A Wrapper for MIDI files from an Object
Contents
1. lt Event gt lt Channel Event gt lt Meta Event gt lt Sysex Event gt Let us have now a closer look on those elementary commands since they hold the most important information in a MIDI file and thereby they are also necessary for the modelling of the object oriented database scheme 2 3 1 Channel Events A channel event is a command to a certain MIDI channel of the playback device The general syntax is as follows lt Channel Event gt lt Status Byte gt lt Data Byte gt lt Data Byte gt The status byte contains the type of the event and the channel number on which the playback device executes the event lt Status Byte gt lt Event Type gt lt Channel Number gt The first leading nibble of the status byte is the event type it specifies the type of the command Common values are 0x90 Note On and 0x80 Note Off see table 1 for details lt Event Type gt 8 9 B C D E The second nibble of the status byte declares the number of the MIDI channel which to perform the command on The numbering starts with 0 lt Channel Number gt 0 F The data byte contains the parameter of the command See Table 2 for explicit values and signification lt Data Byte gt 00 7E Setting the status byte only in the first event and omitting it in the following events can shorten a chain of channel events with the same status byte This2. resolution currentSound getResolution divisionType currentSound getDivisionType To get a reverence to the available Tracks in the Sequence we create a Track object and invoke Sequence getTracks Track tracks currentSound getTracks Once the sequence contains tracks we can access the contents of the tracks by invoking methods of the Track class The MidiEvents contained in the Track are stored as a java util Vector inthe Track object and Track provides a set of methods for accessing adding and removing the events in the list The methods add and remove are fairly self explanatory adding or removing a specified MidiEvent froma Track A get method is provided which takes an index into Track s event list and returns the 14 MidikEvent stored there In addition there are size and tick methods which respectively return the number of MidiEvents in the track and the track s duration expressed as a total number of Ticks Loop all MidiEvents in a Track object for int i 0 i lt tracks length i Get number of events in a track events tracks i size ticks tracks i ticks Create the MidiEvent object in a Track object midiEvent new MidikEvent events loop the MidiEvent object for int j 0 j lt events j obtain the event at the specified index midiEvent j tracks i get j timestamp midiEvent j getTick midiMessage midiEvent j getMessage Check if the Mi
3. the project was divided in the following 6 issues 1 I had to acquire consolidated knowledge about the MIDI standard and its protocols I will expatiate this issue in chapter 1 2 The second task was to look after and select a development environment especially for Java classes which can access MIDI files To my advantage Sun s JDK 1 3 natively supports MIDI and sampled audio access The Java Sound API will be discussed in Chapter 3 3 One of the most important tasks was the investigation of an object oriented database scheme for the MIDI structure according to the Java Sound API 4 Inthe next phase I designed primitive foreign functions which take the name of a MIDI file as a parameter accessing them trough the web and then emitting a stream of AMOS II objects and attributes according to the schema to the mediator 5 In chapter 5 I will show that useful queries can be specified over the schema and therefore the usefulness of a foreign function for MIDI 6 Last but not least the whole application had to be packaged and installed in a running AMOS II environment at the University of Uppsala 2 What is midi The Musical Instrument Digital Interface MIDI standard defines a communication protocol for electronic music devices such as electronic keyboard instruments and personal computers MIDI data can be transmitted over special cables during a live performance and can also be stored in a standard type of file for later playback or
4. variants 10 Representation in the file FO lt Length gt lt Commands gt F7 Significance Complete sysex event The final signal F7 is included in the length To transmit FO lt Commands gt F7 FO lt Length gt lt Commands gt The first portion of a separated event FO lt Commands gt F7 lt Length gt lt Commands gt Sequel of a separated event lt Commands gt F7 lt Length gt lt Commands gt F7 End of a separated event The end signal F7 is included in the length lt Commands gt F7 Table 5 Syntactic variants of sysex events 11 3 The Java Sound API The Java Sound API is a low level API for effecting and controlling the input and output of sound media including both audio and Musical Instrument Digital Interface MIDI data The Java Sound API provides explicit control over the capabilities normally required for sound input and output in a framework that promotes extensibility and flexibility The Java Sound API provides the lowest level of sound support on the Java platform It provides application programs with a great amount of control over sound operations and it is extensible For example the Java Sound API supplies mechanisms for installing accessing and manipulating system resources such as audio mixers MIDI synthesizers other audio or MIDI devices file readers and writers and sound format converters The Java Sound API does not include sophistica
