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>(); }
222 /** Returns a collection of float identifying sample rates that are
223 * potentially usable with the hardware identified by @param device.
224 * Any of these values may be supplied in other calls to this backend
225 * as the desired sample rate to use with the name device, but the
226 * requested sample rate may turn out to be unavailable, or become invalid
229 virtual std::vector<float> available_sample_rates (const std::string& device) const = 0;
231 /* backends that support separate input and output devices should
232 * implement this function and return an intersection (not union) of available
233 * sample rates valid for the given input + output device combination.
235 virtual std::vector<float> available_sample_rates2 (const std::string& input_device, const std::string& output_device) const {
236 std::vector<float> input_sizes = available_sample_rates (input_device);
237 std::vector<float> output_sizes = available_sample_rates (output_device);
238 std::vector<float> rv;
239 std::set_union (input_sizes.begin (), input_sizes.end (),
240 output_sizes.begin (), output_sizes.end (),
241 std::back_inserter (rv));
245 /* Returns the default sample rate that will be shown to the user when
246 * configuration options are first presented. If the derived class
247 * needs or wants to override this, it can. It also MUST override this
248 * if there is any chance that an SR of 44.1kHz is not in the list
249 * returned by available_sample_rates()
251 virtual float default_sample_rate () const {
255 /** Returns a collection of uint32 identifying buffer sizes that are
256 * potentially usable with the hardware identified by @param device.
257 * Any of these values may be supplied in other calls to this backend
258 * as the desired buffer size to use with the name device, but the
259 * requested buffer size may turn out to be unavailable, or become invalid
262 virtual std::vector<uint32_t> available_buffer_sizes (const std::string& device) const = 0;
264 /* backends that support separate input and output devices should
265 * implement this function and return an intersection (not union) of available
266 * buffer sizes valid for the given input + output device combination.
268 virtual std::vector<uint32_t> available_buffer_sizes2 (const std::string& input_device, const std::string& output_device) const {
269 std::vector<uint32_t> input_rates = available_buffer_sizes (input_device);
270 std::vector<uint32_t> output_rates = available_buffer_sizes (output_device);
271 std::vector<uint32_t> rv;
272 std::set_union (input_rates.begin (), input_rates.end (),
273 output_rates.begin (), output_rates.end (),
274 std::back_inserter (rv));
277 /* Returns the default buffer size that will be shown to the user when
278 * configuration options are first presented. If the derived class
279 * needs or wants to override this, it can. It also MUST override this
280 * if there is any chance that a buffer size of 1024 is not in the list
281 * returned by available_buffer_sizes()
283 virtual uint32_t default_buffer_size (const std::string& device) const {
287 /** Returns the maximum number of input channels that are potentially
288 * usable with the hardware identified by @param device. Any number from 1
289 * to the value returned may be supplied in other calls to this backend as
290 * the input channel count to use with the name device, but the requested
291 * count may turn out to be unavailable, or become invalid at any time.
293 virtual uint32_t available_input_channel_count (const std::string& device) const = 0;
295 /** Returns the maximum number of output channels that are potentially
296 * usable with the hardware identified by @param device. Any number from 1
297 * to the value returned may be supplied in other calls to this backend as
298 * the output channel count to use with the name device, but the requested
299 * count may turn out to be unavailable, or become invalid at any time.
301 virtual uint32_t available_output_channel_count (const std::string& device) const = 0;
303 /* Return true if the derived class can change the sample rate of the
304 * device in use while the device is already being used. Return false
305 * otherwise. (example: JACK cannot do this as of September 2013)
307 virtual bool can_change_sample_rate_when_running () const = 0;
308 /* Return true if the derived class can change the buffer size of the
309 * device in use while the device is already being used. Return false
312 virtual bool can_change_buffer_size_when_running () const = 0;
314 /* Set the hardware parameters.
316 * If called when the current state is stopped or paused,
317 * the changes will not take effect until the state changes to running.
319 * If called while running, the state will change as fast as the
320 * implementation allows.
322 * All set_*() methods return zero on success, non-zero otherwise.
325 /** Set the name of the device to be used
327 virtual int set_device_name (const std::string&) = 0;
329 /** Set the name of the input device to be used if using separate
330 * input/output devices.
332 * @see use_separate_input_and_output_devices()
334 virtual int set_input_device_name (const std::string&) { return 0;}
336 /** Set the name of the output device to be used if using separate
337 * input/output devices.
