Module: RQTRotate

Defined in:
lib/rqtrotate/movie.rb,
lib/rqtrotate.rb,
lib/rqtrotate/rqtrotate.rb

Overview

Copyright 2011 The Skunkworx.

Licensed under the Apache License, Version 2.0 (the “License”); you may not use this file except in compliance with the License. You may obtain a copy of the License at

http://www.apache.org/licenses/LICENSE-2.0

Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on an “AS IS” BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

Defined Under Namespace

Classes: Movie

Instance Method Summary collapse

Instance Method Details

#find_atoms(size, stream, &block) ⇒ Object

read through the stream and yield each atom to the specified block



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# File 'lib/rqtrotate/rqtrotate.rb', line 51

def find_atoms(size, stream, &block)
  stop = stream.pos + size
  
  while stream.pos < stop
    atom_size, atom_type = read_atom(stream)

    exit(1) if atom_size == 0

    # 'trak's contiain child atoms
    if atom_type == 'trak'
      find_atoms(atom_size - 8, stream) do |sub_atom_type|
        block.call sub_atom_type
      end
    elsif ['mvhd', 'tkhd'].include?(atom_type)
      block.call atom_type
    else
      stream.seek(atom_size - 8, IO::SEEK_CUR)
    end
  end
end

#get_index(stream) ⇒ Object

return a list of top-level atoms and their absolute positions



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# File 'lib/rqtrotate/rqtrotate.rb', line 23

def get_index(stream)
  index = []

  while not stream.eof?
    atom_size, atom_type = read_atom(stream)
    index << [atom_type, stream.pos - 8, atom_size]

    if atom_size < 8
      break
    else
      stream.seek(atom_size - 8 , IO::SEEK_CUR)
    end
  end

  top_level_atoms = index.collect{|atom| atom[0]}

  ['ftyp', 'moov', 'mdat'].each do |atom_type|
    if not top_level_atoms.include?(atom_type)
      print "#{atom_type} atom not found, is this a valid MOV/MP4 file?"
      exit(1)
    end
  end

  index
end

#get_rotation(stream) ⇒ Object

determine if an existing stream is rotated



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# File 'lib/rqtrotate/rqtrotate.rb', line 73

def get_rotation(stream)
  degrees = []

  process_stream(stream) do |atom_type, matrix|
    9.times do |i|
      if (i + 1) % 3 == 0
        matrix[i] = matrix[i].to_f / (1 << 30)
      else
        matrix[i] = matrix[i].to_f / (1 << 16)
      end
    end   

    if ['mvhd', 'tkhd'].include?(atom_type)
      # convert radians to degrees
      deg = -(Math::asin(matrix[3]) * (180.0 / Math::PI)) % 360
      deg = (Math::acos(matrix[0]) * (180.0 / Math::PI)) if deg == 0
      degrees << deg if deg != 0
    end        
  end
  
  if degrees.count == 0
    0
  elsif degrees.uniq.count == 1
    degrees.pop
  else
    -1
  end
end

#process_stream(stream, &block) ⇒ Object

core of the whole thing. find all relevant atoms and yield to consumers



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# File 'lib/rqtrotate/rqtrotate.rb', line 125

def process_stream(stream, &block)
  index = get_index(stream)
  moov_size = -1

  index.each do |atom, pos, size| 
    if atom == 'moov'
      moov_size = size
      stream.seek(pos + 8)
      break
    end
  end

  find_atoms(moov_size - 8, stream) do |atom_type|
    vf = stream.read(4)
    version = vf.unpack("C4")[0]
    flags = vf.unpack("N")[0] & 0x00ffffff

    if version == 1
      if atom_type == 'mvhd'
        stream.read(28)
      elsif atom_type == 'tkhd'
        stream.read(32)
      end
    elsif version == 0
      if atom_type == 'mvhd'
        stream.read(16)
      elsif atom_type == 'tkhd'
        stream.read(20)
      end
    end

    stream.read(16)
    raw = stream.read(36)
    # matrix = raw.unpack('O*') # pending patch acceptance to pack.c
    matrix = raw.signed_bigendian_unpack

    block.call atom_type, matrix
    
    if atom_type == 'mvhd'
      stream.read(28)
    elsif atom_type == 'tkhd'
      stream.read(8)
    end
  end # find_atoms
end

#read_atom(stream) ⇒ Object

Read a single atom and return an array of [size, type].



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# File 'lib/rqtrotate/rqtrotate.rb', line 17

def read_atom(stream)
  stream.read(8).unpack("NA4")
end

#set_rotation(stream, rotation) ⇒ Object

take an existing stream and rotate it



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# File 'lib/rqtrotate/rqtrotate.rb', line 103

def set_rotation(stream, rotation)
  process_stream(stream) do |atom_type, matrix|
    if atom_type == 'tkhd'
      # degrees to radians
      rad = rotation * Math::PI / 180.0
      # rotate
      cos_deg = ((1 << 16) * Math::cos(rad)).to_i
      sin_deg = ((1 << 16) * Math::sin(rad)).to_i

      # pending patch acceptance to pack.c
      # value = [cos_deg, sin_deg, 0, -sin_deg, cos_deg, 0, 0, 0, (1 << 30)].pack("O9")
      # build data to write back into stream
      value = [cos_deg, sin_deg, 0, -sin_deg, cos_deg, 0, 0, 0, (1 << 30)].signed_bigendian_pack()
      
      stream.seek(-36, IO::SEEK_CUR)
      stream.write(value)
    end
  end
end