in the frame memory 112 is calculated. Then, the frame stored in the frame memory 112 is referred to, the data corresponding to the calculated address is read and input to the addition unit 113. At this time, the adding unit 113 does not use the prediction error signal input from the inverse IDCT unit 106 at the corresponding address, but does not use the prediction error signal.
The data input from 2 is used as it is.

If there is an error in the decoded image data and the random access interval is less than the predetermined value, the switching control unit 109 disconnects the switch 114,
The previously obtained image is displayed on the display unit 116. Therefore, when there is an error and the random access interval is less than the predetermined value, a still image is displayed on the display unit 116. This is for the following reason.

If the random access interval is less than the predetermined value, it is predicted that the key frame will be received in a short time. That is, if the key frame is received in a short time, the image quality can be recovered in a short time by the key frame. Therefore, when the random access interval is less than a predetermined value, it is possible to display an image that is easier to see when displaying a still image than when displaying an errored and disordered image as it is. That is, if a key frame is frequently received, it is possible to display an image that is easier to see by waiting for the next key frame to be transmitted without displaying the frame whose image quality is deteriorated due to an error. Therefore, when there is an error and the random access interval is less than the predetermined value, the previously obtained image is continuously displayed and the still image is displayed.

As described above, according to the present embodiment, when a transmission error occurs, the receiving device can autonomously perform the switching control of the display image according to the strength of the error tolerance, so that the transmitting side Even if a transmission error occurs, it is possible to display an easy-to-see image without depending on the function of (1) and by only the function of the receiving side. Particularly, in wireless communication in which the transmission error rate is much higher than that in wired communication, it is possible to perform an optimal display that is easy to see. Further, it is not necessary to make an agreement regarding the procedure of signal transmission / reception between the receiving side and the transmitting side when a transmission error occurs, and it is possible to flexibly design the system and the receiving device. Further, this configuration is particularly suitable for performing display control when an error occurs in a receiving device capable of both real-time communication (for example, a videophone) in which no key frame exists and video streaming in which a key frame exists. It is valid.

Further, according to this embodiment, an appropriate image can be displayed according to the strength of error tolerance. That is, when it is determined that the random access interval is relatively short, the image quality is expected to be restored in a relatively short time by the key frame, and a still image is temporarily displayed when an error is detected. , Distorted images are no longer displayed. On the other hand, if it is determined that the random access interval is relatively long, the image obtained this time is displayed even if an error is detected without expecting the image quality to be restored by the key frame. Will not be displayed. In other words, when it is determined that the random access interval is short, the image whose image quality has been restored by the key frame is displayed, so a still image is displayed temporarily, but a disordered image is displayed even if an error occurs. Will disappear. On the other hand, when it is determined that the random access interval is long, the decoded image can be continuously displayed.

(Embodiment 2) On the transmission side, a plurality of macroblocks are regarded as one transmission unit, and a packet in which a specific synchronization word and header information are added to the head is called a video packet. By configuring a video packet, when a transmission error occurs in image data, the video packet with an error cannot be decoded, but it can be decoded from the video packet next to the video packet with the error. . In this way, by constructing a video packet from a synchronization word and a plurality of macroblocks following it, the range of image quality deterioration can be suppressed to a narrow range. Further, the smaller the number of macroblocks forming a video packet and the larger the number of video packets included in one frame, the higher the error resistance strength and the faster the image quality recovery speed. On the contrary, as the number of macroblocks forming a video packet is increased and the number of video packets included in one frame is decreased, the error resistance strength becomes lower and the image quality recovery speed becomes slower.

On the transmitting side, some of a plurality of macroblocks included in one frame are made into macroblocks called refresh macroblocks. This refresh macroblock is an intraframe-encoded macroblock and can be decoded without using the information of the previous frame. Hereinafter, the intra-frame coded macro block is referred to as an intra macro block. By inserting the intra macroblock in this way, it is possible to recover the image quality with the lapse of time while circling a part of the frame little by little.
Further, the greater the number of intra macroblocks included in one frame, the higher the error resistance strength and the faster the image quality recovery speed. Conversely, the smaller the number of intra macroblocks included in one frame, the stronger the error resistance strength. The lower the image quality, the slower the recovery speed.

