JP2001309375A - Media separating method and method/device for decoding image - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress image deterioration in occurrence of the erroneous transmission of the moving image communication of a video telephone, etc. SOLUTION: In media separation processing, when detecting an error in an image signal, a specific code is inserted and an image decoding part 107 is informed of an error occurring position by the unit of a packet. When detecting the specific code in the received image signal, the part 107 displays an image which can be decoded by the time just before the occurrence of an error and makes a period from the time just after the occurrence of the error to the detection of the next synchronous word.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a media separation method and an image decoding method and apparatus suitable for use in video communication such as a videophone.

[0002]

2. Description of the Related Art Conventionally, as a technique for encoding a moving picture signal or an audio signal and multiplexing them into one signal, it has been recommended by the International Telecommunication Union (ITU-T: International Telecommunication Union). Recommendati
on H.223. In this H.223, an adaptation layer (there are three types from AL1 to AL3) that packetizes with an appropriate layer according to the characteristics of the media to be transmitted (audio and video are called media), and each adaptation layer And a multiplex layer that combines and multiplexes the packets output from the.

[0003] As described above, an appropriate adaptation layer is selected according to the characteristics of the medium, but AL3 is generally applied to a moving image signal. This AL3 has an error detection function and a retransmission control function, and is said to be suitable for real-time image communication.
AL packetized by the adaptation layer
-Called an SDU (Adaptation Layer Service Data Unit) packet.

[0004] The max layer is a layer for collecting AL-SDU packets output from AL1 to AL3 as one transmission data, and multiplex processing is performed here. At the time of reception, first, separation is performed for each medium in the max layer, and the separated packets are input to the corresponding adaptation layers. In this case, if it is a moving image signal, an AL-SDU packet is input to AL3, and error detection processing is performed. Thereafter, the data is passed to the image decoder. When an error is detected by the error detection processing, whether or not to retransmit the erroneous AL-SDU packet and whether or not to pass the AL-SDU packet to the image decoder are outside the recommendations of the ITU-T. Since it is a content, it can be freely selected.

[0005] As a technique for encoding a moving image signal, there is ISO / IEC 14496 part 2 (Visual) (commonly known as MPEG-4) recommended by the International Standards Committee (ISO / IEC: ISO / IEC). . MPEG-4 Visual is a multimedia encoding method, and is a technology capable of encoding various video materials.

[0006] The MPEG-4 image coding technique is realized by three techniques of "motion compensated predictive coding", "discrete cosine transform" and "variable length code". In the motion-compensated predictive coding, first, an input image is compared with a previous coded image, and the amount of motion between the images is measured (motion detection). Then, an input image is predicted from the measured amount of motion and the previous encoded image. Next, a difference (prediction error signal) between the predicted image (prediction image) and the input image is calculated, and the prediction error signal and the aforementioned motion amount are transmitted to the receiving side. This enables image information transmission with a small data amount.

[0007] The discrete cosine transform is for transforming the above-mentioned prediction error signal into the frequency domain. When the prediction error signal is converted to the frequency domain, there is a characteristic that power is concentrated in a specific frequency region (low frequency region). By utilizing this characteristic, an image with a smaller data amount can be combined with the method described below. Information transmission becomes possible.

In variable length coding, when the frequency of appearance of the data to be coded has a bias, the bias is used to make a short code length for an event with a high frequency of occurrence and a short code length for an event with a low frequency of occurrence. This is a method of shortening the average code length by expressing it with a long code length. By using this method,
Image information transmission with a small data amount becomes possible. The three element technologies are not applied to the entire image, but are applied to each coded block obtained by dividing one image into blocks of 16 × 16 pixels (referred to as coded blocks).

In recent years, with the spread of wireless communication terminals such as mobile phones, attention has been paid to wireless transmission techniques for moving image signals. Since wireless transmission has a higher transmission error rate than wired transmission, an encoding technique having transmission error resistance is essential. As a technique for suppressing image quality deterioration due to transmission errors, a technique called an image packet is known. This is a method of transmitting data of one screen or one or more encoded blocks as one transmission unit (image packet).

