The flowchart reads from a top down perspective. At the top is a container marked MediaSource, with three arrows flowing down to containers each marked SourceBuffer. (Not indicated, but for sake of clarity in this description referred to here-after as SourceBuffer 1, shown with a blue background; SourceBuffer 2, shown with a mauve background; and SourceBuffer 3, shown with a rose background; as described from Left to Right).
Below these three SourceBuffer containers is a dashed line, with an indication that the top half (MediaSource plus the three SourceBuffer containers) are taken from the Media Source API, while the details to follow are taken from the HTMLMediaElement.
Flowing down from SourceBuffer 1 is a blue triangle with three arrows pointing to three process indications, each labeled Track Buffer.
The first Track Buffer from the left then flows to a red box labeled Video Decoder, which then flows to a switch that selects between one of three inputs, and the output of the switch connects to an output destination, labeled Video Tag Display Region. The switch indicates that one Video Decoder output (from SourceBuffer 2) is selected to flow into the Video Tag Display Region.
The second Track Buffer flows to a green box labeled Audio Decoder, which then follows to an indicator of an open switch, which then continues to a summing junction indicator. The output of the summing junction connects to a green output desination, labeled Audio Device.
The third Track Buffer also flows to a green box labeled Audio Decoder, which also flows to a switch, this time however indicated closed, which then also continues to the same summing junction as the second Track Buffer, which connects to the Audio Device.
Flowing down from SourceBuffer 2 is a mauve triangle with an arrow flowing to a process indication labeled Track Buffer.
This Track Buffer then flows to a red box labeled Video Decoder, which then flows to the same switch that feeds to the Video Tag Display Region previously mentioned in SourceBuffer 1. The switch is positioned so that this Video Decoder ouptut is connected to the Video Tag Display Region.
Flowing down from SourceBuffer 3 is a rose triangle with an arrow flowing to a process indication labeled Track Buffer.
This Track Buffer then flows to a green box labeled Audio Decoder, which then flows through a closed switch, which then also continues to the same summing junction previously mentioned in SourceBuffer 1, which connects to the Audio Device.
With thanks to J. Foliot, Deque Systems