cyberchef
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The Cyber Swiss Army Knife for encryption, encoding, compression and data analysis.
631 lines (545 loc) • 26.4 kB
JavaScript
/**
* Format-specific audio metadata parsers.
*
* @author d0s1nt [d0s1nt@cyberchefaudio]
* @copyright Crown Copyright 2025
* @license Apache-2.0
*/
/* eslint-disable camelcase */
import {
ascii4, indexOfAscii,
u32be, u32le, u16le, u64le, synchsafeToInt,
decodeUtf16LE, readNullTerminated, decodeText,
safeUtf8, decodeLatin1Trim,
} from "./AudioBytes.mjs";
/** Parses MP3 metadata: ID3v2 frames, ID3v1 footer, APEv2 tags. */
export function parseMp3(b, report) {
processId3v2(b, report);
processId3v1(b, report);
const ape = parseApeV2BestEffort(b);
if (ape) {
report.detections.metadata_systems.push("apev2");
report.tags.raw.apev2 = ape;
}
}
/** Iterates ID3v2 frames and populates the report. */
function processId3v2(b, report) {
report.detections.metadata_systems.push("id3v2");
const id3 = parseId3v2(b);
report.tags.raw.id3v2 = id3 ? { header: id3.header, frames: [] } : null;
if (id3) {
for (const f of id3.frames) {
const entry = { id: f.id, size: f.size, description: ID3_FRAME_DESCRIPTIONS[f.id] || null };
if (f.id[0] === "T" && f.id !== "TXXX") {
const text = f.data?.length >= 1 ?
decodeText(f.data.slice(1), f.data[0]).replace(/\u0000/g, "").trim() :
"";
entry.decoded = text;
if (f.id === "TLEN") {
const ms = normalizeTlen(text);
if (ms !== null) entry.normalized_ms = ms;
}
mapCommonId3(report, f.id, text);
} else if (f.id === "TXXX") {
const txxx = decodeTxxx(f.data);
entry.decoded = txxx;
if (!report.tags.raw.id3v2.txxx) report.tags.raw.id3v2.txxx = [];
report.tags.raw.id3v2.txxx.push(txxx);
} else if (f.id === "COMM") {
const comm = decodeCommFrame(f.data);
entry.decoded = comm;
if (comm?.text && !report.tags.common.comment) report.tags.common.comment = comm.text;
} else if (f.id === "GEOB") {
processGeobFrame(f, entry, report);
}
report.tags.raw.id3v2.frames.push(entry);
}
} else {
report.detections.metadata_systems = report.detections.metadata_systems.filter((x) => x !== "id3v2");
}
}
/** Parses GEOB frame contents, populates entry, embedded objects, and C2PA provenance. */
function processGeobFrame(f, entry, report) {
const d = f.data, enc = d[0];
let off = 1;
const mime = readNullTerminated(d, off, 0);
const mimeType = decodeLatin1Trim(mime.valueBytes);
off = mime.next;
const file = readNullTerminated(d, off, enc);
const filename = decodeText(file.valueBytes, enc).replace(/\u0000/g, "").trim();
off = file.next;
const desc = readNullTerminated(d, off, enc);
const description = decodeText(desc.valueBytes, enc).replace(/\u0000/g, "").trim();
off = desc.next;
const objLen = d.length - off;
entry.geob = { mimeType, filename, description, object_bytes: objLen };
const geobId = `geob_${report.embedded.filter((x) => x.source === "id3v2:GEOB").length}`;
report.embedded.push({
id: geobId, source: "id3v2:GEOB",
content_type: mimeType || null, byte_length: objLen,
description: description || null, filename: filename || null,
});
const mt = (mimeType || "").toLowerCase();
if (mt.includes("c2pa") || mt.includes("jumbf") || mt.includes("application/x-c2pa-manifest-store")) {
