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 () {}
91 BackendInitializationError = -64,
92 BackendDeinitializationError,
94 AudioDeviceCloseError,
95 AudioDeviceNotAvailableError,
96 AudioDeviceNotConnectedError,
97 AudioDeviceReservationError,
100 MidiDeviceCloseError,
101 MidiDeviceNotAvailableError,
102 MidiDeviceNotConnectedError,
104 SampleRateNotSupportedError,
105 RequestedInputLatencyNotSupportedError,
106 RequestedOutputLatencyNotSupportedError,
107 PeriodSizeNotSupportedError,
108 PeriodCountNotSupportedError,
109 DeviceConfigurationNotSupportedError,
110 InputChannelCountNotSupportedError,
111 OutputChannelCountNotSupportedError,
112 AquireRealtimePermissionError,
113 SettingAudioThreadPriorityError,
114 SettingMIDIThreadPriorityError
117 static std::string get_error_string (ErrorCode);
119 enum StandardDeviceName {
124 static std::string get_standard_device_name (StandardDeviceName);
126 /** Return the AudioBackendInfo object from which this backend
129 AudioBackendInfo& info() const { return _info; }
131 /** Return the name of this backend.
133 * Should use a well-known, unique term. Expected examples
134 * might include "JACK", "CoreAudio", "ASIO" etc.
136 virtual std::string name() const = 0;
138 /** Return true if the callback from the underlying mechanism/API
139 * (CoreAudio, JACK, ASIO etc.) occurs in a thread subject to realtime
140 * constraints. Return false otherwise.
142 virtual bool is_realtime () const = 0;
144 /* Discovering devices and parameters */
146 /** Return true if this backend requires the selection of a "driver"
147 * before any device can be selected. Return false otherwise.
149 * Intended mainly to differentiate between meta-APIs like JACK
150 * which can still expose different backends (such as ALSA or CoreAudio
151 * or FFADO or netjack) and those like ASIO or CoreAudio which
154 virtual bool requires_driver_selection() const { return false; }
156 /** If the return value of requires_driver_selection() is true,
157 * then this function can return the list of known driver names.
159 * If the return value of requires_driver_selection() is false,
160 * then this function should not be called. If it is called
161 * its return value is an empty vector of strings.
163 virtual std::vector<std::string> enumerate_drivers() const { return std::vector<std::string>(); }
165 /** Returns zero if the backend can successfully use @param name as the
166 * driver, non-zero otherwise.
168 * Should not be used unless the backend returns true from
169 * requires_driver_selection()
171 virtual int set_driver (const std::string& /*drivername*/) { return 0; }
173 /** used to list device names along with whether or not they are currently
176 struct DeviceStatus {
180 DeviceStatus (const std::string& s, bool avail) : name (s), available (avail) {}
183 /** An optional alternate interface for backends to provide a facility to
184 * select separate input and output devices.
186 * If a backend returns true then enumerate_input_devices() and
187 * enumerate_output_devices() will be used instead of enumerate_devices()
188 * to enumerate devices. Similarly set_input/output_device_name() should
189 * be used to set devices instead of set_device_name().
191 virtual bool use_separate_input_and_output_devices () const { return false; }
193 /** Returns a collection of DeviceStatuses identifying devices discovered
194 * by this backend since the start of the process.
196 * Any of the names in each DeviceStatus may be used to identify a
197 * device in other calls to the backend, though any of them may become
198 * invalid at any time.
200 virtual std::vector<DeviceStatus> enumerate_devices () const = 0;
202 /** Returns a collection of DeviceStatuses identifying input devices
203 * discovered by this backend since the start of the process.
205 * Any of the names in each DeviceStatus may be used to identify a
206 * device in other calls to the backend, though any of them may become
207 * invalid at any time.
209 virtual std::vector<DeviceStatus> enumerate_input_devices () const
210 { return std::vector<DeviceStatus>(); }
212 /** Returns a collection of DeviceStatuses identifying output devices
213 * discovered by this backend since the start of the process.
215 * Any of the names in each DeviceStatus may be used to identify a
216 * device in other calls to the backend, though any of them may become
217 * invalid at any time.
