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a27dca557e
Fix: Don't silently drop ChapterAtom elements that omit MkChapterUID
parseChapterAtom() returned chapterUid = 0 when the source file omitted
the MkChapterUID element, and the existing call sites in
MkChapters::parse() (ebmlmkchapters.cpp lines 106 and 127) use a C++17
init-if `chapter.uid()` predicate that silently dropped such chapters.
The caller saw an empty ChapterEditionList for files that mkvinfo,
MediaInfo and FFmpeg all handle gracefully — produced by some audiobook
generators and older muxers that omit the per-chapter UID. The
companion orphan-EditionEntry fix in PR #1311 / commit e07b956f doesn't
cover this case because the ChapterAtoms there ARE wrapped in an
EditionEntry, just without a ChapterUID inside each atom.
This change:
- Synthesises a process-unique ChapterUID inside parseChapterAtom() when
the source file lacks MkChapterUID. The synthetic value sets the high
bit (1ULL << 63) and increments via a static std::atomic counter; real
ChapterUIDs are random 64-bit values from muxers, so collision with a
generated one is practically impossible while keeping the distinction
local to TagLib.
- The existing chapter.uid() filters at the call sites then always
evaluate truthy and the chapter is exposed through the public
ChapterEditionList API as if it were spec-compliant.
No existing behavior is changed — files that already conform to the spec
(ChapterAtoms with a ChapterUID element) parse identically; only
previously-dropped chapters are now surfaced.
Reported and verified against real-world chaptered Matroska audiobook
files where mkvinfo / MediaInfo see all chapters but TagLib 2.3 returned
an empty ChapterEditionList.
TagLib
TagLib Audio Metadata Library
TagLib is a library for reading and editing the metadata of several popular audio formats. Currently, it supports various metadata containers such as ID3v1, ID3v2 and Vorbis comments for MP3, MP4, AAC, Ogg, Opus, FLAC, Speex, APE, MPC, WavPack, WAV, AIFF, TrueAudio, Matroska, WebM, ASF, WMA, DSF, DFF and tracker (MOD, XM, S3M, IT) files.
TagLib is distributed under the GNU Lesser General Public License (LGPL) and Mozilla Public License (MPL). Essentially that means that it may be used in proprietary applications, but if changes are made to TagLib they must be contributed back to the project. Please review the licenses if you are considering using TagLib in your project.