An image data transmission apparatus comprising: an image data receiving unit configured to receive stereoscopic image data for displaying a stereoscopic image; and an image data transmission unit configured to transmit the stereoscopic image data received by the image data receiving unit to an external device through a transmission path provided by transmission lines, wherein the image data transmission unit is operable to read, via a second data path provided by data lines separate to the transmission lines, format data and request information stored in a storage unit provided in the external device, the format data indicating stereoscopic image data format which can be handled by the external device and the request information indicating whether the external device has requested that transmission of stereoscopic image data be performed without performing format conversion; and wherein the image data transmission unit is operable to transmit, when a format of the stereoscopic image data received by the image data receiving unit is a format that can be handled by the external device, and the external device has requested that transmission of the stereoscopic image data be performed without performing format conversion, the stereoscopic image data received by the image data receiving unit to the external device without performing format conversion, and wherein the image data transmission unit is operable to convert, when the format of the stereoscopic image data received by the image data receiving unit is not a format that can be handled by the external device or when the external device has not requested that transmission of the stereoscopic image data be performed without performing format conversation, the stereoscopic image data received by the image data receiving unit into a preset format and transmits the stereoscopic image data to the external device. an image data receiving unit configured to receive stereoscopic image data for displaying a stereoscopic image; and an image data transmission unit configured to transmit the stereoscopic image data received by the image data receiving unit to an external device through a transmission path provided by transmission lines, wherein the image data transmission unit is operable to read, via a second data path provided by data lines separate to the transmission lines, format data and request information stored in a storage unit provided in the external device, the format data indicating stereoscopic image data format which can be handled by the external device and the request information indicating whether the external device has requested that transmission of stereoscopic image data be performed without performing format conversion; and wherein the image data transmission unit is operable to transmit, when a format of the stereoscopic image data received by the image data receiving unit is a format that can be handled by the external device, and the external device has requested that transmission of the stereoscopic image data be performed without performing format conversion, the stereoscopic image data received by the image data receiving unit to the external device without performing format conversion, and wherein the image data transmission unit is operable to convert, when the format of the stereoscopic image data received by the image data receiving unit is not a format that can be handled by the external device or when the external device has not requested that transmission of the stereoscopic image data be performed without performing format conversation, the stereoscopic image data received by the image data receiving unit into a preset format and transmits the stereoscopic image data to the external device.