setVideoEnabled

Parks or resumes video decoding in place, without reopening anything.

Parked, video packets are discarded before the decoder and the picture freezes on the last frame; audio keeps playing and subtitles keep timing, because the container is still being read. This is what an application going to the background wants, because the decoder stays and the frozen picture is still there to look at until the new one arrives. Deselecting the video track stops the picture in place too while a sound plays, but it closes the decoder and takes the last picture off the screen, which suits a viewer who chose to only listen.

Resumed, decoding restarts at a keyframe. On a seekable source the engine seeks precisely to where playback already is, so the picture returns at the right frame rather than at whatever the container keys next; an unseekable source waits for that next keyframe.

Parked frames are not counted as drops. A drop means the engine could not keep up, and this is a decision.