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• 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 !

• FFmpeg seeking in Mpeg4 streams

  4 juillet 2012, par Chris Robinson

  I am currently attempting to develop a player that can perform accurate seeking based on an mpeg4 elementary video stream. I'm in the planning stage and trying to decide how to go about things and I'd like some advice before I start.
  Some things to note are :

  • I will have complete control over the encoding of the file.
  • The original content will be I-frame only
  • FFmpeg is the encoding/decoding library
  • Audio can be disregarded for now. I will only be dealing with the video stream.
  • Frame accurate seeking must be implemented

  So, when I'm encoding the content, can I query what type of frame (I, P, B) has been encoded so I can construct an additional index stream for the seeking operation. If not, I can query the GOP after it has been encoded to find the I-frame.

  As for playback, the user needs to be able to type in a specific time and go to that frame (the nearest I-frame will be suitable for now). We can assume that the GOP is closed and the length is fairly short (e.g. 15 frames). My thoughts are to query the index stream that I created during encode and determine the relevant distance into the stream for the requested time.

  I'm not sure how to seek using the FFMpeg library when playing back files.

  Has anyone done anything similar and if so, can you give a brief explanation of how you did it ?

• python multiprocessing and ffmpeg corrupts files

  1er juillet 2012, par misterte

  I'm currently trying to convert several videos to three different outputs, all using ffmpeg : mp4, webm and jpeg. I also need to run this script in different directories and create within the directories webm, mp4 and jpeg subdirectories where the respective converted files are stored.

  I am running the following script inside a directory with 8 .mov test files in it. Files work ok as .mov.

  (It's a bit long, so here you can view it online)

  The script creates all files and directories. I can also note that all Consumer processes take tasks and complete them. The problem is resulting .mp4 and .webm files are corrupted.

  Here you can see an example output. It's a bit long, so I think it's best if I point out the part I think is relevant.

  ...
  
  [h264 @ 0x121815a00]no frame!
  
  Error while decoding stream #0.0
  
  [h264 @ 0x121815a00]AVC: nal size -6554108
  
  [h264 @ 0x121815a00]no frame!
  
  Error while decoding stream #0.0
  
  [h264 @ 0x121815a00]AVC: nal size 391580264
  
  [h264 @ 0x121815a00]no frame!
  
  ...

  This does not happen if I run ffmpeg straight from the console.

  ffmpeg -i movie.mov -b 500k -s 640x360 -padtop 60 -padbottom 60 movie_out.webm

  I can even run it in parallel shells and the output will not be affected.

  Can anyone see what the problem is ?

  thnx !

  A.