5. editing MIDI is both a hardware specification and a software specification To understand MIDI s design it helps to understand its history MIDI was originally designed for passing musical events such as key depressions between electronic keyboard instruments such as synthesizers Hardware devices known as sequencers stored sequences of notes Those sequences could control a synthesizer allowing musical performances to be recorded and subsequently played back Later hardware interfaces were developed that connected MIDI instruments to a computer s serial port allowing sequencers to be implemented in software More recently computer sound cards have incorporated hardware for MIDI I O and for synthesizing musical sound Today many users of MIDI deal only with sound cards never connecting to external MIDI devices CPUs have become fast enough that synthesizers too can be implemented in software A sound card is needed only for audio I O and in some applications for communicating with external MIDI devices The brief hardware portion of the MIDI specification prescribes the pin outs for MIDI cables and the jacks into which these cables are plugged This portion need not concern us Because devices that originally required hardware such as sequencers and synthesizers are now capable of being implemented in software perhaps the only reason for most programmers to know anything about MIDI hardware devices is simply to understand the metapho
6. known relational database models were not able to suffice the new demands to describe more complex objects The User of so called non standard applications CAD CAM etc demanded a database model with which they also could store and manage the objects of their world Due to this fact the search for a new database model started This time the goal was the object oriented database model The goal of this project is to extend the Object Oriented OO multi database system Amos II with a wrapper implemented in Java which can access MIDI files trough the net by giving the wrapper an URL of a midi file and store it in the database To understand what is AMOS II I will give a brief description about it AMOS II is a descendant of AMOS which has its roots in a main memory version of Hewlett Packard s DBMS IRIS The entire database is stored in main memory and is saved on disk only through explicit commands AMOS II can be used as a single user database a multi user server or as a collection of interacting AMOS II multi database servers AMOS II has a functional data model with a relationally complete object oriented query language AMOSQL The AMOS II data manager is extensible so that new data types and operators can be added to AMOSQL implemented in some external programming language Java C or Lisp AMOS II is implemented in C and runs under Windows 95 98 and Windows NT 4 0 For more information about AMOS II see 1 To achieve the goal
7. use is practically always made The coding is explicit since data bytes are smaller than 80 bytes and status bytes greater or equal 80 bytes MIDI message HEX value Dec value Description Active Sensing OxFE 254 Status byte for Active Sensing Channel Pressure OxDO 208 Command value for Channel Pressure Aftertouch message Continue OxFB 251 Status byte for Continue message Control Change 0xBO 176 Command value for Control Change message End of Exclusive OxF7 247 Status byte for End of System Exclusive message MIDI Time Code OxF1 241 Status byte for MIDI Time Quarter Frame message Note Off 0x80 128 Command value for Note Off message Note On 0x90 144 Command value for Note On message Pitch Bend OxE0 224 Command value for Pitch Bend message Poly Pressure OxA0 160 Command value for Polyphonic Key Pressure Aftertouch message Program Change OxCO 192 Command value for Program Change message Song Position Pointer OxF2 242 Status byte for Song Position Pointer message Song Select OxF3 243 Status byte for MIDI Song Select message Start OxFA 250 Status byte for Start message Stop OxFC 252 Status byte for Stop message System Exclusive OxFO 240 Status byte for System Exclusive message System Reset OxFF 255 Status byte for System Reset message Timing Clock OxF8 248 Status byte for Timing Clock message Tune Request OxF6 246 Status byte for Tune Request message Tabl
8. A Wrapper for MIDI files from an Object Relational Mediator System Semester thesis in informatics for the University of Ziirich Written by Martin Jost Z rich Switzerland Studentnumber 97 709 968 Made at the Department of Information Science at Uppsala University Sweden Prof Tore Risch TINTRODUGTION iiinn ee Addai 4 2WHAT IS MIDI zesarea 5 2 1 Streaming Data in the MIDI Wire Protocol seseososeseseesessososeoeseesessososeosoe 5 2 2 Sequenced Data in Standard MIDI Files sesesessososeseseesessososeoessesessososeosee 6 2 3 The basic structure OF MEDD MU sisissstasccsesosavenevenexcsaidasessnguesssbvcsdvonsuasteasionssonvepieniousans 6 2 3 1 Channel EE Vents AEA N dedecuvvava led teaa E E OTe 7l 23 2 Meta Eyen e E E E E de asic A A leaves 10 PAA REES DATED EVENS A E EE N EA A 10 3 THE JAVA SOUND AP rosina 12 3 1 The Java Sound API s Representation of MIDI Data sesssosoesossosesseesosse 12 3 1 1 MIDI Messa peSant n E E aeae i aeiaai a e 12 3V2 MIDI EVE MS Sehen r e e e E dal antes e a E E e EE E ee 13 3 1 3 Seg cnces and Tracks wx 21s sccsslsisesevenseccvsnsshgeesonnedeseccsasea EEE EAEE EE EE Ean SaS a 13 3 2 Use of the Java Sound API seseseesesssesseesseorceessosseoseeeseceseecoseeeeosecossessseseseeseees 13 4 DATABASE SCHEMA non0n000000010001110000rrsosos51uuuu11eroorsossssnnnnnnnrerrrernsse 16 5 EXAMPLES oranana e N 20 SUMMAR Yaren aa a a ad 23 T REFERENCES acrnnsas
