JP2016105536A - Image transmission device, image transmission method, and image transmission program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image transmission device capable of reducing a possibility that real-time transmission of coded moving image data may collapse.SOLUTION: An encoding unit 3a encodes moving image data to generate coded moving image data. A transmission buffer 4 stores the coded moving image data. A transmission/reception unit 6 transmits the coded moving image data to an image receiving device via a radio communication channel. A collapse detection unit 111 predicts whether or not the real-time transmission of the coded moving image data may collapse, and detects a time until it collapses. When it is predicted that it may collapse, an encoding control unit 112 controls the encoding unit 3a, such that a target bit rate when the encoding unit 3a encodes the moving image data is lowered within the detected time.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an image transmission apparatus, an image transmission method, and an image transmission program that transmit moving image data to an image reception apparatus via a wireless communication line.

  In recent years, with the expansion of the transmission band of wireless communication lines and the development of image compression technology that can greatly reduce the data capacity of image data, moving image data is often transmitted and received via wireless communication lines. Has been done.

JP 2008-11077 A

  However, when the radio field intensity is weak, the transmission rate for transmitting image data is low. Then, the encoded moving image data cannot be transmitted from the image transmitting device to the image receiving device in real time, and the image receiving device cannot receive the encoded moving image data necessary for reproducing the moving image in real time. There is.

  When the image transmission apparatus is provided in a moving body such as a vehicle, the radio wave intensity may vary depending on the location where the moving body travels. Therefore, there is a problem that real-time transmission of encoded moving image data is likely to fail.

  In view of such problems, an object of the present invention is to provide an image transmission device, an image transmission method, and an image transmission program that can reduce the possibility of failure of real-time transmission of encoded moving image data.

  In order to solve the above-described problems of the related art, the present invention encodes moving image data to generate encoded moving image data, a transmission buffer that accumulates the encoded moving image data, A transmitting unit that transmits the encoded moving image data stored in the transmission buffer to the image receiving device via a wireless communication line; position information, speed information, and direction information of the moving body; and at least the moving body moves. Based on the radio field intensity distribution information of the wireless communication line in the path, the encoding bit rate in the encoding unit, and the state information indicating the storage state of the encoded moving image data in the transmission buffer, the encoded moving image Predicting whether or not a real-time transmission failure occurs in a state where image data is not transmitted from the transmission unit to the image receiving device in real time, A failure detection unit for detecting a time until the occurrence of the failure, and when the failure detection unit predicts that the failure occurs, a target bit rate at which the encoding unit encodes the moving image data is determined within the time period. And an encoding control unit that controls the encoding unit so as to be lowered.

  In order to solve the above-described problems of the conventional technique, the present invention generates encoded moving image data by encoding moving image data, stores the encoded moving image data in a transmission buffer, and transmits the transmission buffer. The encoded moving image data stored in the image data is transmitted to the image receiving device via a wireless communication line, and the wireless communication in the path along which the moving body moves, at least the position information, the speed information, and the direction information of the moving body. Based on the radio wave intensity distribution information of the line, the encoding bit rate when generating the encoded moving image data, and the state information indicating the storage state of the encoded moving image data in the transmission buffer, the encoding A time until the failure occurs by predicting whether or not a failure of real-time transmission occurs, in which moving image data is not transmitted to the image receiving device in real time; Detects, when the collapse has been predicted to occur, to provide an image transmission method characterized by lowering the target bit rate for generating the encoded video data within said time.

  Furthermore, in order to solve the above-described problems of the conventional technology, the present invention encodes moving image data to generate encoded moving image data, and a transmission buffer that stores the encoded moving image data. In a computer mounted on an image transmission device including a transmission unit that transmits the encoded moving image data stored in the transmission buffer to an image reception device via a wireless communication line, the position information of the moving object and Speed information and direction information, radio wave intensity distribution information of the wireless communication line on at least a path along which the moving body moves, an encoding bit rate when generating the encoded moving image data, and the code in the transmission buffer The encoded moving image data is not transmitted to the image receiving device in real time based on the state information indicating the storage state of the encoded moving image data Predicting whether or not a failure of real-time transmission occurs, detecting a time until the failure occurs, and when the failure is predicted to occur, the encoding unit And a step of controlling the encoding unit so as to lower a target bit rate for encoding within the time period.

  According to the image transmission device, the image transmission method, and the image transmission program of the present invention, it is possible to reduce the possibility of failure of real-time transmission of encoded moving image data.

