AU audio format: Java parsing library

This page hosts a formal specification of AU audio format using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.

Usage

Runtime library

All parsing code for Java generated by Kaitai Struct depends on the Java runtime library. You have to install it before you can parse data.

The Java runtime library is published in the Maven Central Repository. Refer to the artifact page for instructions how to add it into your project with the build tool that you use.

Code

Parse a local file and get structure in memory:

Au data = Au.fromFile("path/to/local/file.["au", "snd"]");

Or parse structure from a byte array:

byte[] someArray = new byte[] { ... };
Au data = new Au(new ByteBufferKaitaiStream(someArray));

After that, one can get various attributes from the structure by invoking getter methods like:

data.magic() // => get magic

Java source code to parse AU audio format

Au.java

// This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild

import io.kaitai.struct.ByteBufferKaitaiStream;
import io.kaitai.struct.KaitaiStruct;
import io.kaitai.struct.KaitaiStream;
import java.io.IOException;
import java.util.Map;
import java.util.HashMap;
import java.util.Arrays;
import java.nio.charset.Charset;


/**
 * The NeXT/Sun audio file format.
 * 
 * Sample files:
 * 
 * * <https://github.com/python/cpython/tree/b8a7daf077da/Lib/test/sndhdrdata>
 * * <ftp://ftp-ccrma.stanford.edu/pub/Lisp/sf.tar.gz>
 * * <http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/AU/Samples.html>
 * @see <a href="http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/AU/AU.html">Source</a>
 * @see <a href="http://soundfile.sapp.org/doc/NextFormat/">Source</a>
 * @see <a href="http://soundfile.sapp.org/doc/NextFormat/soundstruct.h">Source</a>
 * @see <a href="https://github.com/andreiw/polaris/blob/deb47cb/usr/src/head/audio/au.h#L87-L112">Source</a>
 * @see <a href="https://github.com/libsndfile/libsndfile/blob/86c9f9eb/src/au.c#L39-L74">Source</a>
 * @see <a href="https://github.com/chirlu/sox/blob/dd8b63bd/src/au.c#L34-L49">Source</a>
 * @see <a href="https://github.com/mpruett/audiofile/blob/b62c902/libaudiofile/NeXT.cpp#L65-L96">Source</a>
 */
public class Au extends KaitaiStruct {
    public static Au fromFile(String fileName) throws IOException {
        return new Au(new ByteBufferKaitaiStream(fileName));
    }

    public enum Encodings {
        MULAW_8(1),
        LINEAR_8(2),
        LINEAR_16(3),
        LINEAR_24(4),
        LINEAR_32(5),
        FLOAT(6),
        DOUBLE(7),
        FRAGMENTED(8),
        NESTED(9),
        DSP_CORE(10),
        FIXED_POINT_8(11),
        FIXED_POINT_16(12),
        FIXED_POINT_24(13),
        FIXED_POINT_32(14),
        DISPLAY(16),
        MULAW_SQUELCH(17),
        EMPHASIZED(18),
        COMPRESSED(19),
        COMPRESSED_EMPHASIZED(20),
        DSP_COMMANDS(21),
        DSP_COMMANDS_SAMPLES(22),
        ADPCM_G721(23),
        ADPCM_G722(24),
        ADPCM_G723_3(25),
        ADPCM_G723_5(26),
        ALAW_8(27),
        AES(28),
        DELTA_MULAW_8(29);

        private final long id;
        Encodings(long id) { this.id = id; }
        public long id() { return id; }
        private static final Map<Long, Encodings> byId = new HashMap<Long, Encodings>(28);
        static {
            for (Encodings e : Encodings.values())
                byId.put(e.id(), e);
        }
        public static Encodings byId(long id) { return byId.get(id); }
    }

    public Au(KaitaiStream _io) {
        this(_io, null, null);
    }

    public Au(KaitaiStream _io, KaitaiStruct _parent) {
        this(_io, _parent, null);
    }