9. DML Data Manipulation Language The query part of the language is similar to SQL The following command answers the question Which song last longer than 2 minutes and has two or more Tracks JavaAMOS 1 gt select distinct m from midi m where duration m gt 120 00 and tracks m gt 2 Or we can simply search for a MIDI object of a certain interpret JavaAMOS 2 gt select m from midi m where like filename m sinatra We can also define functions to retrieve or manipulate data in AMOS II A function defined in terms of other functions is called a derived function Especially if we often need to look for specific information in the database we define derived functions There are already some derived functions defined in our database scheme For example to find out which track or which midi object a midi event belongs to we have defined the following derived functions in the database scheme create function track midievent e gt track t as select t from integer i where 20 midievents t i e create function midi midievent m gt midi as select midi track m Now we can use these derived functions to get for example all MIDI objects that play a guitar as instrument JavaAMOS 3 gt select distinct midi m from metaevent m where like metaDataString m guitar To answer the question Which songs are written in C major we have to perform several commands As you
10. For more detailed information about the implementation of the database model in AMOS II see the database creation scripts in Appendix B The database model consists of eight types whereof three are inherited and three serve as lookup types for some translations of data The program takes a loaded MIDI file as a sequence in which all tracks and events are contained as we have seen in the previous chapters The sequence is decomposed in accordance with the MIDI specification into single elements and then stored as objects into AMOS II The type MIDI represents the core MIDI object it contains following attributes MIDI URL String of the URL which we downloaded the file of FileName String of the name of the file Length Integer of the size of the file in KB Duration Real of the Length of the file in seconds NumberOfTracks Integer of the number of existing tracks in the MIDI file TickLength Integer of the duration of the MIDI sequence expressed in MIDI ticks Resolution Integer of the timing resolution for the MIDI sequence That is the number of ticks per beat or per frame DivisionType Real of the timing division type for this MIDI sequence As we know already the MIDI sequence consists of at least one track These Track objects are designed under the type Track and are connected over the relation tracks with its MIDI object Since there can be several tracks in a MIDI sequence the relation is implemented as a set of objects The type Tr
11. GRE cae ae iB of of 1f 2 3 al 5 e 7l a l o wo nun if 2 n 14 a 16 17 18 19 2l a 2 23 2f 24 235 2 27 2 2 30 3 32 3 34 35 3f sel 37 3 3 40 al a g 44 s W 47 4 l 4a 50 51 52 53 54 55 56 57 58 59 5 sol 61 62 63 64 65 66 67 68 69 70 71 6 72 73 74 75 76 77 78 79 80 81 a 83 7 4 85 86 87 s 89 90 91 92 93 94 95 sf 96 97 99 100 101 102 103 104 105 106 107 9f i103 109 nol 11 12 13 114 15 116 117 118 119 10 120 121 122 123 124 1235 126 127 Table 3 Summary of MIDI Note Numbers for Different Octaves 2 3 2 Meta Events Meta events are not transmitted to the playback device They control the playback tempo and provide additional information for better reading and understanding of a MIDI file The general syntax is as follows lt Meta Event gt FF lt Event Type gt lt Length gt lt Content gt The type of the meta event is determined by the lt Event Type gt The lt Length gt parameter contains the following content in bytes There is no content if the length equals 0 Based on that syntax meta events can be delimited in a data stream A MIDI program doesn t have to know therefore the content of all meta events Selected meta events are represented in order of their meaning the most important first Event Type Length Content Description Track End 2F 00 None M
12. ack has the attributes Track NumberOfEvents Integer of the number of events in this track Ticks Integer of the length of the track expressed in MIDI ticks The single events in the track are created as objects of type MidiEvent in AMOS II Each single MidiEvent is connected with its Track object by the relation midievents Since there can be several MidiEvents per Track object the relation is implemented as a vector of MidiEvent MidiEvent TimeStamp Integer obtaining the time stamp for the event in MIDI ticks Length Integer of the number of bytes in the MIDI event including the status byte and any data bytes StatusByte Integer obtaining the status byte for the MIDI event 16 MidiMessage Byte array containing the MIDI event data The first byte is the status byte for the event subsequent bytes up to the length of the event are data bytes for this event In our database scheme the bytes are transformed into integers and stored as a vector of integers The created MidiEvent object can either be a channel event a meta event or a sysex event system exclusive This is now the point where our database scheme gets object oriented All this different events are implemented as a type under the type MidiEvent and therefore are directly inherited from MidiEvent Each event channel meta and sysex has the same attributes TimeStamp StatusByte and MidiMessage which are inherited of the MidiEvent type The types ChannelEvent MetaEvent and S