It is a block diagram which shows the image transmission apparatus which comprises the transmission / reception system of 1st Embodiment. It is a block diagram which shows the image receiver which comprises the transmission / reception system of 1st Embodiment. It is a block diagram which shows the structural example in case an image transmission apparatus acquires electromagnetic wave intensity distribution information from a server. It is a figure which shows notionally an example of electromagnetic wave intensity distribution information. It is a figure which shows notionally other examples of radio wave intensity distribution information. It is a figure which shows the example in case the failure of real-time transmission of an encoding moving image data generate | occur | produces. It is a figure which shows the example of control of the target bit rate in an encoding part, and switching of a moving image compression system. FIG. 3 is a diagram schematically illustrating a bit stream transmitted from the image transmission device illustrated in FIG. 1 to the image reception device illustrated in FIG. 2. It is a block diagram which shows the image transmission apparatus which comprises the transmission / reception system of 2nd Embodiment. It is a block diagram which shows the image receiving apparatus and dispatcher which comprise the transmission / reception system of 2nd Embodiment. It is a figure which shows roughly the encoding information transmitted to the image receiving apparatus shown in FIG. 10 from the image transmitting apparatus shown in FIG. FIG. 10 is a diagram schematically showing position / direction / speed information transmitted from the image transmission apparatus illustrated in FIG. 9 to the image reception apparatus illustrated in FIG. 10. FIG. 11 is a diagram schematically illustrating transmission buffer information transmitted from the image transmission device illustrated in FIG. 9 to the image reception device illustrated in FIG. 10.

  Hereinafter, an image transmission apparatus, an image transmission method, and an image transmission program according to an embodiment will be described with reference to the accompanying drawings.

<First Embodiment>
The image transmission apparatus 101 shown in FIG. 1 and the image reception apparatus 201 shown in FIG. 2 constitute the transmission / reception system of the first embodiment. The image transmitting apparatus 101 is configured as follows, and transmits encoded moving image data (hereinafter sometimes abbreviated as encoded data) to the image receiving apparatus 201. Assume that the image transmission apparatus 101 is mounted on a vehicle as an example of a moving object.

  The camera 1 captures a subject and outputs moving image data. When the camera 1 outputs an analog moving image signal, it may be converted into digital moving image data by an A / D converter (not shown).

  The camera 1 is an example of a moving image data generation unit. The moving image data generation unit may be a playback device that plays back moving image data recorded on a recording medium.

  The moving image data is input to the encoding unit 3a via the terminal Ta of the switch 2. As will be described later, moving image data may be input to the encoding unit 3b via the terminal Tb of the switch 2. The encoding units 3a and 3b encode moving image data using different moving image compression methods.

  The moving picture compression method employed by the encoding units 3a and 3b may be MPEG-4, H.264 / MPEG-4 AVC / MPEG-4 SVC, H.265 / HEVC / SHVC, or the like. In the present embodiment, it is assumed that the compression rate of the moving image compression method adopted by the encoding unit 3b is larger than the compression rate of the moving image compression method adopted by the encoding unit 3a. The encoding units 3a and 3b may employ Motion JPEG, Motion JPEG2000, or the like that does not use correlation between images having different times as a moving image compression method.

  Here, when the target bit rate is lowered from the normal transmission rate, the encoding units 3a and 3b perform predetermined encoding processing so as to be within the target bit rate, and perform encoding as a base layer. Video compression that can generate moving image data and realize hierarchical coding that generates extended encoded moving image data as an extension layer to compensate for the difference between the encoding quality of the base layer and the encoding quality that should be transmitted It should be a method.

  As a result, encoded moving image data corresponding to a code amount that cannot be transmitted when the target bit rate is reduced can be generated as extended encoded moving image data as an enhancement layer.

  The image transmitting apparatus 101 preferably includes a plurality of encoding units that encode moving image data using different moving image compression methods, but includes a plurality of encoding units that encode moving image data using a single moving image compression method. It is good also as a structure provided with the structure provided, and one encoding part which encodes moving image data with one moving image compression system.

  The encoded data output from the encoding unit 3a (or 3b) is input to the transmission buffer 4 and temporarily accumulated. The transmission signal of the bit stream including the encoded data stored in the transmission buffer 4 is transmitted to the image reception device 201 by the transmission / reception unit 6 via the wireless communication line. The encoded data accumulated in the transmission buffer 4 is input to the storage unit 5 and stored.

  The enhancement layer extension encoded data, which is a part of the encoded data, may be stored in the storage unit 5 via the transmission buffer 4 and accumulated in the transmission buffer 4 as necessary. Further, the extension layer extended encoded data may be directly supplied to the storage unit 5 from the encoding unit 3a (or 3b).

  The image transmitting apparatus 101 may transmit / receive a signal or data to / from the image receiving apparatus 201 by a half-duplex communication method, or may transmit / receive a signal or data by a full-duplex communication method.

