fix(rva2): use big-endian byte order for volume adjustment#664
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ID3v2.4 §4.11 specifies RVA2 volume adjustment as a 16-bit signed fixed-point value. Per §3, all multi-byte integers in ID3 are big-endian. The reader was using `getInt16(offset, true)` (little- endian flag) and the writer was using `new Int16Array([v]).buffer`, which is host byte order (little-endian on every common platform). The two errors were symmetric, so a mp3tag.js-to-mp3tag.js round-trip preserved values — but the bytes on disk were wrong, and every standards-compliant v2.4 reader saw corrupted volumes for every RVA2 frame written by this library. The new test asserts the raw bytes on disk are big-endian (0x1234 serialises as 0x12 0x34, not 0x34 0x12), so the regression cannot recur.
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Summary
ID3v2.4 §4.11 specifies RVA2 volume adjustment as a 16-bit signed fixed-point value, big-endian per §3. The reader used
getInt16(offset, true)(little-endian flag) and the writer usednew Int16Array([v]).buffer(host byte order, little-endian on x86/ARM).The two errors were symmetric, so mp3tag.js-to-mp3tag.js round-trips preserved values — but the bytes on disk are wrong, and every standards-compliant v2.4 reader sees corrupted volumes for every RVA2 frame this library writes.
Changes
src/id3v2/parse.mjs: drop thetrueLE flag ongetInt16src/id3v2/write.mjs: manual big-endian byte split[(v >> 8) & 0xff, v & 0xff]test/id3v2/index.cjs: new test asserts raw bytes on disk are big-endian (0x1234 → 0x12 0x34), plus round-trip for positive and negative valuesTest plan
npm test— 79 passing (78 → 79)