class Moshy::Prep

Public Instance Methods

cli(args) click to toggle source
# File lib/moshy/prep.rb, line 3
                def cli(args)
                        opts = Slop::Options.new
                        opts.banner = "Usage: moshy.rb -m prep -i <file> -o <output> [options]\n"
                        opts.separator 'Required Parameters:'
                        opts.string '-i', '--input', 'Input file path - can be anything that ffmpeg supports.'
                        opts.string '-o', '--output', 'File output path - should end in .avi.'
                        opts.separator 'Optional Parameters:'
                        opts.integer '-b', '--bitrate', 'Bitrate amount (kb/s). Defaults to 4196. Larger number means higher quality, but larger size.'
                        opts.on '-h', '--help' do
                                puts opts
                                puts "\n"
                                puts \
"Preps a video file for datamoshing with moshy by converting it into an
AVI with no B-Frames (they're not good for moshing), and placing as
few I-Frames as possible. Requires ffmpeg be installed locally. Check
the repository's README.md for more information on how to install ffmpeg.

This command is meant to be a simple one-liner that makes your datamoshing
workflow faster. Under the covers, it runs the following ffmpeg command:

ffmpeg -i <moshy input> -bf 0 -g 600 -b:v <moshy bitrate> -o <moshy output>

This takes in an input file (it should theoretically work with any video
file type that ffmpeg supports), makes sure that no B-Frames are rendered,
and sets the ideal I-frame interval to 600 (ffmpeg's max). This seems to
mean that an I-frame will only show up every 30 to 25 seconds
(600f / 30fps = 20s or 600f / 24fps = 25s), but I-Frames must be deposited
wherever there is a hard cut or transition in a video where a P-frame would
not be able to properly predict the motion of pixels."
                                exit
                        end

                        default = {
                                :bitrate => 4196
                        }

                        parser = Slop::Parser.new(opts)
                        slop_options = parser.parse(ARGV)
                        @options = default.merge(slop_options) { |key, oldval, newval|
                                if newval.nil?
                                        oldval
                                else
                                        newval
                                end
                        }

                        # Check mandatory params
                        mandatory = [:input, :output]
                        missing = mandatory.select{ |param| @options[param].nil? }
                        unless missing.empty?
                                puts "Missing options: #{missing.join(', ')}"
                                puts slop_options
                                exit
                        end

                        prep @options[:input], @options[:output], @options[:bitrate]
                end
prep(input, output, bitrate) click to toggle source
# File lib/moshy/prep.rb, line 61
def prep(input, output, bitrate)
        ffmpeg = Av::Commands::Ffmpeg.new
        ffmpeg.add_source input
        ffmpeg.add_destination output

        # Ensures all frames come out as P-frames, B-frames don't
        # dupe or mosh properly
        ffmpeg.add_output_param ['bf', 0]
        # Keyframe interval, sets as few I-frames as possible.
        # ffmpeg will complain about anything over 600 and cap it.
        ffmpeg.add_output_param ['g', 600]
        # Bitrate
        ffmpeg.add_output_param ['b:v', bitrate.to_s + 'k']

        ffmpeg.run
end