JP2010119015A - Image transmission apparatus, transmitting device, receiving device, and image transmitting system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an image transmission apparatus capable of achieving synchronization. <P>SOLUTION: A transmission unit 100 includes: a transmission-side synchronization signal generating part 112; a packet generating part 102 for converting image data into a data packet; a data transmitting part 104 for transmitting the data packet; and a synchronization information adding part 103 for adding information I, concerned with a phase difference between a synchronizing signal and the data packet in the transmission of the data packet by the data transmitting part 104 to the data packet. There are included: a data receiving part 106 for receiving the data packet, to which the information I is added; a reception-side synchronization signal generating unit 109 for generating a reception-side synchronization signal uniquely in the inside; and correction parts 107, 108, 110 for estimating the synchronizing signal based on the information I and outputting a correction signal for suppressing errors between the estimated synchronization signal and the reception-side synchronization signal. Image data obtained reconverting the received data packet are processed, in synchronism with the synchronization signal corrected, based on the correction signal or the reception-side synchronization signal. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an image transmission device, a transmission device, a reception device, and an image transmission system.

  When digital image data is communicated wirelessly, the image data is transmitted as a data packet, so the transmitting side sends out a synchronization signal, and the receiving (display) side displays the image on the display device in synchronization with the signal. I can't. Further, in packet transfer, there is an overhead in data transmission / reception, and it is difficult to transmit data with one clock accuracy. In addition, depending on the radio wave condition, processing such as “retransmission” of data that failed to be received may be performed. Therefore, the receiving side must display an image while eliminating various “fluctuations” in such data acquisition.

  As a countermeasure against such “fluctuation”, Japanese Patent Laid-Open No. 2001-156845 proposes a method of eliminating a synchronization shift by providing a buffer. FIG. 13 shows the configuration of the delay fluctuation absorber proposed in the publication, including a reception buffer 1 (11), a reception buffer 2 (12), a buffer 1 monitoring circuit 13, and a buffer 2 monitoring circuit 14. , Silence data generation circuit 15, switching circuit 16, continuous silence period monitoring circuit 17, AND circuit 1 (18), AND circuit 2 (19), AND circuit 3 (20), and AND circuit 4 (21 ), An S / R circuit 22, an INV circuit 1 (23), an INV circuit 2 (24), and an INV circuit 3 (25). The operation of the delay fluctuation absorber having the same configuration will be briefly described below.

During normal times, the reception buffer 1 (11) as an auxiliary buffer performs a bypass operation for passing reception data to the reception buffer 2 (12) as a main buffer. However, when the data reception interval fluctuates and data reception occurs continuously and the reception buffer 2 (12) overflows, the reception buffer 1 (11) accumulates the overflow data from the reception buffer 2 (12). . In this way, it is possible to cope with sudden and excessive delay fluctuations, and by selecting the respective capacities of the two buffers, the tolerance level against normal fluctuations (corresponding to the main buffer 12) and the tolerance level against excessive fluctuations (the auxiliary buffer 11 Response) can be set freely.
JP 2001-156845 A

  However, as described above, the conventional technology makes no mention of the operation clocks on the transmission side and the reception side. For example, in the moving image processing, if the clock frequency is different between the transmitting side and the receiving side, the time for one frame of the moving image generated based on these clocks also differs between the two. For example, when the clock on the transmission side is faster than the clock on the reception side, the time for one frame is shorter on the transmission side than on the reception side. As a result, the data processing amount (buffer read amount) on the reception side cannot catch up with the data transmission amount on the transmission side, and the reception buffer overflows sometime regardless of the presence or absence of fluctuation (buffer overflow).

  On the contrary, when the clock on the transmission side is slower than the clock on the reception side, the transmission side is longer than the reception side with respect to the time of one frame, and the data processing amount on the reception side (buffer read amount) The amount of transmission cannot keep up, and there is a state where there is no data to be displayed (buffer underrun). In the former case, it is necessary to absorb the time lag by discarding the overflowed image frames that cannot be received and in the latter case by displaying the same image frames again.

  The present invention has been made paying attention to such problems, and the purpose of the present invention is to achieve proper synchronization between the transmitting side and the receiving side even if they operate at different operating frequencies. An object of the present invention is to provide an image transmission apparatus that can perform the above-described process.

  In order to achieve the above object, an image transmission apparatus according to a first aspect of the present invention is an image transmission apparatus including a transmission unit and a reception unit that receives image data transmitted from the transmission unit. The transmission unit includes a synchronization signal generation unit that generates a synchronization signal, a packet generation unit that converts the image data into a data packet, a data transmission unit that transmits the converted data packet to the reception unit, and A synchronization information adding unit that adds information about a phase difference between the synchronization signal and the data packet when the data transmission unit transmits the data packet, to the data packet; and A data reception unit that receives the data packet to which the information regarding the phase difference is added from a transmission unit, and a reception side synchronization signal generation that independently generates a reception side synchronization signal within the reception unit And a correction unit that estimates the synchronization signal based on information on the phase difference added to the data packet and outputs a correction signal that suppresses an error between the estimated synchronization signal and the reception-side synchronization signal; The image data obtained by reconverting the received data packet is processed in synchronization with the synchronization signal corrected based on the correction signal or the reception-side synchronization signal.