  As will be described later, the image receiving apparatus 201 may transmit a predetermined signal to the image transmitting apparatus 101. When the half-duplex communication method is adopted, if the image receiving apparatus 201 transmits a predetermined signal to the image transmitting apparatus 101 at a timing when the image transmitting apparatus 101 does not transmit encoded data to the image receiving apparatus 201. Good.

  The position detector 7 receives radio waves from a satellite for the Global Navigation Satellite System (GNSS), for example, and detects position information of the vehicle (image transmission device 101). GNSS is GPS (Global Positioning System) as an example. The position information detected by the position detection unit 7 is input to the failure detection unit 111 in the control unit 11.

  When the vehicle is equipped with a navigation device and the navigation device detects position information of the vehicle, the position information detected by the navigation device may be supplied to the failure detection unit 111. The position detection unit 7 may be provided in the control unit 11.

  The speed acquisition unit 8 acquires vehicle travel speed information by a predetermined method. The speed acquisition unit 8 may acquire travel speed information based on vehicle speed pulses generated by the vehicle. The speed acquisition unit 8 may acquire travel speed information based on the amount of change in position information detected by the position detection unit 7 per unit time. The travel speed information acquired by the speed acquisition unit 8 is input to the failure detection unit 111.

  The gyro sensor 9 detects direction information when the vehicle travels. The direction information detected by the gyro sensor 9 is input to the failure detection unit 111. When the navigation device includes a gyro sensor, the direction information output from the gyro sensor of the navigation device may be supplied to the failure detection unit 111.

  The radio wave intensity distribution information holding unit 10 holds radio wave intensity distribution information of a wireless communication line. The radio wave intensity distribution information holding unit 10 holds in advance radio wave intensity distribution information including at least a region where the vehicle moves. Alternatively, the radio wave intensity distribution information holding unit 10 may acquire necessary radio wave intensity distribution information from, for example, radio wave intensity distribution information held in an external server (cloud).

  In the latter case, the image transmission apparatus 101 may be configured as shown in FIG. As shown in FIG. 3, the server 50 holds the radio wave intensity distribution information. Based on the control by the control unit 11, the transmission / reception unit 6 requests the server 50 to transmit the radio wave intensity distribution information and receives the radio wave intensity distribution information. The control unit 11 holds the received radio wave intensity distribution information in the radio wave intensity distribution information holding unit 10.

  At this time, the control unit 11 refers to the position information of the vehicle detected by the position detection unit 7 and performs control so as to acquire the radio field intensity distribution information in a predetermined range including the point where the vehicle is located. May be.

  The holding of the radio wave intensity distribution information by the radio wave intensity distribution information holding unit 10 includes not only the continuous holding of the radio wave intensity distribution information but also the temporary holding of the radio wave intensity distribution information acquired from the server 50.

  The radio wave intensity distribution information is generated based on data measured by a transmission / reception system provider or a third party.

  FIG. 4 conceptually shows the radio wave intensity distribution information held by the radio wave intensity distribution information holding unit 10. In the area shown in FIG. 4, the area Ar <b> 1 indicates an area where the radio wave intensity is relatively strong, and the area Ar <b> 2 indicates an area where the radio wave intensity is relatively weak. The radio wave intensity distribution information can be composed of data indicating the radio wave intensity at a plurality of points Ps obtained by dividing the region into, for example, a mesh shape.

  As shown in FIG. 5, it is assumed that the vehicle is located at the current position P0 and it is decided to travel on the road indicated by the travel route R0. In such a case, the radio wave intensity distribution information holding unit 10 may only hold data indicating the radio wave intensity at a plurality of points Ps on the travel route R0.

  Even if the control unit 11 obtains information on the travel route R0 of the vehicle from the navigation device, obtains the radio field intensity at a plurality of points Ps on the travel route R0 from the server 50, and causes the radio field intensity distribution information holding unit 10 to hold it. Good.

  Further, when a plurality of travel route information can be acquired from the navigation device, the radio wave intensity at a plurality of points Ps on the plurality of travel routes may be acquired from the server 50 and held in the radio wave intensity distribution information holding unit 10 Good.

  Here, when the storage capacity of the radio wave intensity distribution information holding unit 10 is not sufficient, the travel route information is acquired from the navigation device in order of priority, and a plurality of points Ps on the travel route with high priority are obtained. The radio wave intensity distribution information holding unit 10 may hold them in order from the radio wave intensity. The radio wave intensity distribution information holding unit 10 may not hold the radio wave intensity at a plurality of points Ps on the travel route with low priority.