As an example of a method of forming an image packet, there is a method of accumulating the generated code amount for each coding block and forming an image packet when a certain code amount is reached (for example, Japanese Patent Application Laid-Open No. 7-014514). See). By using this method, an image packet is composed of many coding blocks in a portion having a small code amount such as a background, and an image packet is formed of a small coding block in a portion having a large motion and a large code amount. You. Even when an error occurs in an image packet due to a transmission error, a portion with large motion is constituted by a small number of coded blocks, so that the range of deterioration can be suppressed small, and a background portion includes many coded blocks. Deterioration is not noticeable because there is no movement. With this configuration, bits can be efficiently allocated.

Conventionally, there is a concealment processing technique as a technique for suppressing image quality deterioration due to transmission errors. This is a technique for compensating for image quality deterioration of a lost portion by replacing a coded block portion lost due to a transmission error with other information. An example of this concealment processing technology is shown as an important technology outside of the recommendation of MPEG-4.

[0012]

However, the conventional media separation processing has the following problems. (I) As described above, in the adaptation layer AL3 of the media separation processing, the AL-S in which an error is detected
There was no provision for handling DU packets.

The following method can be considered for handling AL-SDU packets in which errors are mixed. (1) The AL-SDU packet in which the error is detected is passed to the image decoder as it is. (2) Discard the AL-SDU packet in which the error is detected as it is. (3) The bit position where the error has occurred is stored.

[0014] These methods have the following problems.
In the method (1), the AL3 error detection processing becomes completely useless. In the method of (2), A
The packets before and after the L-SDU packet are connected, and the AL-SDU packet before and after the L-SDU packet has no error, but inconsistency occurs at the boundary portion.

In the method (3), it is necessary to manage a memory and a pointer for storing a bit position where an error has occurred, and if transmission errors frequently occur, it is not possible to determine a memory capacity to be theoretically secured. .

(II) Next, a problem when a transmission error occurs in the conventional image coding technique will be described. The above-mentioned variable length codes have different code lengths in order to increase coding efficiency. For this reason, when a transmission error occurs, the delimiter position of the code is shifted, and the data may be decoded as data different from the original data from the encoder. In addition, a transmission error may result in a code that does not exist in the variable length code, and may not be decoded. However, as described above, when a transmission error occurs once, decoding is continued with the code delimiting position being shifted, and a code that cannot be decoded is often detected. Therefore, it cannot be specified that an error has occurred in the bit where the code that cannot be decoded is detected. As described above, when a transmission error occurs in a bit string using a variable length code, the image decoder cannot identify the position where the transmission error has occurred.

When a transmission error is detected, a coded block having a transmission error is not displayed in order to prevent a distorted image from being displayed, but is replaced with, for example, an image at the same position as the previous screen. Concealment processing is performed. In order to perform the concealment process, it is necessary to determine from which coding block to which coding block is to be targeted. However, as described above, even if a transmission error can be detected, the position of the error cannot be specified, so that the coded block that may have been correctly decoded is discarded on the assumption that it will be discarded. Do the processing or
Alternatively, it is general to perform either concealment processing from a coded block in which an error is detected on the assumption that an erroneously decoded image is displayed. As described above, since the error position cannot be specified, an appropriate concealment processing range cannot be determined, and there is a problem that the image quality deteriorates.

SUMMARY OF THE INVENTION The present invention has been made in view of the above, and an object of the present invention is to provide a media separation method, an image decoding method, and an apparatus capable of suppressing image quality degradation when a transmission error occurs.

[0019]

A media separation method according to the present invention is obtained by dividing encoded data for one image into a plurality of pieces and adding an error detection code to the divided pieces of encoded data. In a media separation method for separating an image packet from a multiplexed signal including the image packet, if there is an error in the separated image packet, the image packet is discarded and a specific code is inserted instead.

