Playback is held waiting for a producer to emit detections for the frame
about to be shown, which is a wait on inference rather than on transfer or
decode. DetectionsBuffering is the transfer of detections that already
exist, and PlaybackBuffering is the wait for media bytes.
The picture is waiting on media the source has not handed over yet, which
is the bytes and their decode rather than anything downstream of them.
PlaybackBuffering is what a transport reports once it has already
stopped; this is reported from the read itself, including the reads a seek
makes while the transport still reads as paused.
The render-preparation gate held the picture for artifacts that never
arrived and let it go. Nothing is blocked: the frames reaching the screen
are the ones whose artifacts were given up on. What is waited on is
preparation finishing another frame, which is what lets the gate hold the
picture again; RenderPreparing covers the holds that are running.
Subsystem currently affecting session readiness or presentation.