13. al events There are three types of different events the channel events the meta events and the system exclusive events Most important though are the channel events since they include information about how to play each tone Meta events are not transmitted to the playback device they control the playback tempo and provide additional information for better reading and understanding of a MIDI file The object oriented database scheme has been developed to carry all the information of a MIDI file which we can access through the Java wrapper There are tree base types Midi Track and MidiEvent and three types which are inherited of the base type MidiEvent Those types are ChannelEvent MidiEvent and SysexEvent To store all the data in the database the wrapper creates the necessary database objects out of the MIDI stream according to our scheme The MIDI file exists now in our database as a numerous and various set of objects What are the benefits of such a MIDI wrapper There are plenty of reasonable queries to approximate the usefulness of such a wrapper You may be interested in all the songs of a specific interpret or you are looking for a song written in c major and played on a piano Since every single note event is stored as an object you could also search for a pattern of notes to retrieve the requested song The future work for this project will surely be to implement a foreign function that plays back a MIDI track through AMOS II This fo
14. data of the meta event represents a string like lyrics text or instrument description the data is stored in MetaDataString MetaTypeAsString String representing the meta type translated to a meaningful String SysexEvent SysexData Obtains a copy of the data for the system exclusive message The returned array of bytes does not include the status byte The array of bytes is transformed into integers and stored as a vector of integers in our database scheme These are all the types and functions that are needed to model the object oriented database scheme for the MIDI 1 0 specification Because a lot of data is stored as simple integers we extend the database model with three lookup types in order to translate the integers into meaningful data In fact it is now much easier for the user to search for a specific string instead of an integer or to understand how the data is represented in a MIDI file The three types are ChannelCommands NoteEvents and MetaCommands The ChannelCommands type is connected with the channelEvent type through the derived function commandAsString It 17 takes the integer of the command of a channel event and translates it into a string The NoteEvents type which is connected through the derived noteEvents function takes the data of a Note On or a Note Off event and translate it into the particular Note Finally the function MetaTypeAsString takes the integer of the metaType and translates it through the MetaCom
15. diEvent is a MetaEvent a ChannelEvent or a SysexEvent if midiMessage instanceof MetaMessage Handle the MetaMessage object and create the necessary objects and functions in AMOS II if midiMessage instanceof ShortMessage Handle the ShortMessage object and create the necessary objects and functions in AMOS ITI if midiMessage instanceof SysexMessage Handle the SysexMessage object and create the necessary objects and functions in AMOS ITI For more detailed information about the classes interfaces and methods of the Java Sound API see the Java 2 Documentation 8 15 4 Database schema After we made ourselves now a picture over the Java Sound API we take a look at the object oriented data base scheme One of the most important targets of this project consisted of developing an object oriented database model in order to be able to store MIDI files in AMOS II There were certain basic conditions to consider First of all the database model is as far as possible supposed to be object oriented i e to deploy the most important concepts of object orientation which AMOS II places to use Secondly the MIDI specification should be illustrated as complete and meaningful as possible And thirdly I could refer to the classes of the Java Sound API at the development of the database model In the following I want to describe briefly my database model as seen in fig 1
16. e 1 Summary of MIDI Status Bytes Type of command 1 Nibble of 1 Data Byte 2 Data Byte the Status Byte Note On 0x90 Tone pitch for detailed Velocity for the Note On Turn on of a MIDI note information about the values see event Value 00 is The note is played until table 3 In percussion the tone illegal a suitable command pitch is interpreted as a certain Note Off happens percussion instrument Note Off 0x90 Tone pitch 00 There are two possibilities 0x80 Tone pitch Velocity for the Note Off event From most devices ignored Aftertouch OxA0 Tone pitch on which the command Modified velocity The velocity of a note is causes if there is a note turned changed on Control Change OxBO Number of the regulator There Controlled variable are some predefined regulators in the MIDI specification e g 00 Choice of the sound bank 07 Volume OA Stereo position Program Change OxCO Number of the program The None Choice of the melodic assignment of instruments is instrument or drums determined in the MIDI specification Enhanced standards use the regulator sound bank for sound variation Channel Pressure OxDO Modified velocity None Changing of the velocity of all running notes in the channel Pitch Bend OxEO Pitch bend Changing the running notes tune Table 2 Summary of most common MIDI Status amp Data Bytes ar S ee p pet WOR eS