Therefore, the image receiving apparatus according to the second embodiment of the present invention measures the number of video packets included in one frame and the number of intra macroblocks included in one frame as the strength of error tolerance, and the received signal is received. When an error is detected in the image data, the display image is switched according to the number of video packets included in one frame and the number of intra macroblocks included in one frame. Specifically, when the number of video packets included in one frame is equal to or larger than a predetermined value and the number of intra macroblocks included in one frame is equal to or larger than a predetermined value, the images reproduced this time are sequentially displayed. Keeps displaying moving images, and if the number of video packets included in one frame is less than the predetermined value, or if the number of intra macroblocks included in one frame is less than the predetermined value, the previously played image is displayed. Display and display a still image until a keyframe is received.

FIG. 3 is a block diagram showing the structure of the image receiving apparatus according to the second embodiment of the present invention. In FIG. 3, the same parts as those in Embodiment 1 (FIG. 1) are designated by the same reference numerals, and the description thereof will be omitted.

In the image receiving apparatus shown in FIG. 3, the variable length decoding unit 104 is a synchronization word (picture start code) indicating that it is the beginning of a frame during decoding of image data.
Alternatively, when a sync word (resync marker) indicating the beginning of a video packet is detected, a sync word detection signal indicating that and a sync word type (picture start code or resync marker) is sent to the VP (video packet). ) Input to the detection unit 201 and the intra MB (macro block) detection unit 202.

Also, the variable length decoding unit 104 decodes the macroblock coding mode, and the intra MB detection unit 20.
Enter 2. Here, the macroblock coding mode indicates whether or not each macroblock forming a video packet is an intra macroblock, and is added to the header portion of each macroblock.

The VP detector 201 measures the number of video packets included in one frame based on the sync word detection signal. Specifically, first, the type of the sync word (picture start code or resync marker) detected by the variable length decoding unit 104 is determined from the input sync word detection signal. Then, the number of resync markers detected from the detection of the picture start code to the detection of the next picture start code is measured. Since the picture start code is a sync word indicating the beginning of the frame and the resync marker is a sync word indicating the beginning of the video packet, the number of resync markers measured in this way is 1 This corresponds to the number of video packets included in the frame. The VP detection unit 20
1 improves the measurement accuracy by setting the average value of the numbers measured a plurality of times as the measurement value. The number of video packets measured in this way is input to the switching control unit 203.

The intra MB detection section 202 measures the number of intra macroblocks included in one frame based on the sync word detection signal and the macroblock coding mode. Specifically, first, the type of the sync word (picture start code or resync marker) detected by the variable length decoding unit 104 is determined from the input sync word detection signal. Then, among the macroblock coding modes detected between the detection of the picture start code and the detection of the next picture start code, the number of macroblock coding modes indicating the intra macroblock is set. taking measurement. Since the picture start code is a sync word indicating the beginning of a frame, the number of macroblock coding modes measured in this way corresponds to the number of intra macroblocks included in one frame. The intra MB detection unit 202 increases the measurement accuracy by setting the average value of the numbers measured a plurality of times as the measurement value. The number of intra macroblocks measured in this way is input to the switching control unit 203.

The switching control unit 203 connects / disconnects the switch 114 based on the presence / absence of an error, the frame coding mode, the number of video packets included in one frame, and the number of intra macroblocks included in one frame. By controlling, the image displayed on the display unit 116 is switched. Specifically, as shown in FIG. 4, the switch 1
Control 14. Note that, as shown in FIG. 4, the operation when there is no error in the decoded image data is the same as in the first embodiment.
The description is omitted because it is the same as (FIG. 2).