219 virtual std::vector<DeviceStatus> enumerate_output_devices () const
220 { return std::vector<DeviceStatus>(); }
223 * @return true if backend supports requesting an update to the device list
224 * and any cached properties associated with the devices.
226 virtual bool can_request_update_devices () { return false; }
229 * Request an update to the list of devices returned in the enumerations.
230 * The Backend must return true from can_request_update_devices to support
232 * @return true if the devices were updated
234 virtual bool update_devices () { return false; }
236 /** Returns a collection of float identifying sample rates that are
237 * potentially usable with the hardware identified by @param device.
238 * Any of these values may be supplied in other calls to this backend
239 * as the desired sample rate to use with the name device, but the
240 * requested sample rate may turn out to be unavailable, or become invalid
243 virtual std::vector<float> available_sample_rates (const std::string& device) const = 0;
245 /* backends that support separate input and output devices should
246 * implement this function and return an intersection (not union) of available
247 * sample rates valid for the given input + output device combination.
249 virtual std::vector<float> available_sample_rates2 (const std::string& input_device, const std::string& output_device) const {
250 std::vector<float> input_sizes = available_sample_rates (input_device);
251 std::vector<float> output_sizes = available_sample_rates (output_device);
252 std::vector<float> rv;
253 std::set_union (input_sizes.begin (), input_sizes.end (),
254 output_sizes.begin (), output_sizes.end (),
255 std::back_inserter (rv));
259 /* Returns the default sample rate that will be shown to the user when
260 * configuration options are first presented. If the derived class
261 * needs or wants to override this, it can. It also MUST override this
262 * if there is any chance that an SR of 44.1kHz is not in the list
263 * returned by available_sample_rates()
265 virtual float default_sample_rate () const {
269 /** Returns a collection of uint32 identifying buffer sizes that are
270 * potentially usable with the hardware identified by @param device.
271 * Any of these values may be supplied in other calls to this backend
272 * as the desired buffer size to use with the name device, but the
273 * requested buffer size may turn out to be unavailable, or become invalid
276 virtual std::vector<uint32_t> available_buffer_sizes (const std::string& device) const = 0;
278 /* backends that support separate input and output devices should
279 * implement this function and return an intersection (not union) of available
280 * buffer sizes valid for the given input + output device combination.
282 virtual std::vector<uint32_t> available_buffer_sizes2 (const std::string& input_device, const std::string& output_device) const {
283 std::vector<uint32_t> input_rates = available_buffer_sizes (input_device);
284 std::vector<uint32_t> output_rates = available_buffer_sizes (output_device);
285 std::vector<uint32_t> rv;
286 std::set_union (input_rates.begin (), input_rates.end (),
287 output_rates.begin (), output_rates.end (),
288 std::back_inserter (rv));
291 /* Returns the default buffer size that will be shown to the user when
292 * configuration options are first presented. If the derived class
293 * needs or wants to override this, it can. It also MUST override this
294 * if there is any chance that a buffer size of 1024 is not in the list
295 * returned by available_buffer_sizes()
297 virtual uint32_t default_buffer_size (const std::string& device) const {
301 /** Returns the maximum number of input channels that are potentially
302 * usable with the hardware identified by @param device. Any number from 1
303 * to the value returned may be supplied in other calls to this backend as
304 * the input channel count to use with the name device, but the requested
305 * count may turn out to be unavailable, or become invalid at any time.
307 virtual uint32_t available_input_channel_count (const std::string& device) const = 0;
309 /** Returns the maximum number of output channels that are potentially
310 * usable with the hardware identified by @param device. Any number from 1
311 * to the value returned may be supplied in other calls to this backend as
312 * the output channel count to use with the name device, but the requested
313 * count may turn out to be unavailable, or become invalid at any time.
315 virtual uint32_t available_output_channel_count (const std::string& device) const = 0;
317 /* Return true if the derived class can change the sample rate of the
318 * device in use while the device is already being used. Return false
319 * otherwise. (example: JACK cannot do this as of September 2013)
321 virtual bool can_change_sample_rate_when_running () const = 0;
322 /* Return true if the derived class can change the buffer size of the
323 * device in use while the device is already being used. Return false
326 virtual bool can_change_buffer_size_when_running () const = 0;
328 /* Set the hardware parameters.