339 * @see use_separate_input_and_output_devices()
341 virtual int set_output_device_name (const std::string&) { return 0;}
343 /** Deinitialize and destroy current device
345 virtual int drop_device() {return 0;};
346 /** Set the sample rate to be used
348 virtual int set_sample_rate (float) = 0;
349 /** Set the buffer size to be used.
351 * The device is assumed to use a double buffering scheme, so that one
352 * buffer's worth of data can be processed by hardware while software works
353 * on the other buffer. All known suitable audio APIs support this model
354 * (though ALSA allows for alternate numbers of buffers, and CoreAudio
355 * doesn't directly expose the concept).
357 virtual int set_buffer_size (uint32_t) = 0;
358 /** Set the preferred underlying hardware data layout.
359 * If @param yn is true, then the hardware will interleave
360 * samples for successive channels; otherwise, the hardware will store
361 * samples for a single channel contiguously.
363 * Setting this does not change the fact that all data streams
364 * to and from Ports are mono (essentially, non-interleaved)
366 virtual int set_interleaved (bool yn) = 0;
367 /** Set the number of input channels that should be used
369 virtual int set_input_channels (uint32_t) = 0;
370 /** Set the number of output channels that should be used
372 virtual int set_output_channels (uint32_t) = 0;
373 /** Set the (additional) input latency that cannot be determined via
374 * the implementation's underlying code (e.g. latency from
375 * external D-A/D-A converters. Units are samples.
377 virtual int set_systemic_input_latency (uint32_t) = 0;
378 /** Set the (additional) output latency that cannot be determined via
379 * the implementation's underlying code (e.g. latency from
380 * external D-A/D-A converters. Units are samples.
382 virtual int set_systemic_output_latency (uint32_t) = 0;
383 /** Set the (additional) input latency for a specific midi device,
384 * or if the identifier is empty, apply to all midi devices.
386 virtual int set_systemic_midi_input_latency (std::string const, uint32_t) = 0;
387 /** Set the (additional) output latency for a specific midi device,
388 * or if the identifier is empty, apply to all midi devices.
390 virtual int set_systemic_midi_output_latency (std::string const, uint32_t) = 0;
392 /* Retrieving parameters */
394 virtual std::string device_name () const = 0;
395 virtual std::string input_device_name () const { return std::string(); }
396 virtual std::string output_device_name () const { return std::string(); }
397 virtual float sample_rate () const = 0;
398 virtual uint32_t buffer_size () const = 0;
399 virtual bool interleaved () const = 0;
400 virtual uint32_t input_channels () const = 0;
401 virtual uint32_t output_channels () const = 0;
402 virtual uint32_t systemic_input_latency () const = 0;
403 virtual uint32_t systemic_output_latency () const = 0;
404 virtual uint32_t systemic_midi_input_latency (std::string const) const = 0;
405 virtual uint32_t systemic_midi_output_latency (std::string const) const = 0;
407 /** override this if this implementation returns true from
408 * requires_driver_selection()
410 virtual std::string driver_name() const { return std::string(); }
412 /** Return the name of a control application for the
413 * selected/in-use device. If no such application exists,
414 * or if no device has been selected or is in-use,
415 * return an empty string.
417 virtual std::string control_app_name() const = 0;
418 /** Launch the control app for the currently in-use or
419 * selected device. May do nothing if the control
420 * app is undefined or cannot be launched.
422 virtual void launch_control_app () = 0;
424 /* @return a vector of strings that describe the available
427 * These can be presented to the user to decide which
428 * MIDI drivers, options etc. can be used. The returned strings
429 * should be thought of as the key to a map of possible
430 * approaches to handling MIDI within the backend. Ensure that
431 * the strings will make sense to the user.
433 virtual std::vector<std::string> enumerate_midi_options () const = 0;
435 /* Request the use of the MIDI option named @param option, which
436 * should be one of the strings returned by enumerate_midi_options()
438 * @return zero if successful, non-zero otherwise
440 virtual int set_midi_option (const std::string& option) = 0;
442 virtual std::string midi_option () const = 0;
444 /** Detailed MIDI device list - if available */
445 virtual std::vector<DeviceStatus> enumerate_midi_devices () const = 0;
447 /** mark a midi-devices as enabled */
448 virtual int set_midi_device_enabled (std::string const, bool) = 0;
450 /** query if a midi-device is enabled */
451 virtual bool midi_device_enabled (std::string const) const = 0;
453 /** if backend supports systemic_midi_[in|ou]tput_latency() */
454 virtual bool can_set_systemic_midi_latencies () const = 0;
458 /** Start using the device named in the most recent call
459 * to set_device(), with the parameters set by various
460 * the most recent calls to set_sample_rate() etc. etc.
