Newest 'ffmpeg' Questions - Stack Overflow

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• Windows console - BAT compatibility

  10 novembre 2011, par Michael

  I have a command line statement which works perfectly when manually typing it into the console, however, when I put it in a bat file it doesn't work.

  for %f in (*.flac) do ffmpeg -i "%f" -acodec alac "%~nf.m4a"
  

  Here is the error message when I try running the bat file

  The following usage of the path operator in batch-parameter
  substitution is invalid: %~nf.m4a"
  

  Is there any way to fix this? The statement converts flac files to alac files using the program ffmpeg.

• Extract RGB values from a AVFrame (FFMPEG) in C++

  9 novembre 2011, par Extrakun

  I am currently trying to read in video frames by using FFMPEG. The format is PIX_FMT_RGB24; For each frame, the RGB values are all combined together in frame->data[0] (Where frame is of the type AVFrame).

  How do I extract the individual R, G and B values for each frame? This is for processing the video. I would think it would work the same way as extracting the RGB values from a bitmap too. Thanks!

• Access each Pixel of AVFrame

  9 novembre 2011, par EBAG

  I need to access each pixel informations of an AVFrame object of FFMPEG ( If it's in RGB then each color, R and G and B of each Pixel )

  How can I achieve that?

• Transcoding to webm with ffmpeg audio problems

  9 novembre 2011, par Max A.

  For the past few days, I have been trying to get my lossless .mov video(that has an audio track) to a .webm format.

  Some info on the video & audio is that the fps is 30. Also the audio track has about 3-5 seconds of silence/blank audio before you start hearing some music.

  My problem is that is seems during the transcoding to webm, it strips away this blank audio because when I go to play the video, the audio starts right away.I've also notice that it jumps right away to ~4 seconds in the video. When i play it on the browser, it jumps to that moment in the timeline. If I try to scrub to the beginning, the video ends.

  I've have figured somethings out.

  1. This is just a webm problem. This does not happen with ogv or mp4
  2. It only happens if they is blank audio in the beginning of the audio track.

  I am using ffmpeg with the libvpx and libvorbis librarys and I am doing just the basic command line setup

  ffmpeg -i "infile" "outfile.webm"
  

• Rails 3 : How can I make Paperclip-FFMPEG work ?

  9 novembre 2011, par remino

  I have Rails 3.0.3 with these gems:

  • delayed_job 2.1.4
  • delayed_paperclip 0.7.1
  • paperclip 2.3.16
  • paperclip-ffmpeg 0.7.0

  (This combination is very specific. Some newer gems will not work with others.)

  Here's my Video model:

  class Video < Upload
    has_attached_file :file, :default_style => :view, :processors => [:ffmpeg],
      :url => '/system/:class/:attachment/:id/:style/:basename.:extension',
      :path => ':rails_root/public/system/:class/:attachment/:id/:style' \
        + '/:basename.:extension',
      :default_url => '/images/en/processing.png',
      :styles => {
        :mp4video => { :geometry => '520x390', :format => 'mp4',
          :convert_options => { :output => { :vcodec => 'libx264',
            :vpre => 'ipod640', :b => '250k', :bt => '50k',
            :acodec => 'libfaac', :ab => '56k', :ac => 2 } } },
        :oggvideo => { :geometry => '520x390', :format => 'ogg',
          :convert_options => { :output => { :vcodec => 'libtheora',
            :b => '250k', :bt => '50k', :acodec => 'libvorbis',
            :ab => '56k', :ac => 2 } } },
        :view => { :geometry => '520x390', :format => 'jpg', :time => 1 },
        :preview => { :geometry => '160x120', :format => 'jpg', :time => 1 }
      }
    validates_attachment_content_type :file, :content_type => VIDEOTYPES,
      :if => Proc.new { |upload| upload.file.file? }
    process_in_background :file
  end
  

  When creating a new Video object with attachment, the original is saved, but no conversion will be done. Even calling Video.last.file.reprocess! won't to a thing except returning true. (Not sure what "true" means in this case as it didn't work.)

  I tried hardcoding the path to ffmpeg in Paperclip::options[:command_path]. I even tried deleting the paperclip-ffmpeg.rb file and replacing it with a blank file. Really thinking I'd get an exception by doing the later, instead, I simply got "true" again.

  It feels like the paperclip-ffmpeg.rb is being loaded, because it is required by config/application.rb, but nothing is called in it when trying to generate a thumbnail or convert a video.

  Can anyone help me with this? Thanks in advance!