report.provenance.c2pa.present = true;
report.provenance.c2pa.embedding.push({
carrier: "id3v2:GEOB", content_type: mimeType || null, byte_length: objLen,
});
}
}
/** Processes the 128-byte ID3v1 footer tag. */
function processId3v1(b, report) {
const id3v1 = parseId3v1(b);
if (!id3v1) return;
report.detections.metadata_systems.push("id3v1");
report.tags.raw.id3v1 = id3v1;
mapCommon(report, id3v1, ID3V1_TO_COMMON);
}
/** Parses WAV/BWF/BW64 RIFF chunks: LIST/INFO, bext, iXML, axml, ds64. */
export function parseRiffWave(b, report, maxTextBytes) {
report.detections.metadata_systems.push("riff_info");
const chunks = enumerateChunks(b, 12, b.length, 50000);
const riff = { chunks: [], info: null, bext: null, ixml: null, axml: null, ds64: null };
const info = {};
for (const c of chunks) {
riff.chunks.push({ id: c.id, size: c.size, offset: c.dataOff });
processRiffChunk(b, c, riff, info, report, maxTextBytes);
}
riff.info = Object.keys(info).length ? info : null;
report.tags.raw.riff = riff;
if (riff.info) mapCommon(report, riff.info, RIFF_TO_COMMON);
}
/** Processes a single RIFF chunk, updating riff state and the report. */
function processRiffChunk(b, c, riff, info, report, maxTextBytes) {
if (c.id === "ds64") {
riff.ds64 = { present: true, size: c.size };
if (!report.detections.metadata_systems.includes("bw64_ds64")) report.detections.metadata_systems.push("bw64_ds64");
if (report.artifact.container.type === "wav") report.artifact.container.type = "bw64";
}
if (c.id === "LIST" && ascii4(b, c.dataOff) === "INFO") {
for (const s of enumerateChunks(b, c.dataOff + 4, c.dataOff + c.size, 10000))
info[s.id] = decodeLatin1Trim(b.slice(s.dataOff, s.dataOff + s.size));
}
if (c.id === "bext") {
if (!report.detections.metadata_systems.includes("bwf_bext")) report.detections.metadata_systems.push("bwf_bext");
riff.bext = parseBext(b, c.dataOff, c.size);
}
if (c.id === "iXML" || c.id === "axml") {
const key = c.id === "iXML" ? "ixml" : "axml";
if (!report.detections.metadata_systems.includes(key)) report.detections.metadata_systems.push(key);
const payload = b.slice(c.dataOff, c.dataOff + c.size);
riff[key] = { xml: safeUtf8(payload.slice(0, Math.min(payload.length, maxTextBytes))), truncated: payload.length > maxTextBytes };
report.embedded.push({
id: `${key}_0`, source: `riff:${c.id}`, content_type: "application/xml",
byte_length: payload.length, description: `${c.id} chunk`, filename: null,
});
}
}
/** Parses FLAC metablocks: STREAMINFO, Vorbis Comment, PICTURE. */
export function parseFlac(b, report, maxTextBytes) {
report.detections.metadata_systems.push("flac_metablocks");
const blocks = parseFlacMetaBlocks(b);
report.tags.raw.flac = { blocks: [] };
for (const blk of blocks) {
report.tags.raw.flac.blocks.push({ type: blk.typeName, length: blk.length });
if (blk.typeName === "VORBIS_COMMENT") {
if (!report.detections.metadata_systems.includes("vorbis_comments")) report.detections.metadata_systems.push("vorbis_comments");
const vc = parseVorbisComment(blk.data);
report.tags.raw.vorbis_comments = vc;
mapVorbisCommon(report, vc);
} else if (blk.typeName === "PICTURE") {
const pic = parseFlacPicture(blk.data, maxTextBytes);
report.embedded.push({
