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Add metadata handling
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‎meta.js‎

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/**
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* Meta parsers — re-export from codec packages.
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* @module audio-decode/meta
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*
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* import { wav, mp3, flac } from 'audio-decode/meta'
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* let result = wav(bytes) // { meta, markers, regions } | null
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*/
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export { parseMeta as wav } from '@audio/decode-wav/meta'
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export { parseMeta as mp3, parseId3v2 } from '@audio/decode-mp3/meta'
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export { parseMeta as flac } from '@audio/decode-flac/meta'

‎package.json‎

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"default": "./audio-decode.js"
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},
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"./stream": "./stream.js",
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"./meta": "./meta.js",
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"./package.json": "./package.json"
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},
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"workspaces": [

‎packages/decode-flac/meta.js‎

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/**
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* FLAC metadata parser — Vorbis comments, pictures, cue sheets.
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* @module @audio/decode-flac/meta
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*/
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const TD_U8 = new TextDecoder('utf-8'), TD_L1 = new TextDecoder('iso-8859-1')
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function str(bytes, enc = 'utf-8') {
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let end = bytes.length
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while (end > 0 && bytes[end - 1] === 0) end--
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return (enc === 'iso-8859-1' ? TD_L1 : TD_U8).decode(bytes.subarray(0, end))
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}
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// ── Constants ───────────────────────────────────────────────────────────
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const STREAMINFO = 0, PADDING = 1, VORBIS_COMMENT = 4, CUESHEET = 5, PICTURE = 6
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export const VORBIS_MAP = {
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TITLE: 'title', ARTIST: 'artist', ALBUM: 'album', ALBUMARTIST: 'albumartist',
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COMPOSER: 'composer', GENRE: 'genre', DATE: 'year', TRACKNUMBER: 'track',
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DISCNUMBER: 'disc', BPM: 'bpm', KEY: 'key', COMMENT: 'comment', DESCRIPTION: 'comment',
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COPYRIGHT: 'copyright', ISRC: 'isrc', PUBLISHER: 'publisher', ENCODER: 'software',
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LYRICS: 'lyrics'
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}
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// ── Binary helpers ──────────────────────────────────────────────────────
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function u32be(b, o) { return (b[o] * 0x1000000) + (b[o + 1] << 16) + (b[o + 2] << 8) + b[o + 3] }
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function u32le(b, o) { return b[o] | (b[o + 1] << 8) | (b[o + 2] << 16) | (b[o + 3] * 0x1000000) }
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function u24be(b, o) { return (b[o] << 16) | (b[o + 1] << 8) | b[o + 2] }
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function fourcc(b, o) { return String.fromCharCode(b[o], b[o + 1], b[o + 2], b[o + 3]) }
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// ── Block parsers ───────────────────────────────────────────────────────
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function parseVorbisComment(b) {
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let off = 0
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let vendorLen = u32le(b, off); off += 4
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off += vendorLen
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let n = u32le(b, off); off += 4
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let out = {}
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for (let i = 0; i < n; i++) {
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let len = u32le(b, off); off += 4
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let s = str(b.subarray(off, off + len), 'utf-8')
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off += len
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let eq = s.indexOf('=')
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if (eq < 0) continue
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let key = s.slice(0, eq).toUpperCase(), val = s.slice(eq + 1)
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let norm = VORBIS_MAP[key]
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if (norm) out[norm] = val
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}
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return out
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}
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function parseFlacPicture(b) {
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let off = 0
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let type = u32be(b, off); off += 4
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let mimeLen = u32be(b, off); off += 4
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let mime = str(b.subarray(off, off + mimeLen), 'iso-8859-1'); off += mimeLen
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let descLen = u32be(b, off); off += 4
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let desc = str(b.subarray(off, off + descLen), 'utf-8'); off += descLen
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off += 16 // width, height, depth, colors
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let dataLen = u32be(b, off); off += 4
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let data = b.slice(off, off + dataLen)
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return { mime, type, description: desc, data }
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}
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function parseCueSheet(b) {
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let markers = [], regions = []
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let off = 395 // media catalog (128) + leadin (8) + flags (1) + reserved (258)
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if (b.length < off + 1) return { markers, regions }
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let numTracks = b[off]; off += 1
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for (let t = 0; t < numTracks; t++) {
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if (off + 36 > b.length) break
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let trackOffLow = u32be(b, off + 4), trackOffHigh = u32be(b, off)
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let trackOffset = trackOffHigh * 0x100000000 + trackOffLow
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let trackNum = b[off + 8]
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let nIdx = b[off + 35]
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off += 36
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if (nIdx > 0 && trackNum < 170) markers.push({ sample: trackOffset, label: `Track ${trackNum}` })
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off += nIdx * 12
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}
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return { markers, regions }
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}
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/** Parse FLAC metadata blocks. Returns {meta, sampleRate, markers, regions} or null. */
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export function parseMeta(bytes) {
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if (!bytes?.length || bytes.length < 4 || fourcc(bytes, 0) !== 'fLaC') return null
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let meta = {}, raw = { blocks: [] }, pictures = []
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let sampleRate = 0, markers = [], regions = []
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let off = 4
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while (off + 4 <= bytes.length) {
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let hdr = bytes[off]
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let last = !!(hdr & 0x80), type = hdr & 0x7f
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let size = u24be(bytes, off + 1)
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let body = bytes.subarray(off + 4, off + 4 + size)
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if (type !== STREAMINFO && type !== PADDING) raw.blocks.push({ type, body })
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if (type === STREAMINFO && body.length >= 18) {
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sampleRate = (body[10] << 12) | (body[11] << 4) | (body[12] >> 4)
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} else if (type === VORBIS_COMMENT) {
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Object.assign(meta, parseVorbisComment(body))
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} else if (type === PICTURE) {
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let p = parseFlacPicture(body)
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if (p) pictures.push(p)
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} else if (type === CUESHEET) {
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let c = parseCueSheet(body)
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markers.push(...c.markers); regions.push(...c.regions)
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}
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off += 4 + size
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if (last) break
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}
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meta.raw = raw
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meta.pictures = pictures
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return { meta, sampleRate, markers, regions }
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}

