music-metadata
Version:
Music metadata parser for Node.js, supporting virtual any audio and tag format.
71 lines • 3.01 kB
JavaScript
import * as Token from 'token-types';
import { FourCcToken } from '../common/FourCC.js';
const SampleRates = [6000, 8000, 9600, 11025, 12000, 16000, 22050, 24000, 32000, 44100,
48000, 64000, 88200, 96000, 192000, -1];
/**
* WavPack Block Header
*
* 32-byte little-endian header at the front of every WavPack block
*
* Ref: http://www.wavpack.com/WavPack5FileFormat.pdf (page 2/6: 2.0 "Block Header")
*/
export const BlockHeaderToken = {
len: 32,
get: (buf, off) => {
const flags = Token.UINT32_LE.get(buf, off + 24);
const res = {
// should equal 'wvpk'
BlockID: FourCcToken.get(buf, off),
// 0x402 to 0x410 are valid for decode
blockSize: Token.UINT32_LE.get(buf, off + 4),
// 0x402 (1026) to 0x410 are valid for decode
version: Token.UINT16_LE.get(buf, off + 8),
// 40-bit total samples for entire file (if block_index == 0 and a value of -1 indicates an unknown length)
totalSamples: /* replace with bigint? (Token.UINT8.get(buf, off + 11) << 32) + */ Token.UINT32_LE.get(buf, off + 12),
// 40-bit block_index
blockIndex: /* replace with bigint? (Token.UINT8.get(buf, off + 10) << 32) + */ Token.UINT32_LE.get(buf, off + 16),
// 40-bit total samples for entire file (if block_index == 0 and a value of -1 indicates an unknown length)
blockSamples: Token.UINT32_LE.get(buf, off + 20),
// various flags for id and decoding
flags: {
bitsPerSample: (1 + getBitAllignedNumber(flags, 0, 2)) * 8,
isMono: isBitSet(flags, 2),
isHybrid: isBitSet(flags, 3),
isJointStereo: isBitSet(flags, 4),
crossChannel: isBitSet(flags, 5),
hybridNoiseShaping: isBitSet(flags, 6),
floatingPoint: isBitSet(flags, 7),
samplingRate: SampleRates[getBitAllignedNumber(flags, 23, 4)],
isDSD: isBitSet(flags, 31)
},
// crc for actual decoded data
crc: new Token.Uint8ArrayType(4).get(buf, off + 28)
};
if (res.flags.isDSD) {
res.totalSamples *= 8;
}
return res;
}
};
/**
* 3.0 Metadata Sub-Blocks
* Ref: http://www.wavpack.com/WavPack5FileFormat.pdf (page 4/6: 3.0 "Metadata Sub-Block")
*/
export const MetadataIdToken = {
len: 1,
get: (buf, off) => {
return {
functionId: getBitAllignedNumber(buf[off], 0, 6), // functionId overlaps with isOptional flag
isOptional: isBitSet(buf[off], 5),
isOddSize: isBitSet(buf[off], 6),
largeBlock: isBitSet(buf[off], 7)
};
}
};
function isBitSet(flags, bitOffset) {
return getBitAllignedNumber(flags, bitOffset, 1) === 1;
}
function getBitAllignedNumber(flags, bitOffset, len) {
return (flags >>> bitOffset) & (0xffffffff >>> (32 - len));
}
//# sourceMappingURL=WavPackToken.js.map