The "TopGun bug" (Top Gun 1986 UHD, DV Profile 7 dual-layer): the auditor
flags the rip `corrupt` with a flood of HEVC "Could not find ref with POC N"
decode errors (POC 114/210/228/234/240/246/252/318/336/354/372/399 — one
cluster per clip join).
Root cause: the title is multiple .m2ts clips joined at non-seamless
boundaries (mpls connection_condition 0x05/0x06), read as one concatenated
stream. Each next clip opens with a CRA whose RASL leading pictures reference
pre-join frames gone after concatenation. hevc.rs already has the spec remedy
(rewrite splice CRA_NUT 21 → BLA_W_LP 16 so a decoder sets NoRaslOutput and
drops the dangling RASL), behind mark_clip_boundary() — but nothing ever
called it: connection_condition is not plumbed through the threaded mux
pipeline, so the whole CRA→BLA mechanism was dead code.
Fix: detect the boundary inside the parser from the bitstream. Each clip
carries its own PES PTS base, so a non-seamless join is a large backward
PTS reset. HevcParser::parse now tracks a PTS high-water mark and, on a
backward step beyond 3 s (270000 ticks @ 90 kHz — mirroring the mux-side
DISCONTINUITY_BACKSTEP_NS), arms the existing CRA→BLA rewrite for the new
clip's first IRAP. Self-contained: works for every mux path, no cross-thread
plumbing. The 3 s threshold sits above any HEVC B-frame reorder dip and far
below any clip duration, so it never false-triggers in-clip; single-clip /
seamless titles never arm it and stay byte-identical.
Adds regression test cra_at_auto_detected_pts_backstep_rewritten_to_bla
(in-clip dip must not trigger; splice CRA after a backward reset must become
BLA; one-shot). hevc suite 55/55, mux suite 780/780.
Matthew Jackson
1cec2aaaf3