3 Linux Audio Developer's Simple Plugin API Version 1.1[LGPL].
4 Copyright (C) 2000-2002 Richard W.E. Furse, Paul Barton-Davis,
7 This library is free software; you can redistribute it and/or
8 modify it under the terms of the GNU Lesser General Public License
9 as published by the Free Software Foundation; either version 2.1 of
10 the License, or (at your option) any later version.
12 This library is distributed in the hope that it will be useful, but
13 WITHOUT ANY WARRANTY; without even the implied warranty of
14 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15 Lesser General Public License for more details.
17 You should have received a copy of the GNU Lesser General Public
18 License along with this library; if not, write to the Free Software
19 Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307
22 #ifndef LADSPA_INCLUDED
23 #define LADSPA_INCLUDED
25 #define LADSPA_VERSION "1.1"
26 #define LADSPA_VERSION_MAJOR 1
27 #define LADSPA_VERSION_MINOR 1
33 /*****************************************************************************/
37 There is a large number of synthesis packages in use or development
38 on the Linux platform at this time. This API (`The Linux Audio
39 Developer's Simple Plugin API') attempts to give programmers the
40 ability to write simple `plugin' audio processors in C/C++ and link
41 them dynamically (`plug') into a range of these packages (`hosts').
42 It should be possible for any host and any plugin to communicate
43 completely through this interface.
45 This API is deliberately short and simple. To achieve compatibility
46 with a range of promising Linux sound synthesis packages it
47 attempts to find the `greatest common divisor' in their logical
48 behaviour. Having said this, certain limiting decisions are
49 implicit, notably the use of a fixed type (LADSPA_Data) for all
50 data transfer and absence of a parameterised `initialisation'
51 phase. See below for the LADSPA_Data typedef.
53 Plugins are expected to distinguish between control and audio
54 data. Plugins have `ports' that are inputs or outputs for audio or
55 control data and each plugin is `run' for a `block' corresponding
56 to a short time interval measured in samples. Audio data is
57 communicated using arrays of LADSPA_Data, allowing a block of audio
58 to be processed by the plugin in a single pass. Control data is
59 communicated using single LADSPA_Data values. Control data has a
60 single value at the start of a call to the `run()' or `run_adding()'
61 function, and may be considered to remain this value for its
62 duration. The plugin may assume that all its input and output ports
63 have been connected to the relevant data location (see the
64 `connect_port()' function below) before it is asked to run.
66 Plugins will reside in shared object files suitable for dynamic
67 linking by dlopen() and family. The file will provide a number of
68 `plugin types' that can be used to instantiate actual plugins
69 (sometimes known as `plugin instances') that can be connected
70 together to perform tasks.
72 This API contains very limited error-handling. */
74 /*****************************************************************************/
76 /* Fundamental data type passed in and out of plugin. This data type
77 is used to communicate audio samples and control values. It is
78 assumed that the plugin will work sensibly given any numeric input
79 value although it may have a preferred range (see hints below).
81 For audio it is generally assumed that 1.0f is the `0dB' reference
82 amplitude and is a `normal' signal level. */
84 typedef float LADSPA_Data;
86 /*****************************************************************************/
88 /* Special Plugin Properties:
90 Optional features of the plugin type are encapsulated in the
91 LADSPA_Properties type. This is assembled by ORing individual
92 properties together. */
95 typedef int LADSPA_Properties;
97 /* Property LADSPA_PROPERTY_REALTIME indicates that the plugin has a
98 real-time dependency (e.g. listens to a MIDI device) and so its
99 output must not be cached or subject to significant latency. */
100 #define LADSPA_PROPERTY_REALTIME 0x1
102 /* Property LADSPA_PROPERTY_INPLACE_BROKEN indicates that the plugin
103 may cease to work correctly if the host elects to use the same data
104 location for both input and output (see connect_port()). This
105 should be avoided as enabling this flag makes it impossible for
106 hosts to use the plugin to process audio `in-place.' */
107 #define LADSPA_PROPERTY_INPLACE_BROKEN 0x2
109 /* Property LADSPA_PROPERTY_HARD_RT_CAPABLE indicates that the plugin
110 is capable of running not only in a conventional host but also in a
111 `hard real-time' environment. To qualify for this the plugin must
112 satisfy all of the following:
114 (1) The plugin must not use malloc(), free() or other heap memory
115 management within its run() or run_adding() functions. All new
116 memory used in run() must be managed via the stack. These
117 restrictions only apply to the run() function.