When the decoded image data has an error, the number of video packets included in one frame is a predetermined value or more, and the number of intra macroblocks included in one frame is a predetermined value or more. First, the switching control unit 203 determines that the error resistance strength is high and the image quality recovery speed is fast, and connects the switch 114. Therefore, the images obtained this time are sequentially displayed on the display unit 116. In this case, concealment processing (concealment) is performed as in the first embodiment.

When the decoded image data has an error and the number of video packets included in one frame is less than a predetermined value, or the decoded image data has an error and one frame is included. If the number of the intra macroblocks included in is less than the predetermined value, the switching control unit 203 determines that the error resistance strength is low and the image recovery speed is slow, and disconnects the switch 114.
Therefore, in these cases, a still image is displayed on the display unit 116, and an errored and disordered image is not displayed.

As described above, according to the present embodiment, as in the first embodiment, when a transmission error occurs, display image switching control can be autonomously performed according to the strength of error tolerance. Therefore, it is possible to display an easy-to-see image even when a transmission error occurs, without depending on the function of the transmitting side and only by the function of the receiving side. Especially in wireless communication where the transmission error rate is much higher than in wired communication,
The optimum display that is easy to see can be performed. Further, it is not necessary to make an agreement regarding the procedure of signal transmission / reception between the receiving side and the transmitting side when a transmission error occurs, and it is possible to flexibly design the system and the receiving device. Further, this configuration is particularly suitable for performing display control when an error occurs in a receiving device capable of both real-time communication (for example, a videophone) in which no key frame exists and video streaming in which a key frame exists. It is valid.

Further, according to this embodiment, an appropriate image can be displayed according to the strength of error tolerance. That is, when it is determined that the image quality recovery by the video packet or the intra macro block is quick, the decoded image in which the error occurs is also displayed. As a result, it becomes possible to reproduce a smooth motion in an image with little image quality deterioration due to an error.

(Third Embodiment) An image receiving apparatus according to a third embodiment of the present invention measures an error rate of image data as a reception quality of the image data and detects an error in the received image data. In addition, the display image is switched according to the error rate.

FIG. 5 is a block diagram showing the structure of the image receiving apparatus according to the third embodiment of the present invention. In FIG. 5, the same parts as those in Embodiment 1 (FIG. 1) will be assigned the same reference numerals and explanations thereof will be omitted.

In the image receiving apparatus shown in FIG. 3, the error rate measuring section 301 receives the sync word detection signal from the variable length decoding section 104 and the signal indicating the presence or absence of an error from the error detecting section 111. The error rate measurement unit 301
The error rate is measured as the reception quality. Specifically, the type of the sync word (picture start code or resync marker) detected by the variable length decoding unit 104 is determined from the input sync word detection signal. Then, it is observed whether or not a signal indicating “error present” is input between the detection of the picture start code and the detection of the next picture start code.

When a signal indicating “with error” is not input between the detection of a picture start code and the detection of the next picture start code, the error rate measurement unit 301 decodes the frame without error. Considered completed.

If there is even one signal indicating "error" between the detection of a picture start code and the detection of the next picture start code, there is an error in that frame. To judge. The error rate measuring unit 301 counts the number of errored frames from the start of communication. The error rate is then measured by dividing the number of erroneous frames by the number of received frames. The error rate thus measured is input to the switching control unit 302.

Here, the higher the error rate is, the poorer the reception quality is, the more likely the distorted image is displayed, and conversely, the lower the error rate is, the better the reception quality is, and the more distorted the image is displayed. Can be said to be low.

Therefore, the switching control unit 302 determines whether the switch 114 is connected or not based on the presence / absence of an error and the error rate.
By controlling the disconnection, the image displayed on the display unit 116 is switched. Specifically, the switch 114 is controlled as shown in FIG. Note that, as shown in FIG. 6, the operation when there is no error in the decoded image data is the same as that in the first embodiment (FIG. 2), and thus the description thereof is omitted.

