Compressió, multiplexació estadística, i serveis avançats sobre TV digital terrestre

Abstract

The current digital television broadcasting (over terrestrial systems, satellite, etc.) is performed following the technical parameters established by the standards published by the DVB consortium. The audiovisual compression procedures are based on the MPEG standards and the multiplexing follows the Transport Stream standard, which is the audiovisual transmission format for noisy communication channels. The broadcasting of multiple signals, with different characteristics, on the same transmission medium leads to the need for improved the multiplexing systems in order to optimize the compressed streams' bandwidth with the objective of maximize the system global quality and, therefore, increase the channel efficiency. In order to carry out this process, a statistical multiplexing system is needed. This degree thesis has focused on studying and developing a MPEG-2 streams coding and multiplexing scenario aimed at DVB-T digital TV content broadcasting. We have considered the acquisition, emission and reception stages, and we have been able to deploy a real-time, operative, complete system of terrestrial digital TV. Encoder and multiplexer devices have a high cost, but there is the alternative of using free software in order to save budget. For this reason, in this project we have used free and open source software running on the Linux operating system. Specific hardware has also been used for the video acquisition and for the output signal modulation and broadcasting. Throughout this thesis we have studied the CBR and VBR bitstream encoding methods, as well as different techniques of statistical multiplexing. The software involved in the signal generation process has been FFmpeg and OpenCaster. MPEG-2 streams analysis software has also been used, with which we have been able to examine the generated audio and video files. Finally, we experimented with advanced multimedia services offered by digital television. We have studied the interactive television world and the HbbTV standard with the aim to deploy a hybrid television service on the scenario.

L’actual difusió de la televisió digital, en els diversos sistemes de distribució (terrestre, satèl·lit, etc.), es realitza seguint els paràmetres tècnics establerts pels diferents estàndards que ofereix l’organisme DVB. Els procediments de compressió de les fonts audiovisuals estan basats en els estàndards MPEG i la multiplexació es realitza a través de l’anomenat Transport Stream, el format de transmissió audiovisual per a canals de comunicacions sorollosos. L’emissió de diversos senyals, amb diferents característiques, sobre un mateix medi de transmissió comporta la necessitat de millorar els sistemes de multiplexació per tal d’optimitzar l’ample de banda dels fluxos comprimits amb l’objectiu de maximitzar la qualitat global del sistema i, per tant, augmentar l’eficiència dels canals. Per dur a terme aquest procés es necessita desenvolupar un sistema de multiplexació estadística.