119 (2) The plugin will not attempt to make use of any library
120 functions with the exceptions of functions in the ANSI standard C
121 and C maths libraries, which the host is expected to provide.
123 (3) The plugin will not access files, devices, pipes, sockets, IPC
124 or any other mechanism that might result in process or thread
127 (4) The plugin will take an amount of time to execute a run() or
128 run_adding() call approximately of form (A+B*SampleCount) where A
129 and B depend on the machine and host in use. This amount of time
130 may not depend on input signals or plugin state. The host is left
131 the responsibility to perform timings to estimate upper bounds for
133 #define LADSPA_PROPERTY_HARD_RT_CAPABLE 0x4
135 #define LADSPA_IS_REALTIME(x) ((x) & LADSPA_PROPERTY_REALTIME)
136 #define LADSPA_IS_INPLACE_BROKEN(x) ((x) & LADSPA_PROPERTY_INPLACE_BROKEN)
137 #define LADSPA_IS_HARD_RT_CAPABLE(x) ((x) & LADSPA_PROPERTY_HARD_RT_CAPABLE)
139 /*****************************************************************************/
143 Plugins have `ports' that are inputs or outputs for audio or
144 data. Ports can communicate arrays of LADSPA_Data (for audio
145 inputs/outputs) or single LADSPA_Data values (for control
146 input/outputs). This information is encapsulated in the
147 LADSPA_PortDescriptor type which is assembled by ORing individual
150 Note that a port must be an input or an output port but not both
151 and that a port must be a control or audio port but not both. */
154 typedef int LADSPA_PortDescriptor;
156 /* Property LADSPA_PORT_INPUT indicates that the port is an input. */
157 #define LADSPA_PORT_INPUT 0x1
159 /* Property LADSPA_PORT_OUTPUT indicates that the port is an output. */
160 #define LADSPA_PORT_OUTPUT 0x2
162 /* Property LADSPA_PORT_CONTROL indicates that the port is a control
164 #define LADSPA_PORT_CONTROL 0x4
166 /* Property LADSPA_PORT_AUDIO indicates that the port is a audio
168 #define LADSPA_PORT_AUDIO 0x8
170 #define LADSPA_IS_PORT_INPUT(x) ((x) & LADSPA_PORT_INPUT)
171 #define LADSPA_IS_PORT_OUTPUT(x) ((x) & LADSPA_PORT_OUTPUT)
172 #define LADSPA_IS_PORT_CONTROL(x) ((x) & LADSPA_PORT_CONTROL)
173 #define LADSPA_IS_PORT_AUDIO(x) ((x) & LADSPA_PORT_AUDIO)
175 /*****************************************************************************/
177 /* Plugin Port Range Hints:
179 The host may wish to provide a representation of data entering or
180 leaving a plugin (e.g. to generate a GUI automatically). To make
181 this more meaningful, the plugin should provide `hints' to the host
182 describing the usual values taken by the data.
184 Note that these are only hints. The host may ignore them and the
185 plugin must not assume that data supplied to it is meaningful. If
186 the plugin receives invalid input data it is expected to continue
187 to run without failure and, where possible, produce a sensible
188 output (e.g. a high-pass filter given a negative cutoff frequency
189 might switch to an all-pass mode).
191 Hints are meaningful for all input and output ports but hints for
192 input control ports are expected to be particularly useful.