330 * If called when the current state is stopped or paused,
331 * the changes will not take effect until the state changes to running.
333 * If called while running, the state will change as fast as the
334 * implementation allows.
336 * All set_*() methods return zero on success, non-zero otherwise.
339 /** Set the name of the device to be used
341 virtual int set_device_name (const std::string&) = 0;
343 /** Set the name of the input device to be used if using separate
344 * input/output devices.
346 * @see use_separate_input_and_output_devices()
348 virtual int set_input_device_name (const std::string&) { return 0;}
350 /** Set the name of the output device to be used if using separate
351 * input/output devices.
353 * @see use_separate_input_and_output_devices()
355 virtual int set_output_device_name (const std::string&) { return 0;}
357 /** Deinitialize and destroy current device
359 virtual int drop_device() {return 0;};
360 /** Set the sample rate to be used
362 virtual int set_sample_rate (float) = 0;
363 /** Set the buffer size to be used.
365 * The device is assumed to use a double buffering scheme, so that one
366 * buffer's worth of data can be processed by hardware while software works
367 * on the other buffer. All known suitable audio APIs support this model
368 * (though ALSA allows for alternate numbers of buffers, and CoreAudio
369 * doesn't directly expose the concept).
371 virtual int set_buffer_size (uint32_t) = 0;
372 /** Set the preferred underlying hardware data layout.
373 * If @param yn is true, then the hardware will interleave
374 * samples for successive channels; otherwise, the hardware will store
375 * samples for a single channel contiguously.
377 * Setting this does not change the fact that all data streams
378 * to and from Ports are mono (essentially, non-interleaved)
380 virtual int set_interleaved (bool yn) = 0;
381 /** Set the number of input channels that should be used
383 virtual int set_input_channels (uint32_t) = 0;
384 /** Set the number of output channels that should be used
386 virtual int set_output_channels (uint32_t) = 0;
387 /** Set the (additional) input latency that cannot be determined via
388 * the implementation's underlying code (e.g. latency from
389 * external D-A/D-A converters. Units are samples.
391 virtual int set_systemic_input_latency (uint32_t) = 0;
392 /** Set the (additional) output latency that cannot be determined via
393 * the implementation's underlying code (e.g. latency from
394 * external D-A/D-A converters. Units are samples.
396 virtual int set_systemic_output_latency (uint32_t) = 0;
397 /** Set the (additional) input latency for a specific midi device,
398 * or if the identifier is empty, apply to all midi devices.
400 virtual int set_systemic_midi_input_latency (std::string const, uint32_t) = 0;
401 /** Set the (additional) output latency for a specific midi device,
402 * or if the identifier is empty, apply to all midi devices.
404 virtual int set_systemic_midi_output_latency (std::string const, uint32_t) = 0;
406 /* Retrieving parameters */
408 virtual std::string device_name () const = 0;
409 virtual std::string input_device_name () const { return std::string(); }
410 virtual std::string output_device_name () const { return std::string(); }
411 virtual float sample_rate () const = 0;
412 virtual uint32_t buffer_size () const = 0;
413 virtual bool interleaved () const = 0;
414 virtual uint32_t input_channels () const = 0;
415 virtual uint32_t output_channels () const = 0;
416 virtual uint32_t systemic_input_latency () const = 0;
417 virtual uint32_t systemic_output_latency () const = 0;
418 virtual uint32_t systemic_midi_input_latency (std::string const) const = 0;
419 virtual uint32_t systemic_midi_output_latency (std::string const) const = 0;
421 /** override this if this implementation returns true from
422 * requires_driver_selection()
424 virtual std::string driver_name() const { return std::string(); }
426 /** Return the name of a control application for the
427 * selected/in-use device. If no such application exists,
428 * or if no device has been selected or is in-use,
429 * return an empty string.
431 virtual std::string control_app_name() const = 0;
432 /** Launch the control app for the currently in-use or
433 * selected device. May do nothing if the control
434 * app is undefined or cannot be launched.
