Abstract:
An information processing method and apparatus of this invention are a method and apparatus for multiplexing data indicating information other than video information on a video signal and transmitting the multiplexed data. Modulated data is formed by inputting the data and modulating the input data. The video signal and the modulated data are input, and the modulated data is multiplexed on the input video signal. When the multiplexed data is output, the modulation mode or the multiplexing interval of the modulated data is controlled in correspondence with the type of input data, thus realizing a function of multiplexing data on a video signal and transmitting the multiplexed data in correspondence with the data type with a simple, small-scale circuit arrangement.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present invention relates to an information transmission method and apparatus for multiplexing data indicating information other than video information on a video signal, and transmitting the multiplexed data. 
     2. Related Background Art 
     A conventional system, which transmits a signal obtained by multiplexing data such as character data on a video signal, and receives and demultiplexes such signal into the video signal and data like in teletext broadcasting, is known. 
     However, the conventional system multiplexes modulated data on a specific interval (a portion of the vertical blanking interval) of a video signal, and the receiving side demodulates the specific interval alone to obtain data. More specifically, the modulation speed, the interval to be multiplexed, and the like of data are predetermined, and cannot be changed depending on the data volume, quality of line, and the like. 
     The arrangement of a video input apparatus shown in FIG. 1 will be described below as an example of a conventional information transmission system. A single-focus camera unit  100  serving as a video input unit is connected to an image processing unit  200  serving as a video processing unit. The image processing unit  200  is connected to a host unit  400  via a bus interface  208 . The host unit  400  controls the image processing unit  200  and the single-focus camera unit  100  via the bus interface  208 . 
     The arrangement of the single-focus camera unit  100  will be explained below. A system control unit  106  comprises a one-chip microcomputer having functions of a CPU, ROM, RAM, control port, communication port, and the like. The system control unit  106  controls the individual devices in the single-focus camera unit to make two-way communications with the image processing unit  200 , and interprets commands as control data from the host unit  400  to execute operations requested by the host unit  400 . 
     A lens unit  101  comprises a phototaking lens, focusing lens, and a focusing ring for manually moving the focusing lens. An iris unit  102  adjusts the amount of incident light that passes through the lens unit  101 , and comprises an iris and an iris ring for manually moving the iris. An image sensing element  103  such as a CCD photoelectrically converts an image obtained via the lens unit  101  and the iris unit  102  into an electrical signal. An image sensing element driving circuit  105  such as a TG controls accumulation, reading, and resetting of the image sensing element  103  in correspondence with the number of pixels of the element  103 . When the driving circuit  105  is controlled by the system control unit  106  via a control signal  110 , the shutter speed can be changed. A synchronization signal generation circuit  108  such as an SSG generates video synchronization signals  112  such as a horizontal synchronization signal (HD), vertical synchronization signal (VD), video clocks, and the like on the basis of the clocks generated by the image sensing element driving circuit (TG)  105 . An S/H·AGC circuit  104  performs sampling and holding to reduce noise in charges accumulated in the image sensing element  103 , and adjusts the gain of a video signal  114 . The S/H·AGC circuit  104  outputs the video signal  114 . When the S/H·AGC circuit  104  is controlled by the system control unit  106  via a control signal  111 , it adjusts the gain of the video signal  114 . A data multiplexing and demultiplexing unit  115  multiplexes the video signal  114  and control data from the system control unit  106 , and transmits multiplexed data to the image processing unit  200 . Also, the data multiplexing and demultiplexing unit  115  demultiplexes data from the image processing unit  200  and supplies the demultiplexed data to the system control unit  106 . A data line &amp; data control line  113  are used for two-way data communications between the single-focus camera unit  100  and the image processing unit  200 , and are connected between the serial communication port of the system control unit  106 , and the data multiplexing and demultiplexing unit  115 . A connector  107  can be detached from the cable  109 . 
