MPhil Thesis Defence


"MIDI TO SP-MIDI AND I-MELODY TRANSCODING USING PHRASE STEALING"

By

Mr. Siu Hang Lui


Abstract

The Musical Instrument Digital Interface (MIDI) is a popular music format
used in multimedia messaging service (MMS), such as mobile phone
ringtones. Scalable Polyphony MIDI (SP-MIDI) is an enhanced format that
allows composers to specify how MIDI data should be performed by hardware
devices with different numbers of polyphonic voices. I-Melody is a popular
standard file format for melodies, and also been adopted as monophonic
ringtone format. Most current mobile phones only support SP-MIDI ringtones
with specific polyphonic limits, (for example, 1 for monophonic, 2, 4, 8,
16, etc) or I-melody ringtones. Since most MIDI files are composed without
regard to polyphonic limits, a common problem in the mobile phone industry
is conversion from MIDI to SP-MIDI. However, simple MIDI to SP-MIDI
reduction algorithms, such as note-stealing, may lose or interrupt
important musical information. This paper presents a phrase stealing
algorithm that drops the perceptually least important notes when reducing
a MIDI file to SP-MIDI, and preserves the most important phrases. The
phrase stealing algorithm produces SP-MIDI files with an average phrase
length of 10 notes, in contrast to the note stealing algorithm which
disrupts perceptually important melodic phrases. Formal listening test
results show that listeners found the phrase stealing reduction very
similar to the original, representing a big improvement over note stealing
which listeners only found somewhat similar to the original.


Date:				Thursday, 18 August 2005

Time:				10:30a.m.-12:30p.m.

Venue:				Room 1504
				Lifts 25-26

Committee Members:		Prof. Andrew Horner (Supervisor)
                        	Dr. Jogesh Muppala (Chairperson)
                        	Dr. Oscar Au (ELEC)


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