msgpack2json.rb

require 'rubygems'
require 'msgpack'
require 'json'

File.open(ARGV[0]) do |f|
  begin
    MessagePack::Unpacker.new(f).each {|obj|
      puts obj.to_json
    }
    rescue EOFError
  end
end

# $ gem install json
# $ gem install msgpack
# $ ruby ./msgpack2json.rb file.mpac