Further, the present invention provides a media separation method for separating an image packet from a multiplexed signal including an image packet obtained by adding an error detection code to encoded data. A separating step for separating an image packet, an error detecting step for detecting whether there is an error in the image packet separated in the separating step, and detecting an error when an error is detected in the error detecting step. And a specific code insertion step of inserting a specific code in place of the image packet discarded in the image packet discarding step.

Further, in the media separation method according to the present invention, in the above-described media separation method, the specific code is a code which is not included in a variable length code table including various codes for representing an image.

According to these methods, if there is an error in an image packet separated from a multiplexed signal, the image packet is discarded and a specific code is inserted instead. It becomes possible to notify the packet. In this case, by setting the specific code as a code that does not exist in the variable length code table including various codes for representing the image, the image decoder detects the specific code and decodes the erroneous image packet. Do not do. Therefore, even if a transmission error occurs, only display corresponding to the erroneous image packet is not performed, so that deterioration in image quality can be minimized.

The recording medium of the present invention is a medium on which data obtained by programming the above-described medium separation method is recorded.

By using this recording medium in a media separation device that performs software control by a microcomputer, the above-described media separation method can be easily realized. Note that examples of the recording medium include a semiconductor memory, a magnetic disk, an optical disk, and a magneto-optical disk.

A media separation device of the present invention employs a configuration including the above-described recording medium and control means for performing control for separating an image packet from a multiplexed signal in accordance with data recorded on the recording medium.

According to this configuration, when the control unit recognizes that there is an error in the image packet separated from the multiplexed signal, the control unit discards the image packet and inserts a specific code in place of the image packet. To inform an image packet having a transmission error. In this case, by setting the specific code as a code that does not exist in the variable length code table including various codes for representing an image, the image decoder detects an error in the image packet when the specific code is detected. Do not decrypt. Therefore, even if a transmission error occurs, only a display corresponding to an erroneous image packet is not displayed, so that deterioration of image quality is minimized.

According to the image decoding method of the present invention, an image signal divided into a plurality of encoded blocks is decoded using a variable length code in a variable length code table. If there is a specific code, the position of the coding block immediately before the specific code is specified, and it is assumed that the coding block before the coding block has been correctly recognized.

Further, according to the image decoding method of the present invention, in an image decoding method for decoding an image signal divided into a plurality of encoded blocks using a variable length code in a variable length code table, the variable length code A specific code detecting step of detecting a specific code that is not a specific code step, and, when the specific code is detected in the specific code step, a coding block position specifying step of specifying a position of a coding block immediately before the detected specific code. And

According to these methods, since the position of the coded block in which the transmission error has occurred can be specified, it is possible to recognize that the coded block before the coded block in which the transmission error has occurred has been correctly decoded. Becomes

Further, according to the image decoding method of the present invention, an image signal for one image is divided into a plurality of coded blocks, and each of the divided coded blocks is coded by a variable length code. Or one or more coded blocks as one transmission unit, decodes an image signal with a synchronization word added to the beginning of each transmission unit, and conceals when a transmission error is detected during the decoding. In the image decoding method for performing the processing, when a specific code that is not a variable length code is detected during the decoding of the image signal, concealment processing is performed from the coded block in which the specific code is detected to the next synchronization word.

Further, according to the image decoding method of the present invention, an image signal for one image is divided into a plurality of coded blocks, and each of the divided coded blocks is coded by a variable length code. Or one or more coded blocks as one transmission unit, decodes an image signal with a synchronization word added to the beginning of each transmission unit, and conceals when a transmission error is detected during the decoding. In the image decoding method for performing the processing, a specific code detection step of detecting a specific code that is not a variable length code during decoding of the image signal, and the specific code is detected when the specific code is detected in the specific code detection step. A coding block position specifying step of specifying the position of the coding block to which the code is added, and the coding block to which the specific code is added in the coding block position specifying step. Location is anda concealment processing object position specifying step of determining the concealed position to be processed based on the specific position and the next sync word to be identified.

