setting content-type for mp4 files on s3

Question

I am adding user uploaded videos to my RoRs site with the help of the paperclip gem and s3 storage. For some reason that I can't figure out, whenever a user uploads an mp4 file, s3 sets content-type for that file as application/mp4 instead of video/mp4.

Note that I have registered mp4 mime type in an initializer file:

Mime::Type.lookup_by_extension('mp4').to_s => "video/mp4"

Here is the relevant part of my Post model:

  has_attached_file :video, 
                :storage => :s3,
                :s3_credentials => "#{Rails.root.to_s}/config/s3.yml",
                :path => "/video/:id/:filename"

  validates_attachment_content_type :video,
     :content_type => ['video/mp4'],
     :message => "Sorry, this site currently only supports MP4 video"

What am I missing in my paperclip and/or s3 set-up.

####Update#####

For some reason that is beyond my knowledge of Rails, my default mime types for mp4 contained files is the following:

    MIME::Types.type_for("my_video.mp4").to_s
 => "[application/mp4, audio/mp4, video/mp4, video/vnd.objectvideo]" 

So, when paperclip send an mp4 file to s3, it seems to identify the file's mime type as the first default, "application/mp4". That is why s3 identifies the file as having a content-type of "application/mp4". Because I want to enable streaming of these mp4 files, I need paperclip to identify the file as having a mime type of "video/mp4".

Is there a way to modify paperclip (maybe in a before_post_process filter) to allow for this, or is there a way to modify rails through an init file to identify mp4 files as being "video/mp4". If I could do either, which way is best.

Thanks for your help

Answer 1

Turns out that I needed to set a default s3 header content_type in the model. This isn't the best solution for me because at some point I might start allowing video containers other than mp4. But it gets me moving on to the next problem.

  has_attached_file :video, 
                :storage => :s3,
                :s3_credentials => "#{Rails.root.to_s}/config/s3.yml",
                :path => "/video/:id/:filename",
                :s3_headers =>  { "Content-Type" => "video/mp4" }

Answer 2

I did the following:

...
MIN_VIDEO_SIZE = 0.megabytes
MAX_VIDEO_SIZE = 2048.megabytes
VALID_VIDEO_CONTENT_TYPES = ["video/mp4", /\Avideo/] # Note: The regular expression /\Avideo/ will match anything that starts with "video"

has_attached_file :video, {
  url: BASE_URL,
  path: "video/:id_partition/:filename"
}

validates_attachment :video,
    size: { in: MIN_VIDEO_SIZE..MAX_VIDEO_SIZE }, 
    content_type: { content_type: VALID_VIDEO_CONTENT_TYPES }

before_validation :validate_video_content_type, on: :create

before_post_process :validate_video_content_type

def validate_video_content_type
  if video_content_type == "application/octet-stream"
    # Finds the first match and returns it. 
    # Alternatively you could use the ".select" method instead which would find all mime types that match any of the VALID_VIDEO_CONTENT_TYPES
    mime_type = MIME::Types.type_for(video_file_name).find do |type| 
      type.to_s.match Regexp.union(VALID_VIDEO_CONTENT_TYPES)
    end

    self.video_content_type = mime_type.to_s unless mime_type.blank?   
  end
end
...