17. e most common messages and have at most two data bytes following the status byte The channel messages such as Note On and Note Off are all short messages as are some other messages e SysexMessages contain system exclusive MIDI messages They may have many bytes and generally contain manufacturer specific instructions 12 e MetaMessages occur in MIDI files but not in MIDI wire protocol Meta messages contain data such as lyrics or tempo settings that might be useful to sequencers but that are usually meaningless for synthesizers 3 1 2 MIDI Events As we ve seen standard MIDI files contain events that are wrappers for raw MIDI messages along with timing information An instance of the Java Sound API s MidiEvent class represents an event such as might be stored in a standard MIDI file The API for MidiEvent includes methods to set and get the event s timing value There s also a method to retrieve its embedded raw MIDI message which is an instance of a subclass of MidiMessage The embedded raw MIDI message can be set only when constructing the MidiEvent 3 1 3 Sequences and Tracks As mentioned earlier a standard MIDI file stores events that are arranged into tracks Usually the file represents one musical composition and usually each track represents a part such as might have been played by a single instrumentalist Each note that the instrumentalist plays is represented by at least two events a Note On that star
18. eate an URL object String s tpl getStringElem 0 try url new URL s catch MalformedURLException e System out printlin e The base module in the Java Sound API s messaging system is MidiDevice a Java language interface MidiDevice include sequencers which record play load and edit sequences of time stamped MIDI messages synthesizers which generate sounds when triggered by MIDI messages and MIDI input and output ports through which data comes from and goes to external MIDI devices In our case we need to load a sequencer to access the MIDI sequence of our URL object We also try to load a synthesizer so we can extend in future our foreign function to play back a MIDI sequence Sequencer sequencer try Try to load the default Sequencer sequencer MidiSystem getSequencer if sequencer instanceof Synthesizer synthesizer Synthesizer sequencer channels synthesizer getChannels catch Exception ex ex printStackTrace return Now we create a sequence we invoke MidiSystem s overloaded method get Sequence The method is able to get the sequence from an InputStream a File or an URL like in our case The method returns a Sequence object which we can access now Sequence currentSound MidiSystem getSequence url Get some information about the MIDI Sequence duration currentSound getMicrosecondLength 1000000 0 tickLength currentSound getTickLength
19. ger ChannelEvent channel integer command integer MetaEvent metaType integer metaData vector of integer metaTypeAsString charstring SysexEvent SysexData vector of integer data1 integer data2 integer commandAssString charstring noteEvent noteEvents note charstring octave integer Fig 1 The object oriented database scheme for Midi 19 5 Examples Well let us see now what are the benefits of this MIDI wrapper for the object oriented database AMOS II In this chapter I want to show some reasonable queries to approximate the usefulness of this wrapper We will load some MIDI files in our AMOS II database through the web and make some queries to retrieve selected information First of all we need to set up the environment properly and create the database Refer to Appendix C to see the installing instructions Once the environment is running we load some MIDI files into AMOS II JavaAMOS 1 gt loadMidi http files midifarm com midifiles general_midi sinatra_frank myway4 mid JavaAMOS 2 gt loadMidi http files midifarm com midifiles general_midi roxette roxette sleepinginmycar mid After we loaded as many MIDI files as we want into AMOS II we save the database by the command save midi dmp Now we can make some queries with AMOS II query language AMOSQL Similarly to SQL AMOSQL is a combination of DDL Data Definition Language and a
20. he status byte in a message are known as data bytes Certain MIDI messages known as channel messages have a status byte that contains four bits to specify the channel number There are therefore 16 MIDI channels devices that receive MIDI messages can be set to respond to channel messages on all or only one of these virtual channels Often each MIDI channel which shouldn t be confused with a channel of audio is used to send the notes for a different instrument As an example two common channel messages are Note On and Note Off which start a note sounding and then stop it respectively These two messages each take two data bytes the first specifies the note s pitch and the second its velocity how fast the key is depressed or released assuming a keyboard instrument is playing the note MIDI wire protocol defines a streaming model for MIDI data A central feature of this protocol is that the bytes of MIDI data are delivered in real time in other words they are streamed The data itself contains no timing information each event is processed as it s received and it s assumed that it arrives at the correct time That model is fine if the notes are being generated by a live musician but it s insufficient if you want to store the notes for later playback or if you want to compose them out of real time This limitation is understandable when you realize that MIDI was originally designed for musical performance as a way for a ke
21. ification 1 0 http www ibiblio org emusic l info docs FA Qs MIDI doc Rainer Jahn Spezifikation MIDI Datei December 5 1999 http www zbs ilmenau de rainer midispez Java 2 Platform SE v1 3 1 Package javax sound midi http java sun com j2se 1 3 docs api javax sound midi package summary html 24