According to these methods, the position of the coded block in which the transmission error has occurred can be specified, so that the position of the coded block to be subjected to the concealment processing can be easily recognized.

The recording medium of the present invention has recorded thereon data obtained by programming the above-mentioned image decoding method.

By using this recording medium, the above-described image decoding method can be easily realized for an image decoding apparatus which performs software control by a microcomputer. Note that examples of the recording medium include a semiconductor memory, a magnetic disk, an optical disk, and a magneto-optical disk.

An image decoding apparatus according to the present invention employs a configuration including the above-described recording medium and control means for controlling decoding of an image signal in accordance with data recorded on the recording medium.

According to this configuration, the control means can easily recognize the position of the coded block to be concealed.

An image communication terminal device of the present invention employs a configuration including the above-described media separation device or the above-described image decoding device.

The base station apparatus of the present invention employs a configuration including the above-described media separation apparatus or the above-described image decoding apparatus.

Since the image communication terminal device and the base station device of the present invention include the above-described media separation device or image decoding device, even if a transmission error occurs, the image quality does not significantly deteriorate.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The gist of the present invention is that when a transmission error occurs in a separated image packet when an image packet is multiplexed from a multiplexed signal, the image packet is discarded and a specific code is inserted instead. , To notify the image decoding unit of an image packet having an error. As the specific code, a code that does not exist in the variable length code table and can be recognized by the image decoding unit is preferable.

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

(Embodiment 1) FIG. 1 is a block diagram showing a configuration on a receiving side of an image communication terminal apparatus according to Embodiment 1 of the present invention. In this figure, an image communication terminal apparatus according to the present embodiment has a receiving antenna 101, a radio receiving section 102 for receiving a modulated wave signal, and a modulated wave signal output from radio receiving section 102 as an original multiplexed signal. A demodulation unit 103 for demodulation, a media separation unit (corresponding to a media separation device) 104 for separating an audio signal and an image signal from the multiplexed signal demodulated by the demodulation unit 103, and a program for performing a media separation process are provided. ROM 105 stored and RAM (work memory) used in media separation processing
106, an image decoding unit 107 for decoding the image signal separated by the media separation unit 104, a ROM 108 storing a program for performing the image decoding process, and a RAM (work memory) used in the image decoding process. ) 109
, A D / A converter 110 for converting a digital signal to an analog signal, a display unit 111 for displaying an image, an audio decoder 112 for decoding audio from an audio signal, and a D / A converter for converting a digital signal into an analog signal. A conversion unit 113,
And a speaker 114 for outputting sound. The media separation unit 104 and the image decoding unit 1
07 is realized by, for example, a DSP (Digital Signal Processor).

As shown in the block diagram of FIG. 2, the media separation section 104 converts the demodulated multiplexed signal into an AL-SD
Synchronization word detector 201 for detecting a U packet delimiter (synchronization word), media separator 202 for separating an image signal and an audio signal from a demodulated multiplexed signal, and a transmission error in the separated image signal. An error detector 203 for detecting whether there is an image packet, a specific code generator 204 for generating a specific code, and a switch 205 are provided.

When the synchronous word detector 201 detects a synchronous word from the multiplexed signal demodulated by the demodulation section 103, it notifies the media separator 202 of the fact. Media separator 20
When receiving a notification from the synchronizing word detector 201 that a synchronizing word has been detected, 2 separates the multiplexed signal at that time into an image signal and an audio signal. Here, the portion sandwiched between the synchronization words becomes one multiplexed packet, and synchronization is established.

The separated image signal is supplied to an error detector 203
Performs an error detection process. That is, it is checked whether there is an erroneous image packet. Error detector 203
When detecting an erroneous image packet, the switch 2
05 is switched to the specific code generator 204 side so that the image packet is not output, and the specific code from the specific code generator 204 is output instead. This specific code is a code that can be completely identified from the variable length code used in the image decoding unit 107 (see FIG. 1). That is, the code is not included in the variable length code table including various codes for expressing the image, and can be recognized by the image decoding unit 107.

