Track objects

GESTrackFileSource — outputs a single media stream from a given file
GESTrackTitleSource — render stand-alone text titles
GESTrackAudioTestSource — produce a simple test waveform or silence
GESTrackVideoTestSource — produce solid colors and patterns
GESTrackTextOverlay — render text onto another video stream in a GESTimelineLayer
GESTrackTransition — base class for audio and video transitions
GESTrackVideoTransition — implements video crossfade transition
GESTrackAudioTransition — implements audio crossfade transition
GESTrackImageSource — outputs the video stream from a media file as a still image.