Class: Kithe::MediainfoAnalyzer

Inherits:
Object
  • Object
show all
Defined in:
app/models/kithe/mediainfo_analyzer.rb

Overview

Determines MIME/Internet Content Type by calling out to ‘mediainfo` CLI, which must be installed on machine.

Catches some A/v types that for some fles ordinary “magic byte” detection does not.

When we had some files not being properly determined to be audio/mpeg, we looked into what Harvard fits used, saw mediainfo was one of the tools, so decided we would use that as a fallback. Since it will be much slower than the magic-byte-based detection.

Not sure how reliable ‘mediainfo` is for non-media files, plus it we use it as a fallback.

The API is similar to the internal Shrine::DetermineMimeType::MimeTypeAnalyzer, it is based on that.

MediainfoAnalyzer.new.call(io)
#=> "audio/mpeg"
#=> nil if mediainfo has no idea

Instance Method Summary collapse

Instance Method Details

#call(io, _options = {}) ⇒ Object

returns mime-type as determined by shell out to mediainfo command

io argument will have ‘rewind` called before returning.



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# File 'app/models/kithe/mediainfo_analyzer.rb', line 31

def call(io, _options ={})
  # To use 'mediainfo' we need a local file, which if the file is currently remote means we
  # will have to download a local copy into a tempfile, this could take a while for a big file.
  Shrine.with_file(io) do |tempfile|
    out, err = tty_command.run("#{mediainfo_command} --Inform=\"General;%InternetMediaType%\"", tempfile.path)

    mime_type = out.chomp
    mime_type = nil if mime_type.blank?

    return mime_type
  end
end