SourceProbe

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Probe a source and keep the open context, so a session over the same source can produce from it instead of opening again.

This is the routing entry point worth using: PrismCoreEngine.decide takes the info, and a source that routes to the remux path can be handed straight to PrismCoreSession(probed:display:), which adopts the context. A source that routes elsewhere simply releases it — see ProbedSource for why the context, and not merely its conclusions, is what has to travel.

• Parameter budget: wall-clock bound on the WHOLE probe — open, stream analysis, interlace verification. On expiry the blocked read aborts and this throws, which is the property the router depends on: a probe that answers nothing is a playback that falls back to nothing (five silent play attempts over four minutes in the 2026-08-14 field log, all blocked inside one open against a starved server).

open, run on a dedicated thread so the cooperative pool never blocks in it.

open is synchronous and blocks on the transport for the whole probe — up to budget (10 s) against a starved server. Called from an async context that is a cooperative-pool thread held hostage, and a host that probes several sources at once (a row of episodes, a fallback racing a transcode) can park enough of them to stall every other await in the process (#44 was the producer-side twin). This hops to a one-shot ProducerThread, hands the ProbedSource back through a continuation, and returns to the pool. The interrupt guard and the budget are open's own; nothing about the probe changes.

Task cancellation is observed at the boundary: a probe already in flight runs to its verdict or its budget (the thread is not killed; an FFmpeg read cannot be interrupted from outside except through the guard, which the budget already arms), and a cancelled caller gets CancellationError while the result is released.

• Parameter input: a host-supplied byte source (PrismCoreInput) for a transport libavformat cannot open itself. One instance is taken for this open; url is then only a naming hint for format probing, never fetched. nil (the default) keeps native FFmpeg I/O.

The hints:-first spelling of open, for callers that have a probe document in hand and nothing else to say.

hints: nil is open(url:) exactly — the same code, not a parallel one. That property is what keeps the hinted path an addition to the engine rather than a fork of it, and SourceProbeHintsTests pins it.

• Parameter structure: how much of a byte-layout and index export to pay for. .none (the default) costs no I/O and reports SourceStructure.unknown; see SourceStructureExport for why the other two are opt-in.
• Parameter hints: what a caller already knows about this source. May make the open read less; may never make it read something else. A hint that turns out not to describe these bytes is recorded in ProbedSource.hints and otherwise ignored.
• Parameter hdr10Plus: whether to read video packets looking for HDR10+ metadata. .off (the default) reads nothing and leaves SourceInfo.hdr10Plus nil; see HDR10PlusScan for the cost.