When the decoded image data has an error and the error rate is less than the predetermined value (that is, the reception quality is equal to or more than the predetermined value), the switching control unit 302 displays an image that is not so easy to see. Judge that there is no such thing,
The switch 114 is connected. Therefore, the images obtained this time are sequentially displayed on the display unit 116. In this case, concealment processing (concealment) is performed as in the first embodiment.

If the decoded image data has an error and the error rate is equal to or higher than a predetermined value (that is, the reception quality is lower than the predetermined value), the switching control section 302
Switch 1 when it determines that an image that is difficult to see is displayed.
Cut 14 Therefore, in this case, the display unit 116
Displays a static image, and does not display an errored and distorted image.

As described above, according to the present embodiment, when a transmission error occurs, the receiving device can autonomously control the switching of the display image according to the reception quality. Even if a transmission error occurs, it is possible to display an easy-to-see image by using only the function of the receiving side, without depending on. Particularly, in wireless communication in which the transmission error rate is much higher than that in wired communication, it is possible to perform an optimal display that is easy to see. Further, it is not necessary to make an agreement regarding the procedure of signal transmission / reception between the receiving side and the transmitting side when a transmission error occurs, and it is possible to flexibly design the system and the receiving device. Further, this configuration is particularly suitable for performing display control when an error occurs in a receiving device capable of both real-time communication (for example, a videophone) in which no key frame exists and video streaming in which a key frame exists. It is valid.

Further, according to the present embodiment, an appropriate image can be displayed according to the reception quality. That is,
When the reception quality is relatively high, it is determined that the image quality deterioration is small, and the image obtained this time is displayed even if an error is detected, so that the image that is easy to see can be continuously displayed. On the other hand, when the reception quality is relatively low, it is determined that the image quality is deteriorated, and when an error is detected, the still image is temporarily displayed, so that the disordered image is not displayed. That is, a moving image is displayed when it is determined that the error rate is low and the image quality is not significantly deteriorated, and a still image is displayed when the error rate is high and the image quality is significantly deteriorated. Since it becomes possible to display a distorted image.

(Embodiment 4) An image receiving apparatus according to Embodiment 4 of the present invention is a combination of Embodiments 1 to 3. That is, when an error is detected in the received image data, the display image is displayed according to the random access interval, the number of video packets included in one frame, the number of intra macroblocks included in one frame, and the error rate. It is to switch.

FIG. 7 is a block diagram showing the structure of the image receiving apparatus according to the fourth embodiment of the present invention. In FIG. 7, the same parts as those in Embodiment 1 (FIG. 1), Embodiment 2 (FIG. 3) and Embodiment 3 (FIG. 5) are designated by the same reference numerals and the description thereof will be omitted. .

In the image receiving apparatus shown in FIG. 7, the switching control section 401 determines whether there is an error, a random access interval,
The image displayed on the display unit 116 is switched by controlling connection / disconnection of the switch 114 based on the number of video packets included in one frame, the number of intra macroblocks included in one frame, and the error rate. . Specifically, the switch 114 is controlled as shown in FIG. Note that, as shown in FIG. 8, the operation when there is no error in the decoded image data is as described in Embodiment 1 (FIG. 2).
The description is omitted because it is the same as.

When there is an error in the decoded image data and the random access interval is equal to or larger than the predetermined value, the switching control section 401 connects the switch 114.

When the decoded image data has an error, the number of video packets included in one frame is a predetermined value or more, and the number of intra macroblocks included in one frame is a predetermined value or more. Is the switching control unit 4
01 connects the switch 114.

If the decoded image data has an error, the number of video packets included in one frame is equal to or more than a predetermined value, and the number of intra macroblocks included in one frame is less than the predetermined value, If the error rate is equal to or higher than the predetermined value, the switching control unit 401 causes the switch 11
Cut 4.