436 virtual void launch_control_app () = 0;
438 /* @return a vector of strings that describe the available
441 * These can be presented to the user to decide which
442 * MIDI drivers, options etc. can be used. The returned strings
443 * should be thought of as the key to a map of possible
444 * approaches to handling MIDI within the backend. Ensure that
445 * the strings will make sense to the user.
447 virtual std::vector<std::string> enumerate_midi_options () const = 0;
449 /* Request the use of the MIDI option named @param option, which
450 * should be one of the strings returned by enumerate_midi_options()
452 * @return zero if successful, non-zero otherwise
454 virtual int set_midi_option (const std::string& option) = 0;
456 virtual std::string midi_option () const = 0;
458 /** Detailed MIDI device list - if available */
459 virtual std::vector<DeviceStatus> enumerate_midi_devices () const = 0;
461 /** mark a midi-devices as enabled */
462 virtual int set_midi_device_enabled (std::string const, bool) = 0;
464 /** query if a midi-device is enabled */
465 virtual bool midi_device_enabled (std::string const) const = 0;
467 /** if backend supports systemic_midi_[in|ou]tput_latency() */
468 virtual bool can_set_systemic_midi_latencies () const = 0;
472 /** Start using the device named in the most recent call
473 * to set_device(), with the parameters set by various
474 * the most recent calls to set_sample_rate() etc. etc.
476 * At some undetermined time after this function is successfully called,
477 * the backend will start calling the ::process_callback() method of
478 * the AudioEngine referenced by @param engine. These calls will
479 * occur in a thread created by and/or under the control of the backend.
481 * @param for_latency_measurement if true, the device is being started
482 * to carry out latency measurements and the backend should this
483 * take care to return latency numbers that do not reflect
484 * any existing systemic latency settings.
486 * Return zero if successful, negative values otherwise.
491 * Why is this non-virtual but ::_start() is virtual ?
492 * Virtual methods with default parameters create possible ambiguity
493 * because a derived class may implement the same method with a different
494 * type or value of default parameter.
496 * So we make this non-virtual method to avoid possible overrides of
497 * default parameters. See Scott Meyers or other books on C++ to understand
498 * this pattern, or possibly just this:
500 * http://stackoverflow.com/questions/12139786/good-pratice-default-arguments-for-pure-virtual-method
502 int start (bool for_latency_measurement=false) {
503 return _start (for_latency_measurement);
506 /** Stop using the device currently in use.
508 * If the function is successfully called, no subsequent calls to the
509 * process_callback() of @param engine will be made after the function
510 * returns, until parameters are reset and start() are called again.
512 * The backend is considered to be un-configured after a successful
513 * return, and requires calls to set hardware parameters before it can be
514 * start()-ed again. See pause() for a way to avoid this. stop() should
515 * only be used when reconfiguration is required OR when there are no
516 * plans to use the backend in the future with a reconfiguration.
518 * Return zero if successful, 1 if the device is not in use, negative values on error
520 virtual int stop () = 0;
524 * Return zero if successful, negative values on error
526 virtual int reset_device() = 0;
528 /** While remaining connected to the device, and without changing its
529 * configuration, start (or stop) calling the process_callback() of @param engine
530 * without waiting for the device. Once process_callback() has returned, it
531 * will be called again immediately, thus allowing for faster-than-realtime
534 * All registered ports remain in existence and all connections remain
535 * unaltered. However, any physical ports should NOT be used by the
536 * process_callback() during freewheeling - the data behaviour is undefined.
538 * If @param start_stop is true, begin this behaviour; otherwise cease this
539 * behaviour if it currently occuring, and return to calling
540 * process_callback() of @param engine by waiting for the device.
542 * Return zero on success, non-zero otherwise.
544 virtual int freewheel (bool start_stop) = 0;
546 /** return the fraction of the time represented by the current buffer
547 * size that is being used for each buffer process cycle, as a value
550 * E.g. if the buffer size represents 5msec and current processing
551 * takes 1msec, the returned value should be 0.2.
553 * Implementations can feel free to smooth the values returned over
554 * time (e.g. high pass filtering, or its equivalent).
