2 Copyright (C) 2013 Paul Davis
4 This program is free software; you can redistribute it and/or modify
5 it under the terms of the GNU General Public License as published by
6 the Free Software Foundation; either version 2 of the License, or
7 (at your option) any later version.
9 This program is distributed in the hope that it will be useful,
10 but WITHOUT ANY WARRANTY; without even the implied warranty of
11 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
12 GNU General Public License for more details.
14 You should have received a copy of the GNU General Public License
15 along with this program; if not, write to the Free Software
16 Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
20 #ifndef __libardour_audiobackend_h__
21 #define __libardour_audiobackend_h__
29 #include <boost/function.hpp>
31 #include "ardour/libardour_visibility.h"
32 #include "ardour/types.h"
33 #include "ardour/audioengine.h"
34 #include "ardour/port_engine.h"
36 #ifdef ARDOURBACKEND_DLL_EXPORTS // defined if we are building the ARDOUR Panners DLLs (instead of using them)
37 #define ARDOURBACKEND_API LIBARDOUR_DLL_EXPORT
39 #define ARDOURBACKEND_API LIBARDOUR_DLL_IMPORT
41 #define ARDOURBACKEND_LOCAL LIBARDOUR_DLL_LOCAL
45 struct LIBARDOUR_API AudioBackendInfo {
48 /** Using arg1 and arg2, initialize this audiobackend.
50 * Returns zero on success, non-zero otherwise.
52 int (*instantiate) (const std::string& arg1, const std::string& arg2);
54 /** Release all resources associated with this audiobackend
56 int (*deinstantiate) (void);
58 /** Factory method to create an AudioBackend-derived class.
60 * Returns a valid shared_ptr to the object if successfull,
61 * or a "null" shared_ptr otherwise.
63 boost::shared_ptr<AudioBackend> (*factory) (AudioEngine&);
65 /** Return true if the underlying mechanism/API has been
66 * configured and does not need (re)configuration in order
67 * to be usable. Return false otherwise.
69 * Note that this may return true if (re)configuration, even though
70 * not currently required, is still possible.
72 bool (*already_configured)();
74 /** Return true if the underlying mechanism/API can be
75 * used on the given system.
77 * If this function returns false, the backend is not
78 * listed in the engine dialog.
83 class LIBARDOUR_API AudioBackend : public PortEngine {
86 AudioBackend (AudioEngine& e, AudioBackendInfo& i) : PortEngine (e), _info (i), engine (e) {}
87 virtual ~AudioBackend () {}
89 /** Return the AudioBackendInfo object from which this backend
92 AudioBackendInfo& info() const { return _info; }
94 /** Return the name of this backend.
96 * Should use a well-known, unique term. Expected examples
97 * might include "JACK", "CoreAudio", "ASIO" etc.
99 virtual std::string name() const = 0;
101 /** Return true if the callback from the underlying mechanism/API
102 * (CoreAudio, JACK, ASIO etc.) occurs in a thread subject to realtime
103 * constraints. Return false otherwise.
105 virtual bool is_realtime () const = 0;
107 /* Discovering devices and parameters */
109 /** Return true if this backend requires the selection of a "driver"
110 * before any device can be selected. Return false otherwise.
112 * Intended mainly to differentiate between meta-APIs like JACK
113 * which can still expose different backends (such as ALSA or CoreAudio
114 * or FFADO or netjack) and those like ASIO or CoreAudio which
117 virtual bool requires_driver_selection() const { return false; }
119 /** If the return value of requires_driver_selection() is true,
120 * then this function can return the list of known driver names.
122 * If the return value of requires_driver_selection() is false,
123 * then this function should not be called. If it is called
124 * its return value is an empty vector of strings.
126 virtual std::vector<std::string> enumerate_drivers() const { return std::vector<std::string>(); }
128 /** Returns zero if the backend can successfully use @param name as the
129 * driver, non-zero otherwise.
131 * Should not be used unless the backend returns true from
132 * requires_driver_selection()
134 virtual int set_driver (const std::string& /*drivername*/) { return 0; }
136 /** used to list device names along with whether or not they are currently
139 struct DeviceStatus {
143 DeviceStatus (const std::string& s, bool avail) : name (s), available (avail) {}
146 /** An optional alternate interface for backends to provide a facility to
147 * select separate input and output devices.