id: `cover_art_${report.embedded.filter((x) => x.id.startsWith("cover_art_")).length}`,
source: "flac:PICTURE", content_type: pic.mime || null,
byte_length: pic.dataLength, description: pic.description || null, filename: null,
});
}
}
}
/** Parses OGG/Opus Vorbis comments. */
export function parseOgg(b, report) {
if (!report.detections.metadata_systems.includes("ogg_opus_tags")) report.detections.metadata_systems.push("ogg_opus_tags");
const scanEnd = Math.min(b.length, 1024 * 1024);
let tags = null;
const opusTagsIdx = indexOfAscii(b, "OpusTags", 0, scanEnd);
if (opusTagsIdx >= 0) {
report.artifact.container.type = "opus";
tags = parseVorbisComment(b.slice(opusTagsIdx + 8, scanEnd));
} else {
const vorbisIdx = indexOfAscii(b, "\x03vorbis", 0, scanEnd);
if (vorbisIdx >= 0) tags = parseVorbisComment(b.slice(vorbisIdx + 7, scanEnd));
}
report.tags.raw.ogg = { has_opustags: opusTagsIdx >= 0, has_vorbis_comment: !!tags };
if (tags) {
if (!report.detections.metadata_systems.includes("vorbis_comments")) report.detections.metadata_systems.push("vorbis_comments");
report.tags.raw.vorbis_comments = tags;
mapVorbisCommon(report, tags);
}
}
/** Best-effort top-level atom scan for MP4/M4A. */
export function parseMp4BestEffort(b, report) {
report.detections.metadata_systems.push("mp4_atoms");
const atoms = [];
let off = 0;
while (off + 8 <= b.length && atoms.length < 2000) {
const size = u32be(b, off);
const type = ascii4(b, off + 4);
if (size < 8) break;
atoms.push({ type, size, offset: off });
off += size;
}
report.tags.raw.mp4 = {
top_level_atoms: atoms.slice(0, 200),
hints: {
hasMoov: atoms.some((a) => a.type === "moov"),
hasUdta: atoms.some((a) => a.type === "udta"),
hasMeta: atoms.some((a) => a.type === "meta"),
hasIlst: atoms.some((a) => a.type === "ilst"),
},
};
}
/** Best-effort AIFF/AIFC chunk scanning for NAME, AUTH, ANNO. */
export function parseAiffBestEffort(b, report, maxTextBytes) {
report.detections.metadata_systems.push("aiff_chunks");
let off = 12;
const chunks = [];
while (off + 8 <= b.length && chunks.length < 2000) {
const id = ascii4(b, off);
const size = u32be(b, off + 4);
const dataOff = off + 8;
chunks.push({ id, size, offset: off });
if (["NAME", "AUTH", "ANNO", "(c) "].includes(id)) {
const txt = safeUtf8(b.slice(dataOff, dataOff + Math.min(size, maxTextBytes)));
if (!report.tags.raw.aiff) report.tags.raw.aiff = { chunks: [] };
report.tags.raw.aiff.chunks.push({ id, value: txt, truncated: size > maxTextBytes });
}
off = dataOff + size + (size % 2);
}
if (!report.tags.raw.aiff) report.tags.raw.aiff = {};
report.tags.raw.aiff.chunk_index = chunks.slice(0, 500);
const nameChunk = report.tags.raw.aiff?.chunks?.find((ch) => ch.id === "NAME")?.value;
if (nameChunk) report.tags.common.title = report.tags.common.title || nameChunk;
}
const AAC_SAMPLE_RATES = [96000, 88200, 64000, 48000, 44100, 32000, 24000, 22050, 16000, 12000, 11025, 8000, 7350];
const AAC_PROFILES = ["Main", "LC", "SSR", "LTP"];
const AAC_CHANNELS = ["defined in AOT", "mono", "stereo", "3.0", "4.0", "5.0", "5.1", "7.1"];
/** Parses AAC ADTS frame header for audio parameters. */
export function parseAacAdts(b, report) {
report.detections.metadata_systems.push("adts_header");
if (b.length < 7) return;
