Polymorphic file upload with paperclip, delayed_job, has_many_polymorphs, swfupload, formtastic and haml. Make same for any other types like Image, Audio, Document and so on.

application_helper.rb

module ApplicationHelper

  # Access Levels
  ACCESS_LEVELS = { :private => 0, :friends => 1, :public => 2 }

  # Access levels i18n translation
  def access_levels
    ACCESS_LEVELS.collect{|k,v| [I18n.t("access." + k.to_s), v]}
  end
end

asset_form.html.haml

- content_for :head do
  = javascript_include_tag 'jquery-1.3.2', 'swfupload/swfupload', 'swfupload/swfupload.swfobject', 'swfupload/handlers', 'swfupload/fileprogress', 'swfupload/swfupload.queue'
- session_key_name = ActionController::Base.session_options[:key]

#form_degrade_gracefully
  %h1 New #{model_name}
  - semantic_form_for [parent, model], :html => {:multipart => true} do |f|
    - f.inputs do
      = f.input :title
      = f.input :description, :as => :text
      = f.input :access, :as => :select, :collection => access_levels, :prompt => false, :selected => 2
      = f.input :data, :as => :file
    - f.buttons do
      = f.commit_button

%div#swfupload_container{:style => 'display: none'}
  %h1 New #{model_name_plural}
  = select("flash", "access", access_levels, {:prompt => false, :selected => 2})
  :javascript
    jQuery(function() {
      jQuery("#flash_access").change(function() {
        swf_upload.addPostParam("access", jQuery('#flash_access').val());
      });
    });
  #fsUploadProgress.fieldset.flash
    %span.legend Queue
  #divStatus 0 uploaded #{model_name} (status kolejki)
  %div
    %span#spanButtonPlaceHolder
    %input#btnCancel{ :type => "button", :value => "Cancel all", :disabled => "disabled", :onclick => "swf_upload.cancelQueue();" }

:javascript
  var swf_upload;
  SWFUpload.onload = function() {
    var swf_settings = {
 
      // SWFObject settings
      minimum_flash_version: "9.0.28",

      // Authencity config (Rails) 
      post_params: {
        "#{session_key_name}": "#{cookies[session_key_name]}",
        "authenticity_token": "#{form_authenticity_token}",
        "access": "2",
      },

      // Backend settings
      upload_url: "#{polymorphic_path([parent, model])}",

      // SWFUpload flash file
      flash_url: '/flash/swfupload/swfupload.swf',
 
      // Flash file settings
      file_size_limit : "#{file_size_limit}",
      file_types : "#{file_types_extensions}",
      file_types_description : "#{file_types_description}",
      file_upload_limit : "0",
      file_queue_limit : "0",


      // Event handler settings
      file_queued_handler : fileQueued,
      file_queue_error_handler : fileQueueError,
      file_dialog_complete_handler : fileDialogComplete,
      upload_start_handler : uploadStart,
      upload_progress_handler : uploadProgress,
      upload_error_handler : uploadError,
      upload_success_handler : uploadSuccess,
      upload_complete_handler : uploadComplete,
      queue_complete_handler : queueComplete,  // Queue plugin event

      // Button Settings
      button_image_url : "/images/swfupload/SmallSpyGlassWithTransperancy_17x18.png",
      button_placeholder_id : "spanButtonPlaceHolder",
      button_width: 17,
      button_height: 18,
      
      custom_settings : {
        progressTarget : "fsUploadProgress",
        cancelButtonId : "btnCancel"
      },

      // Degrade gracefully normal form
      swfupload_pre_load_handler: function() {
        $('#form_degrade_gracefully').hide();
        $('#swfupload_container').show();
      },

      // Debug settings
     debug: false

    }
    swf_upload = new SWFUpload(swf_settings);
  };

create_video.rb

class CreateVideos < ActiveRecord::Migration
  def self.up
    create_table :videos do |t|
      # Security
      t.integer   :access, :default => 2
      t.string    :secure_token

      # Default data
      t.string    :title
      t.text      :description

      # For Delayed Job status
      t.boolean   :processing, :default => true

      # Paperclip
      t.string    :data_file_name
      t.string    :data_content_type
      t.integer   :data_file_size
      t.datetime  :data_updated_at

      t.timestamps
    end

    add_index :videos, :secure_token
    add_index :videos, :title
    add_index :videos, :description
    add_index :videos, :data_file_name
    add_index :videos, [:title, :description, :data_file_name]
  end

  def self.down
    drop_table :videos
  end
end

routes.rb

ActionController::Routing::Routes.draw do |map|
  map.resources :users do |u|
    u.resources :videos, :controller => 'videos'
    u.resources :images, :controller => 'images'
  end
end

user.rb

class User < ActiveRecord::Base
  # Used plugin has_many_polymorphs for easy polymorphic associations
  # Example:
  # User.first.assets # => [#Video, #Image, #Image]
  # User.first.images # => [#Image, #Image]
  has_many_polymorphs :assets, :from => [:videos, :images]
end

video.rb

class Video < ActiveRecord::Base

  # Allowable content types for file upload
  VIDEO_TYPES = MIME::Types[/(video)/].map(&:content_type) + [ 'application/x-flv', 'application/x-wmv', 'application/x-avi', 'application/x-mpg' ]

  # Video formats for ffmpeg (http://ffmpeg.org/ffmpeg-doc.html)
  # qvga => 320x240 
  # vga => 640x480
  # hd480 => 852x480