22. mands type into a string ChannelCommands Command Integer obtaining the channel commands commandsString String representing the translated integer value of a channel command NoteEvents notelnt Integer obtaining the integer value of a Note On or Note Off event noteString String representing the note of a Note On or Note Off event as a string Octave Integer obtaining the octave of a Note On or Note Off event MetaCommands MetaTypelInt Integer obtaining the meta type of a meta event MetaTypeString String representing the meta type translated into a string 18 Midi url charstring fileName charstring length integer duration real numberOfTracks integer tickLength integer resolution integer divisionType real ChannelCommands commandsString charstring command integer NoteEvents octave integer notelnt integer noteString charstring tracks gt MetaCommands metaT ypelnt integer metaT ypeString charstring Legend Entitiy_name Track numberOfEvents integer ticks integer attribute type midievents gt Entities with attributes and their data types E gt Inheritance is a relationship gt gt Relationship with logical direction Single Object __ Set of objects e Vector of objects MidiEvent timeStamp integer length integer statusByte integer midiMessage vector of inte
23. may remember key signature data is stored as a meta event in our database scheme The key signature has the meta type value 89 that is translated into the string Key Signature The data itself is represented as a vector of two integers To find now a song written in c major we have to look for a vector with two zeros as integers For more details see table 4 First we create a derived function to look for the specific vector of integers that represents a c major song JavaAMOS 4 gt create function major metaevent m gt metaevent as select m from metaevent m where metadataint m 0 0 and metadataint m 1 0 and metatypeasstring m Key Signature The following command will now retrieve all the MIDI songs written in c major JavaAMOS 5 gt select major m from metaevent m Analogical we can look for all MIDI songs written in a minor JavaAMOS 6 gt create function minor metaevent m gt metaevent as select m from metaevent m where metadataint m 0 0 and metadataint m 1 1 and metatypeasstring m Key Signature JavaAMOS 7 gt select minor m from metaevent m There are many other valuable queries that can be executed Last but not least I want to show a query which can be improved later on to find patterns of note events in a MIDI object We want to retrieve all Note On events on a specific channel of a certain MIDI object in order of their appearance First we have to create a derived function to c
24. ompare two channel events ordered by their timestamps JavaAMOS 8 gt create function orderByTimestamp channelevent ca channelevent cb gt boolean as select true where timestamp ca lt timestamp cb 21 The following command will retrieve all Note On events in channel four of the MIDI song My way by Frank Sinatra The sort function will order the results regarding our derived function orderByTimestamp JavaAMOS 9 gt sort select ce from channelevent ce wher command ce 144 and channel ce 4 and filename ce midifiles general_midi sinatra_frank myway4 mid orderByTimestamp 22 6 Summary Today we find databases in many kind of use to store every kind of data we can imagine The goal of this project was now to access any given midi file through a database wrapper and store the data of the MIDI file in an object oriented database called AMOS II This database wrapper is implemented in Java and runs as a foreign function in AMOS II The function takes the name of a MIDI file as a parameter accesses it trough the web and then emits a stream of AMOS II objects and attributes according to the developed schema to the mediator To understand how this works I want to give a brief overview over the MIDI specification and the object oriented database scheme How does the MIDI structure look like Each MIDI stream can be divided in its single tracks those tracks in turn consist of different sequenti
25. re of MIDI Finally I want to give a short set over the basic structure of MIDI on a rather low level of the MIDI specification A standard MIDI file consists of a header and one or more tracks lt Standard MIDI File gt lt Header gt lt Track gt lt Track gt The first 4 bytes of the header are the identifier of a MIDI file followed by some information bytes lt Header gt 4D 54 68 64 00 00 00 06 00 xx yy yy ZZ zz 00 01 Type of the MIDI File Type 0 File has only one track Type 1 File has several tracks XX yy yy Number of Tracks ZZ Zz Timestamp Number of Time elements per 1 4 note should be divided trough 24 Common values are 00 78 120 00 FO 240 01 EO 480 03 CO 960 A track consists of a header and one or more events separated by a time difference lt Track gt lt Track Header gt lt Time difference gt lt Event gt lt Time difference gt lt Event gt The track header has following information bytes lt Track Header gt 4D 54 72 6B xx XX XX XX Whereby xx xx xx xx is the length of the track in bytes without the track header itself The time difference between the events is measured in timestamps The first time difference counts from the beginning of the piece of music to the first event of the track and is coded in variable length An event can be either a channel event a meta event or a sysex event and is the elementary command to the playback device
