diff options
Diffstat (limited to 'core.lv2')
| -rw-r--r-- | core.lv2/lv2.ttl | 140 |
1 files changed, 72 insertions, 68 deletions
diff --git a/core.lv2/lv2.ttl b/core.lv2/lv2.ttl index 8d33877..f77a2c4 100644 --- a/core.lv2/lv2.ttl +++ b/core.lv2/lv2.ttl @@ -34,12 +34,11 @@ An LV2 Resource (e.g. plugin, specification, or any other LV2 related thing). lv2:Specification a rdfs:Class , owl:Class ; rdfs:subClassOf lv2:Resource ; - rdfs:comment """ + lv2:documentation """ An LV2 specification (i.e. this specification, or an LV2 extension). -Specification data, like plugin data, is distributed in standardized bundles -so hosts may discover all present LV2 data. See http://lv2plug.in/docs for -more details. +Specification data, like plugin data, is distributed in bundles +so hosts may discover <em>all</em> present LV2 data. """ . lv2:documentation a rdf:Property , owl:DatatypeProperty ; @@ -85,75 +84,72 @@ devices). See <a href="http://www.w3.org/TR/xhtml-basic/#s_xhtmlmodules" lv2:documentation """ <h4>Overview</h4> -<p>LV2 gives programmers the ability to write audio processors (or -<q>plugins</q>) in C/C++ which can be dynamically loaded into a range of -applications (or <q>hosts</q>).</p> - -<p>This <q>core</q> specification is deliberately as short and simple as -possible, but is designed so that <q>extensions</q> can be defined to add more -advanced features. The shared library portion of the API includes only what -must necessarily be written in code. The information required to use a plugin -is in a companion data file, written in <a -href="http://www.w3.org/TeamSubmission/turtle/">Turtle</a>. Plugin libraries do -not contain enough information to make use of the plugin possible; the data -file is mandatory. This makes using, adding, and manipulating plugin data -flexible and avoids binary compatibility issues.</p> - -<p>Plugins can operate on any type of data, which is input/output via -<q>ports</q>. Data is processed by first <q>connecting</q> each port to a -buffer, then repeatedly calling a plugin's <code>run()</code> method to process -a <q>block</q> of data of some host-specified length (measured in audio -frames).</p> - -<p>The LV2 core specification defines two types of port, equivalent to those in -<a href="http://www.ladspa.org/">LADSPA</a>: <q>control</q> and -<q>audio</q>. Audio data is communicated using arrays with one -<code>float</code> element per sample, allowing a block of audio to be -processed by the plugin in a single call to <code>run()</code>. Control data is -communicated using single <code>float</code> values, which are fixed and valid -for the duration of the call to <code>run()</code>. Thus the <q>control -rate</q> is determined by the block size, which is controlled by the host (and -not necessarily constant).</p> - -<p>Plugins reside in shared object files suitable for dynamic linking (e.g. via -<code>dlopen()</code>). This <q>library</q> provides one or more <a +<p>LV2 is an interface for writing audio processors, or <q>plugins</q>, in +C/C++ which can be dynamically loaded into many applications, or <q>hosts</q>. +This <q>core</q> specification is simple and minimal, but is designed so that +<q>extensions</q> can be defined to add more advanced features, making it +possibly to implement nearly any feature imaginable.</p> + +<p>LV2 maintains a strong distinction between <q>code</q> and <q>data</q>. +Plugin code is in a shared library, while data is in a companion data file +written in <a href="http://www.w3.org/TeamSubmission/turtle/">Turtle</a>. +Code, data, and any other resources (e.g. waveforms) are shipped together in a +<q>bundle</q> directory. The code contains only the executable portions of the +plugin which inherently <em>must</em> be written in code. All other data is +provided in the data file(s). This makes plugin data flexible and extensible, +and allows the host to do everything but run the plugin without executing any +code at all. Among other advantages, this makes hosts more robust (broken +plugins can't crash a host during discovery) and allows non-C programs to work +with LV2 data (such as the pure <a href="http://python.org">Python</a> script +which generated this page). LV2 itself and extensions are distributed +similarly.