AU audio format: Python 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 Python generated by Kaitai Struct depends on the Python runtime library. You have to install it before you can parse data.

The Python runtime library can be installed from PyPI:

python3 -m pip install kaitaistruct

Code

Parse a local file and get structure in memory:

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

Or parse structure from a bytes:

from kaitaistruct import KaitaiStream, BytesIO

raw = b"\x00\x01\x02..."
data = Au(KaitaiStream(BytesIO(raw)))

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

data.magic # => get magic

Python source code to parse AU audio format

au.py

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

from pkg_resources import parse_version
import kaitaistruct
from kaitaistruct import KaitaiStruct, KaitaiStream, BytesIO
from enum import Enum


if parse_version(kaitaistruct.__version__) < parse_version('0.9'):
    raise Exception("Incompatible Kaitai Struct Python API: 0.9 or later is required, but you have %s" % (kaitaistruct.__version__))

class Au(KaitaiStruct):
    """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>
    
    .. seealso::
       Source - http://www-mmsp.ece.mcgill.ca/Documents/AudioFormats/AU/AU.html
    
    
    .. seealso::
       Source - http://soundfile.sapp.org/doc/NextFormat/
    
    
    .. seealso::
       Source - http://soundfile.sapp.org/doc/NextFormat/soundstruct.h
    
    
    .. seealso::
       Source - https://github.com/andreiw/polaris/blob/deb47cb/usr/src/head/audio/au.h#L87-L112
    
    
    .. seealso::
       Source - https://github.com/libsndfile/libsndfile/blob/86c9f9eb/src/au.c#L39-L74
    
    
    .. seealso::
       Source - https://github.com/chirlu/sox/blob/dd8b63bd/src/au.c#L34-L49
    
    
    .. seealso::
       Source - https://github.com/mpruett/audiofile/blob/b62c902/libaudiofile/NeXT.cpp#L65-L96
    """

    class Encodings(Enum):
        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
    def __init__(self, _io, _parent=None, _root=None):
        self._io = _io
        self._parent = _parent
        self._root = _root if _root else self
        self._read()

    def _read(self):
        self.magic = self._io.read_bytes(4)
        if not self.magic == b"\x2E\x73\x6E\x64":
            raise kaitaistruct.ValidationNotEqualError(b"\x2E\x73\x6E\x64", self.magic, self._io, u"/seq/0")
        self.ofs_data = self._io.read_u4be()
        self._raw_header = self._io.read_bytes(((self.ofs_data - 4) - 4))
        _io__raw_header = KaitaiStream(BytesIO(self._raw_header))
        self.header = Au.Header(_io__raw_header, self, self._root)

    class Header(KaitaiStruct):
        def __init__(self, _io, _parent=None, _root=None):
            self._io = _io
            self._parent = _parent
            self._root = _root if _root else self
            self._read()

        def _read(self):
            self.data_size = self._io.read_u4be()
            self.encoding = KaitaiStream.resolve_enum(Au.Encodings, self._io.read_u4be())
            self.sample_rate = self._io.read_u4be()
            self.num_channels = self._io.read_u4be()
            if not self.num_channels >= 1:
                raise kaitaistruct.ValidationLessThanError(1, self.num_channels, self._io, u"/types/header/seq/3")
            self.comment = (KaitaiStream.bytes_terminate(self._io.read_bytes_full(), 0, False)).decode(u"ASCII")


    @property
    def len_data(self):
        if hasattr(self, '_m_len_data'):
            return self._m_len_data if hasattr(self, '_m_len_data') else None

        self._m_len_data = ((self._io.size() - self.ofs_data) if self.header.data_size == 4294967295 else self.header.data_size)
        return self._m_len_data if hasattr(self, '_m_len_data') else None