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• WebRTC books – a brief review

  30 décembre 2013, par silvia

  I just finished reading Rob Manson’s awesome book “Getting Started with WebRTC” and I can highly recommend it for any Web developer who is interested in WebRTC.

  Rob explains very clearly how to create your first video, audio or data peer-connection using WebRTC in current Google Chrome or Firefox (I think it also now applies to Opera, though that wasn’t the case when his book was published). He makes available example code, so you can replicate it in your own Web application easily, including the setup of a signalling server. He also points out that you need a ICE (STUN/TURN) server to punch through firewalls and gives recommendations for what software is available, but stops short of explaining how to set them up.

  Rob’s focus is very much on the features required in a typical Web application :

  • video calls
  • audio calls
  • text chats
  • file sharing

  In fact, he provides the most in-depth demo of how to set up a good file sharing interface I have come across.

  Rob then also extends his introduction to WebRTC to two key application areas : education and team communication. His recommendations are spot on and required reading for anyone developing applications in these spaces.

  —

  Before Rob’s book, I have also read Alan Johnson and Dan Burnett’s “WebRTC” book on APIs and RTCWEB protocols of the HTML5 Real-Time Web.

  Alan and Dan’s book was written more than a year ago and explains that state of standardisation at that time. It’s probably a little out-dated now, but it still gives you good foundations on why some decisions were made the way they are and what are contentious issues (some of which still remain). If you really want to understand what happens behind the scenes when you call certain functions in the WebRTC APIs of browsers, then this is for you.

  Alan and Dan’s book explains in more details than Rob’s book how IP addresses of communication partners are found, how firewall holepunching works, how sessions get negotiated, and how the standards process works. It’s probably less useful to a Web developer who just wants to implement video call functionality into their Web application, though if something goes wrong you may find yourself digging into the details of SDP, SRTP, DTLS, and other cryptic abbreviations of protocols that all need to work together to get a WebRTC call working.

  —

  Overall, both books are worthwhile and cover different aspects of WebRTC that you will stumble across if you are directly dealing with WebRTC code.

• Carrierwave video not being processsed before uploading to S3

  12 décembre 2013, par Cramps

  I'm using Carrierwave, Carrierwave-video and Carrierwave-video-thumbnailer to process videos and make a thumbnail when they're uploaded. This was all working nicely while I was saving the files on my file system. However, now that I've added uploading to Amazon S3 using the carrierwave-aws gem, the videos are being uploaded to S3 without being processed first. It's as if the process encode_video and version :thumb are being skipped by the uploader.

  Here's what was working for me at first (before adding S3) :

  class VideoUploader < CarrierWave::Uploader::Base
  
  
  
  include CarrierWave::Video
  
  include CarrierWave::Video::Thumbnailer
  
  
  
  storage :file
  
  
  
  def store_dir
  
      "upload/path/"
  
  end
  
  
  
  process encode_video: [{ bunch of video options}]
  
  
  
  version :thumb do
  
      process thumbnail: [{ bunch of thumbnailer options }]
  
      def full_filename for_file
  
          png_name for_file, version_name
  
      end  
  
  end
  
  
  
  def png_name for_file, version_name
  
      %Q{#{version_name}_#{for_file.chomp(File.extname(for_file))}.png}
  
  end

  Now it's really just the same, except it's using storage :aws instead.

• "File doesn't exist" - streamio FFMPEG on screenshot after create method

  3 mai 2013, par dodgerogers747

  I have videos being directly uploaded to S3 using Amazon's CORS configuration. Videos are uploaded via a dedicated S3 form, once they have been uploaded successfully the URL of the video is appended to the @video.file hidden_field via javascript and then the video saves.

  I can't get this after_save method to work which takes a screenshot of the video and saves it to S3 via carrierwave after the video has been saved as a rails object. ( It was previously working using a carrierwave video upload instance )

  It errors out withErrno::ENOENT - No such file or directory - the file 'http://bucket-name.s3.amazonaws.com/uploads/video/file/secure-random-hex/video_name.m4v' does not exist: I have tried running this method as a class method to call it from the console but it always comes back with the same error, even though the video exists.

  My bucket is set to public, read and write. How come it doesn't think the file exists ?

