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)();
75 class LIBARDOUR_API AudioBackend : public PortEngine {
78 AudioBackend (AudioEngine& e, AudioBackendInfo& i) : PortEngine (e), _info (i), engine (e) {}
79 virtual ~AudioBackend () {}
81 /** Return the AudioBackendInfo object from which this backend
84 AudioBackendInfo& info() const { return _info; }
86 /** Return the name of this backend.
88 * Should use a well-known, unique term. Expected examples
89 * might include "JACK", "CoreAudio", "ASIO" etc.
91 virtual std::string name() const = 0;
93 /** Return true if the callback from the underlying mechanism/API
94 * (CoreAudio, JACK, ASIO etc.) occurs in a thread subject to realtime
95 * constraints. Return false otherwise.
97 virtual bool is_realtime () const = 0;
99 /* Discovering devices and parameters */
101 /** Return true if this backend requires the selection of a "driver"
102 * before any device can be selected. Return false otherwise.
104 * Intended mainly to differentiate between meta-APIs like JACK
105 * which can still expose different backends (such as ALSA or CoreAudio
106 * or FFADO or netjack) and those like ASIO or CoreAudio which
109 virtual bool requires_driver_selection() const { return false; }
111 /** If the return value of requires_driver_selection() is true,
112 * then this function can return the list of known driver names.
114 * If the return value of requires_driver_selection() is false,
115 * then this function should not be called. If it is called
116 * its return value is an empty vector of strings.
118 virtual std::vector<std::string> enumerate_drivers() const { return std::vector<std::string>(); }
120 /** Returns zero if the backend can successfully use @param name as the
121 * driver, non-zero otherwise.
123 * Should not be used unless the backend returns true from
124 * requires_driver_selection()
126 virtual int set_driver (const std::string& /*drivername*/) { return 0; }
128 /** used to list device names along with whether or not they are currently
131 struct DeviceStatus {
135 DeviceStatus (const std::string& s, bool avail) : name (s), available (avail) {}
138 /** Returns a collection of DeviceStatuses identifying devices discovered
139 * by this backend since the start of the process.
141 * Any of the names in each DeviceStatus may be used to identify a
142 * device in other calls to the backend, though any of them may become
143 * invalid at any time.
145 virtual std::vector<DeviceStatus> enumerate_devices () const = 0;
147 /** Returns a collection of float identifying sample rates that are
148 * potentially usable with the hardware identified by @param device.
149 * Any of these values may be supplied in other calls to this backend
150 * as the desired sample rate to use with the name device, but the
151 * requested sample rate may turn out to be unavailable, or become invalid
154 virtual std::vector<float> available_sample_rates (const std::string& device) const = 0;
156 /* Returns the default sample rate that will be shown to the user when
157 * configuration options are first presented. If the derived class
158 * needs or wants to override this, it can. It also MUST override this
159 * if there is any chance that an SR of 44.1kHz is not in the list
160 * returned by available_sample_rates()
162 virtual float default_sample_rate () const {
166 /** Returns a collection of uint32 identifying buffer sizes that are
167 * potentially usable with the hardware identified by @param device.
168 * Any of these values may be supplied in other calls to this backend
169 * as the desired buffer size to use with the name device, but the
170 * requested buffer size may turn out to be unavailable, or become invalid
173 virtual std::vector<uint32_t> available_buffer_sizes (const std::string& device) const = 0;
175 /* Returns the default buffer size that will be shown to the user when
176 * configuration options are first presented. If the derived class
177 * needs or wants to override this, it can. It also MUST override this
178 * if there is any chance that a buffer size of 1024 is not in the list
179 * returned by available_buffer_sizes()
181 virtual uint32_t default_buffer_size () const {
185 /** Returns the maximum number of input channels that are potentially
186 * usable with the hardware identified by @param device. Any number from 1
187 * to the value returned may be supplied in other calls to this backend as
188 * the input channel count to use with the name device, but the requested
189 * count may turn out to be unavailable, or become invalid at any time.
