Music on Mobile PhonesIssuesOverview
Music on Mobile Phones Issues Overview
MobileMusicFormatsCommonMusic Formats used-inMultimediaMessagingServices(MMS)are:MIDISP-MIDII-MelodySP-MIDIis inprincipleaMIDI file withaspecialSystemExclusivemessageI-Melody is a simple single polyphonicformat whichdoesnotdefine anyinstruments.TranscodingbetweenMIDI,SP-MIDI,andI-Melodyingeneralisaproblemofpolyphonyreduction
Mobile Music Formats Common Music Formats used in Multimedia Messaging Services (MMS) are: ◼ MIDI ◼ SP-MIDI ◼ I-Melody SP-MIDI is in principle a MIDI file with a special System Exclusive message. I-Melody is a simple single polyphonic format which does not define any instruments. Transcoding between MIDI, SP-MIDI, and I-Melody, in general is a problem of polyphony reduction
ProblemsMobiledevicesusuallyhavealimitationonthe MaximumInstantaneousPolyphony(MiP)thehardwarecansupportMost MIDI were composed without the MIP consideration.Problemswhen downloading these MIDI files into a mobiledevice:SomeMIDIfile cannotbeplayed backat allSome play back witha poor qualitySP-MIDIisan attempttosolvetheproblem,butearlySP-MIDIhardware introduce moreproblems:Itmayfail toplaySomeSP-MIDIwhentheMIPintheSP-MIDIexceedsthehardwarelimitationAnevenextremecaseisI-Melody,whichalwayshasanMIPvalueof 1
Problems Mobile devices usually have a limitation on the Maximum Instantaneous Polyphony (MIP) the hardware can support. Most MIDI were composed without the MIP consideration. Problems when downloading these MIDI files into a mobile device: ◼ Some MIDI file cannot be played back at all ◼ Some play back with a poor quality SP-MIDI is an attempt to solve the problem, but early SP-MIDI hardware introduce more problems: ◼ It may fail to play some SP-MIDI when the MIP in the SP-MIDI exceeds the hardware limitation An even extreme case is I-Melody, which always has an MIP value of 1
ExperimentonN7250Nokia-7250a representative of the Nokia Series 40 mobile phoneplatformsupportsa MIP of 4.The MIDI to be tested is Canyon.midAnoldmidifilecomeswithMSWindows,sinceWindows3.1SingleTrack,11ChannelsMIPwasfoundtobe28TheMIDI itselfcannotbeplayedonN7250atallTwo approacheswereused inanattemptto makeitplayableregardlessofthequalityThrowingawaynotestoguaranteeMIPto bewithinacertain valueConverttoa SP-MIDI
Experiment on N7250 Nokia 7250 ◼ a representative of the Nokia Series 40 mobile phone platform ◼ supports a MIP of 4. The MIDI to be tested is Canyon.mid ◼ An old midi file comes with MS Windows, since Windows 3.1 ◼ Single Track, 11 Channels ◼ MIP was found to be 28 ◼ The MIDI itself cannot be played on N7250 at all Two approaches were used in an attempt to make it playable regardless of the quality ◼ Throwing away notes to guarantee MIP to be within a certain value ◼ Convert to a SP-MIDI
ExperimentResults forN7250WithoutSP-MIDlWithSP-MIDISySMIPSys Ex EventEx EventPASSPASS31FAILPASS45PASSPASS6FAILPASSFAIL7FAILFAIL8FAIL9FAILPASSPASS10FAILSP-MIDIis notguaranteedto be playable!MIDI within MIP is not guaranteed to be payable!
Experiment Results for N7250 MIP Without SP-MIDI Sys Ex Event With SP-MIDI Sys Ex Event 3 PASS PASS 4 FAIL PASS 5 PASS PASS 6 FAIL PASS 7 FAIL FAIL 8 FAIL FAIL 9 FAIL PASS 10 FAIL PASS SP-MIDI is not guaranteed to be playable! MIDI within MIP is not guaranteed to be payable!