26. reign function should select a MIDI object and load it into a sequencer to play back the song Also many other fields of applications can be implemented such as editing tracks or events For example adding new tracks to a MIDI object or removing them changing the instrument on a channel or adding lyrics or text to the MIDI object Pattern matching functions can also be invented to search for a pattern of note events That might be very useful if you remember a piece of the melody of a song but have forgotten the name or interpret 23 7 References 1 2 3 4 5 6 7 8 Tore Risch Vanja Josifovski Timour Katchaounov AMOS II Concepts June 23 2000 http www dis uu se udbl amos doc amos_concepts html Staffan Flodin Vanja Josifovski Timour Katchaounov Tore Risch Martin Sk ld and Magnus Werner AMOS II User s Manual AMOS II Beta Release 3 June 23 2000 http www dis uu se udbl amos doc amos_users_guide html Tore Risch Introduction to AMOSQL Department of Information Science Uppsala University Sweden April 23 2001 http www dis uu se udbl engdb amosql pdf Gustav Fahl and Tore Risch AMOS II Introduction Uppsala Database Laboratory Department of Information Science Uppsala University Sweden October 1 1999 Daniel Elin and Tore Risch AMOS II Java Interfaces Uppsala Database Laboratory Department of Information Science Uppsala University Sweden August 25 2000 Joe M MIDI Spec
27. rs in MIDI However external MIDI hardware devices are still essential for some important music applications The software portion of the MIDI specification is extensive This portion concerns the structure of MIDI data and how devices such as synthesizers should respond to that data It is important to understand that MIDI data can be streamed or sequenced This duality reflects two different parts of the Complete MIDI 1 0 Detailed Specification e MIDI 1 0 e Standard MIDI Files I will explain what streaming and sequencing means by examining the purpose of each of these two parts of the MIDI specification 2 1 Streaming Data in the MIDI Wire Protocol The first of these two parts of MIDI specification describes what is known informally as MIDI wire protocol MIDI wire protocol which is the original MIDI protocol is based on the assumption that the MIDI data is being sent over a MIDI cable the wire The cable transmits digital data from one MIDI device to another Each of the MIDI devices might be a musical instrument or a similar device or it might be a general purpose computer equipped with a MIDI capable sound card or a MIDI to serial port interface MIDI data as defined by MIDI wire protocol is organized into messages The different kinds of message are distinguished by the first byte in the message known as the status byte Status bytes are the only bytes that have the highest order bit set to 1 The bytes that follow t
28. ted sound editors or graphical tools but it provides capabilities upon which such programs can be built It emphasizes low level control beyond that commonly expected by the end user The Java Sound API includes support for both digital audio and MIDI data These two major modules of functionality are provided in separate packages e javax sound sampled This package specifies interfaces for capture mixing and playback of digital sampled audio e javax sound midi This package provides interfaces for MIDI synthesis sequencing and event transport Two other packages permit service providers as opposed to application developers to create custom software components that extend the capabilities of an implementation of the Java Sound API e javax sound sampled spi e javax sound midi spi The rest of the chapter I will concentrate on the classes of the javax sound midi package which are relevant for accessing and manipulating MIDI files 3 1 The Java Sound API s Representation of MIDI Data 3 1 1 MIDI Messages MidiMessage is an abstract class that represents a raw MIDI message A raw MIDI message is usually a message defined by the MIDI wire protocol It can also be one of the events defined by the Standard MIDI Files specification but without the event s timing information There are three categories of raw MIDI message represented in the Java Sound API by these three respective MidiMessage subclasses e ShortMessages are th
29. ts the note and a Note Off that ends it The track may also contain events that don t correspond to notes such as meta events which were mentioned above The Java Sound API organizes MIDI data in a three part hierarchy e Sequence e Track e MidiEvent A Track is a collection of MidiEvents and a Sequence is a collection of Tracks This hierarchy reflects the files tracks and events of the Standard MIDI files specification Note this is a hierarchy in terms of containment and ownership it s not a class hierarchy in terms of inheritance Each of these three classes inherits directly from java lang Object Sequences can be read from MIDI files or created from scratch and edited by adding Tracks to the Sequence or removing them Similarly MidiEvents can be added to or removed from the tracks in the sequence 3 2 Use of the Java Sound API In this chapter I want to show some basic functions of the Java Sound API relating to my foreign function It should show how the classes and interfaces of the Java Sound API are used to stream a MIDI file through the net and accessing its tracks events and so on The following code fragments are taken of my foreign function and can be read more detailed in Appendix A 13 In order to load a MIDI file into a sequencer and finally into AMOS II we have to deliver an URL of an existing MIDI file to the foreign function We take the URL parameter of the foreign function from Amos toploop to cr
