Fix MP3 detection for raw audio files without ID3 tags#498
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karlobencic merged 2 commits intomainfrom Feb 2, 2026
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🦋 Changeset detectedLatest commit: 13544ad The changes in this PR will be included in the next version bump. This PR includes changesets to release 1 package
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cyraxx
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Feb 2, 2026
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Summary
Fixed MP3 detection to properly handle raw MP3 files without ID3 tags. This fixes the "unsupported image format" error when protecting MP3 files generated by encoders like lamejs that produce raw audio frames.
Problem
The previous implementation only checked for the exact byte sequence
0xFF 0xFBfor MP3 frame sync, but MP3 frame sync headers can have different second bytes depending on:The proper check is the 11-bit sync word: first byte is
0xFF, and upper 3 bits of second byte must be set (& 0xE0 === 0xE0).Additionally,
parseFromBuffer()assumed all MP3 files had ID3 tags and would try to read the ID3 version from byte 3, which caused errors for raw MP3 files.Testing
Tested with MP3 files generated by lamejs encoder (used in web audio recording) which produce raw MP3 frames without ID3 tags.