194 More hint information is encapsulated in the
195 LADSPA_PortRangeHintDescriptor type which is assembled by ORing
196 individual hint types together. Hints may require further
197 LowerBound and UpperBound information.
199 All the hint information for a particular port is aggregated in the
200 LADSPA_PortRangeHint structure. */
203 typedef int LADSPA_PortRangeHintDescriptor;
205 /* Hint LADSPA_HINT_BOUNDED_BELOW indicates that the LowerBound field
206 of the LADSPA_PortRangeHint should be considered meaningful. The
207 value in this field should be considered the (inclusive) lower
208 bound of the valid range. If LADSPA_HINT_SAMPLE_RATE is also
209 specified then the value of LowerBound should be multiplied by the
211 #define LADSPA_HINT_BOUNDED_BELOW 0x1
213 /* Hint LADSPA_HINT_BOUNDED_ABOVE indicates that the UpperBound field
214 of the LADSPA_PortRangeHint should be considered meaningful. The
215 value in this field should be considered the (inclusive) upper
216 bound of the valid range. If LADSPA_HINT_SAMPLE_RATE is also
217 specified then the value of UpperBound should be multiplied by the
219 #define LADSPA_HINT_BOUNDED_ABOVE 0x2
221 /* Hint LADSPA_HINT_TOGGLED indicates that the data item should be
222 considered a Boolean toggle. Data less than or equal to zero should
223 be considered `off' or `false,' and data above zero should be
224 considered `on' or `true.' LADSPA_HINT_TOGGLED may not be used in
225 conjunction with any other hint except LADSPA_HINT_DEFAULT_0 or
226 LADSPA_HINT_DEFAULT_1. */
227 #define LADSPA_HINT_TOGGLED 0x4
229 /* Hint LADSPA_HINT_SAMPLE_RATE indicates that any bounds specified
230 should be interpreted as multiples of the sample rate. For
231 instance, a frequency range from 0Hz to the Nyquist frequency (half
232 the sample rate) could be requested by this hint in conjunction
233 with LowerBound = 0 and UpperBound = 0.5. Hosts that support bounds
234 at all must support this hint to retain meaning. */
235 #define LADSPA_HINT_SAMPLE_RATE 0x8
237 /* Hint LADSPA_HINT_LOGARITHMIC indicates that it is likely that the
238 user will find it more intuitive to view values using a logarithmic
239 scale. This is particularly useful for frequencies and gains. */
240 #define LADSPA_HINT_LOGARITHMIC 0x10
242 /* Hint LADSPA_HINT_INTEGER indicates that a user interface would
243 probably wish to provide a stepped control taking only integer
244 values. Any bounds set should be slightly wider than the actual
245 integer range required to avoid floating point rounding errors. For
246 instance, the integer set {0,1,2,3} might be described as [-0.1,
248 #define LADSPA_HINT_INTEGER 0x20
250 /* The various LADSPA_HINT_HAS_DEFAULT_* hints indicate a `normal'
251 value for the port that is sensible as a default. For instance,
252 this value is suitable for use as an initial value in a user
253 interface or as a value the host might assign to a control port
254 when the user has not provided one. Defaults are encoded using a
255 mask so only one default may be specified for a port. Some of the
256 hints make use of lower and upper bounds, in which case the
257 relevant bound or bounds must be available and
258 LADSPA_HINT_SAMPLE_RATE must be applied as usual. The resulting
259 default must be rounded if LADSPA_HINT_INTEGER is present. Default
260 values were introduced in LADSPA v1.1. */
261 #define LADSPA_HINT_DEFAULT_MASK 0x3C0
263 /* This default values indicates that no default is provided. */
264 #define LADSPA_HINT_DEFAULT_NONE 0x0
266 /* This default hint indicates that the suggested lower bound for the
267 port should be used. */
268 #define LADSPA_HINT_DEFAULT_MINIMUM 0x40
270 /* This default hint indicates that a low value between the suggested
271 lower and upper bounds should be chosen. For ports with
272 LADSPA_HINT_LOGARITHMIC, this should be exp(log(lower) * 0.75 +
273 log(upper) * 0.25). Otherwise, this should be (lower * 0.75 + upper
275 #define LADSPA_HINT_DEFAULT_LOW 0x80
277 /* This default hint indicates that a middle value between the
278 suggested lower and upper bounds should be chosen. For ports with
279 LADSPA_HINT_LOGARITHMIC, this should be exp(log(lower) * 0.5 +
280 log(upper) * 0.5). Otherwise, this should be (lower * 0.5 + upper *
282 #define LADSPA_HINT_DEFAULT_MIDDLE 0xC0
284 /* This default hint indicates that a high value between the suggested