If the error detector 203 does not detect an erroneous image packet, the switch 205 remains switched to the media separator 202 side.
The image signal separated by the media separator 202 is output as it is. After switching the switch 205 to the specific code generator 204 side, the error detector 203 switches the switch 205 to the media separator 202 side at the timing of the synchronization word of the multiplex signal transmitted next.

FIG. 3 is a diagram showing a process of creating / separating a multiplexed signal and assigning a specific code. One image is 16x16
After that, each block is encoded. And
For example, an image packet is generated with the encoding blocks # 1 to # 4 as one transmission unit (video packet). An error detection code or the like is added to this transmission unit to form an image packet (AL-SDU). At this time, if one transmission unit is long, it may be divided into a plurality of image packets, and in the case of this figure, it is divided into two. Next, it is multiplexed with the voice packet and transmitted as a multiplexed signal.

When the multiplexed signal is received,
It is divided into image packets and audio packets based on information in the header of the multiplexed signal. If there is an error in the divided image packet, the image packet is discarded, and a specific code is inserted instead. When the specific code is detected by the image decoding unit 107, decoding is not performed until the next transmission unit.

Next, the operation of the image communication terminal having the above configuration will be described. After the modulated wave signal captured by antenna 101 is received by radio receiving section 102, the multiplexed signal is demodulated by demodulating section 103. The demodulated multiplex signal is
The media separation unit 104 separates the audio signal and the image signal. In this separation processing, the data to be separated is temporarily stored in the RAM 106. The image signal separated by the media separation unit 104 is decoded by the image decoding unit 107 into a digital image signal.

Then, the decoded digital image signal is converted into an analog image signal by the D / A conversion unit 110, output to the display unit 111, and displayed on the display unit 111. When the specific code is detected by the error detector 203, the image packet to which the code is added is not output, and the corresponding image is not displayed on the display unit 11. On the other hand, the separated audio signal is decoded into a digital audio signal by the audio decoding unit 112, converted into an audio signal by the D / A conversion unit 113, and output from the speaker 114.

As described above, according to the present embodiment, error detection is performed in units of image packets, and only image packets having no error are passed to image decoding section 107. Then, the image decoding unit 107 is notified that the image packet has been lost by replacing the image packet with a specific code that can be detected by. Accordingly, since the image decoding unit 107 does not decode the erroneous image packet, deterioration in image quality when a transmission error occurs is suppressed.

(Embodiment 2) FIG. 4 is a diagram showing an image decoding section 1 on the receiving side of an image communication terminal apparatus according to Embodiment 2 of the present invention.
It is a block diagram which shows the structure of 07. Note that the components on the receiving side other than the image decoding unit 107 are the same as those of the image communication terminal device according to Embodiment 1 described above, and therefore, FIG.

As shown in FIG. 4, image decoding section 107 of the image communication terminal apparatus according to the present embodiment
01, an inverse quantizer 302, and an inverse discrete cosine transformer 3
03, the frame memory 304, and the frame memory 30
4, an address generator 305 for generating a read / write address, an adder 306 for adding the output of the discrete cosine transformer 303 and the data read from the frame memory 304, and a specific code detector for detecting a specific code. 307 and a switch 308.

A variable-length decoder 301 decodes a motion vector such as the position of a coded block in an image and how much the coded block has moved with respect to a previous frame, and a signal obtained by frequency-converting the difference between the images. (Hereinafter, frequency signal) is decoded. The inverse quantizer 302 inversely quantizes the frequency signal of the image with a predetermined value and returns the frequency signal to the frequency signal. The inverse discrete cosine transformer 303 converts a frequency signal into an image signal. This image signal is a prediction error signal for the previous image. The address generator 305 generates a read address from which the region of the previous frame can be cut out and read based on the coded block address and the motion vector decoded by the variable length decoder 301. Note that the image signal read by this address is a predicted image.

