Node.js MP3 Header Parsing

npm install mp3-header

Full working example (mp3)

const fs        = require("fs");
const Mp3Header = require("mp3-header").Mp3Header;

const HEADER_LENGTH = 4;

fs.open("filename.mp3", 'r', function(err, fd) {

    var buffer  = new Buffer(HEADER_LENGTH);

    // The offset in the mp3 file where there is a valid MP3 frame
    var offset  = 0;

    fs.read(fd, buffer, 0, HEADER_LENGTH, offset, function(err, bytesRead, buffer) {

        if (err) {
            return fs.close(fd);
        }

        var header = new Mp3Header(buffer);
        if (header.parsed && header.is_valid) {
            console.info("MP3 Sample Rate: ", header.mpeg_samplerate);
        }

        fs.close(fd);
    });
});

Full working example (XING)

const fs         = require("fs");
const XingHeader = require("mp3-header").XingHeader;

const MAX_FRAME_LENGTH = 2881; // Theoretical max mp3 frame length

fs.open( "filename.mp3", 'r', function(err, fd) {

    var buffer  = new Buffer(MAX_FRAME_LENGTH);

    // The offset in the mp3 file where there is a valid Xing header
    var offset  = 0;

    fs.read(fd, buffer, 0, MAX_FRAME_LENGTH, offset, function(err, bytesRead, buffer) {

        if (err) {
            return fs.close(fd);
        }

        var header = new XingHeader(buffer);
        if (header.parsed && header.is_valid) {
            console.info("Number of audio frames: ", header.xing_frames);
        }

        fs.close(fd);
    });
});

Classes

The package exports two classes for parsing MP3 file headers: Mp3Header and XingHeader.

Mp3Header is the one that takes care of parsing the MPEG header of an MP3 audio frame, and provides informations about the encoding.

XingHeader is an extension Mp3Header that also takes care of parsing the metadata related to the Xing table of the MP3 file.

Properties

Once you parse a header, these are the properties you can access from the package classes:

Parameter	Type	Present in	Example
parsed	Boolean	Both	true
is_valid	Boolean	Both	true
mpeg_version	Integer	Both	2
mpeg_layer	Integer	Both	3
mpeg_has_padding	Boolean	Both	true
mpeg_channels	Integer	Both	1 (mono) or 2 (stereo)
mpeg_bitrate	Integer	Both	128000
mpeg_samplerate	Integer	Both	44100
mpeg_num_samples	Integer	Both	1152
mpeg_frame_length	Integer	Both	384
xing_offset	Integer	XingHeader	21
xing_frames	Integer	XingHeader	223
xing_bytes	Integer	XingHeader	43008
xing_keyword	String	XingHeader	Xing (VBR) or Info (CBR)
xing_flags	Integer	XingHeader
xing_has_frames	Boolean	XingHeader	true
xing_has_bytes	Boolean	XingHeader	true
xing_frames_offset	Integer	XingHeader
xing_bytes_offset	Integer	XingHeader

Run test suite

grunt test

More info

• https://www.codeproject.com/Articles/8295/MPEG-Audio-Frame-Header
• http://gabriel.mp3-tech.org/mp3infotag.html

License

MIT