All possible combinations from a hash of arrays in Ruby

Just FYI I took fl00r's approach and monkey-patched it. I like it a bit better.

class Hash
  def product
    product = values[0].product(*values[1..-1])
    product.map{|p| Hash[keys.zip p]}
  end
end

Please try OCG options combination generator.

require "ocg"

generator = OCG.new(
  :bitrate => %w[100 500 1000],
  :fps => %w[15 30],
  :qp => %w[20 30]
)

puts generator.next until generator.finished?

Generator includes much more functionality that will help you to deal with other options.

a = {}
a[:bitrate] = ["100", "500", "1000"]
a[:fps] = ["15", "30"]
a[:qp] = ["20", "30"]

def product_hash(hsh)
  attrs   = hsh.values
  keys    = hsh.keys
  product = attrs[0].product(*attrs[1..-1])
  product.map{ |p| Hash[keys.zip p] }
end

product_hash(a)

you'll get

[{:bitrate=>"100", :fps=>"15", :qp=>"20"},
 {:bitrate=>"100", :fps=>"15", :qp=>"30"},
 {:bitrate=>"100", :fps=>"30", :qp=>"20"},
 {:bitrate=>"100", :fps=>"30", :qp=>"30"},
 {:bitrate=>"500", :fps=>"15", :qp=>"20"},
 {:bitrate=>"500", :fps=>"15", :qp=>"30"},
 {:bitrate=>"500", :fps=>"30", :qp=>"20"},
 {:bitrate=>"500", :fps=>"30", :qp=>"30"},
 {:bitrate=>"1000", :fps=>"15", :qp=>"20"},
 {:bitrate=>"1000", :fps=>"15", :qp=>"30"},
 {:bitrate=>"1000", :fps=>"30", :qp=>"20"},
 {:bitrate=>"1000", :fps=>"30", :qp=>"30"}]

You can also add new key to your hash.

a = {}
a[:bitrate] = ["100", "500", "1000"]
a[:fps] = ["15", "30"]
a[:qp] = ["20", "30"]
a[:bw] = [true, false]

product_hash(a)

#=>
[{:bitrate=>"100", :fps=>"15", :qp=>"20", :bw=>true},
 {:bitrate=>"100", :fps=>"15", :qp=>"20", :bw=>false},
 {:bitrate=>"100", :fps=>"15", :qp=>"30", :bw=>true},
 {:bitrate=>"100", :fps=>"15", :qp=>"30", :bw=>false},
 {:bitrate=>"100", :fps=>"30", :qp=>"20", :bw=>true},
 {:bitrate=>"100", :fps=>"30", :qp=>"20", :bw=>false},
 {:bitrate=>"100", :fps=>"30", :qp=>"30", :bw=>true},
 {:bitrate=>"100", :fps=>"30", :qp=>"30", :bw=>false},
 {:bitrate=>"500", :fps=>"15", :qp=>"20", :bw=>true},
 {:bitrate=>"500", :fps=>"15", :qp=>"20", :bw=>false},
 {:bitrate=>"500", :fps=>"15", :qp=>"30", :bw=>true},
 {:bitrate=>"500", :fps=>"15", :qp=>"30", :bw=>false},
 {:bitrate=>"500", :fps=>"30", :qp=>"20", :bw=>true},
 {:bitrate=>"500", :fps=>"30", :qp=>"20", :bw=>false},
 {:bitrate=>"500", :fps=>"30", :qp=>"30", :bw=>true},
 {:bitrate=>"500", :fps=>"30", :qp=>"30", :bw=>false},
 {:bitrate=>"1000", :fps=>"15", :qp=>"20", :bw=>true},
 {:bitrate=>"1000", :fps=>"15", :qp=>"20", :bw=>false},
 {:bitrate=>"1000", :fps=>"15", :qp=>"30", :bw=>true},
 {:bitrate=>"1000", :fps=>"15", :qp=>"30", :bw=>false},
 {:bitrate=>"1000", :fps=>"30", :qp=>"20", :bw=>true},
 {:bitrate=>"1000", :fps=>"30", :qp=>"20", :bw=>false},
 {:bitrate=>"1000", :fps=>"30", :qp=>"30", :bw=>true},
 {:bitrate=>"1000", :fps=>"30", :qp=>"30", :bw=>false}]