After unrecoverable loss the host keeps sending delta frames that reference a
picture the client never received; hardware decoders conceal these as gray/
garbage with a success status. Linux already withheld them and held the last
good frame until a proven clean re-anchor — this brings that behavior to the
Android and Apple clients.
Extract the Linux pump's freeze state machine into a shared `ReanchorGate` in
punktfunk-core (reanchor.rs, 18 tests) exposed over the C ABI (ABI v6, additive —
no wire change) for the Swift clients. Migrate the Linux/Deck pump
(pf-client-core) onto it as the parity proof (no-op refactor). Then wire:
- Android (decode.rs, both sync + async loops): arm on the frame-index gap, a
pts-keyed flag map carries the wire flags to the output-buffer release, fold
the gate per drained output, gate.poll replaces the dropped-climb block.
- Apple Stage2Pipeline (default): arm on a gap (new noteFrameIndexGap), withhold
at the ring-submit seam (CAMetalLayer holds its last drawable), poll
framesDropped, fold VT decode errors through the no-output streak.
- Apple StreamPump (stage-1): fold at enqueue, withhold via
kCMSampleAttachmentKey_DoNotDisplay so the layer keeps decoding (reference
chain intact) but holds the last displayed frame.
- Apple VideoDecoder: thread the AU's wire flags to the async decode callback via
a retained FrameContext refcon (replaces the receivedNs bit-pattern scalar).
Lifts only on a proven re-anchor (IDR / RFI anchor / 2nd recovery mark) with a
500 ms backstop so a lost re-anchor can never freeze forever. Apple: swift build
clean, 123/123 tests pass (incl. VideoToolboxRoundTripTests). On-glass
loss-injection validation still owed.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