  # Paperclip attachment
  has_attached_file :data,
    :url => "/uploads/videos/:id/:style/:basename.:extension",
    :path => ":rails_root/public/uploads/videos/:id/:style/:basename.:extension",
    :styles => {
      :i_icon => { :size => "32x32", :format => "jpg" },
      :i_small => { :size => "120x90", :format => "jpg" },
      :i_normal => { :size => "320x240", :format => "jpg" },
      :i_large => { :size => "640x480", :format => "jpg" },
      :i_hd => { :size => "852x480", :format => "jpg" },
      :v_normal => { :vid_size => "qvga", :format => "flv" },
      :v_large => { :vid_size => "vga", :format => "flv" },
      :v_hd => { :vid_size => "hd480", :format => "flv" }
    },
    :processors => "video_transcoder"

  # Secure mass assignment
  attr_protected :data_file_name, :data_content_type, :data_size, :secure_token

  # Validations
  validates_presence_of :title
  validates_attachment_presence :data
  validates_attachment_size :data, :less_than => 200.megabytes
  validates_attachment_content_type :data, :content_type => VIDEO_TYPES

  # Stop processing after upload
  before_post_process do |video|
    false if video.processing?
  end

  # Push processing to Delayed Job
  after_create { |video| video.send_later(:perform) }

  # Named scopes
  named_scope :private, :conditions => ['access = ?', 0]
  named_scope :friends, :conditions => ['access = ?', 1]
  named_scope :public, :conditions => ['access = ?', 2]

  # Processings pushed to Delayed Job
  def perform
    update_attribute(:processing, false)
    set_token
    data.reprocess!
    save
  end

  # Default URL with processing checks
  def url(style = :original)
    if (self.data && processing? && style != :original) or !File.exist?(self.data.path(style))
      return data.url(:original)
    end
    data.url(style)
  end

  # Default secure URL with processing checks
  def secure_url(style = :original)
    if (self.data && processing? && style != :original) or !File.exist?(self.data.path(style))
      return "/not_generated_yet"
    end
    "/#{secure_token}##{style.to_s}"
  end

  # Set secure token
  def set_token
    update_attribute(:secure_token, Digest::MD5.hexdigest(data_file_name + created_at.to_s + id.to_s + self.class.name))
  end

end

video_new.html.haml

= render :partial => "shared/asset_form", :locals => { :model => @video, :parent => @parent, :model_name => "Video", :model_name_plural => "Videos", :file_size_limit => "200 MB", :file_types_extensions => "*.avi; *.flv; *.mov; *.mpg; *.mpeg; *.mp4; *.wmv; *.3g2; *.3gp; *.m4v; *.asf;", :file_types_description => "Any file video" }

video_transcoder_processor.rb

module Paperclip

  class VideoTranscoder < Processor

    attr_accessor :options

    def initialize file, options = {}, attachment = nil
      super
      @current_format     = File.extname(@file.path)
      @basename           = File.basename(@file.path, @current_format)

      @options            = options
      @format             = options[:format]
    end

    def make
      dst = Tempfile.new([@basename, @format].compact.join("."))
      dst.binmode

      RVideo.logger = RAILS_DEFAULT_LOGGER

      # Screenshot grabbing
      if @format == 'jpg'
        # Initalize transcoder
        transcoder = RVideo::Transcoder.new

        # Calculate time offset (50%)
        offset = "50"
        inspector = RVideo::Inspector.new :file => file.path
        time = (inspector.duration.to_i / 1000.0) * (offset.to_f / 100.0)

        # Recipe for ffmpeg screenshot grabbing
        recipe = "ffmpeg -y -i $input_file$ -ss $time_offset$ -vframes 1 -vcodec mjpeg -f image2 -s $vid_size$ $output_file$"

        begin
          transcoder.execute(recipe, {:input_file => file.path, :output_file => dst.path, :vid_size => @options[:size], :time_offset => time})
        rescue TranscoderError => e
          puts "Unable to generate screenshot: #{e.class} - #{e.message}"
        end
      end

      # Video transcoder
      if @format == 'flv'
        # Initalize transcoder
        transcoder = RVideo::Transcoder.new

        # Recipe for ffmpeg video transcoding
        recipe = "ffmpeg -y -i $input_file$ -vcodec libx264 -acodec libmp3lame -ac 2 -ar 44100 -ab 64000 -b 650kb -f flv -r 25 -s $vid_size$ -vpre default $output_file$"

        begin
          transcoder.execute(recipe, {:input_file => file.path, :output_file => dst.path, :vid_size => @options[:vid_size]})
        rescue TranscoderError => e
          puts "Unable to transcode file: #{e.class} - #{e.message}"
        end
      end

      dst

    end

  end

end

videos_controller.rb

class VideosController < ApplicationController

  before_filter :find_parent

  def index
    @videos = @parent.videos.all

    respond_to do |format|
      format.html
    end
  end

  def new
    @video = @parent.videos.new

    respond_to do |format|
      format.html # new.html.erb
    end
  end

  def create
    if params[:Filedata]
      # SWFUpload
      @data = params[:Filedata]
      @data.content_type = MIME::Types.type_for(@data.original_filename).to_s

      @video = @parent.videos.create(:title => @data.original_filename, :data => @data, :access => params[:access])
  
      if @video.save
        render :nothing => true # Sends 200 OK
      else
        render :text => "Error"
      end
    else
      # Standard form
      @video = @parent.videos.create(params[:video])
  
      if @video.save
        redirect_to([@parent, :videos])
      else
        render :action => "new"
      end
    end
  end

  private
    def find_parent
      params.each do |name, value|
        if name =~ /(.+)_id$/
          @parent = $1.classify.constantize.find(value) and return
        end
      end
      nil
    end

end