The adder 306 adds the prediction error signal and the prediction image to form a reproduced image. Specific code detector 307
Detects a specific code from the received image signal. If the specific code has not been detected, the decoded block data that has been decoded is output while the switch 308 remains switched to the adder 306 side. If a specific code is detected,
By switching the switch 308 from the adder 306 side to the “0” data side, the output of the encoded block data is stopped. The output coded block data is stored in a frame memory 3 for use as a predicted image of the next frame.
04 is written.

FIG. 5 is a diagram showing an example of the operation of the present embodiment. For example, when a specific code is detected at the position shown in the drawing of the coding block # 3, the position of the coding block immediately before the specific code, that is, the position of the coding block # 2, is specified, and the coding before the coding block # 2 is performed. It is determined that blocks # 2 and # 1 have been correctly recognized, and display is performed on these encoded blocks. In this example, the video packet is divided into three, and each of them is provided with an error detection code.

As described above, according to the present embodiment, it is possible to decode and display an error-free coded block immediately before a specific code is detected.

(Embodiment 3) FIG. 6 shows an image decoding section 1 on the receiving side of an image communication terminal apparatus according to Embodiment 3 of the present invention.
FIG. 17 is a block diagram showing a configuration of No. 17. In this figure, the same parts as those in FIG. 4 are denoted by the same reference numerals. In the present embodiment, the image decoding unit 11
Since the components on the receiving side other than 7 are the same as those of the image communication terminal device according to the above-described first embodiment, for the sake of explanation, FIG.

As shown in FIG. 6, image decoding section 117 of the image communication terminal apparatus according to the present embodiment
01, an inverse quantizer 302, and an inverse discrete cosine transformer 3
03, the frame memory 304, and the address generator 30.
5, an adder 306, a specific code detector 307, a switch 308, and a synchronous word detector 309.

The image signal separated by the media separation unit 104 is output to the variable-length decoder 301, where the position of the coded block in the image and the degree to which the position of the block has moved with respect to the previous frame are determined. The motion vector is decoded, and the frequency signal of the image is decoded. The frequency signal of the image is inversely quantized by the inverse quantizer 302 and returned to the frequency signal. Then, the returned frequency signal is converted into an image signal by the inverse discrete cosine transformer 303. This image signal is a prediction error signal for the previous frame.

Further, based on the coded block address and the motion vector decoded by the variable length decoder 301, a read address from which the area of the previous frame can be cut out and read is output from the address generator 305. Then, an image signal corresponding to this address is read from the frame memory 304. The read image signal is a predicted image.

On the other hand, when the specific code detector 307 detects a specific code from the image signal separated by the media separation unit 104, the address generator 305 discards the generated address and sets the coding block. Outputs the address calculated from the address only. As a result, data at the same position as that of the current block to be processed in the previous frame is output from the frame memory 304.

When the synchronizing word detector 309 detects a synchronizing word indicating the start of an image packet or a frame from the image signals separated by the media separating unit 104, the address generator 305 outputs Outputs the address generated from the coded block address. In this case, if the specific code is detected by the specific code detector 307 and the address calculated from only the coded block address is output, the address generated from the motion vector and the coded block address is output from this output. Switch to output.

The address generator 305 maintains the current output state when nothing is detected by the specific code detector 307 and the synchronization word detector 309. Specific code detector 30
When the specific code is detected in step 7, the switch 308 is switched to the "0" data side, and "0" data is output instead of the prediction error signal of the coded block partially decoded. Also, when the synchronizing word is detected by the synchronizing word detector 309, the switch 308 is switched to the inverse discrete cosine transformer 303 side, and the prediction error signal is output. That is, when the specific code detector 307 detects a specific code, the switch 308 switches to the “0” data side, and when the synchronous word detector 309 detects a synchronous word, the switch 308 is turned on. Inverse discrete cosine transformer 3
Switch to 03 side.