const id = (b[1] >> 3) & 0x01;
const profile = (b[2] >> 6) & 0x03;
const freqIdx = (b[2] >> 2) & 0x0f;
const chanCfg = ((b[2] & 0x01) << 2) | ((b[3] >> 6) & 0x03);
report.tags.raw.aac = {
mpeg_version: id === 1 ? "MPEG-2" : "MPEG-4",
profile: AAC_PROFILES[profile] || `Profile ${profile}`,
sample_rate: AAC_SAMPLE_RATES[freqIdx] || null,
sample_rate_index: freqIdx,
channel_configuration: chanCfg,
channel_description: AAC_CHANNELS[chanCfg] || null,
};
}
const AC3_SAMPLE_RATES = [48000, 44100, 32000];
const AC3_BITRATES = [32, 40, 48, 56, 64, 80, 96, 112, 128, 160, 192, 224, 256, 320, 384, 448, 512, 576, 640];
const AC3_ACMODES = [
"2.0 (Ch1+Ch2)", "1.0 (C)", "2.0 (L R)", "3.0 (L C R)",
"2.1 (L R S)", "3.1 (L C R S)", "2.2 (L R SL SR)", "3.2 (L C R SL SR)",
];
/** Parses AC3 (Dolby Digital) bitstream info. */
export function parseAc3(b, report) {
report.detections.metadata_systems.push("ac3_bsi");
if (b.length < 8) return;
const fscod = (b[4] >> 6) & 0x03;
const frmsizecod = b[4] & 0x3f;
const bsid = (b[5] >> 3) & 0x1f;
const bsmod = b[5] & 0x07;
const acmod = (b[6] >> 5) & 0x07;
report.tags.raw.ac3 = {
sample_rate: AC3_SAMPLE_RATES[fscod] || null,
fscod,
bitrate_kbps: AC3_BITRATES[frmsizecod >> 1] || null,
frmsizecod, bsid, bsmod, acmod,
channel_layout: AC3_ACMODES[acmod] || null,
};
}
/** Parses WMA files (ASF container) for content description metadata. */
export function parseWmaAsf(b, report) {
report.detections.metadata_systems.push("asf_header");
if (b.length < 30) return;
const headerSize = Number(u64le(b, 16));
const numObjects = u32le(b, 24);
const headerEnd = Math.min(b.length, headerSize);
const objects = [];
let off = 30;
for (let i = 0; i < numObjects && off + 24 <= headerEnd; i++) {
const guid4 = [b[off], b[off + 1], b[off + 2], b[off + 3]];
const objSize = Number(u64le(b, off + 16));
if (objSize < 24 || off + objSize > headerEnd) break;
const dataOff = off + 24;
const dataLen = objSize - 24;
if (guid4[0] === 0x33 && guid4[1] === 0x26 && guid4[2] === 0xb2 && guid4[3] === 0x75 && dataLen >= 10) {
const cd = parseAsfContentDescription(b, dataOff);
if (!report.detections.metadata_systems.includes("asf_content_desc"))
report.detections.metadata_systems.push("asf_content_desc");
if (!report.tags.raw.asf) report.tags.raw.asf = {};
report.tags.raw.asf.content_description = cd;
mapCommon(report, cd, ASF_CD_TO_COMMON);
}
if (guid4[0] === 0x40 && guid4[1] === 0xa4 && guid4[2] === 0xd0 && guid4[3] === 0xd2 && dataLen >= 2) {
const ext = parseAsfExtContentDescription(b, dataOff, dataOff + dataLen);
if (!report.detections.metadata_systems.includes("asf_ext_content_desc"))
report.detections.metadata_systems.push("asf_ext_content_desc");
if (!report.tags.raw.asf) report.tags.raw.asf = {};
report.tags.raw.asf.extended_content = ext;
const c = report.tags.common;
for (const d of ext) {
const field = WMA_TO_COMMON[(d.name || "").toUpperCase()];
if (field && d.value) c[field] = c[field] || d.value;
}
}
objects.push({ guid_prefix: guid4.map(x => x.toString(16).padStart(2, "0")).join(""), size: objSize });
off += objSize;
}
if (!report.tags.raw.asf) report.tags.raw.asf = {};
report.tags.raw.asf.header_objects = objects;
}
const ID3_FRAME_DESCRIPTIONS = {