     The video processing unit  200  will be described below. A system control unit  250  comprises a one-chip microcomputer having functions of a CPU, ROM, RAM, control port, communication port, and the like. The system control unit  250  performs control of the individual devices in the image processing unit  200 , auto white balance control, communications with the single-focus camera unit  100 , and communications with the host unit  400  via the bus interface  208 . Also, the system control unit  250  interprets commands as control data from the host unit  400  and executes operations requested by the host unit  400 . 
     A data multiplexing and demultiplexing unit  231  demultiplexes a video/data multiplexed signal  232  which multiplexes a video signal and data signal into a video signal  217  and a control data signal  222 . Also, the data multiplexing and demultiplexing unit  231  multiplexes data from the system control unit  250  into a signal within the vertical synchronization interval, and transmits the signal to the single-focus camera unit  100 . 
     An A/D conversion circuit  201  converts the video signal  217  transmitted from the single-focus camera unit  100  via the cable  109  into a digital signal  218 . A signal processing circuit  202  performs processing for converting the converted digital video signal  218  into a standardized digital video signal  219 . The signal processing circuit  202  generates an interrupt signal for informing the system control unit  250  of white balance data for white balance control. Upon recognizing the interrupt, the system control unit  250  reads out such information (white balance data, and the like) via a serial data line  223 , and writes them in its RAM area. 
     An encoder circuit  204  converts the standardized digital video signal  219  into a multiplexed composite signal  221 , and outputs the composite signal to a video output connector  210 . An image memory  206  stores digital video signals  216  and  213  from the signal processing circuit  202  and an SRC (scan rate converter circuit)  207 . A memory controller circuit  205  controls reads/writes in/from the image memory  206 . The SRC  207  converts and absorbs the difference between the aspect ratios of the digital video signal  213  of the image processing unit  200  and a digital video signal  214  of the host unit  400 . A switch circuit  203  selects an output signal  225  to the encoder  204  from a digital video signal  219  of the signal processing circuit  202  and the digital video signal  216  of the image memory  206 , and is controlled by the system control unit  250  via a control line  224 . The bus interface  208  is connected to the bus of a computer as the host unit  400 . The bus interface  208  performs data communications of the digital video signal  214  and control data  226  between the host unit  400  and the image processing unit  200 , and allows the host unit  400  to control the memory controller  205  and the SRC  207 . 
     Video synchronization signals  215  of the image processing unit  200  correspond to the video synchronization signals  112  of the single-focus camera unit  100 , and provide video synchronization signals to the signal processing circuit  202 , the memory controller  205 , and the encoder  204 . 
     A serial data line &amp; serial data control unit  222  are used for performing two-way data communications between the single-focus camera unit  100  and the image processing unit  200 , and are connected to the serial data port of the system control unit  250 . 
     A parallel data line &amp; control unit  226  are used for performing two-way data communications between the host unit  400  and the image processing unit  200 , and are connected to the control port of the system control unit  250 . 
     FIG. 2 shows the transmission sequence of data  10  during the vertical blanking interval between the single-focus camera unit  100  and the image processing unit  200 . A vertical synchronization interval Vhd t consists of a vertical blanking interval V b  and an effective video interval V a . Each data  10  is multiplexed on a video signal during the vertical blanking interval V b . 
     When data communications are to be made between the single-focus camera unit  100  and the image processing unit  200 , the length of data that can be transmitted within one vertical blanking interval V b  is limited. 
     In the case of FIG. 1, when the image processing unit  200  transmits control data such as command data and ACK data to the single-focus camera unit  100  within one vertical synchronization interval V t , a maximum of 19 bytes=16 bytes (command data)+3 bytes (ACK data) must normally be transmitted. In this case, since this number of bytes is smaller than 32 bytes as the maximum number of bytes that can be transmitted within a single vertical blanking period V b , all the data can be transmitted. 
     However, in the case of a zoom head which requires a large information volume to be transmitted, when vertical synchronization data generated for each synchronization interval is to be transmitted together with control data such as command data and ACK data, a maximum of 45 bytes=16 bytes (command data)+3 bytes (ACK data)+26 bytes (vertical synchronization data) must be transmitted. This number of bytes exceeds 32 bytes as the maximum number of bytes that can be transmitted within a single vertical blanking period V b . 
