An apparatus comprising a transmission device and a reception device configured to communicate with the transmission device, wherein the transmission device comprises: a first subtraction section configured to calculate a first subtraction value obtained by subtracting a number of bits having a second value from a number of bits having a first value in input data constituted by a collection of a predetermined number of bits each of which has the first or the second value; a first data processing section configured to perform a first predetermined process for the input data to generate intermediate data constituted by the predetermined number of bits; a second subtraction section configured to calculate a second subtraction value obtained by subtracting the number of bits having the second value from the number of bits having the first value in the intermediate data; a first accumulation section configured to calculate a cumulative value of the second subtraction value; and a transmission section configured to transmit the intermediate data by a serial signal; wherein the first predetermined process is a process of: comparing a sign of the first subtraction value of the input data and a sign of the cumulative value of the first accumulation section; generating the intermediate data by exchanging the first value and the second value with each other for all the bits of the input data and generating predetermined information indicating inversion of all the bits when the sign of the first subtraction value and the sign of the cumulative value are the same sign; and setting the input data as the intermediate data when the sign of the first subtraction value and the sign of the cumulative value are different signs; the transmission section is configured to cause the predetermined information of each input data to be included during a blanking period in a video signal so that the predetermined information is collectively transmitted with the input data representing image information; and the reception device comprises: a serial reception section configured to receive the serial signal and output the serial signal as received data for each predetermined number of bits; and a second data processing section configured to generate, for the received data, output data by exchanging the first value and the second value with each other for all the bits of the received data when the predetermined information is generated, and generate the received data which is received as the output data when the predetermined information is not generated, characterized in that the reception device further comprises: a third subtraction section configured to calculate a third subtraction value obtained by subtracting the number of bits having the second value from the number of bits having the first value in the received data; and a second accumulation section configured to calculate a cumulative value of the third subtraction value; and an abnormality detection section configured to compare a sign of the third subtraction value of the received data and a sign of the cumulative value of the second accumulation section, and, when the sign of the third subtraction value and the sign of the cumulative value of the second accumulation section are the same sign, generate predetermined error information. a first subtraction section configured to calculate a first subtraction value obtained by subtracting a number of bits having a second value from a number of bits having a first value in input data constituted by a collection of a predetermined number of bits each of which has the first or the second value; a first data processing section configured to perform a first predetermined process for the input data to generate intermediate data constituted by the predetermined number of bits; a second subtraction section configured to calculate a second subtraction value obtained by subtracting the number of bits having the second value from the number of bits having the first value in the intermediate data; a first accumulation section configured to calculate a cumulative value of the second subtraction value; and a transmission section configured to transmit the intermediate data by a serial signal; wherein a serial reception section configured to receive the serial signal and output the serial signal as received data for each predetermined number of bits; and a second data processing section configured to generate, for the received data, output data by exchanging the first value and the second value with each other for all the bits of the received data when the predetermined information is generated, and generate the received data which is received as the output data when the predetermined information is not generated, a third subtraction section configured to calculate a third subtraction value obtained by subtracting the number of bits having the second value from the number of bits having the first value in the received data; and a second accumulation section configured to calculate a cumulative value of the third subtraction value; and an abnormality detection section configured to compare a sign of the third subtraction value of the received data and a sign of the cumulative value of the second accumulation section, and, when the sign of the third subtraction value and the sign of the cumulative value of the second accumulation section are the same sign, generate predetermined error information.