Class: TranscodeFilter

Inherits:
Nanoc3::Filter
  • Object
show all
Defined in:
lib/filters/transcode_filter.rb

Overview

Uses ffmpeg to transcode a video into h.264 and MP4box to interleave the metadata for fast playback and streaming.

Instance Method Summary collapse

Instance Method Details

#run(filename, params = {}) ⇒ Object 



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# File 'lib/filters/transcode_filter.rb', line 9

def run(filename, params={})
  width = params[:width] || 480
  height = params[:height] || 320
  bitrate = params[:bitrate] || '400k'
  audio_bitrate = params[:audio_bitrate] || '64k'
  title = @item[:title] || filename
 
  intermediate_filename = output_filename + '.mp4'

  # Create iPod/iPhone compatible h.264 video
  command = [
    'ffmpeg',
    '-i','"' + filename + '"',
    '-acodec','libfaac',
    '-ab',audio_bitrate,
    '-s',"#{width}x#{height}",
    '-vcodec', 'libx264',
    '-vpre', 'hq', 
    '-vpre', 'ipod320',
    '-b', bitrate,
    '-bt', bitrate,
    '-metadata', "\"title=#{title}\"",
    '-threads', '0',
    '-f', 'ipod',
    '"' + intermediate_filename + '"'
  ].join(' ')

  output = ''
  error = ''
  status = POpen4::popen4(command) do |stdout,stderr,stdin,pid|
    output = stdout.read.strip
    err = stderr.read.strip
  end
  if status != 0
    raise "Error running ffmpeg: #{command} - #{error}"
  end

  # Interleave the metadata to support fast playback and seeking.
  command = "MP4Box -inter 500 -hint #{intermediate_filename}"
  status = POpen4::popen4(command) do |stdout,stderr,stdin,pid|
    output = stdout.read.strip
    err = stderr.read.strip
  end
  raise "Error running MP4Box: #{command} - #{error}" unless status == 0

  `mv "#{intermediate_filename}" "#{output_filename}"`
end