Problem: files with E-AC-3 audio (MP4 ec-3, MOV, Matroska A_EAC3, MPEG-TS)
imported silent: filmcraft-ac3 refused bsid 11-16.
Fix: clean-room E-AC-3 decoding from ATSC A/52:2012 Annex E in filmcraft-ac3:
bsi and audfrm syntax, 1/2/3/6-block syncframes, reduced sample rates,
frame-based exponent strategies (exponents reused across short syncframes),
SNR offset strategies, default band structures, spectral extension
(translation, notch filter, noise blending). Independent substream 0 is
decoded; dependent substreams and other programs are skipped (7.1 plays as
its 5.1 core). AHT and enhanced coupling are refused as unsupported. The
audio blocks share the AC-3 path; AC-3 output is unchanged. filmcraft-codecs
routes E-AC-3 in MP4/MOV, Matroska and TS to the decoder; the TS splitter
joins dependent substream frames to their access unit.
Tests: ffmpeg oracle for raw E-AC-3 (64.8-91.0 dB SNR) and in MP4, MOV,
Matroska and TS (79.5-91.3 dB, random access identical), mutation fuzz,
synthetic frames for headers, substream skipping, refusals and exponent
reuse across 1-block syncframes, spectral extension unit tests.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
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