If the decoded image data has an error, the number of video packets included in one frame is equal to or greater than a predetermined value, and the number of intra macroblocks included in one frame is less than the predetermined value, If the error rate is less than the predetermined value, the switching control unit 401 determines that the switch 11
Connect 4

If the decoded image data has an error, the random access interval is greater than or equal to a predetermined value, and the number of video packets included in one frame is less than the predetermined value, the switching control unit 401 , Switch 114 is disconnected.

As described above, according to the present embodiment, by combining the first to third embodiments,
The display image can be switched in various ways when an error occurs. Specifically, if the random access interval is equal to or greater than a predetermined value when an error occurs, a moving image is displayed. Even if the random access interval is less than the predetermined value, the moving image is displayed when it is determined that the image quality is recovered quickly or when the deterioration of the image quality is small. It becomes possible to display a moving image. Further, when it is determined that the image quality is slow to recover or the error rate is high and the image quality is largely deteriorated, the still image is displayed, so that it is possible to prevent the image having the significantly deteriorated image quality from being displayed. .

In the first to fourth embodiments, the variable length decoding unit 1 detects the error of the image data.
This is done by matching the code word of the macro block decoded by 04 with the code word on the variable length code word table. However, the error detection method is not limited to this. For example, it is possible to detect an error using an error detection code or the like.

Further, the image receiving devices according to the first to fourth embodiments are suitable for use as a communication terminal device used in a mobile communication system or the like. By mounting the image receiving device according to Embodiments 1 to 4 on the communication terminal device, it is possible to provide a communication terminal device having the same operation and effect.

Further, in the first to fourth embodiments, the present invention has been described as the image receiving apparatus, but the present invention is not limited to this, and the present invention can be implemented as a software. For example, a program for receiving an image may be stored in the ROM in advance, and the program may be operated by the CPU. Alternatively, the program for receiving the image may be stored in a computer-readable storage medium, the program stored in the storage medium may be recorded in the RAM of the computer, and the computer may be operated in accordance with the program.
Even in such a case, the same operation and effect as those of the first to fourth embodiments are exhibited.

Further, a program for receiving an image may be stored in the server, the program stored in the server may be transmitted to the client in response to a request from the client, and the program may be executed on the client. Further, a program for receiving images may be stored in the server and the program may be executed on the server in response to a request from the client.

[0092]

As described above, according to the present invention,
When an error is detected in the image data, it is possible to display an easily viewable image by the autonomous control of the receiving device.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of an image receiving device according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a display switching operation of the image receiving device according to the first embodiment of the present invention.

FIG. 3 is a block diagram showing a configuration of an image receiving device according to a second embodiment of the present invention.

FIG. 4 is a diagram for explaining a display switching operation of the image receiving device according to the second embodiment of the present invention.

FIG. 5 is a block diagram showing a configuration of an image receiving apparatus according to Embodiment 3 of the present invention.

FIG. 6 is a diagram for explaining a display switching operation of the image receiving device according to the third embodiment of the present invention.

FIG. 7 is a block diagram showing a configuration of an image receiving apparatus according to Embodiment 4 of the present invention.

FIG. 8 is a diagram for explaining a display switching operation of the image receiving device according to the fourth embodiment of the present invention.

[Explanation of symbols]

101 antenna 102 wireless receiver 103 receive buffer 104 variable length decoding unit 105 inverse quantizer 106 Inverse IDCT section 107 memory control unit 108 Concealment range determination unit 109, 203, 302, 401 Switching control unit 110 Reception interval measurement unit 111 Error detector 112 frame memory 113 adder 114 switch 115 Display data memory 116 display 201 VP (video packet) detector 202 Intra MB (macro block) detector 301 Error rate measurement unit

Claims (14)