  If anyone needs more code just shout, thanks in advance.

  application trace

  Started POST "/videos" for 127.0.0.1 at 2013-05-03 10:48:07 -0700
  
  Processing by VideosController#create as JS
  
    Parameters: {"utf8"=>"✓", "authenticity_token"=>"MAHxrVcmPDtVIMfDWZBwL0YnzaAaAe1PTGip5M4OVoY=", "video"=>{"user_id"=>"5", "file"=>"http://bucket-name.s3.amazonaws.com/uploads/video/file/secure-random-hex/video.m4v"}}
  
    User Load (0.3ms)  SELECT `users`.* FROM `users` WHERE `users`.`id` = 5 LIMIT 1
  
     (0.1ms)  BEGIN
  
    SQL (20.5ms)  INSERT INTO `videos` (`created_at`, `file`, `question_id`, `screenshot`, `updated_at`, `user_id`) VALUES ('2013-05-03 17:48:07', 'http://teebox-network.s3.amazonaws.com/uploads/video/file/secure-random-hex/video.m4v', NULL, NULL, '2013-05-03 17:48:07', 5)
  
     (44.0ms)  ROLLBACK
  
  Completed 500 Internal Server Error in 71ms
  
  
  
  Errno::ENOENT - No such file or directory - the file 'http://teebox-network.s3.amazonaws.com/uploads/video/file/secure-random-hex/video.m4v' does not exist:
  
    (gem) streamio-ffmpeg-0.9.0/lib/ffmpeg/movie.rb:10:in `initialize'
  
    app/models/video.rb:25:in `new'
  
    app/models/video.rb:25:in `take_screenshot'

  video.rb

    attr_accessible :user_id, :question_id, :file, :screenshot
  
    belongs_to :question
  
    belongs_to :user
  
  
  
    default_scope order('created_at DESC')
  
  
  
    after_create :take_screenshot
  
  
  
    mount_uploader :screenshot, ImageUploader
  
  
  
    validates_presence_of :user_id, :file
  
  
  
    def take_screenshot
  
      FFMPEG.ffmpeg_binary = '/opt/local/bin/ffmpeg'
  
      movie = FFMPEG::Movie.new("#{self.file}")
  
      self.screenshot = movie.screenshot("#{Rails.root}/public/uploads/tmp/screenshots/#{File.basename(self.file)}.jpg", seek_time: 2 )
  
      self.save!
  
    end

  videos/_form.html.erb

  <form action="http://bucket-name.s3.amazonaws.com" data-remote="true" class="direct-upload" enctype="multipart/form-data" method="post">
  
    <input type="hidden" />
  
    <input type="hidden" value="ACCESS_KEY" />
  
    <input type="hidden" value="public-read" />
  
    <input type="hidden" />
  
    <input type="hidden" />
  
    <input type="hidden" value="201" />
  
    <input type="file" />
  
  </form>
  
  
  
  &lt;%= form_for @video, html: { multipart: true, id: "new_video" }, remote: true do |f| %>
  
          &lt;% if @video.errors.any? %>
  
      <div>
  
      <h2>&lt;%= pluralize(@video.errors.count, "error") %> prohibited this post from being saved:</h2>
  
  
  
    <ul>
  
      &lt;% @video.errors.full_messages.each do |msg| %>
  
          <li>&lt;%= msg %></li>
  
          &lt;% end %>
  
      </ul>
  
      </div>
  
  &lt;% end %>
  
  
  
      &lt;%= f.hidden_field :user_id, value: current_user.id %>
  
      &lt;%= f.hidden_field :file %><br />
  
  
  
      &lt;% end %>

  ImageUploader

  class ImageUploader < CarrierWave::Uploader::Base
  
  
  
    include CarrierWave::RMagick
  
  
  
     include Sprockets::Helpers::RailsHelper
  
     include Sprockets::Helpers::IsolatedHelper
  
  
  
    storage :fog
  
  
  
    before :store, :remember_cache_id
  
    after :store, :delete_tmp_dir
  
  
  
      def cache_dir
  
        Rails.root.join('public/uploads/tmp/') 
  
      end
  
  
  
      def remember_cache_id(new_file)
  
        @cache_id_was = cache_id
  
      end
  
  
  
      def delete_tmp_dir(new_file)
  
        if @cache_id_was.present? && @cache_id_was =~ /\A[\d]{8}\-[\d]{4}\-[\d]+\-[\d]{4}\z/
  
          FileUtils.rm_rf(File.join(root, cache_dir, @cache_id_was))
  
        end
  
      end
  
  
  
    process resize_and_pad: [306, 150, '#000']
  
  
  
    def store_dir
  
      "uploads/#{model.class.to_s.underscore}/#{mounted_as}/#{model.id}"
  
    end
  
  
  
    def extension_white_list
  
      %w(jpg)
  
      # %w(ogg ogv 3gp mp4 m4v webm mov)
  
    end