With the above control, when the specific code detection unit 307 detects a specific code, the switch 3
08 outputs “0” data, and the frame memory 3
Since the image at the same position in the previous frame is output from 04, the reproduced image is the same coded block as the previous frame. This is an example of concealment processing in which, when an error occurs in an encoding block being processed, the image is replaced with an image located at the same position as the previous frame. This concealment process is continued until the synchronization word is detected by the synchronization word detection unit 309.

When the synchronizing word is detected by the synchronizing word detector 309, a prediction error signal is output from the switch 308, and a prediction signal is output from the frame memory 304. Then, these are added by the adder 306 to obtain a reproduced image.

FIG. 7 is a diagram showing an example of the operation of the present embodiment. For example, coding blocks # 1 to # 6 are one transmission unit, and are divided into three. That is,
A part of coding blocks # 1, # 2 and # 3, a remaining part of coding block # 3, a part of # 4 and # 5,
It consists of the rest of the encoded block # 5 and # 6. Each part is assigned an error detection code. A synchronization word is added to the head of each transmission unit.

For example, if a specific code is detected in the remaining portion of the coding block # 3, the coding block in which the specific code is detected, that is, from the coding block # 3 to the next synchronizing word is to be subjected to concealment processing. Then, the image at the same position in the previous frame is output.

As described above, according to the present embodiment, when the specific code is detected from the image signal separated by the media separation unit 104, the output of the prediction error signal of the coded block partially decoded is stopped, and Output the image at the same position in the previous frame held in 304,
This output is continued until the next synchronization word is detected. As a result, it is possible to suppress image quality degradation when a transmission error occurs.

In the present embodiment, the description has been made in such a manner that replacement is performed with a coding block located at the same position as the previous frame. However, since the present invention is an invention for specifying a concealment processing target, a concealment method (for example , Using the neighboring coded block information).

Further, in the first to third embodiments of the present invention, the hardware configuration has been described by taking the image communication terminal device as an example.
It can also be realized by software. That is, the method of the present invention may be programmed and stored in a writable recording medium such as a ROM, and the stored program may be processed by a CPU (control means). Further, according to the present invention, this software can be read out from a recording medium and executed by a computer, and it goes without saying that the same operation is performed.

Although Embodiments 1 to 3 of the present invention have been applied to an image communication terminal apparatus, they can of course be applied to a base station apparatus.

Further, by providing Embodiments 1 to 3 of the present invention and having a configuration including a multiplexing section and an encoding section and using them on the transmitting side and the receiving side, bidirectional wireless image communication becomes possible.

The present invention is particularly effective in a wireless transmission path in which an error easily occurs during transmission, but is also effective in a wired transmission path.

[0075]

As described above, according to the present invention, when an error is detected in an image signal in media separation processing, it is possible to easily notify the image decoding unit of the position where the error has occurred in packet units. .

When a specific code is detected in a received image signal, the image decoding unit enables display of an image that could be decoded immediately before the occurrence of an error, and displays the image from immediately after the occurrence of the error until the next synchronization. It is possible to set the interval as a concealment processing target. Since the error position can be specified while using the variable length code as described above, the display of the correctly decoded portion and the portion to be concealed can be realized efficiently and with simple means. In other words, it is possible to realize high image quality when a transmission error occurs with extremely few hardware or software resources.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a receiving side of an image communication terminal device according to Embodiment 1 of the present invention.

FIG. 2 is a block diagram showing a configuration of an image decoding unit of the image communication terminal device according to Embodiment 1 of the present invention.

FIG. 3 is a diagram for explaining an operation of the image communication terminal device according to Embodiment 1 of the present invention;

FIG. 4 is a block diagram illustrating a configuration of an image decoding unit of the image communication terminal device according to Embodiment 2 of the present invention.

FIG. 5 is a diagram for explaining an operation of an image decoding unit of the image communication terminal device according to Embodiment 2 of the present invention.

FIG. 6 is a block diagram illustrating a configuration of an image decoding unit of an image communication terminal device according to Embodiment 3 of the present invention.

FIG. 7 is a diagram for explaining an operation of an image decoding unit of the image communication terminal device according to Embodiment 3 of the present invention.