191 virtual uint32_t available_input_channel_count (const std::string& device) const = 0;
193 /** Returns the maximum number of output channels that are potentially
194 * usable with the hardware identified by @param device. Any number from 1
195 * to the value returned may be supplied in other calls to this backend as
196 * the output channel count to use with the name device, but the requested
197 * count may turn out to be unavailable, or become invalid at any time.
199 virtual uint32_t available_output_channel_count (const std::string& device) const = 0;
201 /* Return true if the derived class can change the sample rate of the
202 * device in use while the device is already being used. Return false
203 * otherwise. (example: JACK cannot do this as of September 2013)
205 virtual bool can_change_sample_rate_when_running () const = 0;
206 /* Return true if the derived class can change the buffer size of the
207 * device in use while the device is already being used. Return false
210 virtual bool can_change_buffer_size_when_running () const = 0;
212 /* Set the hardware parameters.
214 * If called when the current state is stopped or paused,
215 * the changes will not take effect until the state changes to running.
217 * If called while running, the state will change as fast as the
218 * implementation allows.
220 * All set_*() methods return zero on success, non-zero otherwise.
223 /** Set the name of the device to be used
225 virtual int set_device_name (const std::string&) = 0;
226 /** Deinitialize and destroy current device
228 virtual int drop_device() { return 0; };
229 /** Set the sample rate to be used
231 virtual int set_sample_rate (float) = 0;
232 /** Set the buffer size to be used.
234 * The device is assumed to use a double buffering scheme, so that one
235 * buffer's worth of data can be processed by hardware while software works
236 * on the other buffer. All known suitable audio APIs support this model
237 * (though ALSA allows for alternate numbers of buffers, and CoreAudio
238 * doesn't directly expose the concept).
240 virtual int set_buffer_size (uint32_t) = 0;
241 /** Set the preferred underlying hardware data layout.
242 * If @param yn is true, then the hardware will interleave
243 * samples for successive channels; otherwise, the hardware will store
244 * samples for a single channel contiguously.
246 * Setting this does not change the fact that all data streams
247 * to and from Ports are mono (essentially, non-interleaved)
249 virtual int set_interleaved (bool yn) = 0;
250 /** Set the number of input channels that should be used
252 virtual int set_input_channels (uint32_t) = 0;
253 /** Set the number of output channels that should be used
255 virtual int set_output_channels (uint32_t) = 0;
256 /** Set the (additional) input latency that cannot be determined via
257 * the implementation's underlying code (e.g. latency from
258 * external D-A/D-A converters. Units are samples.
260 virtual int set_systemic_input_latency (uint32_t) = 0;
261 /** Set the (additional) output latency that cannot be determined via
262 * the implementation's underlying code (e.g. latency from
263 * external D-A/D-A converters. Units are samples.
265 virtual int set_systemic_output_latency (uint32_t) = 0;
267 /* Retrieving parameters */
269 virtual std::string device_name () const = 0;
270 virtual float sample_rate () const = 0;
271 virtual uint32_t buffer_size () const = 0;
272 virtual bool interleaved () const = 0;
273 virtual uint32_t input_channels () const = 0;
274 virtual uint32_t output_channels () const = 0;
275 virtual uint32_t systemic_input_latency () const = 0;
276 virtual uint32_t systemic_output_latency () const = 0;
278 /** override this if this implementation returns true from
279 * requires_driver_selection()
281 virtual std::string driver_name() const { return std::string(); }
283 /** Return the name of a control application for the
284 * selected/in-use device. If no such application exists,
285 * or if no device has been selected or is in-use,
286 * return an empty string.
288 virtual std::string control_app_name() const = 0;
289 /** Launch the control app for the currently in-use or
290 * selected device. May do nothing if the control
291 * app is undefined or cannot be launched.