‎packages/decode-flac/package.json‎

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"types": "decode-flac.d.ts",
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"exports": {
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".": "./decode-flac.js",
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"./meta": "./meta.js",
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"./package.json": "./package.json"
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},
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"files": [
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"decode-flac.js",
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"decode-flac.d.ts",
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"meta.js",
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"LICENSE"
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],
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"scripts": {

‎packages/decode-mp3/meta.js‎

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/**
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* ID3v2 metadata parser for MP3 files.
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* @module @audio/decode-mp3/meta
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*/
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const TD_U8 = new TextDecoder('utf-8'), TD_L1 = new TextDecoder('iso-8859-1')
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function str(bytes, enc = 'utf-8') {
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let end = bytes.length
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if (enc === 'utf-16') {
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while (end >= 2 && bytes[end - 1] === 0 && bytes[end - 2] === 0) end -= 2
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return new TextDecoder('utf-16').decode(bytes.subarray(0, end))
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}
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while (end > 0 && bytes[end - 1] === 0) end--
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return (enc === 'iso-8859-1' ? TD_L1 : TD_U8).decode(bytes.subarray(0, end))
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}
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// ── Constants ───────────────────────────────────────────────────────────
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export const ID3_MAP = {
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TIT2: 'title', TPE1: 'artist', TALB: 'album', TPE2: 'albumartist',
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TCOM: 'composer', TCON: 'genre', TYER: 'year', TDRC: 'year',
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TRCK: 'track', TPOS: 'disc', TBPM: 'bpm', TKEY: 'key',
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TCOP: 'copyright', TSRC: 'isrc', TPUB: 'publisher', TENC: 'software',
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COMM: 'comment', USLT: 'lyrics'
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}
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// ── Binary helpers ──────────────────────────────────────────────────────
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function u32be(b, o) { return (b[o] * 0x1000000) + (b[o + 1] << 16) + (b[o + 2] << 8) + b[o + 3] }
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function synchsafe(b, o) { return (b[o] << 21) | (b[o + 1] << 14) | (b[o + 2] << 7) | b[o + 3] }
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// ── ID3v2 parsing ───────────────────────────────────────────────────────
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function splitEncodedStrings(b) {
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if (!b.length) return []
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let enc = b[0], data = b.subarray(1)
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let out = []
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if (enc === 1 || enc === 2) {
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let start = 0
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if (enc === 1 && data.length >= 2 && ((data[0] === 0xFF && data[1] === 0xFE) || (data[0] === 0xFE && data[1] === 0xFF))) start = 2
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let i = start
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for (let j = start; j < data.length - 1; j += 2) {
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if (data[j] === 0 && data[j + 1] === 0) {
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let td = new TextDecoder(enc === 1 ? (start === 2 && data[0] === 0xFE ? 'utf-16be' : 'utf-16le') : 'utf-16be')
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out.push(td.decode(data.subarray(i, j)))
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i = j + 2
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}
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}
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if (i < data.length) {
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let td = new TextDecoder(enc === 1 ? (start === 2 && data[0] === 0xFE ? 'utf-16be' : 'utf-16le') : 'utf-16be')
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out.push(td.decode(data.subarray(i, data.length - (data[data.length - 1] === 0 && data[data.length - 2] === 0 ? 2 : 0))))
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}
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} else {
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let i = 0
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for (let j = 0; j < data.length; j++) {
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if (data[j] === 0) { out.push(str(data.subarray(i, j), enc === 3 ? 'utf-8' : 'iso-8859-1')); i = j + 1 }
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}
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if (i < data.length) out.push(str(data.subarray(i), enc === 3 ? 'utf-8' : 'iso-8859-1'))
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}
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return out
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}
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function parseApic(body) {
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let enc = body[0], i = 1
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let mime = '', desc = ''
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while (i < body.length && body[i] !== 0) i++
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mime = str(body.subarray(1, i), 'iso-8859-1')
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i++
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let type = body[i++]
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let descStart = i
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if (enc === 1 || enc === 2) {
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while (i + 1 < body.length && !(body[i] === 0 && body[i + 1] === 0)) i += 2