  Returning to FIG. 1, the control unit 11 includes a failure detection unit 111, an encoding control unit 112, and an extended information transmission control unit 113. The request signal extraction unit 12 is connected to the extended information transmission control unit 113. The operations of the request signal extraction unit 12 and the extended information transmission control unit 113 will be described together with the operation description of the image reception device 201.

  The encoding control unit 112 instructs the encoding unit 3a about a target bit rate when the encoding unit 3a encodes moving image data. The failure detection unit 111 receives information indicating an encoding bit rate that is a generated code amount when the encoding unit 3a actually encodes moving image data.

  Similarly, when the encoding unit 3b is operating instead of the encoding unit 3a, the encoding control unit 112 encodes a target bit rate when the encoding unit 3b encodes moving image data. Instruct the unit 3b. The failure detection unit 111 receives information indicating an encoding bit rate that is a generated code amount when the encoding unit 3b actually encodes moving image data.

  In addition, the failure detection unit 111 receives state information indicating an accumulation state of encoded data in the transmission buffer 4. The storage state of the transmission buffer 4 can be, for example, a margin that is a capacity capable of further storing encoded data at a certain point in time.

  When the image transmitting apparatus 101 transmits encoded data to the image receiving apparatus 201, when the radio wave intensity is weak, the encoded data stored in the transmission buffer 4 is not sufficiently transmitted to the image receiving apparatus 201. It becomes. Then, there is no room for storing the encoded data in the transmission buffer 4, and real-time transmission of the encoded data fails.

  Therefore, the failure detection unit 111 uses the vehicle position information, the traveling speed information, the direction information, the radio wave intensity distribution information, the encoding bit rate of the encoding unit 3a (or 3b), and the state information of the transmission buffer 4. Based on this, it is predicted whether or not a real-time transmission failure will occur. When the failure detection unit 111 predicts that a failure of real-time transmission will occur, it detects the time until the failure occurs.

  As shown in FIG. 6, when the vehicle is located at the current position P0 and travels on the travel route R0, the failure detection unit 111 determines when the vehicle is at the boundary point P12 between the areas Ar1 and Ar2 based on the above information. Can be detected. The failure detection unit 111 detects a time T012 from the current position P0 until reaching the boundary point P12.

  As shown in FIG. 7A, it is assumed that the encoding unit 3a has encoded moving image data at the target bit rate Br1 until time t0. If the target bit rate Br1 is continued as it is at time t0 shown in FIG. 7A, the failure detection unit 111 predicts that real-time transmission will fail after the elapse of time T012, and notifies the encoding control unit 112 of it.

  For example, from time t1 to time t2, the encoding control unit 112 controls the encoding unit 3a to continuously decrease the target bit rate in the encoding unit 3a from the target bit rate Br1 to the target bit rate Br2.

  The target bit rate Br2 is a bit rate that is lower than the target bit rate Br1 and in which real-time transmission does not fail even in the area Ar2 where the radio field intensity is weak.

  When the time T012 is short, the encoding control unit 112 may control the encoding unit 3a to decrease the target bit rate from time t0. The time t2 may be before time t12 when the vehicle reaches the boundary point P12. Since it is not easy to accurately obtain the time t12 and includes an error, the encoding control unit 112 controls the encoding unit 3a to set the target bit rate Br2 at the time t2 that is a predetermined time before the time t12. Is good.

  The encoding control unit 112 controls the encoding unit 3a not to rapidly decrease the target bit rate in the encoding unit 3a but to decrease from the target bit rate Br1 to the target bit rate Br2 within the time T012.

  The encoding control unit 112 may control the encoding unit 3a to lower the target bit rate from the target bit rate Br1 to the target bit rate Br2 based on a predetermined rule within the time T012. For example, the encoding control unit 112 may control the encoding unit 3a to decrease the target bit rate continuously or stepwise over a predetermined time.

  In this case, the encoding bit rate in the encoding unit 3a does not change abruptly, so that the image quality is hardly deteriorated.

  It is assumed that the vehicle further travels and moves to an area where the radio field intensity is strong as in the area Ar1. In this case, for example, from time t3 to time t4, the encoding control unit 112 increases the target bit rate in the encoding unit 3a from the target bit rate Br2 to the target bit rate Br1 based on a predetermined rule. Can be controlled.

  For example, the encoding control unit 112 may control the encoding unit 3a to increase the target bit rate continuously or stepwise over a predetermined time. The time t3 should just be after the time which moved to the area where radio field intensity is strong.

  For example, when the maximum transmission rate is greatly reduced to 1/5, such as the maximum transmission rate in the area Ar1 is 5 Mbps and the maximum transmission rate in the area Ar2 is 1 Mbps, the target bit rate shown in FIG. In some cases, it is not possible to avoid the failure of real-time transmission only by reducing this.

