Code cleanup: removed more deprecated FFmpeg API usage
Code cleanup: removed more deprecated FFmpeg API usage

This time in qt-tracker application.

SoylentGraham/libmv,SoylentGraham/libmv,petertsoi/libmv,SoylentGraham/libmv,rgkoo/libmv-blender,rgkoo/libmv-blender,rgkoo/libmv-blender,SoylentGraham/libmv,petertsoi/libmv,rgkoo/libmv-blender,petertsoi/libmv,petertsoi/libmv,rgkoo/libmv-blender