     In this manner, when auto-focusing or automatic exposure is performed in a zoom camera unit, since the image processing unit  200  transmits data required for such control to the zoom head for each vertical blanking interval V b , the volume of data to be transmitted increases. In the apparatus in which the density of the volume of information to be transmitted is high, data transmission cannot be completed within a single vertical blanking interval V b . 
     SUMMARY OF THE INVENTION 
     It is an object of the present invention to provide an information transmission method and apparatus, which can solve the above-mentioned problems. 
     It is another object of the present invention to provide an information transmission apparatus which can realize a function of multiplexing data on a video signal in accordance with the data format used and transmitting multiplexed data, with an inexpensive, simple, and small-scale circuit arrangement. 
     In order to achieve the above objects, according to one embodiment of the present invention, an information transmission apparatus for multiplexing data indicating information other than video information on a video signal and transmitting the multiplexed data, comprises modulation means for forming modulated data by inputting the data and modulating the input data, and outputting the formed modulated data, multiplexing means for inputting the video signal and the modulated data output from the modulation means, multiplexing the modulated data on the input video data, and outputting the multiplexed data, and control means for controlling a modulation mode in the modulation means or a multiplexing interval of the modulated data in the multiplexing means in accordance with a type of data input to the modulation means. 
     It is still another object of the present invention to provide an information transmission apparatus which can efficiently transmit data together with a video signal. 
     In order to achieve the above object, according to one embodiment of the present invention, an information transmission apparatus for multiplexing data indicating information other than video information on a video signal and transmitting the multiplexed data, comprises transmission means for multiplexing and transmitting control data in a vertical blanking interval of the video signal in an identifiable state, and control means for controlling the transmission means to preferentially multiplex and transmit the control data when the transmission means has data to be multiplexed and transmitted in the vertical blanking interval in addition to the control data, and to multiplex and transmit the data, which cannot be multiplexed in the vertical blanking interval, during an interval other than the vertical blanking interval. 
     It is still another object of the present invention to provide an information transmission method which can efficiently transmit data together with a video signal. 
     In order to achieve the above object, according to one embodiment of the present invention, an information transmission method for multiplexing data indicating information other than video information on a video signal and transmitting the multiplexed data, comprises the transmission step of multiplexing and transmitting control data in a vertical blanking interval of the video signal in an identifiable state, and the control step of controlling a transmission operation in the transmission step to preferentially multiplex and transmit the control data when there is in the transmission step data to be multiplexed and transmitted in the vertical blanking interval in addition to the control data, and to multiplex and transmit the data, which cannot be multiplexed in the vertical blanking interval, during an interval other than the vertical blanking interval. 
    
    
     Other objects and features of the present invention will become apparent from the following detailed description of the embodiments of the present invention taken in conjunction with the accompanying drawings. 
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a block diagram showing an example of the arrangement of a conventional information transmission system; 
     FIG. 2 is an explanatory view of the data transmission sequence in the conventional information transmission system; 
     FIG. 3 is a block diagram showing an information transmission apparatus according to the first embodiment of the present invention; 
     FIG. 4 is a block diagram showing the arrangement of a modulation unit and a demodulation unit shown in FIG. 3; 
     FIGS. 5A and 5B are timing charts for explaining the operation of the arrangement shown in FIG. 4; 
     FIG. 6 is a block diagram showing an information transmission apparatus according to the second embodiment of the present invention; 
     FIG. 7 is a block diagram showing the arrangement of a video input apparatus according to the fourth embodiment of the present invention; 
     FIG. 8 is a block diagram showing the arrangement of a system control unit in a video processing unit shown in FIG. 7; 
     FIGS. 9A and 9B are explanatory views showing the transmission sequence of command data, in which FIG. 9A is an explanatory view showing the transmission sequence between a host unit and the video processing unit, and FIG. 9B is an explanatory view showing the transmission sequence between the video processing unit and a camera unit; 
     FIG. 10 is an explanatory view showing the transmission sequence of vertical synchronization data; 
     FIG. 11A is an explanatory view showing the frame format of command data, 
     FIG. 11B is an explanatory view showing the frame format of ACK data, and 
     FIG. 11C is an explanatory view showing the frame format of vertical synchronization data; 
     FIG. 12A is an explanatory view showing the format of a frame identifier, and 
     FIG. 12B is an explanatory view showing the format of a command identifier; and 
     FIG. 13 is a flow chart showing the transmission operation of a system control unit to the camera unit. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 3 is a block diagram showing an information transmission apparatus according to the first embodiment of the present invention. 
