music-metadata
Version:
Music metadata parser for Node.js, supporting virtual any audio and tag format.
66 lines (65 loc) • 2.23 kB
JavaScript
import * as Token from 'token-types';
import * as util from '../common/Util.js';
import { ExtendedLameHeader } from './ExtendedLameHeader.js';
/**
* Info Tag: Xing, LAME
*/
export const InfoTagHeaderTag = new Token.StringType(4, 'ascii');
/**
* LAME TAG value
* Did not find any official documentation for this
* Value e.g.: "3.98.4"
*/
export const LameEncoderVersion = new Token.StringType(6, 'ascii');
/**
* Info Tag
* Ref: http://gabriel.mp3-tech.org/mp3infotag.html
*/
export const XingHeaderFlags = {
len: 4,
get: (buf, off) => {
return {
frames: util.isBitSet(buf, off, 31),
bytes: util.isBitSet(buf, off, 30),
toc: util.isBitSet(buf, off, 29),
vbrScale: util.isBitSet(buf, off, 28)
};
}
};
// /**
// * XING Header Tag
// * Ref: http://gabriel.mp3-tech.org/mp3infotag.html
// */
export async function readXingHeader(tokenizer) {
const flags = await tokenizer.readToken(XingHeaderFlags);
const xingInfoTag = { numFrames: null, streamSize: null, vbrScale: null };
if (flags.frames) {
xingInfoTag.numFrames = await tokenizer.readToken(Token.UINT32_BE);
}
if (flags.bytes) {
xingInfoTag.streamSize = await tokenizer.readToken(Token.UINT32_BE);
}
if (flags.toc) {
xingInfoTag.toc = new Uint8Array(100);
await tokenizer.readBuffer(xingInfoTag.toc);
}
if (flags.vbrScale) {
xingInfoTag.vbrScale = await tokenizer.readToken(Token.UINT32_BE);
}
const lameTag = await tokenizer.peekToken(new Token.StringType(4, 'ascii'));
if (lameTag === 'LAME') {
await tokenizer.ignore(4);
xingInfoTag.lame = {
version: await tokenizer.readToken(new Token.StringType(5, 'ascii'))
};
const match = xingInfoTag.lame.version.match(/\d+.\d+/g);
if (match !== null) {
const majorMinorVersion = match[0]; // e.g. 3.97
const version = majorMinorVersion.split('.').map(n => Number.parseInt(n, 10));
if (version[0] >= 3 && version[1] >= 90) {
xingInfoTag.lame.extended = await tokenizer.readToken(ExtendedLameHeader);
}
}
}
return xingInfoTag;
}