285 lower and upper bounds should be chosen. For ports with
286 LADSPA_HINT_LOGARITHMIC, this should be exp(log(lower) * 0.25 +
287 log(upper) * 0.75). Otherwise, this should be (lower * 0.25 + upper
289 #define LADSPA_HINT_DEFAULT_HIGH 0x100
291 /* This default hint indicates that the suggested upper bound for the
292 port should be used. */
293 #define LADSPA_HINT_DEFAULT_MAXIMUM 0x140
295 /* This default hint indicates that the number 0 should be used. Note
296 that this default may be used in conjunction with
297 LADSPA_HINT_TOGGLED. */
298 #define LADSPA_HINT_DEFAULT_0 0x200
300 /* This default hint indicates that the number 1 should be used. Note
301 that this default may be used in conjunction with
302 LADSPA_HINT_TOGGLED. */
303 #define LADSPA_HINT_DEFAULT_1 0x240
305 /* This default hint indicates that the number 100 should be used. */
306 #define LADSPA_HINT_DEFAULT_100 0x280
308 /* This default hint indicates that the Hz frequency of `concert A'
309 should be used. This will be 440 unless the host uses an unusual
310 tuning convention, in which case it may be within a few Hz. */
311 #define LADSPA_HINT_DEFAULT_440 0x2C0
313 #define LADSPA_IS_HINT_BOUNDED_BELOW(x) ((x) & LADSPA_HINT_BOUNDED_BELOW)
314 #define LADSPA_IS_HINT_BOUNDED_ABOVE(x) ((x) & LADSPA_HINT_BOUNDED_ABOVE)
315 #define LADSPA_IS_HINT_TOGGLED(x) ((x) & LADSPA_HINT_TOGGLED)
316 #define LADSPA_IS_HINT_SAMPLE_RATE(x) ((x) & LADSPA_HINT_SAMPLE_RATE)
317 #define LADSPA_IS_HINT_LOGARITHMIC(x) ((x) & LADSPA_HINT_LOGARITHMIC)
318 #define LADSPA_IS_HINT_INTEGER(x) ((x) & LADSPA_HINT_INTEGER)
320 #define LADSPA_IS_HINT_HAS_DEFAULT(x) ((x) & LADSPA_HINT_DEFAULT_MASK)
321 #define LADSPA_IS_HINT_DEFAULT_MINIMUM(x) (((x) & LADSPA_HINT_DEFAULT_MASK) \
322 == LADSPA_HINT_DEFAULT_MINIMUM)
323 #define LADSPA_IS_HINT_DEFAULT_LOW(x) (((x) & LADSPA_HINT_DEFAULT_MASK) \
324 == LADSPA_HINT_DEFAULT_LOW)
325 #define LADSPA_IS_HINT_DEFAULT_MIDDLE(x) (((x) & LADSPA_HINT_DEFAULT_MASK) \
326 == LADSPA_HINT_DEFAULT_MIDDLE)
327 #define LADSPA_IS_HINT_DEFAULT_HIGH(x) (((x) & LADSPA_HINT_DEFAULT_MASK) \
328 == LADSPA_HINT_DEFAULT_HIGH)
329 #define LADSPA_IS_HINT_DEFAULT_MAXIMUM(x) (((x) & LADSPA_HINT_DEFAULT_MASK) \
330 == LADSPA_HINT_DEFAULT_MAXIMUM)
331 #define LADSPA_IS_HINT_DEFAULT_0(x) (((x) & LADSPA_HINT_DEFAULT_MASK) \
332 == LADSPA_HINT_DEFAULT_0)
333 #define LADSPA_IS_HINT_DEFAULT_1(x) (((x) & LADSPA_HINT_DEFAULT_MASK) \
334 == LADSPA_HINT_DEFAULT_1)
335 #define LADSPA_IS_HINT_DEFAULT_100(x) (((x) & LADSPA_HINT_DEFAULT_MASK) \
336 == LADSPA_HINT_DEFAULT_100)
337 #define LADSPA_IS_HINT_DEFAULT_440(x) (((x) & LADSPA_HINT_DEFAULT_MASK) \
338 == LADSPA_HINT_DEFAULT_440)
340 typedef struct _LADSPA_PortRangeHint {
342 /* Hints about the port. */
343 LADSPA_PortRangeHintDescriptor HintDescriptor;
345 /* Meaningful when hint LADSPA_HINT_BOUNDED_BELOW is active. When
346 LADSPA_HINT_SAMPLE_RATE is also active then this value should be
347 multiplied by the relevant sample rate. */
348 LADSPA_Data LowerBound;
350 /* Meaningful when hint LADSPA_HINT_BOUNDED_ABOVE is active. When
351 LADSPA_HINT_SAMPLE_RATE is also active then this value should be
352 multiplied by the relevant sample rate. */
353 LADSPA_Data UpperBound;
355 } LADSPA_PortRangeHint;
357 /*****************************************************************************/
361 This plugin handle indicates a particular instance of the plugin
362 concerned. It is valid to compare this to NULL (0 for C++) but
363 otherwise the host should not attempt to interpret it. The plugin
364 may use it to reference internal instance data. */
366 typedef void * LADSPA_Handle;
368 /*****************************************************************************/
370 /* Descriptor for a Type of Plugin:
372 This structure is used to describe a plugin type. It provides a
373 number of functions to examine the type, instantiate it, link it to
374 buffers and workspaces and to run it. */
376 typedef struct _LADSPA_Descriptor {
378 /* This numeric identifier indicates the plugin type
379 uniquely. Plugin programmers may reserve ranges of IDs from a
380 central body to avoid clashes. Hosts may assume that IDs are
382 unsigned long UniqueID;
384 /* This identifier can be used as a unique, case-sensitive
385 identifier for the plugin type within the plugin file. Plugin