149 * If a backend returns true then enumerate_input_devices() and
150 * enumerate_output_devices() will be used instead of enumerate_devices()
151 * to enumerate devices. Similarly set_input/output_device_name() should
152 * be used to set devices instead of set_device_name().
154 virtual bool use_separate_input_and_output_devices () const { return false; }
156 /** Returns a collection of DeviceStatuses identifying devices discovered
157 * by this backend since the start of the process.
159 * Any of the names in each DeviceStatus may be used to identify a
160 * device in other calls to the backend, though any of them may become
161 * invalid at any time.
163 virtual std::vector<DeviceStatus> enumerate_devices () const = 0;
165 /** Returns a collection of DeviceStatuses identifying input devices
166 * discovered by this backend since the start of the process.
168 * Any of the names in each DeviceStatus may be used to identify a
169 * device in other calls to the backend, though any of them may become
170 * invalid at any time.
172 virtual std::vector<DeviceStatus> enumerate_input_devices () const
173 { return std::vector<DeviceStatus>(); }
175 /** Returns a collection of DeviceStatuses identifying output devices
176 * discovered by this backend since the start of the process.
178 * Any of the names in each DeviceStatus may be used to identify a
179 * device in other calls to the backend, though any of them may become
180 * invalid at any time.
182 virtual std::vector<DeviceStatus> enumerate_output_devices () const
183 { return std::vector<DeviceStatus>(); }
185 /** Returns a collection of float identifying sample rates that are
186 * potentially usable with the hardware identified by @param device.
187 * Any of these values may be supplied in other calls to this backend
188 * as the desired sample rate to use with the name device, but the
189 * requested sample rate may turn out to be unavailable, or become invalid
192 virtual std::vector<float> available_sample_rates (const std::string& device) const = 0;
194 /* Returns the default sample rate that will be shown to the user when
195 * configuration options are first presented. If the derived class
196 * needs or wants to override this, it can. It also MUST override this
197 * if there is any chance that an SR of 44.1kHz is not in the list
198 * returned by available_sample_rates()
200 virtual float default_sample_rate () const {
204 /** Returns a collection of uint32 identifying buffer sizes that are
205 * potentially usable with the hardware identified by @param device.
206 * Any of these values may be supplied in other calls to this backend
207 * as the desired buffer size to use with the name device, but the
208 * requested buffer size may turn out to be unavailable, or become invalid
211 virtual std::vector<uint32_t> available_buffer_sizes (const std::string& device) const = 0;
213 /* Returns the default buffer size that will be shown to the user when
214 * configuration options are first presented. If the derived class
215 * needs or wants to override this, it can. It also MUST override this
216 * if there is any chance that a buffer size of 1024 is not in the list
217 * returned by available_buffer_sizes()
219 virtual uint32_t default_buffer_size (const std::string& device) const {
223 /** Returns the maximum number of input channels that are potentially
224 * usable with the hardware identified by @param device. Any number from 1
225 * to the value returned may be supplied in other calls to this backend as
226 * the input channel count to use with the name device, but the requested
227 * count may turn out to be unavailable, or become invalid at any time.
229 virtual uint32_t available_input_channel_count (const std::string& device) const = 0;
231 /** Returns the maximum number of output channels that are potentially
232 * usable with the hardware identified by @param device. Any number from 1
233 * to the value returned may be supplied in other calls to this backend as
234 * the output channel count to use with the name device, but the requested
235 * count may turn out to be unavailable, or become invalid at any time.
237 virtual uint32_t available_output_channel_count (const std::string& device) const = 0;
239 /* Return true if the derived class can change the sample rate of the
240 * device in use while the device is already being used. Return false
241 * otherwise. (example: JACK cannot do this as of September 2013)
243 virtual bool can_change_sample_rate_when_running () const = 0;
244 /* Return true if the derived class can change the buffer size of the
245 * device in use while the device is already being used. Return false
248 virtual bool can_change_buffer_size_when_running () const = 0;
250 /* Set the hardware parameters.