  In the image transmission device according to the second aspect of the present invention, in the image transmission device according to the first aspect of the present invention, the correction signal is a correction signal for correcting the reception-side synchronization signal, and the reception signal is received. The side synchronization signal generation unit receives the correction signal, corrects the reception side synchronization signal based on the correction signal, and the image data is processed in synchronization with the corrected reception side synchronization signal. The

  An image transmission apparatus according to a third aspect of the present invention is the image transmission apparatus according to the second aspect of the present invention, wherein the reception-side synchronization signal generation unit relates to the phase difference added to the data packet. The correction is performed only when an error between the synchronization signal estimated based on the information and the reception-side synchronization signal is outside a predetermined range.

  An image transmission apparatus according to a fourth aspect of the present invention is the image transmission apparatus according to the first aspect of the present invention, wherein the correction signal is a correction signal for correcting the synchronization signal, and the correction unit The correction signal is transmitted to the transmission unit, and the synchronization signal generation unit of the transmission unit corrects the synchronization signal based on the correction signal.

  In the image transmission device according to the fifth aspect of the present invention, in the image transmission device according to the first aspect of the present invention, the synchronization signal generation unit generates a vertical synchronization signal as the synchronization signal.

  An image transmission apparatus according to a sixth aspect of the present invention is the image transmission apparatus according to the first aspect of the present invention, wherein the data transmission unit wirelessly transmits the converted data packet to the reception unit. Send.

  The image transmission device according to a seventh aspect of the present invention is the image transmission device according to the first aspect of the present invention, wherein the transmission unit further includes an imaging unit that captures an image, and the synchronization signal Is a synchronization signal generated during the imaging.

  The transmission device according to an eighth aspect of the present invention is a transmission device that transmits image data to a reception device in an image transmission device, the synchronization signal generation unit generating a synchronization signal, and the image data A packet generation unit that converts the data packet into a data packet, a data transmission unit that transmits the converted data packet to the receiving device, and the synchronization signal and the data packet when the data transmission unit transmits the data packet. And a synchronization information adding unit for adding information related to the phase difference to the data packet.

  Further, in the transmission device according to the ninth aspect of the present invention, in the transmission device according to the eighth aspect of the present invention, the synchronization signal generation unit generates a vertical synchronization signal as the synchronization signal.

  Further, in the receiving apparatus according to the tenth aspect of the present invention, in the image transmission apparatus, when transmitting the data packet obtained by converting the image data, information regarding the phase difference between the synchronization signal and the data packet is obtained. A receiving device that receives image data from a transmitting device that adds the data packet and transmits the data packet, the data receiving unit receiving the data packet to which the information regarding the phase difference is added from the transmitting device; A receiving-side synchronization signal generating unit that independently generates a receiving-side synchronization signal within the receiving device; and estimating the synchronization signal based on information relating to the phase difference added to the data packet, and the estimated synchronization signal and the A correction unit that outputs a correction signal that suppresses an error from the reception-side synchronization signal, and an image obtained by reconverting the received data packet Chromatography data is processed the correction signal to synchronize the corrected the synchronization signal or the receiver synchronous signal based in.

  The receiving device according to an eleventh aspect of the present invention is the receiving device according to the tenth aspect of the present invention, wherein the correction signal is a correction signal for correcting the receiving side synchronization signal, and the receiving side synchronization The signal generation unit receives the correction signal, corrects the reception-side synchronization signal based on the correction signal, and the image data is processed in synchronization with the corrected reception-side synchronization signal.

  The receiving apparatus according to the twelfth aspect of the present invention is the receiving apparatus according to the eleventh aspect of the present invention, wherein the receiving-side synchronization signal generating unit uses the information relating to the phase difference added to the data packet. The correction is performed only when an error between the synchronization signal estimated based on the received signal and the reception-side synchronization signal is outside a predetermined range.

  The receiving device according to a thirteenth aspect of the present invention is the receiving device according to the tenth aspect of the present invention, wherein the correction signal is a correction signal for correcting the synchronization signal, and the correction unit A correction signal is transmitted to the transmission unit, and a synchronization signal generation unit of the transmission unit corrects the synchronization signal based on the correction signal.

  In the receiver according to the fourteenth aspect of the present invention, in the receiver according to the tenth aspect of the present invention, the synchronization signal generation unit generates a vertical synchronization signal as the synchronization signal.

  An image transmission system according to a fifteenth aspect of the present invention is an image transmission system including a transmission device and a reception device that receives image data transmitted from the transmission device. A synchronization signal generation unit that generates a signal; a packet generation unit that converts the image data into a data packet; a data transmission unit that transmits the converted data packet to the reception device; and the data transmission unit that transmits the data packet A synchronization information adding unit that adds information about a phase difference between the synchronization signal and the data packet to the data packet when transmitting the data, and the receiving device receives the phase difference from the transmitting device. A data receiver for receiving the data packet to which information on the receiver is added, and a receiver-side synchronization signal that uniquely generates a receiver-side synchronization signal in the receiver And a correction unit that estimates the synchronization signal based on information regarding the phase difference added to the data packet and outputs a correction signal that suppresses an error between the estimated synchronization signal and the reception-side synchronization signal. The image data obtained by reconverting the received data packet is processed in synchronization with the synchronization signal or the reception-side synchronization signal corrected based on the correction signal.