386 types should be identified by file and label rather than by index
387 or plugin name, which may be changed in new plugin
388 versions. Labels must not contain white-space characters. */
391 /* This indicates a number of properties of the plugin. */
392 LADSPA_Properties Properties;
394 /* This member points to the null-terminated name of the plugin
395 (e.g. "Sine Oscillator"). */
398 /* This member points to the null-terminated string indicating the
399 maker of the plugin. This can be an empty string but not NULL. */
402 /* This member points to the null-terminated string indicating any
403 copyright applying to the plugin. If no Copyright applies the
404 string "None" should be used. */
405 const char * Copyright;
407 /* This indicates the number of ports (input AND output) present on
409 unsigned long PortCount;
411 /* This member indicates an array of port descriptors. Valid indices
412 vary from 0 to PortCount-1. */
413 const LADSPA_PortDescriptor * PortDescriptors;
415 /* This member indicates an array of null-terminated strings
416 describing ports (e.g. "Frequency (Hz)"). Valid indices vary from
418 const char * const * PortNames;
420 /* This member indicates an array of range hints for each port (see
421 above). Valid indices vary from 0 to PortCount-1. */
422 const LADSPA_PortRangeHint * PortRangeHints;
424 /* This may be used by the plugin developer to pass any custom
425 implementation data into an instantiate call. It must not be used
426 or interpreted by the host. It is expected that most plugin
427 writers will not use this facility as LADSPA_Handle should be
428 used to hold instance data. */
429 void * ImplementationData;
431 /* This member is a function pointer that instantiates a plugin. A
432 handle is returned indicating the new plugin instance. The
433 instantiation function accepts a sample rate as a parameter. The
434 plugin descriptor from which this instantiate function was found
435 must also be passed. This function must return NULL if
438 Note that instance initialisation should generally occur in
439 activate() rather than here. */
440 LADSPA_Handle (*instantiate)(const struct _LADSPA_Descriptor * Descriptor,
441 unsigned long SampleRate);
443 /* This member is a function pointer that connects a port on an
444 instantiated plugin to a memory location at which a block of data
445 for the port will be read/written. The data location is expected
446 to be an array of LADSPA_Data for audio ports or a single
447 LADSPA_Data value for control ports. Memory issues will be
448 managed by the host. The plugin must read/write the data at these
449 locations every time run() or run_adding() is called and the data
450 present at the time of this connection call should not be
451 considered meaningful.
453 connect_port() may be called more than once for a plugin instance
454 to allow the host to change the buffers that the plugin is
455 reading or writing. These calls may be made before or after
456 activate() or deactivate() calls.
458 connect_port() must be called at least once for each port before
459 run() or run_adding() is called. When working with blocks of
460 LADSPA_Data the plugin should pay careful attention to the block
461 size passed to the run function as the block allocated may only
462 just be large enough to contain the block of samples.
464 Plugin writers should be aware that the host may elect to use the
465 same buffer for more than one port and even use the same buffer
466 for both input and output (see LADSPA_PROPERTY_INPLACE_BROKEN).
467 However, overlapped buffers or use of a single buffer for both
468 audio and control data may result in unexpected behaviour. */
469 void (*connect_port)(LADSPA_Handle Instance,
471 LADSPA_Data * DataLocation);
473 /* This member is a function pointer that initialises a plugin
474 instance and activates it for use. This is separated from
475 instantiate() to aid real-time support and so that hosts can
476 reinitialise a plugin instance by calling deactivate() and then
477 activate(). In this case the plugin instance must reset all state
478 information dependent on the history of the plugin instance
479 except for any data locations provided by connect_port() and any
480 gain set by set_run_adding_gain(). If there is nothing for
481 activate() to do then the plugin writer may provide a NULL rather
482 than an empty function.