252 * If called when the current state is stopped or paused,
253 * the changes will not take effect until the state changes to running.
255 * If called while running, the state will change as fast as the
256 * implementation allows.
258 * All set_*() methods return zero on success, non-zero otherwise.
261 /** Set the name of the device to be used
263 virtual int set_device_name (const std::string&) = 0;
265 /** Set the name of the input device to be used if using separate
266 * input/output devices.
268 * @see use_separate_input_and_output_devices()
270 virtual int set_input_device_name (const std::string&) { return 0;}
272 /** Set the name of the output device to be used if using separate
273 * input/output devices.
275 * @see use_separate_input_and_output_devices()
277 virtual int set_output_device_name (const std::string&) { return 0;}
279 /** Deinitialize and destroy current device
281 virtual int drop_device() {return 0;};
282 /** Set the sample rate to be used
284 virtual int set_sample_rate (float) = 0;
285 /** Set the buffer size to be used.
287 * The device is assumed to use a double buffering scheme, so that one
288 * buffer's worth of data can be processed by hardware while software works
289 * on the other buffer. All known suitable audio APIs support this model
290 * (though ALSA allows for alternate numbers of buffers, and CoreAudio
291 * doesn't directly expose the concept).
293 virtual int set_buffer_size (uint32_t) = 0;
294 /** Set the preferred underlying hardware data layout.
295 * If @param yn is true, then the hardware will interleave
296 * samples for successive channels; otherwise, the hardware will store
297 * samples for a single channel contiguously.
299 * Setting this does not change the fact that all data streams
300 * to and from Ports are mono (essentially, non-interleaved)
302 virtual int set_interleaved (bool yn) = 0;
303 /** Set the number of input channels that should be used
305 virtual int set_input_channels (uint32_t) = 0;
306 /** Set the number of output channels that should be used
308 virtual int set_output_channels (uint32_t) = 0;
309 /** Set the (additional) input latency that cannot be determined via
310 * the implementation's underlying code (e.g. latency from
311 * external D-A/D-A converters. Units are samples.
313 virtual int set_systemic_input_latency (uint32_t) = 0;
314 /** Set the (additional) output latency that cannot be determined via
315 * the implementation's underlying code (e.g. latency from
316 * external D-A/D-A converters. Units are samples.
318 virtual int set_systemic_output_latency (uint32_t) = 0;
319 /** Set the (additional) input latency for a specific midi device,
320 * or if the identifier is empty, apply to all midi devices.
322 virtual int set_systemic_midi_input_latency (std::string const, uint32_t) = 0;
323 /** Set the (additional) output latency for a specific midi device,
324 * or if the identifier is empty, apply to all midi devices.
326 virtual int set_systemic_midi_output_latency (std::string const, uint32_t) = 0;
328 /* Retrieving parameters */
330 virtual std::string device_name () const = 0;
331 virtual std::string input_device_name () const { return std::string(); }
332 virtual std::string output_device_name () const { return std::string(); }
333 virtual float sample_rate () const = 0;
334 virtual uint32_t buffer_size () const = 0;
335 virtual bool interleaved () const = 0;
336 virtual uint32_t input_channels () const = 0;
337 virtual uint32_t output_channels () const = 0;
338 virtual uint32_t systemic_input_latency () const = 0;
339 virtual uint32_t systemic_output_latency () const = 0;
340 virtual uint32_t systemic_midi_input_latency (std::string const) const = 0;
341 virtual uint32_t systemic_midi_output_latency (std::string const) const = 0;
343 /** override this if this implementation returns true from
344 * requires_driver_selection()
346 virtual std::string driver_name() const { return std::string(); }
348 /** Return the name of a control application for the
349 * selected/in-use device. If no such application exists,
350 * or if no device has been selected or is in-use,
351 * return an empty string.
353 virtual std::string control_app_name() const = 0;
354 /** Launch the control app for the currently in-use or
355 * selected device. May do nothing if the control
356 * app is undefined or cannot be launched.
