datamoshing.rb

#!/usr/bin/env ruby
# Usage: ruby datamoshing.rb input.avi > output.avi

input = ARGV.shift
data = File.open(input) {|f| f.read }

header, main = data.split('movi')
frames, indices = main.split('idx1').map do |x| 
  x.split(/(00dc)/)
end
indices.each_with_index do |d, i|
  next if i < 10  # keep keyframes around beginning
  if d[0] == 0x10
    frames[i] = frames[i].split(/(01wb)/)[1..-1].join
    frames[i - 1] = nil
  end
end
frames.compact!

print header + 'movi' + frames.join + 'idx1' + indices.join