293 virtual void launch_control_app () = 0;
295 /* @return a vector of strings that describe the available
298 * These can be presented to the user to decide which
299 * MIDI drivers, options etc. can be used. The returned strings
300 * should be thought of as the key to a map of possible
301 * approaches to handling MIDI within the backend. Ensure that
302 * the strings will make sense to the user.
304 virtual std::vector<std::string> enumerate_midi_options () const = 0;
306 /* Request the use of the MIDI option named @param option, which
307 * should be one of the strings returned by enumerate_midi_options()
309 * @return zero if successful, non-zero otherwise
311 virtual int set_midi_option (const std::string& option) = 0;
313 virtual std::string midi_option () const = 0;
317 /** Start using the device named in the most recent call
318 * to set_device(), with the parameters set by various
319 * the most recent calls to set_sample_rate() etc. etc.
321 * At some undetermined time after this function is successfully called,
322 * the backend will start calling the ::process_callback() method of
323 * the AudioEngine referenced by @param engine. These calls will
324 * occur in a thread created by and/or under the control of the backend.
326 * @param for_latency_measurement if true, the device is being started
327 * to carry out latency measurements and the backend should this
328 * take care to return latency numbers that do not reflect
329 * any existing systemic latency settings.
331 * Return zero if successful, negative values otherwise.
336 * Why is this non-virtual but ::_start() is virtual ?
337 * Virtual methods with default parameters create possible ambiguity
338 * because a derived class may implement the same method with a different
339 * type or value of default parameter.
341 * So we make this non-virtual method to avoid possible overrides of
342 * default parameters. See Scott Meyers or other books on C++ to understand
343 * this pattern, or possibly just this:
345 * http://stackoverflow.com/questions/12139786/good-pratice-default-arguments-for-pure-virtual-method
347 int start (bool for_latency_measurement=false) {
348 return _start (for_latency_measurement);
351 /** Stop using the device currently in use.
353 * If the function is successfully called, no subsequent calls to the
354 * process_callback() of @param engine will be made after the function
355 * returns, until parameters are reset and start() are called again.
357 * The backend is considered to be un-configured after a successful
358 * return, and requires calls to set hardware parameters before it can be
359 * start()-ed again. See pause() for a way to avoid this. stop() should
360 * only be used when reconfiguration is required OR when there are no
361 * plans to use the backend in the future with a reconfiguration.
363 * Return zero if successful, 1 if the device is not in use, negative values on error
365 virtual int stop () = 0;
367 /** While remaining connected to the device, and without changing its
368 * configuration, start (or stop) calling the process_callback() of @param engine
369 * without waiting for the device. Once process_callback() has returned, it
370 * will be called again immediately, thus allowing for faster-than-realtime
373 * All registered ports remain in existence and all connections remain
374 * unaltered. However, any physical ports should NOT be used by the
375 * process_callback() during freewheeling - the data behaviour is undefined.
377 * If @param start_stop is true, begin this behaviour; otherwise cease this
378 * behaviour if it currently occuring, and return to calling
379 * process_callback() of @param engine by waiting for the device.
381 * Return zero on success, non-zero otherwise.
383 virtual int freewheel (bool start_stop) = 0;
385 /** return the fraction of the time represented by the current buffer
386 * size that is being used for each buffer process cycle, as a value
389 * E.g. if the buffer size represents 5msec and current processing
390 * takes 1msec, the returned value should be 0.2.
392 * Implementations can feel free to smooth the values returned over
393 * time (e.g. high pass filtering, or its equivalent).
395 virtual float dsp_load() const = 0;
397 /* Transport Control (JACK is the only audio API that currently offers
398 the concept of shared transport control)
401 /** Attempt to change the transport state to TransportRolling.
403 virtual void transport_start () {}
404 /** Attempt to change the transport state to TransportStopped.