TIT2: "Title/songname/content description", TPE1: "Lead performer(s)/Soloist(s)",
TRCK: "Track number/Position in set", TALB: "Album/Movie/Show title",
TDRC: "Recording time", TYER: "Year", TCON: "Content type",
TPE2: "Band/orchestra/accompaniment", TLEN: "Length (ms)", TCOM: "Composer",
COMM: "Comments", APIC: "Attached picture", GEOB: "General encapsulated object",
TXXX: "User defined text information frame", UFID: "Unique file identifier", PRIV: "Private frame",
};
const ID3_TO_COMMON = {
TIT2: "title", TPE1: "artist", TALB: "album", TDRC: "date", TYER: "date",
TRCK: "track", TCON: "genre", COMM: "comment", TCOM: "composer", TCOP: "copyright", TLAN: "language",
};
const VORBIS_TO_COMMON = {
TITLE: "title", ARTIST: "artist", ALBUM: "album", DATE: "date",
TRACKNUMBER: "track", GENRE: "genre", COMMENT: "comment", COMPOSER: "composer", LANGUAGE: "language",
};
const WMA_TO_COMMON = {
"WM/ALBUMTITLE": "album", "WM/GENRE": "genre", "WM/YEAR": "date",
"WM/TRACKNUMBER": "track", "WM/COMPOSER": "composer", "WM/LANGUAGE": "language",
};
const ID3V1_TO_COMMON = { title: "title", artist: "artist", album: "album", year: "date", comment: "comment", genre: "genre", track: "track" };
const RIFF_TO_COMMON = { INAM: "title", IART: "artist", ICMT: "comment", IGNR: "genre", ICRD: "date", ICOP: "copyright" };
const ASF_CD_TO_COMMON = { title: "title", author: "artist", copyright: "copyright", description: "comment" };
/** Maps source object fields to the common tags layer via a mapping table. */
function mapCommon(report, source, mapping) {
const c = report.tags.common;
for (const [sk, ck] of Object.entries(mapping))
c[ck] = c[ck] || source[sk] || null;
}
/** Maps an ID3v2 frame value to the common tags layer. */
function mapCommonId3(report, frameId, text) {
const field = ID3_TO_COMMON[frameId];
if (field) report.tags.common[field] = report.tags.common[field] || text || null;
}
/** Decodes an ID3v2 COMM (Comments) frame. */
function decodeCommFrame(data) {
if (!data || data.length < 5) return null;
const enc = data[0];
const language = String.fromCharCode(data[1], data[2], data[3]);
const { valueBytes: descBytes, next } = readNullTerminated(data, 4, enc);
const short_description = decodeText(descBytes, enc).replace(/\u0000/g, "").trim() || null;
const text = decodeText(data.slice(next), enc).replace(/\u0000/g, "").trim() || null;
return { language, short_description, text };
}
/** Normalizes TLEN to integer milliseconds. */
function normalizeTlen(s) {
if (!s) return null;
if (/^\s*\d+\s*$/.test(s)) return parseInt(s.trim(), 10);
const f = Number(s);
if (Number.isFinite(f) && f > 0 && f < 100000) return Math.round(f * 1000);
return null;
}
/** Parses the ID3v2 tag header and frames. */
function parseId3v2(mp3) {
if (mp3.length < 10 || mp3[0] !== 0x49 || mp3[1] !== 0x44 || mp3[2] !== 0x33) return null;
const major = mp3[3], minor = mp3[4], flags = mp3[5];
const tagSize = synchsafeToInt(mp3[6], mp3[7], mp3[8], mp3[9]);
let offset = 10;
const end = 10 + tagSize;
const frames = [];
while (offset + 10 <= end) {
const id = String.fromCharCode(mp3[offset], mp3[offset + 1], mp3[offset + 2], mp3[offset + 3]);
if (!/^[A-Z0-9]{4}$/.test(id)) break;
const size = major === 4 ?