     Referring to FIG. 3, a transmitting terminal  10  and a receiving terminal  20  are connected via a transmission line  1 . The transmitting terminal  10  comprises a camera  11 , a control CPU  12 , a data modulation unit  13  (including a modulation control unit), a signal multiplexing unit  14 , and an output unit  15 . The receiving terminal  20  comprises a reception unit  21 , a signal separation unit  22 , a monitor  23 , a demodulation unit  24  (including a demodulation control unit), and a control CPU  25 . 
     The operation will be described below. 
     In the transmitting terminal  10 , a video signal sensed by the camera  11  is supplied to the multiplexing unit  14 . On the other hand, data generated by the CPU  12  is modulated by the modulation unit  13 , and the modulated data signal is supplied to the multiplexing unit  14 . The modulated data signal is multiplexed on the video signal, and the multiplexed signal is output onto the transmission line  1  via the output unit  15 . Note that the modulation speed, modulation timing, and the like of data are set under the control of the CPU  12 . 
     In the receiving terminal  20 , the signal received from the transmission line  1  via the reception unit  21  is separated into the video signal and the modulated data signal by the signal separation unit  22 . The video signal is input to and displayed on the monitor  23 . The modulated data signal is input to the demodulation unit  24  and is demodulated. The demodulated data is supplied to the CPU  25 . Note that the demodulation speed, demodulation timing, and the like of data are set under the control of the CPU  25 , and the modulated data is demodulated according to them. 
     FIG. 4 is a block diagram showing the arrangement of the modulation unit  13  (including the modulation control unit) and the demodulation unit  24  (including the demodulation control unit) shown in FIG.  3 . Note that the arrangement shown in this block diagram is used by a terminal which integrates the transmitting terminal  10  and the receiving terminal  20  shown in FIG. 3, and a common CPU is used as the CPUs  12  and  25 . In FIG. 4, the modulation and demodulation unit comprises a CPU interface  1101 , an address generator  1102 , transmission and reception buffers  1103 , a modulation control unit  1104 , a CRC addition unit  1105  for adding a CRC check code, a demodulation control unit  1106 , and a CRC detection unit  1107  for detecting CRC errors. 
     The operation will be described below. 
     The CPU interface  1101  exchanges commands, data, status, and the like with the control CPU. The CPU sets commands of the modulation speed and modulation timing (modulation line and the like) in the modulation control unit  1104  via the CPU interface  1101  to generate signals such as a control signal (TXVIDS gate) and the like in synchronism with vertical and horizontal synchronization signals TxVD and TxHD, a clock signal TxCLK, and the like. Transmission data input from the CPU is temporarily stored in the transmission buffer  1103  in accordance with the address generated by the address generator  1102 . Thereafter, the transmission data is read out by the address generator  1102  in accordance with the control signal from the modulation control unit  1104 , and a CRC code is added to the readout data by the CRC addition unit  1105 , thus outputting the sum data as data VIDSTx. 
     On the receiving side, the CPU sets commands of the demodulation speed and demodulation timing (demodulation line and the like) in the demodulation control unit  1106  via the CPU interface  1101  to generate signals such as a reception control signal (RxVIDS gate) and the like in synchronism with reception synchronization signals such as vertical and horizontal synchronization signals RxVD and RxHD, a clock signal RxCLK, and the like. The modulated data signal VIDSRx separated by the signal separation unit  22  is input to the CRC detection unit  1107  to check the presence/absence of errors, and thereafter, is temporarily stored in the reception buffer  1103  in accordance with the address generated by the address generator  1102 . The received data is then read out upon designation of the address generator  1102  via the CPU interface  1101 . 
