Scream Tracker 3 module: Python parsing library

Scream Tracker 3 module is a tracker music file format that, as all tracker music, bundles both sound samples and instructions on which notes to play. It originates from a Scream Tracker 3 music editor (1994) by Future Crew, derived from original Scream Tracker 2 (.stm) module format.

Instrument descriptions in S3M format allow to use either digital samples or setup and control AdLib (OPL2) synth.

Music is organized in so called patterns. "Pattern" is a generally a 64-row long table, which instructs which notes to play on which time measure. "Patterns" are played one-by-one in a sequence determined by orders, which is essentially an array of pattern IDs

  • this way it's possible to reuse certain patterns more than once for repetitive musical phrases.

File extension

s3m

KS implementation details

License: CC0-1.0

References

This page hosts a formal specification of Scream Tracker 3 module 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 = S3m.from_file("path/to/local/file.s3m")

Or parse structure from a bytes:

from kaitaistruct import KaitaiStream, BytesIO

raw = b"\x00\x01\x02..."
data = S3m(KaitaiStream(BytesIO(raw)))

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

data.num_orders # => Number of orders in a song

Python source code to parse Scream Tracker 3 module

s3m.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 S3m(KaitaiStruct):
    """Scream Tracker 3 module is a tracker music file format that, as all
    tracker music, bundles both sound samples and instructions on which
    notes to play. It originates from a Scream Tracker 3 music editor
    (1994) by Future Crew, derived from original Scream Tracker 2 (.stm)
    module format.
    
    Instrument descriptions in S3M format allow to use either digital
    samples or setup and control AdLib (OPL2) synth.
    
    Music is organized in so called `patterns`. "Pattern" is a generally
    a 64-row long table, which instructs which notes to play on which
    time measure. "Patterns" are played one-by-one in a sequence
    determined by `orders`, which is essentially an array of pattern IDs
    - this way it's possible to reuse certain patterns more than once
    for repetitive musical phrases.
    
    .. seealso::
       Source - http://hackipedia.org/browse.cgi/File%20formats/Music%20tracker/S3M%2c%20ScreamTracker%203/Scream%20Tracker%203.20%20by%20Future%20Crew.txt
    """
    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.song_name = KaitaiStream.bytes_terminate(self._io.read_bytes(28), 0, False)
        self.magic1 = self._io.read_bytes(1)
        if not self.magic1 == b"\x1A":
            raise kaitaistruct.ValidationNotEqualError(b"\x1A", self.magic1, self._io, u"/seq/1")
        self.file_type = self._io.read_u1()
        self.reserved1 = self._io.read_bytes(2)
        self.num_orders = self._io.read_u2le()
        self.num_instruments = self._io.read_u2le()
        self.num_patterns = self._io.read_u2le()
        self.flags = self._io.read_u2le()
        self.version = self._io.read_u2le()
        self.samples_format = self._io.read_u2le()
        self.magic2 = self._io.read_bytes(4)
        if not self.magic2 == b"\x53\x43\x52\x4D":
            raise kaitaistruct.ValidationNotEqualError(b"\x53\x43\x52\x4D", self.magic2, self._io, u"/seq/10")
        self.global_volume = self._io.read_u1()
        self.initial_speed = self._io.read_u1()
        self.initial_tempo = self._io.read_u1()
        self.is_stereo = self._io.read_bits_int_be(1) != 0
        self.master_volume = self._io.read_bits_int_be(7)
        self._io.align_to_byte()
        self.ultra_click_removal = self._io.read_u1()
        self.has_custom_pan = self._io.read_u1()
        self.reserved2 = self._io.read_bytes(8)
        self.ofs_special = self._io.read_u2le()
        self.channels = [None] * (32)
        for i in range(32):
            self.channels[i] = S3m.Channel(self._io, self, self._root)

        self.orders = self._io.read_bytes(self.num_orders)
        self.instruments = [None] * (self.num_instruments)
        for i in range(self.num_instruments):
            self.instruments[i] = S3m.InstrumentPtr(self._io, self, self._root)

        self.patterns = [None] * (self.num_patterns)
        for i in range(self.num_patterns):
            self.patterns[i] = S3m.PatternPtr(self._io, self, self._root)

        if self.has_custom_pan == 252:
            self.channel_pans = [None] * (32)
            for i in range(32):
                self.channel_pans[i] = S3m.ChannelPan(self._io, self, self._root)



    class ChannelPan(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.reserved1 = self._io.read_bits_int_be(2)
            self.has_custom_pan = self._io.read_bits_int_be(1) != 0
            self.reserved2 = self._io.read_bits_int_be(1) != 0
            self.pan = self._io.read_bits_int_be(4)


