add progress option for progress notifications from ffmpeg

lib/carrierwave/video.rb

@@ -53,8 +53,16 @@ def encode_video(format, opts={})
 
       yield(file, @options.format_options) if block_given?
 
+      progress = @options.progress(model)
+
       with_trancoding_callbacks do
-        file.transcode(tmp_path, @options.format_params, @options.encoder_options)
+        if progress
+          file.transcode(tmp_path, @options.format_params, @options.encoder_options) {
+              |value| progress.call(value)
+          }
+        else
+          file.transcode(tmp_path, @options.format_params, @options.encoder_options)
+        end
         File.rename tmp_path, current_path
       end
     end

lib/carrierwave/video/ffmpeg_options.rb

@@ -10,6 +10,7 @@ def initialize(format, options)
         @callbacks = options[:callbacks] || {}
         @logger = options[:logger]
         @unparsed = options
+        @progress = options[:progress]
 
         @format_options = defaults.merge(options)
       end
@@ -22,6 +23,10 @@ def logger(model)
         model.send(@logger) if @logger.present?
       end
 
+      def progress(model)
+        lambda {|val| model.send(@progress, val)}
+      end
+
       def encoder_options
         { preserve_aspect_ratio: :width }
       end

spec/lib/carrierwave_video_spec.rb

@@ -1,7 +1,7 @@
 require 'spec_helper'
 
 describe CarrierWave::Video do
-  class Video; end
+  class Video;end
 
   class TestVideoUploader
     include CarrierWave::Video
@@ -150,6 +150,18 @@ def model
       end
     end
 
+    context "with progress set" do
+      before do
+        File.should_receive(:rename)
+        movie.stub(:transcode).and_yield(0.0).and_yield(1.0)
+      end
+      it "logs progress" do
+        converter.model.should_receive(:progress).with(0.0)
+        converter.model.should_receive(:progress).with(1.0)
+        converter.encode_video(format, progress: :progress)
+      end
+    end
+
     context "with watermark set" do
       before { File.should_receive(:rename) }