supervision-js
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    Interface MediaSessionMediaPreparation

    What the session did with the media it was handed, recorded as it did it.

    The renderer opens a src and a source through different readers, so which of the two a branch set decides which one opens the clip. Nothing else reports it.

    interface MediaSessionMediaPreparation {
        branch: MediaSessionMediaBranch;
        opened: "src" | "source";
    }
    Index
    opened: "src" | "source"

    Which of the renderer's two media options this branch filled in.