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desc = enc === 1 ? new TextDecoder('utf-16le').decode(body.subarray(descStart, i)) : new TextDecoder('utf-16be').decode(body.subarray(descStart, i))
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i += 2
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} else {
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while (i < body.length && body[i] !== 0) i++
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desc = str(body.subarray(descStart, i), enc === 3 ? 'utf-8' : 'iso-8859-1')
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i++
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}
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let data = body.slice(i)
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return { mime, type, description: desc, data }
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}
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/** Parse ID3v2 tag. Returns {meta, size, markers: [], regions: []} or null. */
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export function parseId3v2(bytes) {
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if (bytes.length < 10 || bytes[0] !== 0x49 || bytes[1] !== 0x44 || bytes[2] !== 0x33) return null
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let ver = bytes[3], flags = bytes[5], size = synchsafe(bytes, 6)
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let end = Math.min(10 + size, bytes.length)
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let meta = {}, raw = { version: ver, frames: [] }, pictures = []
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let headerSize = ver === 2 ? 6 : 10
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let sizeFn = ver >= 4 ? synchsafe : (b, o) => u32be(b, o)
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let off = 10
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if (flags & 0x40) {
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let extSize = ver >= 4 ? synchsafe(bytes, off) : u32be(bytes, off)
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off += extSize + (ver >= 4 ? 0 : 4)
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}
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while (off + headerSize <= end) {
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let id, frameSize
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if (ver === 2) {
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id = String.fromCharCode(bytes[off], bytes[off + 1], bytes[off + 2])
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frameSize = (bytes[off + 3] << 16) | (bytes[off + 4] << 8) | bytes[off + 5]
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off += 6
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} else {
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id = String.fromCharCode(bytes[off], bytes[off + 1], bytes[off + 2], bytes[off + 3])
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frameSize = sizeFn(bytes, off + 4)
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off += 10
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}
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if (!id.match(/^[A-Z0-9]+$/)) break
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if (frameSize === 0 || off + frameSize > end) break
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let body = bytes.subarray(off, off + frameSize)
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raw.frames.push({ id, body })
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let key = ID3_MAP[id]
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if (id === 'APIC' && body.length > 0) {
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let p = parseApic(body)
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if (p) pictures.push(p)
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} else if (id === 'COMM' || id === 'USLT') {
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if (body.length >= 4) {
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let lang = str(body.subarray(1, 4), 'iso-8859-1')
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let enc = body[0], rest = body.subarray(4)
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let parts = splitEncodedStrings(Uint8Array.from([enc, ...rest]))
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let text = parts[parts.length - 1] || ''
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if (key) meta[key] = text
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if (id === 'COMM') (meta.comments = meta.comments || []).push({ lang, description: parts[0] || '', text })
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}
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} else if (key) {
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let parts = splitEncodedStrings(body)
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meta[key] = parts.join('; ')
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}
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off += frameSize
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}
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meta.raw = raw
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meta.pictures = pictures
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return { meta, size: 10 + size, markers: [], regions: [] }
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}
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/** Parse MP3 metadata. Returns {meta, markers, regions} or null. */
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export function parseMeta(bytes) {
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if (!bytes?.length) return null
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let r = parseId3v2(bytes)
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return r ? { meta: r.meta, markers: r.markers, regions: r.regions } : null
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}

‎packages/decode-mp3/package.json‎

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"types": "decode-mp3.d.ts",
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"exports": {
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".": "./decode-mp3.js",
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"./meta": "./meta.js",
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"./package.json": "./package.json"
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},
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"files": [
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"decode-mp3.js",
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"decode-mp3.d.ts",
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"meta.js",
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"LICENSE"
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],
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"scripts": {

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