Popovych P. Improvement of video stream control methods in digital television systems by video image quality criterion

The thesis submitted for the degree of candidate in technical sciences, specialty 05.12.17 - radio engineering and television systems. - National Technical University of Ukraine "Igor Sikorsky Kyiv Polytechnic Institute ", Kyiv, 2017. The thesis is devoted to decision of actual scientific problem of improving the methods of automatic control of the video stream in digital television systems depending on the content and quality of the video picture of the TV program formed for further transmission to the consumer. The criterion of video quality assessment in digital television systems is proposed based on maximizing the correlation of objective quality indexes and subjective quality evaluations that allows to build an automatic video quality control system at the stages of preparation and transmission of TV programs. The developed method of video stream control is based on the application in the technological process of TV production of the video content automatic quality control system, which uses a close loop video transcoder that allows changing the bit rate of the video stream in accordance with the measured quality of the generated video picture. A mathematical model of close loop video transcoder is proposed, which differs from known transcoder models by an adaptive change in the global quantization factor of video stream depending on the results of the conformity assessment to the quality criterion. The developed structure and algorithm of close loop video transcoder enable it to be realized using standard hardware for primary video stream formation in digital television systems.