358 virtual void launch_control_app () = 0;
360 /* @return a vector of strings that describe the available
363 * These can be presented to the user to decide which
364 * MIDI drivers, options etc. can be used. The returned strings
365 * should be thought of as the key to a map of possible
366 * approaches to handling MIDI within the backend. Ensure that
367 * the strings will make sense to the user.
369 virtual std::vector<std::string> enumerate_midi_options () const = 0;
371 /* Request the use of the MIDI option named @param option, which
372 * should be one of the strings returned by enumerate_midi_options()
374 * @return zero if successful, non-zero otherwise
376 virtual int set_midi_option (const std::string& option) = 0;
378 virtual std::string midi_option () const = 0;
380 /** Detailed MIDI device list - if available */
381 virtual std::vector<DeviceStatus> enumerate_midi_devices () const = 0;
383 /** mark a midi-devices as enabled */
384 virtual int set_midi_device_enabled (std::string const, bool) = 0;
386 /** query if a midi-device is enabled */
387 virtual bool midi_device_enabled (std::string const) const = 0;
389 /** if backend supports systemic_midi_[in|ou]tput_latency() */
390 virtual bool can_set_systemic_midi_latencies () const = 0;
394 /** Start using the device named in the most recent call
395 * to set_device(), with the parameters set by various
396 * the most recent calls to set_sample_rate() etc. etc.
398 * At some undetermined time after this function is successfully called,
399 * the backend will start calling the ::process_callback() method of
400 * the AudioEngine referenced by @param engine. These calls will
401 * occur in a thread created by and/or under the control of the backend.
403 * @param for_latency_measurement if true, the device is being started
404 * to carry out latency measurements and the backend should this
405 * take care to return latency numbers that do not reflect
406 * any existing systemic latency settings.
408 * Return zero if successful, negative values otherwise.
413 * Why is this non-virtual but ::_start() is virtual ?
414 * Virtual methods with default parameters create possible ambiguity
415 * because a derived class may implement the same method with a different
416 * type or value of default parameter.
418 * So we make this non-virtual method to avoid possible overrides of
419 * default parameters. See Scott Meyers or other books on C++ to understand
420 * this pattern, or possibly just this:
422 * http://stackoverflow.com/questions/12139786/good-pratice-default-arguments-for-pure-virtual-method
424 int start (bool for_latency_measurement=false) {
425 return _start (for_latency_measurement);
428 /** Stop using the device currently in use.
430 * If the function is successfully called, no subsequent calls to the
431 * process_callback() of @param engine will be made after the function
432 * returns, until parameters are reset and start() are called again.
434 * The backend is considered to be un-configured after a successful
435 * return, and requires calls to set hardware parameters before it can be
436 * start()-ed again. See pause() for a way to avoid this. stop() should
437 * only be used when reconfiguration is required OR when there are no
438 * plans to use the backend in the future with a reconfiguration.
440 * Return zero if successful, 1 if the device is not in use, negative values on error
442 virtual int stop () = 0;
446 * Return zero if successful, negative values on error
448 virtual int reset_device() = 0;
450 /** While remaining connected to the device, and without changing its
451 * configuration, start (or stop) calling the process_callback() of @param engine
452 * without waiting for the device. Once process_callback() has returned, it
453 * will be called again immediately, thus allowing for faster-than-realtime
456 * All registered ports remain in existence and all connections remain
457 * unaltered. However, any physical ports should NOT be used by the
458 * process_callback() during freewheeling - the data behaviour is undefined.
460 * If @param start_stop is true, begin this behaviour; otherwise cease this
461 * behaviour if it currently occuring, and return to calling
462 * process_callback() of @param engine by waiting for the device.
464 * Return zero on success, non-zero otherwise.
466 virtual int freewheel (bool start_stop) = 0;
468 /** return the fraction of the time represented by the current buffer
469 * size that is being used for each buffer process cycle, as a value
472 * E.g. if the buffer size represents 5msec and current processing
473 * takes 1msec, the returned value should be 0.2.
475 * Implementations can feel free to smooth the values returned over
476 * time (e.g. high pass filtering, or its equivalent).
478 virtual float dsp_load() const = 0;
480 /* Transport Control (JACK is the only audio API that currently offers
481 the concept of shared transport control)
484 /** Attempt to change the transport state to TransportRolling.