</p> + +<p>An LV2 plugin library is suitable for dynamic loading (e.g. via +<code>dlopen()</code>) and provides one or more <a href="urn:struct:LV2_Descriptor">plugin descriptors</a> via the -<code>lv2_descriptor()</code> function. These plugins can be instantiated to -create plugin <q>instances</q>, which can be run directly on data or connected +<code>lv2_descriptor()</code> function. These can be instantiated to create +plugin <q>instances</q>, which can be run directly on data or connected together to perform advanced signal processing tasks.</p> -<h4>Threading Rules</h4> - -<p>Certain hosts may need to call the functions provided by a plugin from -multiple threads. For this to be safe, the plugin must be written so that those -functions can be executed simultaneously without problems. To facilitate this, -the functions provided by a plugin are divided into classes:</p> +<p>Plugins communicate via <q>ports</q>, which can transmit any type of data. +Data is processed by first <q>connecting</q> each port to a buffer, then +repeatedly calling a plugin's <code>run()</code> method to process blocks of +data.</p> + +<p>This core specification defines two types of port, equivalent to those in <a +href="http://www.ladspa.org/">LADSPA</a>: <a +href="#ControlPort">ControlPort</a> and <a href="#AudioPort">AudioPort</a>. +Audio ports contain arrays with one <code>float</code> element per sample, +allowing a block of audio to be processed in a single call to +<code>run()</code>. Control ports contain single <code>float</code> values, +which are fixed and valid for the duration of the call to <code>run()</code>. +Thus the <q>control rate</q> is determined by the block size, which is +controlled by the host (and not necessarily constant).</p> -<dl> -<dt>Discovery Class</dt> -<dd>lv2_descriptor(), -LV2_Descriptor::extension_data()</dd> - -<dt>Instantiation Class</dt> -<dd>LV2_Descriptor::instantiate(), -LV2_Descriptor::cleanup(), -LV2_Descriptor::activate(), -LV2_Descriptor::deactivate()</dd> - -<dt>Audio Class</dt> -<dd>LV2_Descriptor::run(), -LV2_Descriptor::connect_port()</dd> -</dl> - -<p>Plugin functions in any class MUST NOT manipulate any state which might -affect other plugin or host code, e.g. by using non-reentrant global -functions.</p> +<h4>Threading Rules</h4> -<p>Extensions to this specification which add new plugin functions MUST declare -in which of these classes the functions belong, or define new classes for -them. Extensions which add new host-provided functions MUST declare from which -of these classes the functions may be called, or otherwise precisely describe -their threading rules.</p> +<p>To faciliate use in multi-threaded programs, LV2 functions are partitioned +into several threading classes:</p> + +<table> +<tr> + <th>Discovery Class</th> + <th>Instantiation Class</th> + <th>Audio Class</th> +</tr> +<tr> + <td>lv2_descriptor()</td> + <td>LV2_Descriptor::instantiate()</td> + <td>LV2_Descriptor::run()</td> +</tr> +<tr> + <td>LV2_Descriptor::extension_data()</td> + <td>LV2_Descriptor::cleanup()</td> + <td>LV2_Descriptor::connect_port()</td> +</tr> +<tr><td></td><td>LV2_Descriptor::activate()</td><td></td></tr> +<tr><td></td><td>LV2_Descriptor::deactivate()</td><td></td></tr> +</table> <p>The rules that hosts MUST follow are:</p> <ul> @@ -168,6 +164,14 @@ no other functions for that instance may run.</li> <p>Any simultaneous calls that are not explicitly forbidden by these rules are allowed. For example, a host may call <code>run()</code> for two different plugin instances simultaneously.</p> + +<p>Plugin functions in any class MUST NOT manipulate any state which might +affect other plugin or host code, e.g. by using non-reentrant global +functions.</p> + +<p>Extensions to this specification which add new functions MUST declare in +which of these classes the functions belong, define new classes for them, or +otherwise precisely describe their threading rules.</p> """ . ############ |