This page hosts a formal specification of Microsoft AVI file using Kaitai Struct. This specification can be automatically translated into a variety of programming languages to get a parsing library.
All parsing code for Ruby generated by Kaitai Struct depends on the Ruby runtime library. You have to install it before you can parse data.
The Ruby runtime library can be installed from RubyGems:
gem install kaitai-structParse a local file and get structure in memory:
data = Avi.from_file("path/to/local/file.avi")
Or parse structure from a string of bytes:
bytes = "\x00\x01\x02..."
data = Avi.new(Kaitai::Struct::Stream.new(bytes))
After that, one can get various attributes from the structure by invoking getter methods like:
data.magic1 # => get magic1
# This is a generated file! Please edit source .ksy file and use kaitai-struct-compiler to rebuild
require 'kaitai/struct/struct'
unless Gem::Version.new(Kaitai::Struct::VERSION) >= Gem::Version.new('0.9')
raise "Incompatible Kaitai Struct Ruby API: 0.9 or later is required, but you have #{Kaitai::Struct::VERSION}"
end
##
# @see https://learn.microsoft.com/en-us/previous-versions/ms779636(v=vs.85) Source
class Avi < Kaitai::Struct::Struct
CHUNK_TYPE = {
829973609 => :chunk_type_idx1,
1263424842 => :chunk_type_junk,
1330007625 => :chunk_type_info,
1413894985 => :chunk_type_isft,
1414744396 => :chunk_type_list,
1718776947 => :chunk_type_strf,
1751742049 => :chunk_type_avih,
1752331379 => :chunk_type_strh,
1769369453 => :chunk_type_movi,
1819436136 => :chunk_type_hdrl,
1819440243 => :chunk_type_strl,
}
I__CHUNK_TYPE = CHUNK_TYPE.invert
STREAM_TYPE = {
1935960429 => :stream_type_mids,
1935960438 => :stream_type_vids,
1935963489 => :stream_type_auds,
1937012852 => :stream_type_txts,
}
I__STREAM_TYPE = STREAM_TYPE.invert
HANDLER_TYPE = {
85 => :handler_type_mp3,
8192 => :handler_type_ac3,
8193 => :handler_type_dts,
1684633187 => :handler_type_cvid,
1684633208 => :handler_type_xvid,
}
I__HANDLER_TYPE = HANDLER_TYPE.invert
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@magic1 = @_io.read_bytes(4)
raise Kaitai::Struct::ValidationNotEqualError.new([82, 73, 70, 70].pack('C*'), magic1, _io, "/seq/0") if not magic1 == [82, 73, 70, 70].pack('C*')
@file_size = @_io.read_u4le
@magic2 = @_io.read_bytes(4)
raise Kaitai::Struct::ValidationNotEqualError.new([65, 86, 73, 32].pack('C*'), magic2, _io, "/seq/2") if not magic2 == [65, 86, 73, 32].pack('C*')
@_raw_data = @_io.read_bytes((file_size - 4))
_io__raw_data = Kaitai::Struct::Stream.new(@_raw_data)
@data = Blocks.new(_io__raw_data, self, @_root)
self
end
class ListBody < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@list_type = Kaitai::Struct::Stream::resolve_enum(Avi::CHUNK_TYPE, @_io.read_u4le)
@data = Blocks.new(@_io, self, @_root)
self
end
attr_reader :list_type
attr_reader :data
end
class Rect < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@left = @_io.read_s2le
@top = @_io.read_s2le
@right = @_io.read_s2le
@bottom = @_io.read_s2le
self
end
attr_reader :left
attr_reader :top
attr_reader :right
attr_reader :bottom
end
class Blocks < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@entries = []
i = 0
while not @_io.eof?
@entries << Block.new(@_io, self, @_root)
i += 1
end
self
end
attr_reader :entries
end
##
# Main header of an AVI file, defined as AVIMAINHEADER structure
# @see https://learn.microsoft.com/en-us/previous-versions/ms779632(v=vs.85) Source
class AvihBody < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@micro_sec_per_frame = @_io.read_u4le
@max_bytes_per_sec = @_io.read_u4le
@padding_granularity = @_io.read_u4le
@flags = @_io.read_u4le
@total_frames = @_io.read_u4le
@initial_frames = @_io.read_u4le
@streams = @_io.read_u4le
@suggested_buffer_size = @_io.read_u4le
@width = @_io.read_u4le
@height = @_io.read_u4le
@reserved = @_io.read_bytes(16)
self
end
attr_reader :micro_sec_per_frame
attr_reader :max_bytes_per_sec
attr_reader :padding_granularity
attr_reader :flags
attr_reader :total_frames
attr_reader :initial_frames
attr_reader :streams
attr_reader :suggested_buffer_size
attr_reader :width
attr_reader :height
attr_reader :reserved
end
class Block < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@four_cc = Kaitai::Struct::Stream::resolve_enum(Avi::CHUNK_TYPE, @_io.read_u4le)
@block_size = @_io.read_u4le
case four_cc
when :chunk_type_list
@_raw_data = @_io.read_bytes(block_size)
_io__raw_data = Kaitai::Struct::Stream.new(@_raw_data)
@data = ListBody.new(_io__raw_data, self, @_root)
when :chunk_type_avih
@_raw_data = @_io.read_bytes(block_size)
_io__raw_data = Kaitai::Struct::Stream.new(@_raw_data)
@data = AvihBody.new(_io__raw_data, self, @_root)
when :chunk_type_strh
@_raw_data = @_io.read_bytes(block_size)
_io__raw_data = Kaitai::Struct::Stream.new(@_raw_data)
@data = StrhBody.new(_io__raw_data, self, @_root)
else
@data = @_io.read_bytes(block_size)
end
self
end
attr_reader :four_cc
attr_reader :block_size
attr_reader :data
attr_reader :_raw_data
end
##
# Stream header (one header per stream), defined as AVISTREAMHEADER structure
# @see https://learn.microsoft.com/en-us/previous-versions/ms779638(v=vs.85) Source
class StrhBody < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
@fcc_type = Kaitai::Struct::Stream::resolve_enum(Avi::STREAM_TYPE, @_io.read_u4le)
@fcc_handler = Kaitai::Struct::Stream::resolve_enum(Avi::HANDLER_TYPE, @_io.read_u4le)
@flags = @_io.read_u4le
@priority = @_io.read_u2le
@language = @_io.read_u2le
@initial_frames = @_io.read_u4le
@scale = @_io.read_u4le
@rate = @_io.read_u4le
@start = @_io.read_u4le
@length = @_io.read_u4le
@suggested_buffer_size = @_io.read_u4le
@quality = @_io.read_u4le
@sample_size = @_io.read_u4le
@frame = Rect.new(@_io, self, @_root)
self
end
##
# Type of the data contained in the stream
attr_reader :fcc_type
##
# Type of preferred data handler for the stream (specifies codec for audio / video streams)
attr_reader :fcc_handler
attr_reader :flags
attr_reader :priority
attr_reader :language
attr_reader :initial_frames
attr_reader :scale
attr_reader :rate
attr_reader :start
attr_reader :length
attr_reader :suggested_buffer_size
attr_reader :quality
attr_reader :sample_size
attr_reader :frame
end
##
# Stream format description
class StrfBody < Kaitai::Struct::Struct
def initialize(_io, _parent = nil, _root = self)
super(_io, _parent, _root)
_read
end
def _read
self
end
end
attr_reader :magic1
attr_reader :file_size
attr_reader :magic2
attr_reader :data
attr_reader :_raw_data
end