  In such a case, as shown in FIG. 7B, the encoding control unit 112 switches the switch 2 to the terminal Tb and replaces the encoding unit 3a with an encoding unit 3b having a large compression rate. The switch 2 and the encoding unit 3b may be controlled so as to encode the moving image data.

  In FIG. 7B, the encoding control unit 112 switches the switch 2 so as to switch from the encoding unit 3a to the encoding unit 3b at time t2 and to switch from the encoding unit 3b to the encoding unit 3a at time t3. The encoders 3a and 3b are controlled.

  The timing to switch from the encoding unit 3a to the encoding unit 3b may be between time t0 and time t12. The timing to switch from the encoding unit 3b to the encoding unit 3a may be after the time when the radio wave intensity is shifted to an area.

  The encoding control unit 112 does not execute the control for lowering the target bit rate in the encoding unit 3a, but only performs control for switching the encoding unit that encodes moving image data from the encoding unit 3a to the encoding unit 3b. You may let them.

  The encoding control unit 112 may avoid failure of real-time transmission by any of the following methods. As a first method, the encoding control unit 112 controls the encoding unit so as to lower the target bit rate when encoding moving image data.

  As a second method, the encoding control unit 112 controls the switch 2 to switch the encoding unit that encodes moving image data to an encoding unit that employs a moving image compression method with a higher compression rate.

  As a third method, the coding control unit 112 controls the coding unit to lower the target bit rate, and switches the coding unit to a coding unit that employs a moving image compression method with a higher compression rate. 2 is controlled.

  In FIG. 1, two encoding units having different video compression schemes are provided, but three or more encoding units are provided, and an encoding unit that encodes moving image data between the three or more encoding units is provided. You may switch.

  The bit stream transmitted from the transmission / reception unit 6 has a format as schematically shown in FIG. The bit stream includes a header at the beginning, an encoded image data area following the header, and a user area following the encoded image data.

  The user area may be provided between the header and the encoded image data area. Further, when there is no information stored in the user area, the user area is not necessarily provided. If there is a possibility that information to be stored in the user area exists, a flag for identifying the presence or absence of the user area may be included in the header.

  The header includes a flag F1 for identifying the type of moving image compression method. When the target bit rate is lowered, for example, a flag F2 indicating that the target bit rate has been lowered is set in the user area. Instead of placing the flag F2 in the user area, the flag F2 may be set in the user area in the header.

  Here, when the extended encoded data of the enhancement layer is not generated, it is preferable not to set the flag F2. In the following description, it is assumed that the flag F2 is set.

  As described above, according to the image transmission apparatus 101 and the image transmission method executed by the image transmission apparatus 101, the possibility of failure of real-time transmission of encoded data can be reduced. Therefore, the image receiving apparatus 201 can receive encoded data necessary for reproducing a moving image in real time, and can reproduce the moving image in real time without interruption.

  The image transmission apparatus 101 in FIG. 1 may be partially configured by a computer program (image transmission program). For example, the control unit 11 can be configured by a microcomputer, and portions corresponding to the failure detection unit 111 and the encoding control unit 112 can be configured by an image transmission program.

  The image transmission program causes a computer to execute a step of predicting whether or not a real-time transmission failure occurs and detecting a time until the failure occurs. When the image transmission program is predicted to fail, the image transmission program controls the computer to cause the encoding unit 3a to lower the target bit rate when the encoding unit 3a encodes moving image data within the time T012. Is executed.

  Each unit of the image transmission apparatus 101 may be configured by hardware or may be configured by software. The use of hardware and software is arbitrary, and both may be mixed. For example, the encoding units 3a and 3b can be configured by software, and the encoding units 3a and 3b can be used as an image transmission program.

  Next, the configuration and operation of the image receiving apparatus 201 illustrated in FIG. 2 will be described. In FIG. 2, the transmission / reception unit 21 receives a transmission signal transmitted from the image transmission apparatus 101. The bit stream acquisition unit 22 acquires a bit stream included in the received signal.

  The bit stream acquired by the bit stream acquisition unit 22 is input to the decoding unit 24 a, the flag determination unit 251 in the control unit 25, and the storage unit 23. The decoding unit 24 a decodes the input bit stream and supplies the decoded bit stream to the display control unit 252 in the control unit 25. The flag determination unit 251 determines whether or not the flag F2 is included in the bitstream. The storage unit 23 stores the bit stream.

  The display control unit 252 causes the display unit 26 to display the decoded moving image data. Accordingly, the moving image encoded and transmitted by the image transmission apparatus 101 is displayed on the display unit 26 in real time. The display unit 26 may be any display device.

