Automatize video encoding for publication

converter.rb

#!/usr/bin/env ruby
# Licence : AGPLv3+
require 'nokogiri'
require 'tempfile'
require 'time'

RESOLUTION = :p576
AUDIO_FREQUENCY = 44100

ROOT_DIRECTORY = File.expand_path (ARGV[0] || '.')
INPUT_DIRECTORY = File.join ROOT_DIRECTORY, 'input'
PASS1_DIRECTORY = File.join ROOT_DIRECTORY, 'pass1'
PASS2_DIRECTORY = File.join ROOT_DIRECTORY, 'pass2'
OUTPUT_DIRECTORY = File.join ROOT_DIRECTORY, 'output'

[PASS1_DIRECTORY, PASS2_DIRECTORY, OUTPUT_DIRECTORY].each do |dir|
	Dir.mkdir dir unless Dir.exists? dir
end

CONFIG = eval File.read(File.join INPUT_DIRECTORY, 'config.rb')

FFMPEG = {
		  audio: {
				vorbis: %w(-strict -2 -codec:a vorbis -b:a 128k -ac 2),
				wav: %W(-acodec pcm_s16le -f s16le -ar #{AUDIO_FREQUENCY} -ac 1)
		  },
		  video: {
			  p480: %w(-codec:v libvpx -b:v 600k -maxrate 600k -bufsize 1200k -qmin 10 -qmax 42 -vf scale=h=480 -threads 8),
			  p576: %w(-codec:v libvpx -b:v 1000k -maxrate 1000k -bufsize 2000k -qmin 10 -qmax 42 -vf scale=h=576 -threads 8),
			  p720: %w(-codec:v libvpx -b:v 2000k -maxrate 2000k -bufsize 4000k -qmin 10 -qmax 42 -vf scale=h=720 -threads 8)
		  }
}

class Args
	def initialize
		@args = []
	end

	def <<(args)
		case (args)
			when Array then
				@args += args.collect { |a| a.to_s }
			else
				@args << args.to_s
		end
		self
	end

	def to_a
		@args
	end
end

def ffmpeg(args)
	args = args.to_a
	args = %w(ffmpeg -y) + args
	#args = %w(avconv -y) + args
	puts args.join ' '
	unless system *args
		puts args.join ' '
		exit -1
	end
end

def generate_svg_begin(file, conference)
	name = conference[:file]
	svg = File.join PASS1_DIRECTORY, "#{name}.svg"
	return if File.exists? svg

	licence = conference[:licence] || file[:licence] || ''
	location = conference[:location] || file[:location] || ''
	author = conference[:author] || ''
	title = conference[:title] || ''

	xml = Nokogiri::XML File.open File.join INPUT_DIRECTORY, 'begin.svg'
	xml.at_css('#title').content = title
	xml.at_css('#location').content = location
	xml.at_css('#author').content = author
	xml.at_css('#licence').content = licence
	File.write svg, xml.to_xml
end

def generate_video_from_image(image, video, duration=5)
	ffmpeg Args.new << %w(-loop 1 -f image2 -i) << image \
				<< %W(-acodec pcm_s16le -f s16le -ac 2 -ar #{AUDIO_FREQUENCY} -i /dev/zero) \
				<< ['-t', duration] \
				<< %w(-map 0:0 -map 1:0) \
				<< FFMPEG[:video][RESOLUTION] << %w(-vf setdar=4/3 -vf setsar=16/15) \
 				<< FFMPEG[:audio][:vorbis] << video
end

def generate_video_begin(conference, duration=5)
	name = conference[:file]
	svg = File.join PASS1_DIRECTORY, "#{name}.svg"
	png = File.join PASS2_DIRECTORY, "#{name}.png"
	title = File.join PASS2_DIRECTORY, "#{name}-title.webm"
	return if File.exists? title

	system 'inkscape', '-e', png, svg
	generate_video_from_image png, title, duration
end

def generate_video_end(duration=5)
	svg = File.join INPUT_DIRECTORY, "end.svg"
	png = File.join PASS1_DIRECTORY, 'end.png'
	video = File.join PASS2_DIRECTORY, 'end.webm'
	return if File.exists? video
	system 'inkscape', '-e', png, svg unless File.exists? png
	
	generate_video_from_image png, video, duration
end

def extract(file, conference)
	name = conference[:file]

	input = File.join INPUT_DIRECTORY, file
	audio = File.join PASS1_DIRECTORY, "#{name}.wav"
	video = File.join PASS1_DIRECTORY, "#{name}.webm"
	return if File.exists? audio and File.exists? video

	from = conference[:from]
	to = conference[:to]
	to = Time.parse(to) - Time.parse(from) if from and to

	args = Args.new
	args << ['-ss', from] if from
	args << ['-i', input]
	args << ['-to', to] if to
	#args << '-vn' << FFMPEG[:audio][:wav] << audio
	args << %w(-vn -ac 1) << audio
	args << ['-t', to] if to
	args << '-an' << FFMPEG[:video][RESOLUTION] << video
   ffmpeg args
end

def merge(conference)
	name = conference[:file]

	audio = File.join PASS1_DIRECTORY, "#{name}.wav"
	video = File.join PASS1_DIRECTORY, "#{name}.webm"
	output = File.join PASS2_DIRECTORY, "#{name}.webm"
	return if File.exists? output

	ffmpeg Args.new << ['-i', audio, '-i', video] \
	 << FFMPEG[:audio][:vorbis] << %w(-codec:v copy) << output
end

def concat(conference)
	name = conference[:file]

	begin_ = File.join PASS2_DIRECTORY, "#{name}-title.webm"
	video = File.join PASS2_DIRECTORY, "#{name}.webm"
	end_ = File.join PASS2_DIRECTORY, 'end.webm'
	output = File.join OUTPUT_DIRECTORY, "#{name}.webm"
	return if File.exists? output

	Tempfile.create 'concat' do |f|
		f.write "file #{begin_}\n"
		f.write "file #{video}\n"
		f.write "file #{end_}\n"
		f.flush

		ffmpeg Args.new << ['-f', 'concat', '-i', f.path, '-c', 'copy', output]
	end
	
	#ffmpeg Args.new << ['-i', "concat:#{begin_}|#{video}|#{end_}", '-c', 'copy', output]
end

generate_video_end
CONFIG.each do |filename, file|
	puts filename
	file[:conferences].each do |conference|
		puts conference[:file]

		# Pass 1
		generate_svg_begin file, conference
		#extract filename, conference

		# Edit SVG if necessary
		# Normalize WAV

		# Pass 2
		
		generate_video_begin conference
		#merge conference
		concat conference
	end
end