[Claims] 1. Receiving means for receiving encoded image data, reproducing means for reproducing the received image data, display means for displaying an image obtained by the reproducing means, and received image data. Of the error resistance of the received image data, the measuring means for measuring the error resistance strength of the received image data, and the error resistance strength measured when an error is detected in the received image data. An image receiving apparatus comprising: a switching unit that switches an image displayed on the display unit. 2. The switching means, when an error is detected in the received image data, displays the image displayed on the display means by the reproducing means in accordance with the measured error resistance strength. The image receiving apparatus according to claim 1, wherein the obtained image and the image obtained this time by the reproducing unit are switched. 3. The measuring means sets the reception interval of frames in which all the coding units included in one frame are intra-coded among the frames forming the received image data as the error resilience strength. The measurement is performed, and the switching unit switches the image displayed on the display unit according to the measured reception interval when an error is detected in the received image data. The image receiving device described. 4. The measuring means measures, as a strength of error tolerance, the number of coding units which are intra-frame coded in a frame forming the received image data, and the switching means receives the received data. The image receiving apparatus according to claim 1, wherein when an error is detected in the image data, the image displayed on the display unit is switched according to the number of measured coding units. 5. The measuring means measures the number of video packets composed of a sync word and a plurality of coding units following the sync word in a frame forming the received image data as an error resilience strength. However, the switching unit switches the image displayed on the display unit in accordance with the number of measured video packets when an error is detected in the received image data. 1. The image receiving device according to 1. 6. Receiving means for receiving the encoded image data, reproducing means for reproducing the received image data, display means for displaying the image obtained by the reproducing means, and received image data. Detecting means for detecting the error, measuring means for measuring the reception quality of the received image data, and when an error is detected in the received image data, the display means according to the measured reception quality An image receiving apparatus comprising: a switching unit that switches an image displayed on the screen. 7. The switching means displays the image obtained this time by the reproducing means when the measured reception quality is equal to or higher than a predetermined value when an error is detected in the received image data. The image display device according to claim 6, wherein the image is displayed on the means. 8. The switching unit displays the image previously obtained by the reproducing unit when an error is detected in the received image data and the measured reception quality is less than a predetermined value. The image display device according to claim 6, wherein the image is displayed on the means. 9. The measuring means measures the error rate of the received image data as the reception quality, and the switching means sets the measured error rate to the measured error rate when an error is detected in the received image data. The image receiving apparatus according to claim 6, wherein the image displayed on the display unit is switched according to the change. 10. A communication terminal device comprising the image receiving device according to any one of claims 1 to 9. 11. A receiving step of receiving encoded image data, a reproducing step of reproducing the received image data, a displaying step of displaying the image obtained in the reproducing step, and an error of the received image data. A detection step of detecting, a measurement step of measuring the error resistance strength of the received image data, and when an error is detected in the received image data, display in the display step according to the measured error resistance strength. An image display control method comprising: a switching step of switching images. 12. A receiving step of receiving the encoded image data, a reproducing step of reproducing the received image data, a displaying step of displaying the image obtained in the reproducing step, and an error of the received image data. Detecting step to detect, measuring step to measure the reception quality of the received image data, and switch the image displayed in the display step according to the measured reception quality when an error is detected in the received image data An image display control method, comprising: 13. A reception step of receiving encoded image data, a reproduction step of reproducing the received image data, a display step of displaying the image obtained in the reproduction step, and an error of the received image data. A detection step for detecting, a measurement step for measuring the strength of error resistance of the received image data, and when an error is detected in the received image data, it is displayed in the display step according to the strength of the measured error resistance. An image display control program characterized by causing a computer to execute a switching step of switching an image. 14. A receiving step of receiving coded image data, a reproducing step of reproducing the received image data, a displaying step of displaying the image obtained in the reproducing step, and an error of the received image data. A detection step of detecting, a measurement step of measuring the reception quality of the received image data, and a switching of the image displayed in the display step according to the measured reception quality when an error is detected in the received image data An image display control program characterized by causing a computer to execute the steps.