  When the flag determination unit 251 determines that the flag F2 is included in the bitstream, the display control unit 252 causes the display unit 26 to display image or character information indicating that the target bit rate has been lowered. The user can know that the target bit rate has been lowered by the image or character information displayed on the display unit 26 and the image quality has deteriorated.

  When the user knows that the image quality has deteriorated by looking at the image or text information, the encoded data corresponding to the amount of code that has not been transmitted to the image transmission apparatus 101 during the period in which the target bit rate has been lowered You can request transmission.

  When the user operates the operation unit 27 to input an instruction for requesting transmission of encoded data corresponding to the amount of code not transmitted, the instruction receiving unit 253 in the control unit 25 sends a request signal generation unit 254 to the request signal generation unit 254. And instructing the image transmission apparatus 101 to generate a request signal. The request signal generation unit 254 supplies the request signal to the transmission / reception unit 21.

  When the half-duplex communication method is adopted, the transmission / reception unit 21 transmits a request signal to the image transmission apparatus 101 at a timing when the transmission signal is not received from the image transmission apparatus 101. When the full-duplex communication method is adopted, the transmission / reception unit 21 transmits a request signal to the image transmission apparatus 101 at an appropriate timing.

  Here, when the user requests transmission of encoded data, the request signal is transmitted to the image transmission apparatus 101. However, when the flag F2 is included in the bitstream, the request signal is automatically transmitted. You may comprise so that it may transmit to the image transmission apparatus 101. FIG.

  That is, as indicated by a broken line, when the flag determination unit 251 determines that the flag F2 is included in the bitstream, the request signal generation unit 254 is instructed to generate a request signal for the image transmission apparatus 101. May be.

  Returning to FIG. 1, when the transmission / reception unit 6 receives a transmission signal from the image reception device 201 including the request signal, the request signal extraction unit 12 extracts the request signal from the reception signal. The request signal extraction unit 12 supplies the request signal to the extended information transmission control unit 113.

  The extended information transmission control unit 113 performs control so that encoded data corresponding to the code amount that has not been transmitted in the period in which the target bit rate is lowered is read from the storage unit 5 and supplied to the transmission buffer 4. The encoded data corresponding to the code amount that has not been transmitted is referred to as extended encoded data.

  The extended encoded data stored in the transmission buffer 4 is transmitted from the transmission / reception unit 6 to the image reception device 201. The transmission / reception unit 6 may transmit the extended encoded data to the image receiving apparatus 201 when there is a margin for storing the extended encoded data in the transmission buffer 4 and there is a sufficient transmission rate.

  In FIG. 2, the transmission / reception unit 21 receives a transmission signal of a bit stream including extended encoded data transmitted from the image transmission apparatus 101. The bit stream acquisition unit 22 stores the extended encoded data in the storage unit 23.

  The user operates the operation unit 27 to input an instruction to display a moving image with a high image quality during a period when the target bit rate is lowered. The instruction receiving unit 253 instructs the storage unit 23 to read out both the encoded data and the extended encoded data during the period when the target bit rate is lowered from the storage unit 23.

  The decoding unit 24a decodes the encoded data during the period when the target bit rate is lowered as the base layer. The base layer is supplied to the decoding unit 24b. The decoding unit 24b decodes the extension encoded data as an extension layer. The decoding unit 24b supplies moving image data in which the base layer and the enhancement layer are combined to the display control unit 252.

  The display control unit 252 causes the display unit 26 to display moving image data with high image quality. The display control unit 252 may display the past moving image with high image quality instead of the moving image transmitted in real time, or the moving image transmitted in real time and the past moving image with high image quality. For example, may be displayed on two screens.

  According to the transmission / reception system of the first embodiment, even if the target bit rate is lowered to avoid a real-time transmission failure and the actual encoding bit rate is lowered and the image quality deteriorates, the moving image of the portion where the image quality is deteriorated Can be displayed with high image quality.

  Each unit of the image receiving apparatus 201 may be configured by hardware or may be configured by software. The use of hardware and software is arbitrary, and both may be mixed.

Second Embodiment
The image transmission apparatus 102 illustrated in FIG. 9 and the image reception apparatus 202 and the dispatcher 302 illustrated in FIG. 10 constitute a transmission / reception system according to the second embodiment. The dispatcher 302 is connected to the image receiving device 202 and controls one or a plurality of image receiving devices 202.

  The dispatcher 302 includes a function of an image transmission control device that controls an operation when the image transmission device 102 encodes moving image data. 9 and 10, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals, and the description thereof may be omitted.

  The control unit 11 in the image transmission apparatus 102 includes an encoded information generation unit 114, a position / direction / speed information generation unit 115, and a transmission buffer information generation unit 116. The image transmission apparatus 102 includes a multiplexer 13 and an encoding control signal extraction unit 14.

