/* LV2 - LADSPA (Linux Audio Developer's Simple Plugin API) Version 2.0 * *** PROVISIONAL *** * * Copyright (C) 2000-2002 Richard W.E. Furse, Paul Barton-Davis, Stefan * Westerfeld * Copyright (C) 2006 Steve Harris, Dave Robillard. * * This header is free software; you can redistribute it and/or modify it * under the terms of the GNU Lesser General Public License as published * by the Free Software Foundation; either version 2.1 of the License, * or (at your option) any later version. * * This header is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Lesser General Public License for more details. * * You should have received a copy of the GNU Lesser General Public * License along with this library; if not, write to the Free Software * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 * USA. */ #ifndef LV2_H_INCLUDED #define LV2_H_INCLUDED #include #ifdef __cplusplus extern "C" { #endif /* ************************************************************************* */ /* Overview: * * There are a large number of open source and free software synthesis * packages in use or development at this time. This API ('LV2') * attempts to give programmers the ability to write simple 'plugin' * audio processors in C/C++ and link them dynamically ('plug') into * a range of these packages ('hosts'). It should be possible for any * host and any plugin to communicate completely through this interface. * * This API is deliberately as short and simple as possible. * The information required to use a plugin is in a companion data * (RDF) file. The shared library portion of the API (defined in this * header) does not contain enough information to make use of the plugin * possible - the data file is mandatory. * * Plugins are expected to distinguish between control rate and audio * rate data. Plugins have 'ports' that are inputs or outputs for audio * or control data and each plugin is 'run' for a 'block' corresponding * to a short time interval measured in samples. Audio rate data is * communicated using arrays with one element per sample processed, * allowing a block of audio to be processed by the plugin in a single * pass. Control rate data is communicated using single values. Control * rate data has a single value at the start of a call to the 'run()' * function, and may be considered to remain this value for its duration. * Thus the 'control rate' is determined by the block size, controlled * by the host. The plugin may assume that all its input and output * ports have been connected to the relevant data location (see the * 'connect_port()' function below) before it is asked to run. * * Plugins will reside in shared object files suitable for dynamic linking * by dlopen() and family. The file will provide a number of 'plugin * types' that can be used to instantiate actual plugins (sometimes known * as 'plugin instances') that can be connected together to perform tasks. * * This API contains very limited error-handling. */ /* ************************************************************************* */ /** Plugin Handle. * * This plugin handle indicates a particular instance of the plugin * concerned. It is valid to compare this to NULL (0 for C++) but * otherwise the host MUST not attempt to interpret it. The plugin * may use it to reference internal instance data. */ typedef void * LV2_Handle; /* ************************************************************************* */ /** Host feature. * * These are passed to a plugin's instantiate method to represent a special * feature the host has which the plugin may depend on. This is to allow * extensions to the LV2 specification without causing any breakage. The base * LV2 specification does not define any host features; hosts are not required * to use this facility. */ typedef struct _LV2_Host_Feature { /** A globally unique, case-sensitive identifier for this feature. * * This MUST be defined in the specification of any LV2 extension which * defines a host feature. */ const char * URI; /** Pointer to arbitrary data. * * This is to allow hosts to pass data to a plugin (simple values, data * structures, function pointers, etc) as part of a 'feature'. The LV2 * specification makes no restrictions on the contents of this data. * The data here MUST be cleary defined by the LV2 extension which defines * this feature. * If no data is required, this may be set to NULL. */ void * data; } LV2_Host_Feature; /* ************************************************************************* */ /** Descriptor for a Type of Plugin. * * This structure is used to describe a plugin type. It provides a number * of functions to instantiate it, link it to buffers and run it. */ typedef struct _LV2_Descriptor { /** A globally unique, case-sensitive identifier for this plugin type. * * All plugins with the same URI MUST be compatible in terms of 'port * signature', meaning they have the same number of ports, same port * shortnames, and roughly the same functionality. URIs should * probably contain a version number (or similar) for this reason. * * Rationale: When serializing session/patch/etc files, hosts MUST * refer to a loaded plugin by the plugin URI only. In the future * loading a plugin with this URI MUST yield a plugin with the * same ports (etc) which is 100% compatible. */ const char * URI; /** Function pointer that instantiates a plugin. * * A handle is returned indicating the new plugin instance. The * instantiation function accepts a sample rate as a parameter as well * as the plugin descriptor from which this instantiate function was * found. This function must return NULL if instantiation fails. * * BundlePath is a string of the path to the plugin's .lv2 bundle * directory, it MUST not include the trailing /. * * HostFeatures is a NULL terminated array of the URIs of the LV2 * features that the host supports. Plugins may refuse to instantiate * if required features are not found here (however hosts SHOULD NOT use * this as a discovery mechanism, instead reading the data file before * attempting to instantiate the plugin). * * Note that instance initialisation should generally occur in * activate() rather than here. If a host calls instantiate, it MUST * call cleanup() at some point in the future. */ LV2_Handle (*instantiate)(const struct _LV2_Descriptor * Descriptor, uint32_t SampleRate, const char * BundlePath, const LV2_Host_Feature** HostFeatures); /** Function pointer that connects a port on a plugin instance to a memory * location