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• Best Web Video Encoding Practices for IOS (FFMpeg)

  21 juin 2012, par MagicMushroom

  I am working on an online video repository system for a client, written mostly in PHP. At the moment I am building a mobile version of our desktop website. Our desktop site allows users to watch videos in the browser, much like YouTube.

  My client uploads videos through the manager interface I have created, and my application uses FFmpeg on the server to transcode his videos into several resolutions and bitrates. I am no expert on FFmpeg, and while I do not know the ins and outs of each individual setting, I do understand how it works as a whole. Right now, we are using the mp4 container format with the h.264 codec to encode our videos. Our command looks like :

  ffmpeg -y -i "INPUT FILE.mov" -f mp4 -s 640x480 -vcodec libx264 -preset fast -maxrate 1500 -bitrate 1000 -bufsize 4096 -acodec libfaac -ab 192 -ac 2 "OUTPUT_FILE.mp4" >> "FILE.log" 2>&1 &

  I'm hoping to gain information about best practices with encoding video for web streaming on IOS and other mobile devices using FFmpeg. What resolutions and settings make for good mobile streaming video ? How can I ensure maximum compatibility across the sea of Android devices ?

• Getting a poster frame(thumbnail) with ffmpeg

  3 juillet 2012, par Tyler

  I am trying to get a poster frame from a video file, using ffmpeg.

  I have been following this tutorial and come up with the following code(which is taken/adapted from the link I gave) :

  public bool GetVideoThumbnail(string path, string saveThumbnailTo, int seconds)
  
          {
  
              string parameters = string.Format("-i {0} {1} -vcodec mjpeg -ss {2} -vframes 1 -an -f rawvideo", path, saveThumbnailTo, seconds);
  
  
  
              if (File.Exists(saveThumbnailTo))
  
              {
  
                  return true;
  
              }
  
              else
  
              {
  
                  using (Process process = Process.Start(pathToConvertor, parameters))
  
                  {
  
                      process.WaitForExit();
  
                  }
  
                  return File.Exists(saveThumbnailTo);
  
              }
  
          }

  At the moment this code is successfully creating a file in the correct destination (saveThumbnailTo) only the picture is completely black. I have tried changing the seconds value in the code to ensure that I am not just getting a blank picture from the start of the video. The path refers to where my video is stored, by the way.

  I am currently calling the above code like so :

  GetVideoThumbnail(videoPath, folderPath + "/poster.jpg", 100)

  ..and then passing it out to my view to display the picture. I just wonder whether ".jpg" is the extension I should be giving to this file as I am not entirely sure ?

  Edit : When I run the same command from the command line I get the following errors :

  Incompatible pixel format 'yuv420p' for codec 'mjpeg', auto-selecting
  format 'yuvj420p'

  which appears in yellow, and

  [image2 @ 02S96AE0] Could not get frame filename number 2 from pattern
  'poster.jpg' an_interleaved_write_frame() : Invalid argument

  which appears in red.

  Could anyone help me with getting this working properly as I am completely unfamiliar with the ffmpeg command line and not sure what I am doing wrong. I have tried removing the vcodec parameter and get the same error message.

• Unable to upload/convert videos using Paperclip-FFMPEG gem

  30 juillet 2012, par Graeme

  I'm still a bit of a Ruby on Rails newbie (running Rails 3.2.6 and Ruby 1.9.3p194), but I'm finding it very difficult to convert video files using the paperclip-ffmpeg gem. No matter what I do, an error message is displayed on the page after attempting to upload the video :

  "cannot load such file : /[...My info...]/lib/paperclip_processors/ffmpeg.rb"

  I'm trying to test using .mov files for the moment.

  I'm trying to follow the instructions on the gem's github page, but without much success.

  Firstly, I'm using a Mac (Snow Leopard) and ffmpeg is installed (running which ffmpeg tells me it's in /user/local/bin/ffmpeg)

  In my application, I've added the following lines to the gemfile :

  gem 'paperclip'
  
  gem 'paperclip-ffmpeg' 

  I've also added Paperclip.options[:command_path] = "/usr/local/bin/" to config/environments/development.rb as per the instructions :

  Myapp::Application.configure do
  
  
  
  ...
  
  
  
  Paperclip.options[:command_path] = "/usr/local/bin/"
  
  end

  (The instructions also suggest "in your environment config file, let Paperclip know to look there by adding that directory to its path", but I don't know what this means - maybe this is the problem ?).

  My class is structured as follows :

  class Myvideo > ActiveRecord::Base
  
  
  
    attr_accessible :description, :title, :video
  
  
  
    has_attached_file :video, :styles => { 
  
        :medium => { :geometry => "640x480", :format => 'flv' }
  
      }, :processors => [:ffmpeg]
  
  
  
  
  
  end

  My understanding is that the above code converts the uploaded movie from .mov (or whatever) to .flv format.

  However, the error I describe above appears whenever the user clicks on the Upload button (save for a few seconds while the video appears to be uploading).

  Note that I can upload a video via the standard Paperclip gem without converting with no problems. Therefore, this code works (i.e. the video is uploaded but no conversion occurs) :

  attr_accessible :description, :title, :video
  
  
  
    has_attached_file :video

  Any ideas where I might be going wrong ? Thanks !