  The encoding information generation unit 114 generates encoding information indicating an encoding bit rate when the encoding unit 3a (or 3b) actually encodes moving image data. As shown in FIG. 11, the encoded information generally includes an identification flag indicating encoded information and encoded bit rate data.

  Based on the position information detected by the position detection unit 7, the travel speed information acquired by the speed acquisition unit 8, and the vehicle direction information detected by the gyro sensor 9, the position / direction / speed information generation unit 115 Generate position, direction and speed information. As shown in FIG. 12, the position / direction / speed information roughly includes an identification flag indicating position / direction / speed information and position / direction / speed data.

  The transmission buffer information generation unit 116 generates transmission buffer information based on the state information indicating the accumulation state of the encoded data from the transmission buffer 4. As shown in FIG. 13, the transmission buffer information generally includes an identification flag indicating transmission buffer information and transmission buffer status data.

  Timing at which the encoded information generation unit 114 generates encoded information, timing at which the position / direction / velocity information generation unit 115 generates position / direction / velocity information, and transmission buffer information generation unit 116 generates transmission buffer information The timing to perform is not necessarily the same timing, but each information corresponding to the encoded data to be transmitted is generated at least by the timing of reading the encoded data to be transmitted from the transmission buffer 4. Good.

  The encoded information, the position / direction / speed information, and the transmission buffer information are input to the multiplexer 13. The multiplexer 13 time-division multiplexes the encoded data read from the transmission buffer 4, the encoded information, the position / direction / speed information, and the transmission buffer information, and supplies them to the transmission / reception unit 6.

  The transmission / reception unit 6 transmits a transmission signal of a bit stream including encoded data, encoding information, position / direction / speed information, and transmission buffer information, which are time-division multiplexed, to the image reception device 202.

  In FIG. 10, the image reception device 202 receives a transmission signal from the image transmission device 102. The demultiplexer 28 separates the encoded data included in the bitstream, the encoded information, the position / direction / speed information, and the transmission buffer information from each other. The encoded data is input to the decoding unit 24 and decoded.

  The encoded information, position / direction / speed information, and transmission buffer information are input to the failure detection unit 31 in the dispatcher 302. In the second embodiment, not the image transmission device side but the image reception device side includes a failure detection unit.

  In FIG. 10, the image receiving apparatus 202 and the dispatcher 302 are separately configured, but may be configured integrally. The entire image receiving apparatus 202 and the dispatcher 302 may be used as the image receiving apparatus.

  The dispatcher 302 includes a failure detection unit 31, a radio wave intensity distribution information holding unit 32, and an encoding control signal generation unit 33. The radio wave intensity distribution information holding unit 32 holds the radio wave intensity distribution information as described with reference to FIG. In a configuration in which information indicating the travel route of the vehicle is not transmitted to the image receiving device 202, the radio wave intensity distribution information holding unit 32 may hold the radio wave intensity distribution information including a region in a range where the vehicle may move.

  If the travel route of the vehicle is determined in advance, the radio wave intensity distribution information holding unit 32 may hold the radio wave intensity distribution information on at least the route along which the vehicle moves, as in FIG.

  Similar to the failure detection unit 111 in FIG. 1, the failure detection unit 31 performs real-time processing by the image transmission device 102 based on the encoded information, position / direction / speed information, transmission buffer information, and radio wave intensity distribution information. Predict whether a transmission failure will occur. The failure detection unit 31 detects the time until the failure occurs when it is predicted that a failure in real-time transmission will occur.

  When the failure detection unit 31 predicts that a real-time transmission failure will occur, the encoding control signal generation unit 33 generates an encoding control signal for controlling the target bit rate in the encoding unit 3a to be lowered.

  The encoding control signal generation unit 33 controls the transmission / reception unit 21 to transmit the encoding control signal to the image transmission apparatus 102.

  The transmission / reception unit 21 transmits the encoding control signal to the image transmission device 102. When the half-duplex communication method is employed, the transmission / reception unit 21 may transmit the encoding control signal to the image transmission apparatus 102 at a timing when the image transmission apparatus 102 does not transmit the encoded data. The encoding control signal generation unit 33 may generate an encoding control signal for switching the switch 2 so that the moving image data is encoded by the encoding unit 3b instead of the encoding unit 3a.

  Returning to FIG. 9, when the transmission / reception unit 6 receives a transmission signal from the image reception device 202 including the encoding control signal, the encoding control signal extraction unit 14 extracts the encoding control signal from the reception signal. The encoding control signal extraction unit 14 supplies the encoding control signal to the encoding control unit 112.