  According to the present invention, even if the transmission side and the reception side are operating at different operating frequencies, there is no problem of buffer overflow or underrun, and image transmission that can always display a constant quality image. An apparatus can be realized.

(First embodiment)
FIG. 1 is a diagram illustrating a configuration of an image transmission apparatus including a transmission unit 100 and a reception unit 105 that receives image data transmitted from the transmission unit 100 according to the first embodiment of the present invention. . The transmission unit 100 transmits a synchronization signal generation unit (synchronization signal generation unit) 112 that generates a synchronization signal, a packet generation unit 102 that converts image data into a data packet, and transmits the converted data packet to the reception unit 105. And a synchronization information adding unit 103 that adds information on the phase difference between the synchronization signal and the data packet when the data transmitting unit 104 transmits the data packet to the data packet. .

  On the other hand, the receiving unit 105 receives the data packet to which the information regarding the phase difference is added from the transmitting unit 100, and the receiving side synchronization signal that independently generates the receiving side synchronization signal in the receiving unit 105. A signal generation unit 109, and a correction unit that estimates the synchronization signal based on information about the phase difference added to the data packet and outputs a correction signal that suppresses an error between the estimated synchronization signal and the reception-side synchronization signal (Synchronization information acquisition unit 107, transmission side synchronization signal estimation unit 108, synchronization error correction unit 110). The data packet received by the data receiving unit 106 is reconverted by the receiving side synchronization signal generating unit 109 into image data. The reception-side synchronization signal generation unit 109 displays the reception-side synchronization signal corrected based on the correction signal from the synchronization error correction unit 110 or the generated reception-side synchronization signal itself together with image data when there is no need for correction. Forward to. The display device 111 processes (displays) the image data in synchronization with the received synchronization signal.

  As shown in FIG. 2, the transmission side synchronization signal estimation unit 108 includes an information conversion unit 120, a free-run counter 121, and a synchronization signal generation unit 123. As shown in FIG. 3, the reception-side synchronization signal generation unit 109 includes a control unit 124, a free-run counter 125, and a synchronization signal generation unit 126, and independently generates a reception synchronization signal within the reception unit 105. Details of this will be described later.

  FIG. 4 is a timing chart during normal packet transmission, FIG. 6 is a diagram showing an allowable range of relative error between two signals, and FIG. 8 is a diagram for explaining error correction control.

(Function)
Next, the operation of this embodiment will be described with reference to FIGS. 1, 2, 3, 4, 6, and 8. The vertical synchronization signal in this embodiment is composed of a plurality of frames as shown in FIG. 12, and pulses are periodically inserted at the beginning of each frame to indicate the start position.

(Transmission operation)
First, the packet transmission operation will be described. The transmission side synchronization signal generation unit 112 of the transmission unit 100 generates a vertical synchronization signal used in the transmission unit 100. The image acquisition unit 101 performs an imaging operation based on the vertical synchronization signal generated by the transmission-side synchronization signal generation unit 112 and inputs the imaging result to the packet generation unit 102 as a digital image signal. The packet generation unit 102 converts the input digital image signal into a packet and inputs the packet to the synchronization information adding unit 103. The synchronization information adding unit 103 is information regarding the phase difference between the vertical synchronization signal of the image acquisition unit 101 and the packet, that is, information indicating how much time has passed since the vertical synchronization signal of the image acquisition unit 101 is used as a reference. This is added to the packet and input to the data transmission unit 104.

  The data transmission unit 104 transmits data wirelessly from the antenna 104-1 to the reception unit 105. The contents of the synchronization information added at this time may be any information as long as the transmission side and the reception side can be associated with each other. For example, the number of clocks required from the pulse position of the vertical synchronization signal shown in FIG. 12 to the transmission processing may be used, or the order in which packets are transmitted within the frame may be used.

  Details of the packet transmission process will be described below with reference to FIG. FIG. 4A is a timing chart at the time of packet transmission. If the packet [A] is input from the packet generator 102 to the synchronization information adding unit 103 at time T0 in the figure, the synchronization information adding unit 103 adds synchronization information indicating the time T0 to the packet [A]. . The data transmission unit 104 transmits the packet [A | T0] to which the synchronization information “T0” is added. Here, the time T0 indicates the elapsed time from the vertical synchronization signal.

(Reception operation)
Next, the packet reception operation will be described. The data receiving unit 106 in the receiving unit 105 receives the transmission data from the transmitting unit 100 and inputs it to the synchronization information acquiring unit 107. The synchronization information acquisition unit 107 acquires synchronization information from the received data packet and inputs it to the transmission side synchronization signal estimation unit 108. Here, the operation of the transmission side synchronization signal estimation unit 108 will be described with reference to FIG.

  The information conversion unit 120 in the transmission side synchronization signal estimation unit 108 converts the input synchronization signal into a numerical value for loading into the free-run counter 121 at the next stage. The free-run counter 121 performs a down-count operation in units of one clock, and after a new value is loaded by the information conversion unit 120, starts a down-count from that value. The synchronization signal generation unit 123 monitors the value of the free-run counter 121 and generates a pulse indicating the start of the frame according to the count value of the free-run counter 121. In this way, the estimated vertical synchronization signal 130 obtained by estimating the vertical synchronization signal in the transmission unit 100 is generated. In this embodiment, synchronization information is attached to each packet, but only the packet received first in each frame is actually used. Although the synchronization information is attached to the subsequent packet, the subsequent synchronization information is not used in the frame.