    class PatternCell(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.has_fx = self._io.read_bits_int_be(1) != 0
            self.has_volume = self._io.read_bits_int_be(1) != 0
            self.has_note_and_instrument = self._io.read_bits_int_be(1) != 0
            self.channel_num = self._io.read_bits_int_be(5)
            self._io.align_to_byte()
            if self.has_note_and_instrument:
                self.note = self._io.read_u1()

            if self.has_note_and_instrument:
                self.instrument = self._io.read_u1()

            if self.has_volume:
                self.volume = self._io.read_u1()

            if self.has_fx:
                self.fx_type = self._io.read_u1()

            if self.has_fx:
                self.fx_value = self._io.read_u1()



    class PatternCells(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.cells = []
            i = 0
            while not self._io.is_eof():
                self.cells.append(S3m.PatternCell(self._io, self, self._root))
                i += 1



    class Channel(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.is_disabled = self._io.read_bits_int_be(1) != 0
            self.ch_type = self._io.read_bits_int_be(7)


    class SwappedU3(KaitaiStruct):
        """Custom 3-byte integer, stored in mixed endian manner."""
        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.hi = self._io.read_u1()
            self.lo = self._io.read_u2le()

        @property
        def value(self):
            if hasattr(self, '_m_value'):
                return self._m_value if hasattr(self, '_m_value') else None

            self._m_value = (self.lo | (self.hi << 16))
            return self._m_value if hasattr(self, '_m_value') else None


    class Pattern(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.size = self._io.read_u2le()
            self._raw_body = self._io.read_bytes((self.size - 2))
            _io__raw_body = KaitaiStream(BytesIO(self._raw_body))
            self.body = S3m.PatternCells(_io__raw_body, self, self._root)


    class PatternPtr(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.paraptr = self._io.read_u2le()

        @property
        def body(self):
            if hasattr(self, '_m_body'):
                return self._m_body if hasattr(self, '_m_body') else None

            _pos = self._io.pos()
            self._io.seek((self.paraptr * 16))
            self._m_body = S3m.Pattern(self._io, self, self._root)
            self._io.seek(_pos)
            return self._m_body if hasattr(self, '_m_body') else None


    class InstrumentPtr(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.paraptr = self._io.read_u2le()

        @property
        def body(self):
            if hasattr(self, '_m_body'):
                return self._m_body if hasattr(self, '_m_body') else None

            _pos = self._io.pos()
            self._io.seek((self.paraptr * 16))
            self._m_body = S3m.Instrument(self._io, self, self._root)
            self._io.seek(_pos)
            return self._m_body if hasattr(self, '_m_body') else None


    class Instrument(KaitaiStruct):

        class InstTypes(Enum):
            sample = 1
            melodic = 2
            bass_drum = 3
            snare_drum = 4
            tom = 5
            cymbal = 6
            hihat = 7
        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.type = KaitaiStream.resolve_enum(S3m.Instrument.InstTypes, self._io.read_u1())
            self.filename = KaitaiStream.bytes_terminate(self._io.read_bytes(12), 0, False)
            _on = self.type
            if _on == S3m.Instrument.InstTypes.sample:
                self.body = S3m.Instrument.Sampled(self._io, self, self._root)
            else:
                self.body = S3m.Instrument.Adlib(self._io, self, self._root)
            self.tuning_hz = self._io.read_u4le()
            self.reserved2 = self._io.read_bytes(12)
            self.sample_name = KaitaiStream.bytes_terminate(self._io.read_bytes(28), 0, False)
            self.magic = self._io.read_bytes(4)
            if not self.magic == b"\x53\x43\x52\x53":
                raise kaitaistruct.ValidationNotEqualError(b"\x53\x43\x52\x53", self.magic, self._io, u"/types/instrument/seq/6")

        class Sampled(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.paraptr_sample = S3m.SwappedU3(self._io, self, self._root)
                self.len_sample = self._io.read_u4le()
                self.loop_begin = self._io.read_u4le()
                self.loop_end = self._io.read_u4le()
                self.default_volume = self._io.read_u1()
                self.reserved1 = self._io.read_u1()
                self.is_packed = self._io.read_u1()
                self.flags = self._io.read_u1()

            @property
            def sample(self):
                if hasattr(self, '_m_sample'):
                    return self._m_sample if hasattr(self, '_m_sample') else None

                _pos = self._io.pos()
                self._io.seek((self.paraptr_sample.value * 16))
                self._m_sample = self._io.read_bytes(self.len_sample)
                self._io.seek(_pos)
                return self._m_sample if hasattr(self, '_m_sample') else None


        class Adlib(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.reserved1 = self._io.read_bytes(3)
                if not self.reserved1 == b"\x00\x00\x00":
                    raise kaitaistruct.ValidationNotEqualError(b"\x00\x00\x00", self.reserved1, self._io, u"/types/instrument/types/adlib/seq/0")
                self._unnamed1 = self._io.read_bytes(16)