synchsafeToInt(mp3[offset + 4], mp3[offset + 5], mp3[offset + 6], mp3[offset + 7]) :
u32be(mp3, offset + 4);
offset += 10;
if (size <= 0 || offset + size > mp3.length) break;
frames.push({ id, size, data: mp3.slice(offset, offset + size) });
offset += size;
}
return { header: { version: `${major}.${minor}`, flags, tag_size: tagSize }, frames };
}
/** Parses the 128-byte ID3v1 tag at the end of the file. */
function parseId3v1(b) {
if (b.length < 128) return null;
const off = b.length - 128;
if (b[off] !== 0x54 || b[off + 1] !== 0x41 || b[off + 2] !== 0x47) return null;
let track = null;
if (b[off + 125] === 0x00 && b[off + 126] !== 0x00) track = String(b[off + 126]);
return {
title: decodeLatin1Trim(b.slice(off + 3, off + 33)),
artist: decodeLatin1Trim(b.slice(off + 33, off + 63)),
album: decodeLatin1Trim(b.slice(off + 63, off + 93)),
year: decodeLatin1Trim(b.slice(off + 93, off + 97)),
comment: decodeLatin1Trim(b.slice(off + 97, off + 127)),
track, genre: String(b[off + 127]),
};
}
/** Decodes an ID3v2 TXXX (user-defined text) frame. */
function decodeTxxx(data) {
if (!data || data.length < 2) return null;
const enc = data[0];
const { valueBytes: descBytes, next } = readNullTerminated(data, 1, enc);
const desc = decodeText(descBytes, enc).replace(/\u0000/g, "").trim();
const val = decodeText(data.slice(next), enc).replace(/\u0000/g, "").trim();
return { description: desc || null, value: val || null };
}
/** Best-effort APEv2 tag parser scanning the last 32 KB. */
function parseApeV2BestEffort(b) {
const scanStart = Math.max(0, b.length - 32768);
const idx = indexOfAscii(b, "APETAGEX", scanStart, b.length);
if (idx < 0) return null;
if (idx + 32 > b.length) return { present: true, warning: "APETAGEX found but footer truncated." };
const ver = u32le(b, idx + 8), size = u32le(b, idx + 12);
const count = u32le(b, idx + 16), flags = u32le(b, idx + 20);
const tagStart = idx + 32 - size;
if (tagStart < 0 || tagStart >= b.length)
return { present: true, version: ver, size, count, flags, warning: "APEv2 bounds invalid (non-standard placement)." };
const items = [];
let off = tagStart + 32;
const end = Math.min(b.length, idx);
while (off + 8 < end && items.length < 5000) {
const valueSize = u32le(b, off), itemFlags = u32le(b, off + 4);
off += 8;
let keyEnd = off;
while (keyEnd < end && b[keyEnd] !== 0x00) keyEnd++;
const key = decodeLatin1Trim(b.slice(off, keyEnd));
off = keyEnd + 1;
if (!key || off + valueSize > end) break;
const value = safeUtf8(b.slice(off, off + valueSize)).replace(/\u0000/g, "").trim();
off += valueSize;
items.push({ key, value, flags: itemFlags });
}
return { present: true, version: ver, size, count, flags, items };
}
/** Enumerates RIFF-style chunks (id + LE32 size) within a byte range, padding to even. */
function enumerateChunks(b, start, end, maxCount) {
const chunks = [];
let off = start;
while (off + 8 <= end && chunks.length < maxCount) {
const id = ascii4(b, off);
const size = u32le(b, off + 4);
const dataOff = off + 8;
if (dataOff + size > end) break;
chunks.push({ id, size, dataOff });
off = dataOff + size + (size % 2);
}
return chunks;
}
/** Parses a BWF bext chunk. */
function parseBext(b, off, size) {
const slice = b.slice(off, off + size);
const timeRefLow = u32le(slice, 338), timeRefHigh = u32le(slice, 342);
return {
description: decodeLatin1Trim(slice.slice(0, 256)) || null,
originator: decodeLatin1Trim(slice.slice(256, 288)) || null,
originator_reference: decodeLatin1Trim(slice.slice(288, 320)) || null,
origination_date: decodeLatin1Trim(slice.slice(320, 330)) || null,
origination_time: decodeLatin1Trim(slice.slice(330, 338)) || null,
time_reference_samples: ((BigInt(timeRefHigh) << 32n) | BigInt(timeRefLow)).toString(),
};
}