406 virtual void transport_stop () {}
407 /** return the current transport state
409 virtual TransportState transport_state () const { return TransportStopped; }
410 /** Attempt to locate the transport to @param pos
412 virtual void transport_locate (framepos_t /*pos*/) {}
413 /** Return the current transport location, in samples measured
414 * from the origin (defined by the transport time master)
416 virtual framepos_t transport_frame() const { return 0; }
418 /** If @param yn is true, become the time master for any inter-application transport
419 * timebase, otherwise cease to be the time master for the same.
421 * Return zero on success, non-zero otherwise
423 * JACK is the only currently known audio API with the concept of a shared
424 * transport timebase.
426 virtual int set_time_master (bool /*yn*/) { return 0; }
428 virtual int usecs_per_cycle () const { return 1000000 * (buffer_size() / sample_rate()); }
429 virtual size_t raw_buffer_size (DataType t) = 0;
433 /** return the time according to the sample clock in use, measured in
434 * samples since an arbitrary zero time in the past. The value should
435 * increase monotonically and linearly, without interruption from any
436 * source (including CPU frequency scaling).
438 * It is extremely likely that any implementation will use a DLL, since
439 * this function can be called from any thread, at any time, and must be
440 * able to accurately determine the correct sample time.
442 * Can be called from any thread.
444 virtual pframes_t sample_time () = 0;
446 /** Return the time according to the sample clock in use when the most
447 * recent buffer process cycle began. Can be called from any thread.
449 virtual pframes_t sample_time_at_cycle_start () = 0;
451 /** Return the time since the current buffer process cycle started,
452 * in samples, according to the sample clock in use.
454 * Can ONLY be called from within a process() callback tree (which
455 * implies that it can only be called by a process thread)
457 virtual pframes_t samples_since_cycle_start () = 0;
459 /** Return true if it possible to determine the offset in samples of the
460 * first video frame that starts within the current buffer process cycle,
461 * measured from the first sample of the cycle. If returning true,
462 * set @param offset to that offset.
464 * Eg. if it can be determined that the first video frame within the cycle
465 * starts 28 samples after the first sample of the cycle, then this method
466 * should return true and set @param offset to 28.
468 * May be impossible to support outside of JACK, which has specific support
469 * (in some cases, hardware support) for this feature.
471 * Can ONLY be called from within a process() callback tree (which implies
472 * that it can only be called by a process thread)
474 virtual bool get_sync_offset (pframes_t& /*offset*/) const { return false; }
476 /** Create a new thread suitable for running part of the buffer process
477 * cycle (i.e. Realtime scheduling, memory allocation, etc. etc are all
478 * correctly setup), with a stack size given in bytes by specified @param
479 * stacksize. The thread will begin executing @param func, and will exit
480 * when that function returns.
482 virtual int create_process_thread (boost::function<void()> func) = 0;
484 /** Wait for all processing threads to exit.
486 * Return zero on success, non-zero on failure.
488 virtual int join_process_threads () = 0;
490 /** Return true if execution context is in a backend thread
492 virtual bool in_process_thread () = 0;
494 /** Return the minimum stack size of audio threads in bytes
496 static size_t thread_stack_size () { return 100000; }
498 /** Return number of processing threads
500 virtual uint32_t process_thread_count () = 0;
502 virtual void update_latencies () = 0;
504 /** Set @param speed and @param position to the current speed and position
505 * indicated by some transport sync signal. Return whether the current
506 * transport state is pending, or finalized.
508 * Derived classes only need implement this if they provide some way to
509 * sync to a transport sync signal (e.g. Sony 9 Pin) that is not
510 * handled by Ardour itself (LTC and MTC are both handled by Ardour).
511 * The canonical example is JACK Transport.
513 virtual bool speed_and_position (double& speed, framepos_t& position) {
520 AudioBackendInfo& _info;
523 virtual int _start (bool for_latency_measurement) = 0;
528 #endif /* __libardour_audiobackend_h__ */