     Note that the CPU independently sends commands to the modulation control unit  1104  and the demodulation control unit  1106  via the CPU interface  1101  to modulate and demodulate data in an arbitrary line. 
     FIGS. 5A and 5B are timing charts for explaining the operation of the arrangement shown in FIG.  4 . 
     In FIG. 5A, a, b, and c respectively indicate a composite synchronization signal Csync, a control signal TxVIDS gate in the vertical blanking interval (Vdelay, Vwidth), and a video signal multiplexed with data. As can be seen from FIG. 5A, data is modulated in synchronism with the synchronization signal of the video signal, and the modulated data signal is multiplexed on the video signal. The data modulation and multiplexing interval (the range of lines) is set in correspondence with the synchronization signal of the video signal, as shown in FIG.  5 A. In FIG. 5B, d and e represent the relationship between data multiplexed on one horizontal line of the video signal and other signals. Note that, for example, PCM modulation is used as the data modulation scheme, but any other modulation schemes may be used. 
     The same applies to the demodulation timings. 
     FIG. 6 shows an information transmission apparatus according to the second embodiment of the present invention, and illustrates a terminal that can attain external synchronization. 
     The terminal shown in FIG. 6 comprises a camera  31 , a control CPU  32 , a modulation and demodulation unit  33  (including modulation and demodulation control units), a multiplexing unit  34 , an output unit  35 , a reception unit  36 , and a signal separation unit  37 . 
     The operation will be explained below. 
     A video signal input by the camera  31  is supplied to the multiplexing unit  34 . On the other hand, data generated by the CPU  32  is modulated by the modulation and demodulation unit  33 , and the modulated data signal is time-division-multiplexed with the video signal while these signals are switched by the multiplexing unit  34 . The multiplexed signal is output from the output unit  35 . 
     A signal transmitted from another terminal is input from the reception unit  36 , and is separated into a video signal (a composite synchronization signal in this case) and a modulated data signal by the signal separation unit  37 . The modulated data signal is demodulated by the modulation and demodulation unit  33 , and the demodulated data is input to the CPU  32 . The separated video signal (composite synchronization signal) is input to the camera  31  to attain external synchronization of the camera  31 . 
     Since the signal to be output from this terminal includes the video signal input by the camera  31 , the data section where data can be multiplexed is limited to the vertical blanking interval of the video signal. In contrast to this, since the received signal is a composite synchronization signal (black burst signal and the like) for attaining external synchronization of the camera  31 , the interval in which data can be multiplexed is not limited to the vertical blanking interval, and data can be multiplexed in the entire section except for the vertical blanking interval. Such processing can be attained by independently setting the modulation and demodulation control units included in the modulation and demodulation unit  33 . 
     Furthermore, as the third embodiment, since communications can be made while setting an arbitrary data multiplexing section, the data multiplexing section can be dynamically changed after negotiation during communications. 
     In the above description, the reception section on the receiving side is set by the demodulation control unit. Alternatively, a section setting unit may be arranged in the signal separation unit, and data to be supplied to the demodulation unit may be separated from only the set section. 
     As described above, according to the above embodiments, at least one of the modulation speed and the multiplexing interval can be controlled upon modulating data and multiplexing the modulated data on the video signal on the transmitting side. On the receiving side, upon demultiplexing and demodulating the multiplexed data, the multiplexed data is demultiplexed by controlling the demodulation speed and the demultiplexing interval. Therefore, according to the present invention, the modulation and demodulation speeds can be controlled and the data communication section can be dynamically assigned in correspondence with the system requirements, generated data volume, quality of line, and the like. 
     The fourth embodiment of the present invention will be described below. FIG. 7 shows the arrangement of a video input apparatus according to the fourth embodiment of the present invention. Note that the same reference numerals in FIG. 7 denote the same parts as in FIGS. 1 and 2 above, and a detailed description thereof will be omitted. 