[Explanation of symbols]

 Reference Signs List 101 reception antenna 102 wireless reception unit 103 demodulation unit 104 media separation unit 105, 108 ROM 106, 109 RAM 107, 117 image decoding unit 110, 113 D / A conversion unit 111 display unit 112 audio decoding unit 114 speaker 201 synchronous word detector 202 Media separator 203 Error detector 204 Specific code generator 205, 308 Switch 301 Variable length decoder 302 Inverse quantizer 303 Inverse discrete cosine transform 304 Frame memory 305 Address generator 306 Adder 307 Specific code detector 309 Synchronization Word detector

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Claims (13)

[Claims] 1. An image packet is divided from a multiplexed signal including an image packet obtained by dividing encoded data of one image into a plurality of pieces and adding an error detection code to the divided encoded data. A method for separating media, comprising: if an error occurs in a separated image packet, discard the image packet and insert a specific code instead. 2. A media separation method for separating an image packet from a multiplexed signal including an image packet obtained by adding an error detection code to encoded data, comprising: a separation step of separating an image packet from the multiplexed signal. An error detecting step of detecting whether there is an error in the image packet separated in the separating step; and an image discarding the image packet in which the error is detected when the error is detected in the error detecting step. A media separation method, comprising: a packet discarding step; and a specific code inserting step of inserting a specific code in place of the image packet discarded in the image packet discarding step. 3. The media separation method according to claim 1, wherein the specific code is a code that does not exist in a variable length code table including various codes for representing an image. 4. A recording medium on which is recorded data obtained by programming the media separation method according to claim 1. 5. A media separation apparatus comprising: the recording medium according to claim 4; and control means for performing control for separating an image packet from a multiplexed signal according to data recorded on the recording medium. . 6. In an image decoding method for decoding an image signal divided into a plurality of encoded blocks using a variable length code in a variable length code table, if there is a specific code that is not a variable length code during decoding, , A position of a coding block immediately before the specific code is specified, and a coding block before the coding block is correctly recognized. 7. An image decoding method for decoding an image signal divided into a plurality of encoded blocks using a variable length code in a variable length code table, wherein a specific code which is not a variable length code is detected during decoding. Code detection step, and when the specific code is detected in the specific code step,
A coding block position specifying step of specifying a position of a coding block immediately before the detected specific code. 8. An image signal for one image is divided into a plurality of encoded blocks, and each of the divided encoded blocks is encoded by a variable-length code to encode one screen of encoded blocks or one or more encoded blocks. An image decoding method for performing an concealment process when decoding an image signal with a synchronization word added to the beginning of each transmission unit, and performing a concealment process when a transmission error is detected during the decoding. An image decoding method characterized in that when a specific code that is not a variable length code is detected during decoding of the image signal, concealment processing is performed from the coded block where the specific code is detected to the next synchronization word. 9. An image signal for one image is divided into a plurality of coded blocks, and each of the divided coded blocks is coded by a variable-length code. An image decoding method for performing an concealment process when decoding an image signal with a synchronization word added to the beginning of each transmission unit, and performing a concealment process when a transmission error is detected during the decoding. A specific code detection step of detecting a specific code that is not a variable length code during decoding of the image signal; and, when the specific code is detected in the specific code detection step, the coding block to which the specific code has been added. A coded block position specifying step of specifying a position, and a position specified when the position of the coded block to which the specific code is added is specified in the coded block position specifying step. A concealment processing target position specifying step of determining a concealment processing target position based on the position and the next synchronization word. 10. A recording medium on which data obtained by programming the image decoding method according to claim 6 is recorded. 11. An image decoding apparatus comprising: the recording medium according to claim 10; and control means for controlling decoding of an image signal in accordance with data recorded on the recording medium. 12. An image communication terminal device comprising the media separation device according to claim 5 or the image decoding device according to claim 11. 13. A base station device comprising the media separation device according to claim 5 or the image decoding device according to claim 11.