  The encoding control unit 112 controls the target bit rate in the encoding unit 3a and encodes an encoding unit that encodes moving image data as necessary, as in (a) and (b) of FIG. The switch 2 is controlled to switch from the encoding unit 3a to the encoding unit 3b.

  As described above, according to the image transmission control device provided in the dispatcher 302 and the image transmission control method executed by the dispatcher 302, the possibility of failure of real-time transmission of encoded data can be reduced. . Therefore, the image receiving apparatus 202 can receive encoded data necessary for reproducing a moving image in real time, and can reproduce the moving image in real time without interruption.

  Each unit of the image receiving apparatus 202 and the dispatcher 302 may be configured by hardware or may be configured by software. The use of hardware and software is arbitrary, and both may be mixed.

  The failure detection unit 31 and the encoding control signal generation unit 33 in the dispatcher 302 can be configured by a computer program (image transmission control program) that causes a computer to execute the above-described processing.

  The present invention is not limited to the first or second embodiment described above, and various modifications can be made without departing from the scope of the present invention. The configuration for displaying the moving image of the portion where the image quality deteriorates in FIGS. 1 and 2 with high image quality may be omitted. In FIG. 9 and FIG. 10, a configuration for displaying a moving image of a portion where the image quality has deteriorated with high image quality may be added.

3a, 3b Encoding unit 4 Transmission buffer 6 Transmission / reception unit (transmission unit)
10, 32 Radio wave intensity distribution information holding unit 31, 111 Failure detection unit 33 Coding control signal generation unit 101, 102 Image transmission device 112 Coding control unit 201, 202 Image reception device 302 Dispatcher (image transmission control device)

Claims (5)

An encoding unit that encodes moving image data to generate encoded moving image data;
A transmission buffer for storing the encoded moving image data;
A transmission unit that transmits the encoded moving image data stored in the transmission buffer to an image reception device via a wireless communication line;
Position information, speed information, and direction information of the moving body, radio wave intensity distribution information of the wireless communication line in at least a path along which the moving body moves, an encoding bit rate in the encoding unit, and the code in the transmission buffer Whether or not a failure of real-time transmission occurs in a state where the encoded moving image data is not transmitted from the transmission unit to the image receiving device in real time based on state information indicating a storage state of the encoded moving image data. Predicting and detecting a time until the failure occurs, a failure detection unit,
Encoding control for controlling the encoding unit so as to lower a target bit rate when the encoding unit encodes the moving image data within the time when the failure is predicted by the failure detection unit And
An image transmitting apparatus comprising:   The encoding control unit, from a first time before the time when the failure is predicted to occur to a second time after the first time and before the time when the failure is predicted to occur, A target bit rate at which the encoding unit encodes the moving image data is based on a predetermined rule from a first target bit rate to a second target bit rate lower than the first target bit rate. The image transmitting apparatus according to claim 1, wherein the image transmitting apparatus is controlled to decrease the bit rate.   The encoding control unit controls the moving image compression method used when the encoding unit encodes the moving image data to a moving image compression method having a high compression rate. The image transmission device described. Encode moving image data to generate encoded moving image data,
Storing the encoded moving image data in a transmission buffer;
Transmitting the encoded moving image data stored in the transmission buffer to an image receiving device via a wireless communication line;
Position information, speed information, and direction information of a moving body, radio wave intensity distribution information of the wireless communication line in at least a path along which the moving body moves, an encoding bit rate when generating the encoded moving image data, Whether or not a failure of real-time transmission occurs in which the encoded moving image data is not transmitted to the image receiving device in real time based on the state information indicating the storage state of the encoded moving image data in the transmission buffer To detect the time until the failure occurs,
When the failure is predicted to occur, the target bit rate for generating the encoded moving image data is reduced within the time period.
An image transmission method characterized by the above. An encoding unit that encodes moving image data to generate encoded moving image data;
A transmission buffer for storing the encoded moving image data;
A transmission unit that transmits the encoded moving image data stored in the transmission buffer to an image reception device via a wireless communication line;
In a computer mounted on an image transmission device comprising:
Position information, speed information, and direction information of a moving body, radio wave intensity distribution information of the wireless communication line in at least a path along which the moving body moves, an encoding bit rate when generating the encoded moving image data, Whether or not a failure of real-time transmission occurs in which the encoded moving image data is not transmitted to the image receiving device in real time based on the state information indicating the storage state of the encoded moving image data in the transmission buffer Detecting the time until the failure occurs, and
When the failure is predicted to occur, the encoding unit controls the encoding unit to reduce a target bit rate when encoding the moving image data within the time period; and
The image transmission program characterized by performing.

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