Class: Thingfish::Processor::MP3

Inherits:
Thingfish::Processor
  • Object
show all
Extended by:
Loggability
Defined in:
lib/thingfish/processor/mp3.rb

Overview

Attach ID3 data to an mp3, along with any embedded album art as a related resource.

Constant Summary collapse

VERSION =

Package version

'0.1.0'
REVISION =

Version control revision

%q$Revision: b0c42d67ea2f $
NULL =

Null character

"\x0"
PIC_FORMAT =

Attached picture “PIC”

Frame size         $xx xx xx
---- mp3info is 'helpfully' cropping out frame size.
Text encoding      $xx
Image format       $xx xx xx
Picture type       $xx
Description        <textstring> $00 (00)
Picture data       <binary data>

'h a3 h Z* a*'
APIC_FORMAT =

Attached picture “APIC”

Text encoding   $xx
MIME type       <text string> $00
Picture type    $xx
Description     <text string according to encoding> $00 (00)
Picture data    <binary data>

'h Z* h Z* a*'

Instance Method Summary collapse

Instance Method Details

#extract_id3_metadata(mp3info) ⇒ Object

Normalize metadata from the MP3Info object and return it as a hash.



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# File 'lib/thingfish/processor/mp3.rb', line 67

def extract_id3_metadata( mp3info )
	self.log.debug "Extracting MP3 metadata"

	mp3_metadata = {
		'mp3:frequency' => mp3info.samplerate,
		'mp3:bitrate'   => mp3info.bitrate,
		'mp3:vbr'       => mp3info.vbr,
		'mp3:title'     => mp3info.tag.title,
		'mp3:artist'    => mp3info.tag.artist,
		'mp3:album'     => mp3info.tag.album,
		'mp3:year'      => mp3info.tag.year,
		'mp3:genre'     => mp3info.tag.genre,
		'mp3:tracknum'  => mp3info.tag.tracknum,
		'mp3:comments'  => mp3info.tag.comments,
	}

	# ID3V2 2.2.0 has three-letter tags, so map those if the artist info isn't set
	if mp3info.hastag2?
		if mp3_metadata['mp3:artist'].nil?
			self.log.debug "   extracting old-style ID3v2 info" % [mp3info.tag2.version]

			mp3_metadata.merge!({
				'mp3:title'     => mp3info.tag2.TT2,
				'mp3:artist'    => mp3info.tag2.TP1,
				'mp3:album'     => mp3info.tag2.TAL,
				'mp3:year'      => mp3info.tag2.TYE,
				'mp3:tracknum'  => mp3info.tag2.TRK,
				'mp3:comments'  => mp3info.tag2.COM,
				'mp3:genre'     => mp3info.tag2.TCO,
			})
		end
	end

	self.log.debug "  raw metadata: %p" % [ mp3_metadata ]
	return sanitize_values( mp3_metadata )
end

#extract_images(mp3info) ⇒ Object

Extract image data from ID3 information, supports both APIC (2.3) and the older style PIC (2.2). Return value is a hash with IO keys and mimetype values. {

io  => { format => 'image/jpeg' }
io2 => { format => 'image/jpeg' }

}

Raises:

  • (LocalJumpError) 


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# File 'lib/thingfish/processor/mp3.rb', line 111

def extract_images( mp3info )
	self.log.debug "Extracting embedded images"
	raise LocalJumpError, "no block given" unless block_given?

	unless mp3info.hastag2?
		self.log.debug "...no id3v2 tag, so no embedded images possible."
		return
	end

	self.log.debug "...id3v2 tag present..."

	if mp3info.tag2.APIC
		self.log.debug "...extracting APIC (id3v2.3+) image data."

		images = [ mp3info.tag2.APIC ].flatten
		images.each do |img|
			blob, mime = img.unpack( APIC_FORMAT ).values_at( 4, 1 )
			yield( StringIO.new(blob),
				:format       => mime,
				:extent       => blob.length,
				:relationship => 'album-art' )
		end

	elsif mp3info.tag2.PIC
		self.log.debug "...extracting PIC (id3v2.2) image data."

		images = [ mp3info.tag2.PIC ].flatten
		images.each do |img|
			blob, type = img.unpack( PIC_FORMAT ).values_at( 4, 1 )
			mime = Mongrel2::Config.mimetypes[ ".#{type.downcase}" ] or next
			yield( StringIO.new(blob),
				:format       => mime,
				:extent       => blob.length,
				:relationship => 'album-art' )
		end

	else
		self.log.debug "...no known image tag types in tags: %p" % [ mp3info.tag2.keys.sort ]
	end
end

#on_request(request) ⇒ Object

Synchronous processor API – extract metadata from uploaded MP3s



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# File 'lib/thingfish/processor/mp3.rb', line 53

def on_request( request )
	mp3info = Mp3Info.new( request.body )

	mp3_metadata = self.extract_id3_metadata( mp3info )
	request.add_metadata( mp3_metadata )

	self.extract_images( mp3info ) do |imageio, metadata|
		metadata[:title] = "Album art for %s - %s" % mp3_metadata.values_at( 'mp3:artist', 'mp3:title' )
		request.add_related_resource( imageio, metadata )
	end
end