This book constitutes the refereed proceedings of the 4th Iberoamerican Conference on Applications and Usability of Interactive TV, jAUTI 2015, and the 6th Congress on Interactive Digital TV, CTVDI 2015, held in Palma de Mallorca, Spain, in October 2015. The 10 revised full papers and two short papers presented together with an invited talk were carefully reviewed and selected for this volume from 30 accepted submissions. The papers are organized in topical sections on Second Screen Applications Immersive TV; Video Consumption Development Tools; IDTV Interoperability; IDTV User Experience; Audiovisual Accessibility.