A damaged audio access unit is now dropped rather than muxed as a
decoder-choking glitch. Sync is preserved — a drop becomes a silence
gap, never a shift — and every drop is logged. Detection is per-codec,
each mirroring the format's authoritative integrity check:
DTS core-header validity gates
AC-3/E-AC-3 native frame CRC-16 + bitstream-id range
FLAC whole-frame CRC-16 residue
MP2/MP3 header sanity + free-format reject
AAC-ADTS header sanity (raw AAC passes through untouched)
TrueHD/MLP major-sync CRC-16 + AU parity; corrupt AUs drop forward
to the next major sync, since decode state carries
across access units
LPCM and video are excluded by design (no in-frame integrity data;
inter-frame prediction). A shared DropTally handles counting, logging,
and a whole-track fallback for a mostly-undecodable track.
