To appropriately display image data and auxiliary information according to performance of a display.

A transmission terminal that is connected to a display device and that outputs image data comprises: means that acquires resolutions that can be displayed by the display device; means that determines whether or not the obtained resolutions that can be displayed by the display device include resolutions other than those of a reference aspect ratio; means that selects a first resolution other than the reference aspect ratio from the resolutions that can be displayed by the display device can display images when the resolution determination means determines that the obtained resolutions include resolutions other than those of the reference aspect ratio, and that selects a second resolution having the reference aspect ratio from the resolutions that can be displayed by the display device when the resolution determination means determines that the obtained resolutions do not include resolutions other than those of the reference aspect ratio; means that performs a processing of adding a segment area to image data to be outputted to the display device after the resolution selecting means selects the first resolution; and means that changes the resolution that is selected by the resolution selecting means.