30. unan niaaa teed en 24 8 APPENDIX zinian ERROR BOOKMARK NOT DEFINED A Code listing and comments ssesessosossososesesscscsecsose Error Bookmark not defined B Database creation scripts ssessososeossosseeeseossseoesoseesese Error Bookmark not defined C Installing instructions seseososeososesessosessososcscsscscsscecse Error Bookmark not defined Table 1 Summary of MIDI Status Bytes 0 eee sscecceessceceesaceecesaececeseneecessseaeeesesaeeeees 8 Table 2 Summary of most common MIDI Status amp Data Bytes eee eeeceeeeseeneeceeenneeeees 9 Table 3 Summary of MIDI Note Numbers for Different Octaves 0 ce eeeeeeeeeseeeceeeneeeeees 9 Table 4 Selected meta event types ceeeeccccesseceecesseeeecesseceeeesaeeceeseaeeecessaeeeceeeeeeeseeaeeeeee 10 Table 5 Syntactic variants Of sysex events 2 0 0 eeeeeseeeeeceseceeeseseeceeseeeecessuceeeceseaeeeseeaeeeeees 11 Fig 1 The object oriented database scheme for Midi e ee eeseeceeseeeeeceeseeeeeceneaeeesenaeeeeees 19 1 Introduction In the 80ties the relational database models prevailed in the practice In many fields of application of the commercial and administrative world they found and find still their use And this is totally entitled because for these areas the data model is optimally developed In the beginning of the 90ties the database world expanded into the area of multimedia applications and one determined quickly that the until now well
31. ust stand at the end of each track The event is represented including the time difference by 00 FF 2F 00 Tempo 51 03 XX XX XX Tempo in microseconds per quarter note Time Signature 58 04 xx yy zz 08 Beat in MIDI ticks per quarter note Key Signature 59 02 xx yy xx gt 0 key has xx crosses xx lt 0 key has xx B s xx 0 C major a minor yy 0 major yy 1 minor Track Name 03 Any Any Name of the track usually description of the instrument The name of the first track is interpreted often as song title Instrument 04 Any Any All sequencers do not indicate description of the instrument Text 01 Any Any Any comment Song Text 05 Any Any Text module to sing with Should stand directly after the relevant Note On event in the melody track Does not become indicated by all sequencers User defined 7F Any Any Any Table 4 Selected meta event types 2 3 3 Sysex Events These are system exclusive commands that are used by the MIDI standard In a standard MIDI file sysex events are represented as follows lt Sysex Event gt FO lt Length gt lt Content gt F7 lt Length gt lt Content gt The lt Length gt parameter indicates the length of the following content in bytes Long command sequences are supposed to be transmitted in little portions with certain intervals Therefore there are several syntactic variants that all can be led back to both named
32. yboard musician to control more than one synthesizer back in the days before many musicians used computers The first version of the specification was released in 1984 2 2 Sequenced Data in Standard MIDI Files The Standard MIDI Files part of the MIDI specification addresses the timing limitation in MIDI wire protocol A standard MIDI file is a digital sequence that contains MIDI events An event is simply a MIDI message as defined in the MIDI wire protocol but with an additional piece of information that specifies the event s timing There are also some events that don t correspond to MIDI wire protocol messages The additional timing information is a series of bytes that indicates when to perform the operation described by the message In other words a standard MIDI file specifies not just which notes to play but exactly when to play each of them It s a bit like a musical score The information in a standard MIDI file is referred to as a sequence A standard MIDI file contains one or more tracks Each track typically contains the notes that a single instrument would play if live musicians performed the music A sequencer is a software or hardware device that can read a sequence and deliver the MIDI message contained in it at the right time A sequencer is a bit like an orchestra conductor it has the information for all the notes including their timings and it tells some other entity when to perform the notes 2 3 The basic structu
33. ysexEvent are connected through an is a relation with the super type Besides the inherited attributes each event type has its own attributes ChannelEvent Channel Integer obtaining the MIDI channel associated with this event Command Integer obtaining the MIDI command associated with this event Data Integer obtaining the first data byte in the message Data2 Integer obtaining the second data byte in the message CommandAsString String representing the command translated to a meaningful String NoteEvent derived function to translate the channel event command into a meaningful string Information is retrieved from type NoteEvents Note String representing the note of a Note On or a Note Off channel event Octave Integer obtaining the octave of a Note On or a Note Off channel event MetaEvent MetaType Integer obtaining the type of the meta event MetaDataInt Obtains a copy of the data for the meta message The returned array of bytes does not include the status byte or the message length data The length of the data for the meta message is the length of the array Note that the length of the entire message includes the status byte and the meta message type byte and therefore may be longer than the returned array In our database scheme the bytes are transformed into integers and stored as a vector of integers if the data is representing an integer value of the MIDI file MetaDataString Same as MetaDatalInt except it contains a string If the
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