VP8 raw file: Ruby parsing library

IVF is a simple container format for raw VP8 data, which is an open and royalty-free video compression format, currently developed by Google.

Test .ivf files are available at https://chromium.googlesource.com/webm/vp8-test-vectors

File extension

ivf

KS implementation details

License: CC0-1.0
Minimal Kaitai Struct required: 0.7

References

This page hosts a formal specification of VP8 raw file 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 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-struct

Code

Parse a local file and get structure in memory:

data = Vp8Ivf.from_file("path/to/local/file.ivf")

Or parse structure from a string of bytes:

bytes = "\x00\x01\x02..."
data = Vp8Ivf.new(Kaitai::Struct::Stream.new(bytes))

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

data.magic1 # => Magic Number of IVF Files

Ruby source code to parse VP8 raw file

vp8_ivf.rb

# 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


##
# IVF is a simple container format for raw VP8 data, which is an open
# and royalty-free video compression format, currently developed by
# Google.
# 
# Test .ivf files are available at https://chromium.googlesource.com/webm/vp8-test-vectors
# @see https://wiki.multimedia.cx/index.php/IVF Source
class Vp8Ivf < Kaitai::Struct::Struct
  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([68, 75, 73, 70].pack('C*'), magic1, _io, "/seq/0") if not magic1 == [68, 75, 73, 70].pack('C*')
    @version = @_io.read_u2le
    @len_header = @_io.read_u2le
    @codec = @_io.read_bytes(4)
    raise Kaitai::Struct::ValidationNotEqualError.new([86, 80, 56, 48].pack('C*'), codec, _io, "/seq/3") if not codec == [86, 80, 56, 48].pack('C*')
    @width = @_io.read_u2le
    @height = @_io.read_u2le
    @framerate = @_io.read_u4le
    @timescale = @_io.read_u4le
    @num_frames = @_io.read_u4le
    @unused = @_io.read_u4le
    @image_data = Array.new(num_frames)
    (num_frames).times { |i|
      @image_data[i] = Blocks.new(@_io, self, @_root)
    }
    self
  end
  class Blocks < Kaitai::Struct::Struct
    def initialize(_io, _parent = nil, _root = self)
      super(_io, _parent, _root)
      _read
    end

    def _read
      @entries = Block.new(@_io, self, @_root)
      self
    end
    attr_reader :entries
  end
  class Block < Kaitai::Struct::Struct
    def initialize(_io, _parent = nil, _root = self)
      super(_io, _parent, _root)
      _read
    end

    def _read
      @len_frame = @_io.read_u4le
      @timestamp = @_io.read_u8le
      @framedata = @_io.read_bytes(len_frame)
      self
    end

    ##
    # size of the frame data
    attr_reader :len_frame
    attr_reader :timestamp
    attr_reader :framedata
  end

  ##
  # Magic Number of IVF Files
  attr_reader :magic1

  ##
  # This should be 0
  attr_reader :version

  ##
  # Normally the header length is 32 byte
  attr_reader :len_header

  ##
  # Name of the codec e.g. 'VP80' for VP8
  attr_reader :codec

  ##
  # The (initial) width of the video, every keyframe may change the resolution
  attr_reader :width

  ##
  # The (initial) height of the video, every keyframe may change the resolution
  attr_reader :height

  ##
  # the (framerate * timescale) e.g. for 30 fps -> 30000
  attr_reader :framerate

  ##
  # the timescale is a divider of the seconds (VPX is integer math only) mostly 1000
  attr_reader :timescale

  ##
  # the number of frames (if not a camera stream)
  attr_reader :num_frames
  attr_reader :unused
  attr_reader :image_data
end