  Details of the packet reception process will be described below with reference to FIG. As shown in FIG. 4B, the synchronization information acquisition unit 107 acquires the synchronization information “T0” from the received packet [A | T0]. The information conversion unit 120 in the transmission side synchronization signal estimation unit 108 converts “T0” into a numerical value “C0”. This numerical value is loaded into the free-run counter 121. Here, for example, when the synchronization information “T0” is the number of clocks required from the pulse position of the vertical synchronization signal to the transmission process, “C0” is [total number of clocks of one frame− “T0”]. Also, if the synchronization information “T0” is the order in which the packets are transmitted, and if the packet transmission interval is W clocks, “T0” is the first packet, so “C0” is [total number of clocks in one frame] -W × 1]. However, in this case, it is assumed that the packet transmission interval (W) can be regarded as substantially constant, and that the reception side knows the interval (W). The free-run counter 121 counts down from the numerical value “C0” and generates a pulse when the count value reaches “0”. In this way, an estimated vertical synchronization signal 130 obtained by estimating the vertical synchronization signal on the transmission side is generated.

  The estimated vertical synchronization signal 130 generated in this way and the vertical synchronization signal 131 generated by the reception-side synchronization signal generation unit 109 and used as the synchronization signal in the reception unit 105 by a method described later are used for synchronization error correction. Input to the unit 110. The synchronization error correction unit 110 measures the relative error between the two signals (the time difference between the frame start pulse positions of the two vertical synchronization signals), and the relative error is within a predetermined error tolerance range as shown in FIG. It is determined whether or not it is within the range. Here, if the error is outside the allowable range, the synchronization error correction unit 110 outputs the correction signal 132 to the reception-side synchronization signal generation unit 109. The correction signal 132 is a signal for controlling the length of one frame on the receiving side in order to suppress errors. The synchronization error correction unit 110 is, for example, 1. Short, 2. Long, 3. The reception side synchronization signal generation unit 109 is notified of the current status maintenance and the like. In some cases, it is convenient that the frame start pulse positions on the transmission side and the reception side are separated from each other because the image data is stored in the buffer. In such a case, the relationship between the allowable error range and the relative error is as shown in FIG.

  If the error is within the allowable range, the receiving side synchronization signal is not corrected.

  On the other hand, the reception-side synchronization signal generator 109 operates as follows with the configuration shown in FIG. That is, the synchronization signal generator 126 generates the reception-side vertical synchronization signal 131 from the count value of the free-run counter 125. The free-run counter 125 performs a count-down operation in units of one clock. When the count value becomes “0”, the load value input from the control unit 124 is loaded and the down-count operation is continued again. When control other than maintaining the current state is input from the correction signal 132, the control unit 124 increases or decreases the load value of the free-run counter 125 according to the content. For example, when the content of the correction signal 132 is “short”, the load value is made smaller than the current numerical value, and when it is “long”, the load value is made larger than the current value. As a result, the down-count cycle changes and the one-frame time on the receiving side can be adjusted. However, it is desirable that one adjustment is performed with very little adjustment so as not to deviate from the time determined by the standard, and gradually approaches the target value over several frames.

  The reception-side synchronization signal generation unit 109 further re-converts the reception data packet input from the data reception unit 106 to obtain image data, and the image data is generated from the generated vertical synchronization signal or synchronization error correction unit 201. Are output to the display device 111 in synchronization with the vertical synchronization signal corrected based on the correction signal 132. The display device 111 processes or displays the image data.

  Note that a buffer not shown in FIG. 3 is provided in the reception-side synchronization signal generation unit 109. Image data is temporarily stored in this buffer and read out in accordance with the vertical synchronizing signal.

  FIG. 8 is a schematic diagram of relative error correction in the synchronization error correction unit 110. The abscissa indicates the elapsed time, and the ordinate indicates the relative error of the reception-side vertical synchronization signal with respect to the estimated transmission-side vertical synchronization signal. In the initial state in this example, one frame period on the receiving side is longer and the relative error increases in the positive direction. As a result, since the relative error exceeds the upper limit threshold at time T0, the synchronization error correction unit 110 changes the one frame period on the receiving side slightly shorter. Conversely, at time T1, the relative error has fallen below the lower threshold, so this time the one-frame period on the receiving side is changed slightly longer. Thereafter, similarly, by controlling so as not to exceed a predetermined threshold value, rough synchronization between the transmission side and the reception side is ensured.

  In order for the synchronization error correction unit 110 to perform the correction operation, the reception-side synchronization signal generation unit 109 must first generate a vertical synchronization signal by some method. Since the vertical sync signal on the receiving side and the vertical sync signal on the transmitting side are finally adjusted to a predetermined time relationship, there is a functional problem even if the initial vertical sync signal is generated at an arbitrary timing. However, since the adjustment performed in the present invention is a delicate adjustment, the adjustment may take time depending on the initial state of both. Therefore, when generating the reception-side vertical synchronization signal for the first time, it is desirable to refer to the transmission-side vertical synchronization signal estimated by the transmission-side synchronization signal estimation unit 108 so that there is no significant deviation.