    public Au(KaitaiStream _io, KaitaiStruct _parent, Au _root) {
        super(_io);
        this._parent = _parent;
        this._root = _root == null ? this : _root;
        _read();
    }
    private void _read() {
        this.magic = this._io.readBytes(4);
        if (!(Arrays.equals(magic(), new byte[] { 46, 115, 110, 100 }))) {
            throw new KaitaiStream.ValidationNotEqualError(new byte[] { 46, 115, 110, 100 }, magic(), _io(), "/seq/0");
        }
        this.ofsData = this._io.readU4be();
        this._raw_header = this._io.readBytes(((ofsData() - 4) - 4));
        KaitaiStream _io__raw_header = new ByteBufferKaitaiStream(_raw_header);
        this.header = new Header(_io__raw_header, this, _root);
    }
    public static class Header extends KaitaiStruct {
        public static Header fromFile(String fileName) throws IOException {
            return new Header(new ByteBufferKaitaiStream(fileName));
        }

        public Header(KaitaiStream _io) {
            this(_io, null, null);
        }

        public Header(KaitaiStream _io, Au _parent) {
            this(_io, _parent, null);
        }

        public Header(KaitaiStream _io, Au _parent, Au _root) {
            super(_io);
            this._parent = _parent;
            this._root = _root;
            _read();
        }
        private void _read() {
            this.dataSize = this._io.readU4be();
            this.encoding = Au.Encodings.byId(this._io.readU4be());
            this.sampleRate = this._io.readU4be();
            this.numChannels = this._io.readU4be();
            if (!(numChannels() >= 1)) {
                throw new KaitaiStream.ValidationLessThanError(1, numChannels(), _io(), "/types/header/seq/3");
            }
            this.comment = new String(KaitaiStream.bytesTerminate(this._io.readBytesFull(), (byte) 0, false), Charset.forName("ASCII"));
        }
        private long dataSize;
        private Encodings encoding;
        private long sampleRate;
        private long numChannels;
        private String comment;
        private Au _root;
        private Au _parent;

        /**
         * don't read this field, access `_root.len_data` instead
         * 
         * value `0xffff_ffff` means unspecified size
         */
        public long dataSize() { return dataSize; }
        public Encodings encoding() { return encoding; }
        public long sampleRate() { return sampleRate; }

        /**
         * number of interleaved channels
         */
        public long numChannels() { return numChannels; }

        /**
         * Most resources claim that this field must be at least 4 bytes long.
         * However, most programs don't enforce it, and [Audacity](
         * https://www.audacityteam.org/) even generates .au files with this field
         * being 0-byte long. According to <https://nixdoc.net/man-pages/IRIX/man4/dmedia/next.4.html>,
         * "NeXT files require that this chunk be at least 4 bytes (chars) long,
         * whereas this chunk may be zerolength in a Sun .au file."
         * 
         * By convention, size should be a multiple of 4 -
         * see <https://github.com/chirlu/sox/blob/dd8b63bd/src/au.c#L132-L133>.
         * Page <http://soundfile.sapp.org/doc/NextFormat/> also mentions that for some
         * sound playing programs, this field must have an even byte size. So a multiple
         * of 4 is probably best for compatibility.
         * 
         * Must be null-terminated. It is usually an ASCII text string, but this space
         * might be also used to store application-specific binary (i.e. non-ASCII) data.
         */
        public String comment() { return comment; }
        public Au _root() { return _root; }
        public Au _parent() { return _parent; }
    }
    private Integer lenData;
    public Integer lenData() {
        if (this.lenData != null)
            return this.lenData;
        int _tmp = (int) ((header().dataSize() == 4294967295L ? (_io().size() - ofsData()) : header().dataSize()));
        this.lenData = _tmp;
        return this.lenData;
    }
    private byte[] magic;
    private long ofsData;
    private Header header;
    private Au _root;
    private KaitaiStruct _parent;
    private byte[] _raw_header;
    public byte[] magic() { return magic; }
    public long ofsData() { return ofsData; }
    public Header header() { return header; }
    public Au _root() { return _root; }
    public KaitaiStruct _parent() { return _parent; }
    public byte[] _raw_header() { return _raw_header; }
}