const FLAC_TYPE_NAMES = { 0: "STREAMINFO", 1: "PADDING", 2: "APPLICATION", 3: "SEEKTABLE", 4: "VORBIS_COMMENT", 5: "CUESHEET", 6: "PICTURE" };
/** Parses FLAC metadata blocks following the "fLaC" marker. */
function parseFlacMetaBlocks(b) {
const blocks = [];
let off = 4;
while (off + 4 <= b.length && blocks.length < 10000) {
const header = b[off];
const isLast = (header & 0x80) !== 0;
const type = header & 0x7f;
const len = (b[off + 1] << 16) | (b[off + 2] << 8) | b[off + 3];
off += 4;
if (off + len > b.length) break;
blocks.push({ type, typeName: FLAC_TYPE_NAMES[type] || `TYPE_${type}`, length: len, data: b.slice(off, off + len) });
off += len;
if (isLast) break;
}
return blocks;
}
/** Parses a Vorbis Comment block (used by FLAC and OGG). */
function parseVorbisComment(buf) {
let off = 0;
const vendorLen = u32le(buf, off); off += 4;
if (off + vendorLen > buf.length) return { vendor: null, comments: [], warning: "vendor_len out of bounds" };
const vendor = safeUtf8(buf.slice(off, off + vendorLen)); off += vendorLen;
const count = u32le(buf, off); off += 4;
const comments = [];
for (let i = 0; i < count && off + 4 <= buf.length && comments.length < 20000; i++) {
const l = u32le(buf, off); off += 4;
if (off + l > buf.length) break;
const s = safeUtf8(buf.slice(off, off + l)); off += l;
const eq = s.indexOf("=");
if (eq > 0) comments.push({ key: s.slice(0, eq).toUpperCase(), value: s.slice(eq + 1) });
}
return { vendor, comments };
}
/** Maps Vorbis Comment fields to the common tags layer. */
function mapVorbisCommon(report, vc) {
const c = report.tags.common;
for (const [vk, ck] of Object.entries(VORBIS_TO_COMMON))
c[ck] = c[ck] || vc.comments?.find((x) => x.key === vk)?.value || null;
}
/** Parses a FLAC PICTURE metadata block (extracts mime, description, data length). */
function parseFlacPicture(data, maxTextBytes) {
let off = 4;
const mimeLen = u32be(data, off); off += 4;
const mime = safeUtf8(data.slice(off, off + Math.min(mimeLen, maxTextBytes))); off += mimeLen;
const descLen = u32be(data, off); off += 4;
const description = safeUtf8(data.slice(off, off + Math.min(descLen, maxTextBytes))); off += descLen + 16;
return { mime, description, dataLength: u32be(data, off) };
}
/** Parses the ASF Content Description Object fields. */
function parseAsfContentDescription(b, off) {
const titleLen = u16le(b, off), authorLen = u16le(b, off + 2);
const copyrightLen = u16le(b, off + 4), descLen = u16le(b, off + 6), ratingLen = u16le(b, off + 8);
let pos = off + 10;
const title = decodeUtf16LE(b, pos, titleLen); pos += titleLen;
const author = decodeUtf16LE(b, pos, authorLen); pos += authorLen;
const copyright = decodeUtf16LE(b, pos, copyrightLen); pos += copyrightLen;
const description = decodeUtf16LE(b, pos, descLen); pos += descLen;
const rating = decodeUtf16LE(b, pos, ratingLen);
return { title, author, copyright, description, rating };
}
/** Parses the ASF Extended Content Description Object descriptors. */
function parseAsfExtContentDescription(b, off, end) {
const count = u16le(b, off);
let pos = off + 2;
const descriptors = [];
for (let i = 0; i < count && pos + 6 <= end && descriptors.length < 5000; i++) {
const nameLen = u16le(b, pos); pos += 2;
if (pos + nameLen > end) break;
const name = decodeUtf16LE(b, pos, nameLen); pos += nameLen;
const valueType = u16le(b, pos); pos += 2;
const valueLen = u16le(b, pos); pos += 2;
if (pos + valueLen > end) break;
let value;
if (valueType === 0) value = decodeUtf16LE(b, pos, valueLen);
else if (valueType === 3) value = u32le(b, pos);
else if (valueType === 5) value = u16le(b, pos);
else if (valueType === 2) value = u32le(b, pos) !== 0;
else value = `(${valueLen} bytes, type ${valueType})`;
pos += valueLen;
descriptors.push({ name, value_type: valueType, value });
}
return descriptors;
}