where the block of data for the port will be read/written. * * The data location is expected to be an array of void * (typically * float *) for audio ports or a single void * value for control * ports. Memory issues are managed by the host. The plugin must * read/write the data at these locations every time run() is called * and the data present at the time of this connection call MUST NOT * be considered meaningful. * * connect_port() may be called more than once for a plugin instance * to allow the host to change the buffers that the plugin is reading * or writing. These calls may be made before or after activate() * or deactivate() calls. * * connect_port() must be called at least once for each port before * run() is called. The plugin must pay careful attention to the block * size passed to the run function as the block allocated may only just * be large enough to contain the block of data (typically samples), and * is not guaranteed to be constant. * * Plugin writers should be aware that the host may elect to use the * same buffer for more than one port and even use the same buffer for * both input and output (see LV2_PROPERTY_INPLACE_BROKEN (FIXME)). * However, overlapped buffers or use of a single buffer for both * audio and control data may result in unexpected behaviour. */ void (*connect_port)(LV2_Handle Instance, uint32_t Port, void * DataLocation); /** Function pointer that initialises a plugin instance and activates * it for use. * * This is separated from instantiate() to aid real-time support and so * that hosts can reinitialise a plugin instance by calling deactivate() * and then activate(). In this case the plugin instance must reset all * state information dependent on the history of the plugin instance * except for any data locations provided by connect_port(). If there * is nothing for activate() to do then the plugin writer may provide * a NULL rather than an empty function. * * When present, hosts MUST call this function once before run() * is called for the first time. This call SHOULD be made as close * to the run() call as possible and indicates to real-time plugins * that they are now live, however plugins MUST NOT rely on a prompt * call to run() after activate(). activate() may not be called again * unless deactivate() is called first (after which activate() may be * called again, followed by deactivate, etc. etc.). If a host calls * activate, it MUST call deactivate at some point in the future. * * Note that connect_port() may be called before or after a call to * activate(). */ void (*activate)(LV2_Handle Instance); /** Function pointer that runs a plugin instance for a block. * * Two parameters are required: the first is a handle to the particular * instance to be run and the second indicates the block size (in * samples) for which the plugin instance may run. * * Note that if an activate() function exists then it must be called * before run(). If deactivate() is called for a plugin instance then * the plugin instance may not be reused until activate() has been * called again. * * If the plugin has the property LV2_PROPERTY_HARD_RT_CAPABLE then * there are various things that the plugin MUST NOT do within the run() * function (see above). */ void (*run)(LV2_Handle Instance, uint32_t SampleCount); /** This is the counterpart to activate() (see above). If there is * nothing for deactivate() to do then the plugin writer may provide * a NULL rather than an empty function. * * Hosts must deactivate all activated units after they have been run() * for the last time. This call SHOULD be made as close to the last * run() call as possible and indicates to real-time plugins that * they are no longer live, however plugins MUST NOT rely on prompt * deactivation. Note that connect_port() may be called before or * after a call to deactivate(). * * Note that deactivation is not similar to pausing as the plugin * instance will be reinitialised when activate() is called to reuse it. * Hosts MUST NOT call deactivate() unless activate() was previously * called. */ void (*deactivate)(LV2_Handle Instance); /** This is the counterpart to instantiate() (see above). Once an instance * of a plugin has been finished with it can be deleted using this * function. The instance handle passed ceases to be valid after * this call. * * If activate() was called for a plugin instance then a corresponding * call to deactivate() MUST be made before cleanup() is called. * Hosts MUST NOT call cleanup() unless instantiate() was previously * called. */ void (*cleanup)(LV2_Handle Instance); } LV2_Descriptor; /* ****************************************************************** */ /** Accessing a Plugin: * * The exact mechanism by which plugins are loaded is host-dependent, * however all most hosts will need to know is the URI of the plugin they * wish to load. The environment variable LV2_PATH, if present, should * contain a colon-separated path indicating directories (containing * plugin bundle subdirectories) that should be searched (in order) * for plugins. It is expected that hosts will use a library to provide * this functionality. * * A plugin programmer must include a function called "lv2_descriptor" * with the following function prototype within the shared object * file. This function will have C-style linkage (if you are using * C++ this is taken care of by the 'extern "C"' clause at the top of * the file). * * A host will find the plugin shared object file by one means or another, * find the lv2_descriptor() function, call it, and proceed from there. * * Plugin types are accessed by index (not ID) using values from 0 * upwards. Out of range indexes must result in this function returning * NULL, so the plugin count can be determined by checking for the least * index that results in NULL being returned. Index has no meaning, * hosts MUST NOT depend on it remaining constant (ie when serialising) * in any way. */ const LV2_Descriptor * lv2_descriptor(uint32_t Index); /** Datatype corresponding to the lv2_descriptor() function. */ typedef const LV2_Descriptor * (*LV2_Descriptor_Function)(uint32_t Index); /* ******************************************************************** */ /* Put this (LV2_SYMBOL_EXPORT) before any functions that are to be loaded * by the host as a symbol from the dynamic library. */ #ifdef WIN32 #define LV2_SYMBOL_EXPORT __declspec(dllexport) #else #define LV2_SYMBOL_EXPORT #endif #ifdef __cplusplus } #endif #endif /* LV2_H_INCLUDED */