556 virtual float dsp_load() const = 0;
558 /* Transport Control (JACK is the only audio API that currently offers
559 the concept of shared transport control)
562 /** Attempt to change the transport state to TransportRolling.
564 virtual void transport_start () {}
565 /** Attempt to change the transport state to TransportStopped.
567 virtual void transport_stop () {}
568 /** return the current transport state
570 virtual TransportState transport_state () const { return TransportStopped; }
571 /** Attempt to locate the transport to @param pos
573 virtual void transport_locate (framepos_t /*pos*/) {}
574 /** Return the current transport location, in samples measured
575 * from the origin (defined by the transport time master)
577 virtual framepos_t transport_frame() const { return 0; }
579 /** If @param yn is true, become the time master for any inter-application transport
580 * timebase, otherwise cease to be the time master for the same.
582 * Return zero on success, non-zero otherwise
584 * JACK is the only currently known audio API with the concept of a shared
585 * transport timebase.
587 virtual int set_time_master (bool /*yn*/) { return 0; }
589 virtual int usecs_per_cycle () const { return 1000000 * (buffer_size() / sample_rate()); }
590 virtual size_t raw_buffer_size (DataType t) = 0;
594 /** return the time according to the sample clock in use, measured in
595 * samples since an arbitrary zero time in the past. The value should
596 * increase monotonically and linearly, without interruption from any
597 * source (including CPU frequency scaling).
599 * It is extremely likely that any implementation will use a DLL, since
600 * this function can be called from any thread, at any time, and must be
601 * able to accurately determine the correct sample time.
603 * Can be called from any thread.
605 virtual framepos_t sample_time () = 0;
607 /** Return the time according to the sample clock in use when the most
608 * recent buffer process cycle began. Can be called from any thread.
610 virtual framepos_t sample_time_at_cycle_start () = 0;
612 /** Return the time since the current buffer process cycle started,
613 * in samples, according to the sample clock in use.
615 * Can ONLY be called from within a process() callback tree (which
616 * implies that it can only be called by a process thread)
618 virtual pframes_t samples_since_cycle_start () = 0;
620 /** Return true if it possible to determine the offset in samples of the
621 * first video frame that starts within the current buffer process cycle,
622 * measured from the first sample of the cycle. If returning true,
623 * set @param offset to that offset.
625 * Eg. if it can be determined that the first video frame within the cycle
626 * starts 28 samples after the first sample of the cycle, then this method
627 * should return true and set @param offset to 28.
629 * May be impossible to support outside of JACK, which has specific support
630 * (in some cases, hardware support) for this feature.
632 * Can ONLY be called from within a process() callback tree (which implies
633 * that it can only be called by a process thread)
635 virtual bool get_sync_offset (pframes_t& /*offset*/) const { return false; }
637 /** Create a new thread suitable for running part of the buffer process
638 * cycle (i.e. Realtime scheduling, memory allocation, etc. etc are all
639 * correctly setup), with a stack size given in bytes by specified @param
640 * stacksize. The thread will begin executing @param func, and will exit
641 * when that function returns.
643 virtual int create_process_thread (boost::function<void()> func) = 0;
645 /** Wait for all processing threads to exit.
647 * Return zero on success, non-zero on failure.
649 virtual int join_process_threads () = 0;
651 /** Return true if execution context is in a backend thread
653 virtual bool in_process_thread () = 0;
655 /** Return the minimum stack size of audio threads in bytes
657 static size_t thread_stack_size () { return 100000; }
659 /** Return number of processing threads
661 virtual uint32_t process_thread_count () = 0;
663 virtual void update_latencies () = 0;
665 /** Set @param speed and @param position to the current speed and position
666 * indicated by some transport sync signal. Return whether the current
667 * transport state is pending, or finalized.
669 * Derived classes only need implement this if they provide some way to
670 * sync to a transport sync signal (e.g. Sony 9 Pin) that is not
671 * handled by Ardour itself (LTC and MTC are both handled by Ardour).
672 * The canonical example is JACK Transport.
674 virtual bool speed_and_position (double& speed, framepos_t& position) {
681 AudioBackendInfo& _info;
684 virtual int _start (bool for_latency_measurement) = 0;
689 #endif /* __libardour_audiobackend_h__ */