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openmusic:dev-resources:containers [2011/01/28 18:43] jean-admin |
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| - | ===== Containers and simple containers ===== | ||
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| - | In OM, every musical object is an instance of some subclass of either **simple-container** (atomic objects) or **container** (compound object). | ||
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| - | This is the (partial) inheritance tree starting at **simple-container**: | ||
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| - | {{ :openmusic:dev-resources:containerclasses.gif| }} | ||
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| - | .. and this is the class definitions: | ||
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| - | <code lisp> | ||
| - | (defclas simple-container () | ||
| - | ((parent :initform nil) | ||
| - | (Qvalue :initform 1) | ||
| - | (QTempo :initform 60) | ||
| - | (offset :initform 0) | ||
| - | (extent :initform 1))) | ||
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| - | (defclas container (simple-container) | ||
| - | ((inside :initform nil))) | ||
| - | </code> | ||
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| - | The slot //inside// in a //container// stores a list of sub-containers that are either instances of //container// (nodes of the container tree) or //simple-container// (leaves of the container tree). | ||
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| - | These sub-containers are positioned and dimensioned in time. | ||
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| - | All the slots that give the time specification (//QValue//, //Qtempo//, //offset//, //extent//) are defined in the class //simple-container// (remember that a //container// is also a //simple-container//). | ||
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| - | Subcontainers are really sub-trees of the container tree. They define a local time scale, in the following way: | ||
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| - | * **qvalue** is an integer, such that 1 / //qvalue// defines a rational fraction of the quarter note.\\ This is the abstract time unit in which the //extent// is expressed | ||
| - | * **qtempo** is an integer. Defines a tempo expressed as a frequency of the quarter note per minute (e.g. q.n. = 60).\\ Gives an interpretation of //Qvalue// in the physical time. | ||
| - | * **offset** is an integer.\\ Time offset of the container from the beginning of its super-container. //offset// is expressed in the time scale defined by the //qvalue// slot of the super-container. | ||
| - | * **extent** is an integer. Expresses the duration of the container, in the time scale defined by the //qvalue//. | ||
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| - | The following pictures show the container tree-structure. The slots //offset, qvalue and extent// are drawn inside or outside the container rectangle, depending on the time scale in which they are expressed. | ||
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| - | <P><CENTER><IMG SRC="D05.gif" WIDTH="230" HEIGHT="96" ALIGN="BOTTOM" | ||
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| - | BORDER="0" NATURALSIZEFLAG="3"></CENTER></P> | ||
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| - | <br><br> | ||
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| - | <P><CENTER><IMG SRC="d04.gif" WIDTH="505" HEIGHT="166" ALIGN="BOTTOM" | ||
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| - | BORDER="0" NATURALSIZEFLAG="3"></CENTER></P> | ||
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| - | <P>Using the qvalue mechanism, a local time scale can be defined | ||
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| - | at each level of the container tree. This helps maintaining complex | ||
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| - | container structures where some parts could belong to score level | ||
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| - | time scales while other could belong to audio level time scales, | ||
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| - | while still restraining to integer computation. Restraining to | ||
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| - | integer computation is very important for rhythm quantization | ||
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| - | issues.</P> | ||
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| - | <P>Here is an example where we use some musical subclasses of | ||
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| - | container and simple-container.</P> | ||
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| - | <P><CODE>voice</CODE> is a subclass of <CODE>container</CODE>. | ||
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| - | It defines a musical voice in a score. Its <CODE>inside</CODE> | ||
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| - | slot is a list of <CODE>measure</CODE>, another <CODE>container</CODE>. | ||
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| - | The <CODE>inside</CODE> slot of measures are either single <CODE>notes</CODE> | ||
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| - | (<CODE>simple-container</CODE>), <CODE>chords</CODE>, or <CODE>groups</CODE> | ||
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| - | (<CODE>container</CODE>). <CODE>Groups</CODE> are groups of chords | ||
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| - | or notes that belong to a beat (e.g. three chords making up a | ||
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| - | triplet).</P> | ||
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| - | <P>The next picture shows the instantiation tree starting from | ||
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| - | <CODE>voice</CODE>. The arrows express the <CODE>inside</CODE> | ||
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| - | slot of the object they start from.</P> | ||
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| - | <P><CENTER><IMG SRC="d02.gif" WIDTH="421" HEIGHT="212" ALIGN="BOTTOM" | ||
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| - | BORDER="0" NATURALSIZEFLAG="3"></CENTER></P> | ||
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| - | <br> | ||
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| - | <P>Here is an example of a measure :</P> | ||
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| - | <P><CENTER><IMG SRC="I13.gif" WIDTH="378" HEIGHT="117" ALIGN="BOTTOM" | ||
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| - | BORDER="0" NATURALSIZEFLAG="3"></CENTER></P> | ||
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| - | <P>and the instantiation tree showing the values for <CODE>qvalue, | ||
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| - | offset </CODE>and <CODE>extent</CODE> slots.</P> | ||
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| - | <P><CENTER><IMG SRC="D06.gif" WIDTH="476" HEIGHT="322"></CENTER></P> | ||
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| - | <P>Here is another example where we superpose the previous voice | ||
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| - | and an audio file which lasts 1230 ms.</P> | ||
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| - | <P><CENTER><IMG SRC="D07.gif" WIDTH="284" HEIGHT="264"</CENTER> | ||
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