     A lens unit  121  comprises a phototaking lens, a focusing lens, a zoom motor for moving a focusing ring, a zoom lens, and a zoom motor for moving a zoom ring. When the lens unit  121  is controlled by a system control unit  106  via a control line  124 , powered zooming and auto-focusing can be realized. An iris unit  122  adjusts the amount of incident light that passes through the lens unit  121 , and comprises an iris and an iris motor for moving an iris ring. When the iris unit  122  is controlled by the system control unit  106  via a control line  125 , the iris can be open/close-controlled. The system control unit  106  can attain automatic exposure by maintaining the brightness data of an object transmitted from a video processing unit  200  constant by controlling the iris, shutter speed, and AGC gain. An image sensing element  123  such as a CCD photoelectrically converts an image obtained via the lens unit  121  and the iris unit  122  into an electrical signal. 
     The difference between the video processing unit  200  of this embodiment and the conventional one will be explained below. In order to realize auto-focusing and automatic exposure, data required for such control must be read out from a signal processing circuit  202  and must be transmitted to a zoom camera unit  150 . 
     The signal processing circuit  202  generates an interrupt signal and supplies it to a system control unit  250  so as to inform the system control unit  250  of synchronization data such as brightness data of the object used in exposure control, white balance data for white balance control, in-focus data for focusing control, and the like. Upon recognizing the interrupt signal, the system control unit  250  reads out such information via a serial data line  223 , and writes the readout information in its RAM  254 . Also, the system control unit  250  transmits synchronization data such as the brightness data of the object for automatic exposure, in-focus data for focusing control, and the like to the zoom camera unit  150  during the vertical blanking interval. 
     FIG. 8 is a block diagram of the system control unit  250 . The system control unit  250  comprises a one-chip microcomputer and a software program for controlling the microcomputer. A CPU  252  is connected to an internal bus  251 . A ROM  253  stores the software program, and a RAM  254  is used as the work area of the software program. A rewritable ROM (EEPROM)  255  stores data necessary for control. A timer unit  256  is connected to the internal bus  251 . An I/O control unit (I/O port)  257  controls various devices. A serial communication port (serial communication control unit)  258  performs command communications between the zoom camera unit  150  and a host computer  400 , and also performs serial communications with the individual devices in the image processing unit  200  to control these devices. 
     Host control data D 5  as control data exchanged between the host unit  400  and the image processing unit  200  and between the host unit  400  and the zoom camera unit  150  will be described below with reference to FIGS. 9A and 9B. 
     A request command D 6  requests an operation. A response command D 7  is a response to the request command D 6 , and is sent back when the requested operation has ended. ACK data D 8  is a frame for informing the transmitting side that the command has been normally received. 
     FIG. 9A shows the sequence when the host unit  400  requests an operation to the image processing unit  200 . Upon reception of the request command D 6  from the host unit  400 , the image processing unit  200  executes the requested command, and transmits the response command D 7  to the host unit  400  upon completion of execution. 
     FIG. 9B shows the sequence when the host unit  400  requests an operation to the zoom camera unit  150 . When the command received from the host unit  400  is addressed to the zoom camera unit  150 , the image processing unit  200  transfers the command to the zoom camera unit  150 . On the other hand, when the command received from the zoom camera unit  150  is addressed to the host unit  400 , the image processing unit  200  transfers the command to the host unit  400 . 
     Command data D 6  and D 7  and ACK data D 8  exchanged between the image processing unit  200  and the zoom camera unit  150  are produced when the host unit  400  controls the zoom camera unit  150 . For this reason, host control data D 5  such as the command data D 6  and D 7 , the ACK data D 8 , and the like are generated not in synchronism with each vertical synchronization interval but intermittently under the control of the host unit  400  in this case. 
     FIG. 10 shows the sequence of vertical synchronization data D 13  as synchronization data. 
