So lately I took it upon myself to play around with some video transcoding.

If you don’t already have ffmpeg, you’re going to have to get the source somewhere.

I do it through subversion in my /usr/local/src directory (where I put all the stuff I want to compile)

svn checkout svn://svn.mplayerhq.hu/ffmpeg/trunk ffmpeg

Then you’re going to need to configure and compile it. Unfortunately it isn’t THAT simple, reason being that some libraries are needed to have audio in your conversions. Specifically, you have to download the LAME MP3 library, and anything else that your video’s may need, or codecs that you do require.

Since I basically only require the LAME library. Go ahead and download it from the sourceforge page.

untar it:

tar zxvf lame-3.xxx_.tar.gz
cd lame-3.xx
./configure
make
sudo make install

You should now have the LAME mp3 library, you’re good to go on compiling FFMPEG w/ LAME support.

There’s actually a really simple way to get a good build of FFMPEG, and that’s to use darwinports. If you do have darwinports you can do the following and be good to go:

sudo port install ffmpeg

In fact, I’d seriously recommend using Darwin Ports for installing FFMPEG, as it does a lot of the pre-requieste libraries (like mp3 lame) for you, but if you can’t, then go ahead and continue compiling FFMPEG by doing the following:

svn checkout svn://svn.mplayerhq.hu/ffmpeg/trunk ffmpeg
cd ffmpeg
./configure --enable-libmp3lame --enable-static --disable-vhook
make
sudo make install

You should now have a functioning FFMPEG program. Try this in your console to verify it:

sparta@phalanx mojobabyt $ ffmpeg --version
FFmpeg version SVN-r9374, Copyright (c) 2000-2007 Fabrice Bellard, et al.
configuration: --enable-libmp3lame --enable-shared --enable-encoder=libavcodec
libavutil version: 49.4.0
libavcodec version: 51.40.4
libavformat version: 51.12.1
built on Jun 20 2007 14:44:55, gcc: 4.0.1 (Apple Computer, Inc. build 5367)
ffmpeg: missing argument for option '--version'

Now, I am not going to get into specific tutorial-like examples of how you should set up your model to handle videos, or file uploading, or anything like that. What I will tell you will work, if you have a somewhat basic understanding of Rails, and Programming in general.

Basically, what you’re going to need is some way to upload a file, then in your model do something like this:

Create an after_save in your model, I did something like this:

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  def after_save
    logger.debug "testing the status of the current file #{self.filename} #{self.content_type} #{self.public_filename} #{self.full_filename}"
    if movie?
      convert_video_to_flv
      grab_screenshot_from_video
    end
  end
 
  def movie?
    if self.content_type == "image/jpeg"
      false
    else
      true
    end
  end
 
  private
 
  def convert_video_to_flv
    logger.debug "currently trying to convert the video ( #{self.filename} ) path ( #{self.full_filename}) from content type of #{self.content_type} to flv"
    # system "ffmpeg -i #{full_filename} -ar 22050 -ab 32 -y -f flv -s 320x240 #{full_filename}.flv"
    system "ffmpeg -i #{full_filename} -r 25 -acodec mp3 -ar 22050 -y -s 320x240 #{full_filename}.flv"
    # system "flvtool2 -U #{full_filename}"
  end
 
  def grab_screenshot_from_video
    logger.debug "Trying to grab a screenshot from #{self.full_filename}"
    system "ffmpeg -i #{full_filename}.flv -s 320x240 -vframes 1 -f image2 -an #{full_filename}.jpg"
  end

Now that’s a good snippet that you can use to convert a video file, into an flv, and then it also grabs a screen-shot that you can use as a thumbnail, or whatever fancies your desires.

I hope this helps, I just wanted to share how simple it was, without getting to detailed. Let me know if you have some specific questions and I may take the time to help you out.

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