  5A and 5B show timing charts when a retransmission operation occurs. FIG. 5A shows packet transmission, and FIG. 5B shows packet reception. This figure shows an example in which the packet [A | T0] transmitted at time T0 cannot be acquired due to the deterioration of the communication state. The data packet A is transmitted again by the retransmission process, but the synchronization information added at this time is changed to information indicating the time T1, and is retransmitted as a packet [A | T1].

  The receiving side acquires the synchronization information T1 from the received packet [A | T1], and loads the count value “C1” related to T1 to the free-run counter. Since the contents of the packet and the synchronization information are irrelevant, the estimated signal does not shift backward even if data retransmission occurs.

  As described above, according to the present embodiment, the transmission-side vertical synchronization signal is estimated on the reception side, and the reception-side vertical synchronization signal is finely adjusted with respect to the estimated signal. It is possible to avoid buffer overflow and underrun due to the difference between both frequencies.

  This embodiment can be variously modified. In the present embodiment, the free-run counters 121 and 125 are constituted by down counters, but naturally they may be constituted by up counters. The transmission-side vertical synchronization signal estimated in the present invention is used to check whether there is a large deviation between the reception-side vertical synchronization signal and the transmission-side vertical synchronization signal. Not meant to take. Therefore, the free counter 121 in the transmission-side synchronization signal estimation unit 108 is practically sufficient even if it is a counter in units of lines (a counter that counts down or counts up for each line) instead of in units of clocks.

  In addition, when a PLL (Phase Locked Loop) is used to generate the operation clock of the receiving unit 105, the operation frequency is changed by changing the low magnification of the PLL instead of changing the load value of the free-run counter. Thus, the time of one frame may be adjusted.

  The relative error allowed by the synchronization error correction unit 110 is determined in advance in the present embodiment, but the value may be calculated from the initial state of the vertical synchronization signal on the reception side and the transmission side. . In this case, since the generation of the first vertical synchronization signal on the reception side can be completely independent of the transmission side, the reception-side synchronization signal generation unit 109 can generate the vertical synchronization signal at an arbitrary timing.

  Further, in this embodiment, only the synchronization information of the first received packet of each frame is used, but the information of the packet at the second and subsequent arbitrary transmission positions may be used.

(Second Embodiment)
FIG. 9 is a diagram illustrating a configuration of an image transmission apparatus according to the second embodiment of the present invention, which includes a transmission unit 200 and a reception unit 205. For those having the same functions as those in the first embodiment, the same reference numerals are given and the description thereof is omitted. In the second embodiment, the receiving unit 201 further sets the response transmitting unit 204 to The transmitting unit 200 includes a response receiving unit 203.

(Function)
Hereinafter, the operation of the present embodiment will be described. The process until the receiving unit 201 receives the data packet transmitted from the transmitting unit 200 and estimates the vertical synchronization signal 130 in the transmitting unit 200 based on the received data packet is the same as in the first embodiment. The synchronization error correction unit 205 compares the transmission-side vertical synchronization signal 130 estimated by the transmission-side synchronization signal estimation unit 108 with the vertical synchronization signal 131 in the reception unit 106 generated by the reception-side synchronization signal generation unit 109, It is determined whether or not the relative error between the two is within a predetermined range, and the determination result is output to the response transmission unit 204 as a correction signal 206. The response transmission unit 204 transmits response data to the transmission unit 200 via the antenna 204-1 based on the correction signal 206.

  The response reception unit 203 in the transmission unit 200 receives the response data from the reception unit 201 via the antenna 203-1, and outputs a correction signal 207 corresponding to the content. As in the first embodiment, the types of responses are as follows: Short, 2. Long, 3. Current status maintenance can be used. The transmission side synchronization signal generation unit 202 finely adjusts the period of the vertical synchronization signal used in the transmission unit 200 according to the correction signal 207. Note that the transmission-side synchronization signal generation unit 202 here may have the same configuration as the reception-side synchronization signal generation unit 109 of FIG. 3, and the operation of time adjustment for one frame may be the same.

(Third embodiment)
Hereinafter, a third embodiment of the present invention will be described with reference to FIG. The basic configuration of this embodiment is the same as that of the first and second embodiments, but the internal configuration of the transmission side synchronization signal estimation unit 108 in the reception unit 105 (205) is different.

  FIG. 10 shows the configuration of transmission side synchronization signal estimation section 108 in the present embodiment. Information conversion section 140, three counters (counters 141, 142, 143), correction counter 144, and synchronization A signal generation unit 145. As described above, this embodiment is characterized in that a plurality of counters serving as a reference for generating the vertical synchronization signal are provided. 11A and 11B are timing charts for explaining the operation of this embodiment. 11A shows packet transmission, and FIG. 11B shows packet reception.

(Function)
Hereinafter, the operation of the present embodiment will be described with reference to FIGS. 10 and 11. The information conversion unit 140 determines the load value “C0” to be loaded into the counter 141 from the synchronization information “T0” obtained from the packet [A | T0] transmitted at the time T0, and loads it into the counter 141. Similarly, the load value “C1” of the counter 142 is determined from the packet transmitted at time T1, and the load value “C2” of the counter 143 is determined from the packet transmitted at time T2, respectively. To be loaded.

  Note that the correction signal 146 is output from the information conversion unit 140 to the correction counter 144 when loading to the counter 143. Each counter 141, 142, 143 starts down-counting after the load value is loaded from the information conversion unit 140.