     The vertical synchronization data D 13  is transmitted from the image processing unit  200  to the zoom camera unit  150  for each vertical synchronization interval. The image processing unit  200  transmits the vertical synchronization data D 13  such as in-focus data, brightness data, and the like to the zoom camera unit  150  for each vertical synchronization interval. 
     The frame formats of command data D 11 , control data of ACK data D 12 , and the vertical synchronization data D 13  will be described below with reference to FIGS. 11A,  11 B and  11 C. 
     FIG. 11A shows the frame format of the command data D 11 . A frame length L (length) D 14  indicates the number of bytes that make up the data. A frame identifier FID D 15  is used for identifying the frame attribute. A command identifier CID D 16  is used for identifying the command type. A parameter D 17  is determined in correspondence with the command. The command frame has a variable length; its minimum length is  3  bytes and the maximum length, 16 bytes. 
     FIG. 11B shows the frame format of the ACK data D 12 . In the ACK data D 12 , a frame length L D 14  is fixed at 2 bytes. A frame identifier FID D 15  assumes a fixed value “80h”. When a parameter D 16  is “00h”, it indicates that the frame has been normally received; otherwise, it indicates that errors have occurred. The cause of errors is identified by the value of the parameter D 16 . The frame of the ACK data D 12  has a fixed length of 3 bytes. 
     FIG. 11C shows the frame format of the synchronization data D 13 . In the case of a zoom camera, the length of the frame to be transmitted from the image processing unit  200  to the zoom camera unit  150  is 26 bytes. V data includes the above-mentioned in-focus data and brightness data. 
     FIGS. 12A and 12B respectively show the formats of the frame identifier (FID) D 15  and the command identifier (CID) D 16 . FIG. 12A shows the bit configuration of the FID D 15 . Bit  7  is used for identifying whether the frame is the frame of the command data D 11  or that of the ACK data D 12 . Bit  6  is effective in the case of communications between the zoom camera unit  150  and the video processing unit  200 , and is used for identifying the vertical synchronization data D 13  or the host control data D 5 . 
     Bits  2  and  3  are destination device identification bits, and are used for designating the command destination. Bits  0  and  1  are sending device identification bits, and are used for designating the sending device of the command. 
     FIG. 12B shows the bit configuration of the CID D 16 . Bit  7  is effective in the case of the response command, and when the function indicated by the request command normally ends, it is set at “0”; otherwise, “1”. A negative or positive response is distinguished using this bit. Bits  10  to  0  are command type bits, which specify the command type. 
     The signal processing circuit  202  transmits the vertical synchronization data D 13  such as brightness data of the object and in-focus data written in the RAM area of the system control unit  250  to the zoom camera unit  150  for each vertical synchronization interval. Using the brightness data of the object, the zoom camera unit  150  realizes automatic exposure by controlling the shutter speed of an image sensing element driving circuit (TG)  105 , the gain of an S/H·AGC circuit  104 , and the iris ring of the iris unit  122 . Also, the zoom camera unit  150  realizes auto-focusing by controlling the focusing ring of the zoom lens unit  121  using the in-focus data. 
     In this case, the length of data that can be transmitted from the image processing unit  200  to the zoom camera unit  150  per vertical synchronization interval is 32 bytes. The maximum frame length of the command data D 11  is 16 bytes, and the data length of the frame of the ACK data D 12  is 3 bytes. One vertical synchronization interval allows transmission of one frame each of the vertical synchronization D 13 , command data D 11 , and ACK data D 12 . 
     As has been described in the paragraphs of the prior art, in the case of the single-focus camera unit  100 , a maximum of 19 bytes (=16 bytes+3 bytes) must be transmitted when the frames of the command data D 11  and ACK data D 12  are to be transmitted. This number of bytes is smaller than the maximum number of transmittable bytes (32 bytes) per vertical blanking interval. However, in the case of the zoom camera unit  150 , when all the frame of the command data D 11 , the frame of the ACK data D 12 , and all the frames of the vertical synchronization data D 13  are to be transmitted, a maximum of 45 bytes (=16 bytes+3 bytes+26 bytes) must be transmitted. This number of bytes exceeds the maximum number of transmittable bytes (32 bytes) per vertical blanking interval. 
