The P3 concealment loop in DecryptingSectorSource::read_sectors keyed on
aacs_unit_needs_decrypt, whose sync check is the majority-vote
ts_sync_destroyed (<=16 of 32 syncs). A successfully padding-aware-
decrypted content-fragment TAIL unit (e.g. 11 content packets + 21 zero
padding) has only 11 syncs, so the majority vote called it "still
encrypted" — and when such a good unit shared a read buffer with a
genuinely-undecryptable one (dropped>0), the loop overwrote the GOOD
decrypted tail with NULL-TS, silently discarding correct video and
over-counting concealed units vs the tallied dropped bytes.
Add aacs_unit_still_ciphertext (padding-aware): encrypted AND at least
one non-zero (non-padding) 192-byte packet missing its 0x47 sync — the
same discriminator decrypt_unit uses to accept a fragment tail. The
conceal loop now uses it, so only genuinely-unrestored ciphertext is
concealed. Full and fully-ciphertext units are unchanged. Regression
test: a decrypted short-padding-tail co-resident with a failed unit is
left byte-for-byte intact while the failed unit is concealed.
Matthew Jackson
067fd207d5