  When the correction counter 144 detects the correction signal 146, it calculates the load value “CC” from the count values (“C0_2”, “C1_1”, “C2” in FIG. 11) of the respective counters 141, 142, and 143 at that time. Then, down-counting starts from that value. The synchronization signal generation unit 145 generates the vertical synchronization signal 130 from the count value of the correction counter 144.

  Determination of the load value of the correction counter 144 is as follows. 1. Average each count value For example, an intermediate value between the count values may be selected. At this time, it is possible to further improve reliability by not using data that is clearly different from other count values.

  Since the disturbance of the vertical synchronization signal directly leads to the disturbance of the display image, the adjustment work should be performed carefully. Since packet overhead cannot be ignored in packet transfer, as shown in FIG. 11, the arrival of data varies inevitably, but the reliability can be improved by increasing the number of data to be referenced.

  This embodiment can be variously modified. For example, the number of counters can be arbitrarily increased or decreased by the system. In the present embodiment, the same number of counters as the number of packets transferred in one frame are provided. However, if the number of data packets is large, the circuit scale increases, so that the number of data is thinned out as long as reliability is not lowered. Better.

  In this embodiment, the load value of the correction counter is calculated after completion of reception of all the packets. However, the count values of a plurality of counters may be constantly monitored and calculated each time. However, in this case, it is necessary for the counter not performing the counting operation to output a special count value that can be understood.

  In addition, the following configurations, operations, and effects of the invention can be derived from the specific embodiments described above.

1. A transmission unit that wirelessly transmits image data obtained by capturing a subject image;
A receiver that receives the image data transmitted from the transmitter and outputs the image data to a display device;
In an image transmission device comprising:
The transmitter
A synchronization information adding unit for adding synchronization information to the data packet;
The receiver
A synchronization information acquisition unit that acquires the synchronization information added by the transmission unit from the received data packet;
A transmission side synchronization signal estimation unit that estimates a synchronization signal in the transmission unit from the synchronization information;
A receiving side synchronization signal generating unit for generating a synchronizing signal in the receiving unit;
A synchronization error correction unit that detects an error between the synchronization signal in the transmission unit estimated by the transmission side synchronization signal estimation unit and the synchronization signal in the reception unit generated by the reception side synchronization signal generation unit, and outputs a correction signal; Prepared,
The image transmission apparatus according to claim 1, wherein the reception-side synchronization signal generation unit controls generation of a reception-side synchronization signal based on the correction signal.

(Corresponding Embodiment of the Invention)
The first and third embodiments described above correspond.

(Function)
The transmission unit converts the captured image data for one frame into a plurality of data packets. When the generated data packet is transmitted, synchronization information is added by the synchronization information adding unit. When the reception unit receives the data packet, the synchronization information acquisition unit extracts the synchronization information added by the transmission unit. The extracted synchronization information is input to the transmission side synchronization signal estimation unit, and the transmission side synchronization signal estimation unit estimates and generates the synchronization signal in the transmission unit based on this synchronization information.

  On the other hand, the reception-side synchronization signal generation unit generates a synchronization signal used by the reception unit to display image data. The transmission side synchronization signal generated by the transmission side synchronization signal estimation unit and the reception side synchronization signal generated by the reception side synchronization signal generation unit are input to the synchronization error correction unit.

  The synchronization error correction unit measures an error (time difference) between the transmission-side synchronization signal and the reception-side synchronization signal, and generates a correction signal based on the information. The generated correction signal is input to the reception-side synchronization signal generation unit. The reception-side synchronization signal generation unit adjusts the period of one frame of the reception-side synchronization signal based on the input correction signal.

(effect)
The receiver estimates the synchronization signal of the transmitter, and adjusts one frame time on the receiver side based on the error between the estimated synchronization signal and the synchronization signal actually used in the receiver. One frame period can be brought close to one frame period on the transmission side.

2. A transmission unit that wirelessly transmits image data obtained by capturing a subject image;
A receiver that receives the image data transmitted from the transmitter and outputs the image data to a display device;
In an image transmission device comprising:
The receiver
A synchronization information acquisition unit that acquires the synchronization information added by the transmission unit from the received data packet;
A transmission side synchronization signal estimation unit that estimates a synchronization signal in the transmission unit from the synchronization information;
A receiving side synchronization signal generating unit for generating a synchronizing signal in the receiving unit;
A synchronization error correction unit that detects an error between the synchronization signal in the transmission unit estimated by the transmission side synchronization signal estimation unit and the synchronization signal in the reception unit generated by the reception side synchronization signal generation unit, and outputs a correction signal;
A response transmitter that transmits the correction signal to the transmitter;
The transmitter
A transmission side synchronization signal generation unit for generating a synchronization signal in the transmission unit;
A synchronization information adding unit for adding synchronization information to the data packet;
A response receiver for receiving the correction signal transmitted from the receiver,
The image transmission apparatus, wherein the transmission side synchronization signal generation unit controls generation of a transmission side synchronization signal based on the correction signal received by the response reception unit.

(Corresponding Embodiment of the Invention)
The second embodiment corresponds to this.