484 When present, hosts must call this function once before run() (or
485 run_adding()) is called for the first time. This call should be
486 made as close to the run() call as possible and indicates to
487 real-time plugins that they are now live. Plugins should not rely
488 on a prompt call to run() after activate(). activate() may not be
489 called again unless deactivate() is called first. Note that
490 connect_port() may be called before or after a call to
492 void (*activate)(LADSPA_Handle Instance);
494 /* This method is a function pointer that runs an instance of a
495 plugin for a block. Two parameters are required: the first is a
496 handle to the particular instance to be run and the second
497 indicates the block size (in samples) for which the plugin
500 Note that if an activate() function exists then it must be called
501 before run() or run_adding(). If deactivate() is called for a
502 plugin instance then the plugin instance may not be reused until
503 activate() has been called again.
505 If the plugin has the property LADSPA_PROPERTY_HARD_RT_CAPABLE
506 then there are various things that the plugin should not do
507 within the run() or run_adding() functions (see above). */
508 void (*run)(LADSPA_Handle Instance,
509 unsigned long SampleCount);
511 /* This method is a function pointer that runs an instance of a
512 plugin for a block. This has identical behaviour to run() except
513 in the way data is output from the plugin. When run() is used,
514 values are written directly to the memory areas associated with
515 the output ports. However when run_adding() is called, values
516 must be added to the values already present in the memory
517 areas. Furthermore, output values written must be scaled by the
518 current gain set by set_run_adding_gain() (see below) before
521 run_adding() is optional. When it is not provided by a plugin,
522 this function pointer must be set to NULL. When it is provided,
523 the function set_run_adding_gain() must be provided also. */
524 void (*run_adding)(LADSPA_Handle Instance,
525 unsigned long SampleCount);
527 /* This method is a function pointer that sets the output gain for
528 use when run_adding() is called (see above). If this function is
529 never called the gain is assumed to default to 1. Gain
530 information should be retained when activate() or deactivate()
533 This function should be provided by the plugin if and only if the
534 run_adding() function is provided. When it is absent this
535 function pointer must be set to NULL. */
536 void (*set_run_adding_gain)(LADSPA_Handle Instance,
539 /* This is the counterpart to activate() (see above). If there is
540 nothing for deactivate() to do then the plugin writer may provide
541 a NULL rather than an empty function.
543 Hosts must deactivate all activated units after they have been
544 run() (or run_adding()) for the last time. This call should be
545 made as close to the last run() call as possible and indicates to
546 real-time plugins that they are no longer live. Plugins should
547 not rely on prompt deactivation. Note that connect_port() may be
548 called before or after a call to deactivate().
550 Deactivation is not similar to pausing as the plugin instance
551 will be reinitialised when activate() is called to reuse it. */
552 void (*deactivate)(LADSPA_Handle Instance);
554 /* Once an instance of a plugin has been finished with it can be
555 deleted using the following function. The instance handle passed
556 ceases to be valid after this call.
558 If activate() was called for a plugin instance then a
559 corresponding call to deactivate() must be made before cleanup()
561 void (*cleanup)(LADSPA_Handle Instance);
565 /**********************************************************************/
567 /* Accessing a Plugin: */
569 /* The exact mechanism by which plugins are loaded is host-dependent,
570 however all most hosts will need to know is the name of shared
571 object file containing the plugin types. To allow multiple hosts to
572 share plugin types, hosts may wish to check for environment
573 variable LADSPA_PATH. If present, this should contain a
574 colon-separated path indicating directories that should be searched
575 (in order) when loading plugin types.
577 A plugin programmer must include a function called
578 "ladspa_descriptor" with the following function prototype within
579 the shared object file. This function will have C-style linkage (if
580 you are using C++ this is taken care of by the `extern "C"' clause
581 at the top of the file).
583 A host will find the plugin shared object file by one means or
584 another, find the ladspa_descriptor() function, call it, and
587 Plugin types are accessed by index (not ID) using values from 0
588 upwards. Out of range indexes must result in this function
589 returning NULL, so the plugin count can be determined by checking
590 for the least index that results in NULL being returned. */
592 const LADSPA_Descriptor * ladspa_descriptor(unsigned long Index);
594 /* Datatype corresponding to the ladspa_descriptor() function. */
595 typedef const LADSPA_Descriptor *
596 (*LADSPA_Descriptor_Function)(unsigned long Index);
598 /**********************************************************************/
604 #endif /* LADSPA_INCLUDED */