486 virtual void transport_start () {}
487 /** Attempt to change the transport state to TransportStopped.
489 virtual void transport_stop () {}
490 /** return the current transport state
492 virtual TransportState transport_state () const { return TransportStopped; }
493 /** Attempt to locate the transport to @param pos
495 virtual void transport_locate (framepos_t /*pos*/) {}
496 /** Return the current transport location, in samples measured
497 * from the origin (defined by the transport time master)
499 virtual framepos_t transport_frame() const { return 0; }
501 /** If @param yn is true, become the time master for any inter-application transport
502 * timebase, otherwise cease to be the time master for the same.
504 * Return zero on success, non-zero otherwise
506 * JACK is the only currently known audio API with the concept of a shared
507 * transport timebase.
509 virtual int set_time_master (bool /*yn*/) { return 0; }
511 virtual int usecs_per_cycle () const { return 1000000 * (buffer_size() / sample_rate()); }
512 virtual size_t raw_buffer_size (DataType t) = 0;
516 /** return the time according to the sample clock in use, measured in
517 * samples since an arbitrary zero time in the past. The value should
518 * increase monotonically and linearly, without interruption from any
519 * source (including CPU frequency scaling).
521 * It is extremely likely that any implementation will use a DLL, since
522 * this function can be called from any thread, at any time, and must be
523 * able to accurately determine the correct sample time.
525 * Can be called from any thread.
527 virtual framepos_t sample_time () = 0;
529 /** Return the time according to the sample clock in use when the most
530 * recent buffer process cycle began. Can be called from any thread.
532 virtual framepos_t sample_time_at_cycle_start () = 0;
534 /** Return the time since the current buffer process cycle started,
535 * in samples, according to the sample clock in use.
537 * Can ONLY be called from within a process() callback tree (which
538 * implies that it can only be called by a process thread)
540 virtual pframes_t samples_since_cycle_start () = 0;
542 /** Return true if it possible to determine the offset in samples of the
543 * first video frame that starts within the current buffer process cycle,
544 * measured from the first sample of the cycle. If returning true,
545 * set @param offset to that offset.
547 * Eg. if it can be determined that the first video frame within the cycle
548 * starts 28 samples after the first sample of the cycle, then this method
549 * should return true and set @param offset to 28.
551 * May be impossible to support outside of JACK, which has specific support
552 * (in some cases, hardware support) for this feature.
554 * Can ONLY be called from within a process() callback tree (which implies
555 * that it can only be called by a process thread)
557 virtual bool get_sync_offset (pframes_t& /*offset*/) const { return false; }
559 /** Create a new thread suitable for running part of the buffer process
560 * cycle (i.e. Realtime scheduling, memory allocation, etc. etc are all
561 * correctly setup), with a stack size given in bytes by specified @param
562 * stacksize. The thread will begin executing @param func, and will exit
563 * when that function returns.
565 virtual int create_process_thread (boost::function<void()> func) = 0;
567 /** Wait for all processing threads to exit.
569 * Return zero on success, non-zero on failure.
571 virtual int join_process_threads () = 0;
573 /** Return true if execution context is in a backend thread
575 virtual bool in_process_thread () = 0;
577 /** Return the minimum stack size of audio threads in bytes
579 static size_t thread_stack_size () { return 100000; }
581 /** Return number of processing threads
583 virtual uint32_t process_thread_count () = 0;
585 virtual void update_latencies () = 0;
587 /** Set @param speed and @param position to the current speed and position
588 * indicated by some transport sync signal. Return whether the current
589 * transport state is pending, or finalized.
591 * Derived classes only need implement this if they provide some way to
592 * sync to a transport sync signal (e.g. Sony 9 Pin) that is not
593 * handled by Ardour itself (LTC and MTC are both handled by Ardour).
594 * The canonical example is JACK Transport.
596 virtual bool speed_and_position (double& speed, framepos_t& position) {
603 AudioBackendInfo& _info;
606 virtual int _start (bool for_latency_measurement) = 0;
611 #endif /* __libardour_audiobackend_h__ */