(Function)
The transmission unit converts the captured image data for one frame into a plurality of data packets. When the generated data packet is transmitted, synchronization information is added by the synchronization information adding unit. When the reception unit receives the data packet, the synchronization information acquisition unit extracts the synchronization information added by the transmission unit. The extracted synchronization information is input to the transmission side synchronization signal estimation unit, and the transmission side synchronization signal estimation unit estimates and generates the synchronization signal in the transmission unit based on this synchronization information. On the other hand, the reception-side synchronization signal generation unit generates a synchronization signal used by the reception unit to display image data.

The transmission side synchronization signal generated by the transmission side synchronization signal estimation unit and the reception side synchronization signal generated by the reception side synchronization signal generation unit are input to the synchronization error correction unit.

  The synchronization error correction unit measures a time interval between the transmission-side synchronization signal and the reception-side synchronization signal, and generates a correction signal based on the information. The generated correction signal is transmitted to the transmission unit as response data by the response transmission unit. The transmission unit receives the response data from the reception unit by the response reception unit and inputs the response data to the transmission side synchronization signal generation unit.

  The transmission side synchronization signal generation unit adjusts one frame period on the transmission side based on the input response data.

(effect)
One frame on the transmission side is estimated by estimating the synchronization signal of the transmission unit in the reception unit, and adjusting one frame time on the transmission side based on an error between the estimated synchronization signal and the synchronization signal used in the reception unit. The period can be close to one frame period on the receiving side.

3. 3. The image transmission apparatus according to claim 1, wherein the synchronization information is information indicating a time difference between a data packet transmission process and a vertical synchronization signal in a transmission unit.

(Corresponding Embodiment of the Invention)
The first, second, and third embodiments correspond.

(Function)
When the packet is transmitted, the synchronization information adding unit adds information indicating how much the time has passed with reference to the vertical synchronization signal in the transmission unit. Note that the information to be added does not need to be information of the time itself, and may be a value such as a symbol, for example, as long as the transmission side and the reception side can correspond to each other. The packet data and the synchronization signal are irrelevant. When the same data packet is retransmitted, a different synchronization signal is given even for the same data.

(effect)
In wireless communication, the same data packet may be retransmitted. If a packet in which a set of data and a synchronization signal is simply generated is generated, a packet with the same synchronization signal is transmitted twice during retransmission. In this case, the transmission side synchronization signal estimated by the reception side is shifted backward by a time corresponding to one packet from the actual time.

  Regardless of the content of the packet, by adding the synchronization information at the time of packet transmission, it is possible to reliably transmit and receive the synchronization information.

4). The synchronization error correction unit has an error between a synchronization signal in the transmission unit estimated by the transmission side synchronization signal estimation unit and a synchronization signal in the reception unit generated by the reception side synchronization signal generation unit within a certain range. The image transmission apparatus according to 1 or 2, wherein the image transmission apparatus is controlled as described above.

(Corresponding Embodiment of the Invention)
The first, second, and third embodiments correspond.

(Function)
The synchronization error correction unit measures an error (time difference) between the synchronization signal in the transmission unit estimated by the transmission side synchronization signal estimation unit and the synchronization signal in the reception unit generated by the reception side synchronization signal generation unit. A correction signal is output when the interval is outside a preset range.

  Hereinafter, description will be made with reference to the synchronization signal in the transmission unit. When the time interval exceeds the upper limit of the setting range, it is determined that one frame time on the reception side is longer than that on the transmission side, and the synchronization error correction unit shortens one frame time on the reception side. Issue a correction signal. Conversely, if the time interval falls below the lower limit of the setting range, it is determined that one frame time on the receiving side is shorter than that on the transmitting side, and the correction signal is set so as to increase the one frame time on the receiving side. Is issued.

(effect)
In packet transfer, some temporal fluctuation cannot be avoided. It is assumed that there is an error in the synchronization signal in the receiver estimated by the packet, and instead of performing strict synchronization control, display that is caused by a sudden change in the synchronization signal by performing control taking that error into account. Can avoid adverse effects on

FIG. 1 is a diagram showing a configuration of an image transmission apparatus according to the first embodiment of the present invention. FIG. 2 is a diagram illustrating a configuration of the transmission side synchronization signal estimation unit 108. FIG. 3 is a diagram illustrating a configuration of the reception-side synchronization signal generation unit 109. FIG. 4 is a timing chart during normal packet transmission. FIG. 5 is a timing chart when a retransmission operation occurs. FIG. 6 is a diagram showing an allowable range of relative error between two signals. FIG. 7 is a diagram illustrating the relationship between the allowable error range and the relative error. FIG. 8 is a diagram for explaining error correction control. FIG. 9 is a diagram showing a configuration of an image transmission apparatus according to the second embodiment of the present invention. FIG. 10 is a diagram illustrating a configuration of a transmission side synchronization signal estimation unit according to the third embodiment of the present invention. FIG. 11 is a timing chart for explaining the operation of the third embodiment of the present invention. It is a figure which shows an example of the vertical synchronizing signal in this embodiment. It is a figure which shows the structure of the delay fluctuation absorber as a prior art example.