     In view of this problem, when data are to be transmitted to the zoom camera unit  150 , the command data D 11  and ACK data D 12  are preferentially sent during one vertical blanking interval, and the vertical synchronization data D 13  is transmitted if possible. The command data D 11  and ACK data D 12  are intermittently generated under the control of the host unit  400 . Although the vertical synchronization data D 13  is generated for each vertical synchronization interval, if it is omitted halfway through the frame to transmit the command data D 11  and ACK data D 12 , it has no serious influence on the automatic exposure and auto-focusing of the zoom camera unit  150 . 
     The operation when the system control unit  250  of the image processing unit  200  transmits the frames of the command data D 11 , ACK data D 12 , and vertical synchronization D 13  to the zoom camera unit  150  during one vertical blanking interval V b  will be described below with reference to the flow chart in FIG.  13 . 
     The image processing unit  200  checks if the destination device identification bits of the FID D 15  in the frame header of the command data D 11  received from the host unit  400  indicate that the command is to be sent to the zoom camera unit  150  (S 1 ). If it is determined that there is command data D 11  to be transmitted, the command data D 11  is set in the transmission buffer to a multiplexing and demultiplexing unit  231  (S 2 ). It is then checked if there is ACK data D 12  to be transmitted (S 3 ). If the command data D 11  was received from the zoom camera unit  150  during the previous vertical blanking interval, the ACK data D 12  need be transmitted. If the ACK data D 12  need be transmitted, the ACK data D 12  is set in the transmission buffer to the multiplexing and demultiplexing unit  231 . It is checked if the transmission buffer to the multiplexing and demultiplexing unit  231  has a 26-byte free space required for transmitting the vertical synchronization data D 13  (S 5 , S 6 ). If the vertical synchronization data D 13  can be transmitted, the vertical synchronization data D 13  is set in the transmission buffer (S 7 ); otherwise, the flow advances to step S 8  without setting any data. Then, the data set in the transmission buffer is transmitted to the multiplexing and demultiplexing unit  231 . 
     In this embodiment, the vertical blanking interval is exemplified as a synchronization interval, and transmission control of data is made in the priority order of host control data D 5  and vertical synchronization data D 13  within the vertical blanking interval. However, the present invention is not limited to this, and transmission control can be similarly made by assigning the priority order of data during the vertical blanking interval within the horizonal synchronization interval. 
     In the above embodiments, the present invention may be applied to either a system made up of a plurality of devices or an apparatus consisting of a single device. Also, in the above embodiments, the present invention may also be applied to the case wherein the invention is attained by supplying a program to the system or apparatus. In this case, by loading a storage medium that stores a program expressed by software for achieving the above embodiments to the system or apparatus, the system or apparatus can enjoy the effects of the information transmission method and apparatus of the above embodiments. 
     As described above, according to the above embodiments, by utilizing a blanking interval (vertical blanking interval or the like) in a synchronization interval (vertical synchronization interval or the like) of an information signal (video signal or the like), data are transmitted in accordance with the priority order of control data (command, ACK data, and the like) generated intermittently and synchronization data (white balance adjustment data and the like) generated for each synchronization interval. In addition, data which can be transmitted only partially within the blanking interval is not transmitted within the blanking interval, and the data which cannot be transmitted is transmitted using a free blanking interval in which the control data or the like, which is generated intermittently, is not transmitted. In this manner, even when the data length to be transmitted exceeds the maximum transmission length within one blanking interval, data can be transmitted efficiently, and information processing power can be improved. 
     In this case, since the control data is generated under the control of an external host device, transmission control can be efficiently attained from a remote place. In this manner, when the present invention is applied to, e.g., a video input device with a remote camera head, automatic exposure and auto-focusing with high processing power and excellent performance can be realized. 
     Many widely different embodiments of the present invention may be constructed without departing from the spirit and scope of the present invention. It should be understood that the present invention is not limited to the specific embodiments described in the specification, except as defined in the appended claims.