A transmission apparatus comprising: a data transmission unit configured to transmit content data through a first transmission path to an external apparatus, said content data comprising data representing an image signal and/or data representing an audio signal; and an information transmission unit configured to transmit further information through a second transmission path to the external apparatus, wherein the second transmission path corresponds to a bidirectional communication path including a certain line of the first, transmission path, the bidirectional communication path corresponds to a pair of differential transmission paths, and at least one of the pair of differential transmission paths has a function of transmitting a connection state of the external apparatus using a direct current bias potential; wherein the information transmission unit is configured to transmit plural units of processing information, said plural units of processing information being indicative of respective audio processing to be applied to content data representing corresponding portions of said audio signal and/or being indicative of respective display processing to be applied to content data representing corresponding portions of said image signal; and there is further provided control means configured to add corresponding index information: to a unit of processing information indicative of audio processing or display processing to be applied to a first portion of said audio signal or image signal, and to a unit of content data, transmitted from the data transmission unit, representing said first portion of the audio signal or image signal. a data transmission unit configured to transmit content data through a first transmission path to an external apparatus, said content data comprising data representing an image signal and/or data representing an audio signal; and an information transmission unit configured to transmit further information through a second transmission path to the external apparatus, wherein the second transmission path corresponds to a bidirectional communication path including a certain line of the first, transmission path, the bidirectional communication path corresponds to a pair of differential transmission paths, and at least one of the pair of differential transmission paths has a function of transmitting a connection state of the external apparatus using a direct current bias potential; wherein the information transmission unit is configured to transmit plural units of processing information, said plural units of processing information being indicative of respective audio processing to be applied to content data representing corresponding portions of said audio signal and/or being indicative of respective display processing to be applied to content data representing corresponding portions of said image signal; and there is further provided control means configured to add corresponding index information: to a unit of processing information indicative of audio processing or display processing to be applied to a first portion of said audio signal or image signal, and to a unit of content data, transmitted from the data transmission unit, representing said first portion of the audio signal or image signal. to a unit of processing information indicative of audio processing or display processing to be applied to a first portion of said audio signal or image signal, and to a unit of content data, transmitted from the data transmission unit, representing said first portion of the audio signal or image signal.