Explanation of symbols

DESCRIPTION OF SYMBOLS 100 Transmission part 101 Image acquisition part 102 Packet generation part 103 Synchronization information addition part 104 Data transmission part 105 Reception part 106 Data reception part 107 Synchronization information acquisition part 108 Transmission side synchronization signal estimation part 109 Reception side synchronization signal generation part 110 Synchronization error correction Unit 111 Display device 112 Transmission-side synchronization signal generation unit

Claims (15)

An image transmission apparatus including a transmission unit and a reception unit that receives image data transmitted from the transmission unit,
The transmitter is
A synchronization signal generator for generating a synchronization signal;
A packet generator for converting the image data into data packets;
A data transmitter that transmits the converted data packet to the receiver;
A synchronization information adding unit that adds information on a phase difference between the synchronization signal and the data packet when the data transmission unit transmits the data packet, to the data packet;
The receiver is
A data receiving unit for receiving the data packet to which information on the phase difference is added from the transmitting unit;
A receiving side synchronization signal generating unit that independently generates a receiving side synchronization signal in the receiving unit;
A correction unit that estimates the synchronization signal based on information about the phase difference added to the data packet and outputs a correction signal that suppresses an error between the estimated synchronization signal and the reception-side synchronization signal; And
The image transmission apparatus, wherein the image data obtained by reconverting the received data packet is processed in synchronization with the synchronization signal or the reception-side synchronization signal corrected based on the correction signal. The correction signal is a correction signal for correcting the reception-side synchronization signal,
The reception-side synchronization signal generation unit receives the correction signal, corrects the reception-side synchronization signal based on the correction signal,
The image transmission apparatus according to claim 1, wherein the image data is processed in synchronization with the corrected reception-side synchronization signal.   The reception side synchronization signal generation unit is only when an error between the synchronization signal estimated based on the information regarding the phase difference added to the data packet and the reception side synchronization signal is outside a predetermined range. The image transmission apparatus according to claim 2, wherein the correction is performed. The correction signal is a correction signal for correcting the synchronization signal,
The correction unit transmits the correction signal to the transmission unit,
The image transmission apparatus according to claim 1, wherein the synchronization signal generation unit of the transmission unit corrects the synchronization signal based on the correction signal.   The image transmission apparatus according to claim 1, wherein the synchronization signal generation unit generates a vertical synchronization signal as the synchronization signal.   The image transmission apparatus according to claim 1, wherein the data transmission unit wirelessly transmits the converted data packet to the reception unit.   The image transmission apparatus according to claim 1, wherein the transmission unit further includes an imaging unit that captures an image, and the synchronization signal is a synchronization signal generated during the imaging. In an image transmission apparatus, a transmission apparatus that transmits image data to a reception apparatus,
A synchronization signal generator for generating a synchronization signal;
A packet generator for converting the image data into data packets;
A data transmission unit for transmitting the converted data packet to the receiving device;
A synchronization information adding unit that adds information on a phase difference between the synchronization signal and the data packet when the data transmission unit transmits the data packet;
A transmission device comprising:   The image transmission apparatus according to claim 8, wherein the synchronization signal generation unit generates a vertical synchronization signal as the synchronization signal. In the image transmission apparatus, when transmitting a data packet obtained by converting image data, the image data is transmitted from the transmission apparatus that adds information related to the phase difference between the synchronization signal and the data packet and transmits the data packet. A receiving device for receiving
A data receiving unit that receives the data packet to which information on the phase difference is added from the transmission device;
A receiving side synchronization signal generating unit that independently generates a receiving side synchronization signal in the receiving device;
A correction unit that estimates the synchronization signal based on information about the phase difference added to the data packet and outputs a correction signal that suppresses an error between the estimated synchronization signal and the reception-side synchronization signal; And
Image data obtained by reconverting the received data packet is processed in synchronization with the synchronization signal or the reception-side synchronization signal corrected based on the correction signal. The correction signal is a correction signal for correcting the reception-side synchronization signal,
The reception-side synchronization signal generation unit receives the correction signal, corrects the reception-side synchronization signal based on the correction signal,
The image transmission apparatus according to claim 10, wherein the image data is processed in synchronization with the corrected reception-side synchronization signal.   The reception side synchronization signal generation unit is only when an error between the synchronization signal estimated based on the information regarding the phase difference added to the data packet and the reception side synchronization signal is outside a predetermined range. The image transmission apparatus according to claim 11, wherein the correction is performed. The correction signal is a correction signal for correcting the synchronization signal,
The correction unit transmits the correction signal to the transmission unit,
The image transmission device according to claim 10, wherein the synchronization signal generation unit of the transmission unit corrects the synchronization signal based on the correction signal.   The image transmission apparatus according to claim 10, wherein the synchronization signal generation unit generates a vertical synchronization signal as the synchronization signal. An image transmission system including a transmission device and a reception device that receives image data transmitted from the transmission device,
The transmitter is
A synchronization signal generator for generating a synchronization signal;
A packet generator for converting the image data into data packets;
A data transmission unit for transmitting the converted data packet to the receiving device;
A synchronization information adding unit that adds information on a phase difference between the synchronization signal and the data packet when the data transmission unit transmits the data packet, to the data packet;
The receiving device is:
A data receiving unit that receives the data packet to which information on the phase difference is added from the transmission device;
A receiving side synchronization signal generating unit that independently generates a receiving side synchronization signal in the receiving device;
A correction unit that estimates the synchronization signal based on information about the phase difference added to the data packet and outputs a correction signal that suppresses an error between the estimated synchronization signal and the reception-side synchronization signal; And
The image transmission system, wherein the image data obtained by reconverting the received data packet is processed in synchronization with the synchronization signal or the reception-side synchronization signal corrected based on the correction signal.

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