462 * At some undetermined time after this function is successfully called,
463 * the backend will start calling the ::process_callback() method of
464 * the AudioEngine referenced by @param engine. These calls will
465 * occur in a thread created by and/or under the control of the backend.
467 * @param for_latency_measurement if true, the device is being started
468 * to carry out latency measurements and the backend should this
469 * take care to return latency numbers that do not reflect
470 * any existing systemic latency settings.
472 * Return zero if successful, negative values otherwise.
477 * Why is this non-virtual but ::_start() is virtual ?
478 * Virtual methods with default parameters create possible ambiguity
479 * because a derived class may implement the same method with a different
480 * type or value of default parameter.
482 * So we make this non-virtual method to avoid possible overrides of
483 * default parameters. See Scott Meyers or other books on C++ to understand
484 * this pattern, or possibly just this:
486 * http://stackoverflow.com/questions/12139786/good-pratice-default-arguments-for-pure-virtual-method
488 int start (bool for_latency_measurement=false) {
489 return _start (for_latency_measurement);
492 /** Stop using the device currently in use.
494 * If the function is successfully called, no subsequent calls to the
495 * process_callback() of @param engine will be made after the function
496 * returns, until parameters are reset and start() are called again.
498 * The backend is considered to be un-configured after a successful
499 * return, and requires calls to set hardware parameters before it can be
500 * start()-ed again. See pause() for a way to avoid this. stop() should
501 * only be used when reconfiguration is required OR when there are no
502 * plans to use the backend in the future with a reconfiguration.
504 * Return zero if successful, 1 if the device is not in use, negative values on error
506 virtual int stop () = 0;
510 * Return zero if successful, negative values on error
512 virtual int reset_device() = 0;
514 /** While remaining connected to the device, and without changing its
515 * configuration, start (or stop) calling the process_callback() of @param engine
516 * without waiting for the device. Once process_callback() has returned, it
517 * will be called again immediately, thus allowing for faster-than-realtime
520 * All registered ports remain in existence and all connections remain
521 * unaltered. However, any physical ports should NOT be used by the
522 * process_callback() during freewheeling - the data behaviour is undefined.
524 * If @param start_stop is true, begin this behaviour; otherwise cease this
525 * behaviour if it currently occuring, and return to calling
526 * process_callback() of @param engine by waiting for the device.
528 * Return zero on success, non-zero otherwise.
530 virtual int freewheel (bool start_stop) = 0;
532 /** return the fraction of the time represented by the current buffer
533 * size that is being used for each buffer process cycle, as a value
536 * E.g. if the buffer size represents 5msec and current processing
537 * takes 1msec, the returned value should be 0.2.
539 * Implementations can feel free to smooth the values returned over
540 * time (e.g. high pass filtering, or its equivalent).
542 virtual float dsp_load() const = 0;
544 /* Transport Control (JACK is the only audio API that currently offers
545 the concept of shared transport control)
548 /** Attempt to change the transport state to TransportRolling.
550 virtual void transport_start () {}
551 /** Attempt to change the transport state to TransportStopped.
553 virtual void transport_stop () {}
554 /** return the current transport state
556 virtual TransportState transport_state () const { return TransportStopped; }
557 /** Attempt to locate the transport to @param pos
559 virtual void transport_locate (framepos_t /*pos*/) {}
560 /** Return the current transport location, in samples measured
561 * from the origin (defined by the transport time master)
563 virtual framepos_t transport_frame() const { return 0; }
565 /** If @param yn is true, become the time master for any inter-application transport
566 * timebase, otherwise cease to be the time master for the same.
568 * Return zero on success, non-zero otherwise
570 * JACK is the only currently known audio API with the concept of a shared
571 * transport timebase.
573 virtual int set_time_master (bool /*yn*/) { return 0; }
575 virtual int usecs_per_cycle () const { return 1000000 * (buffer_size() / sample_rate()); }
576 virtual size_t raw_buffer_size (DataType t) = 0;
580 /** return the time according to the sample clock in use, measured in
581 * samples since an arbitrary zero time in the past. The value should
582 * increase monotonically and linearly, without interruption from any
583 * source (including CPU frequency scaling).
585 * It is extremely likely that any implementation will use a DLL, since
586 * this function can be called from any thread, at any time, and must be
587 * able to accurately determine the correct sample time.
589 * Can be called from any thread.
591 virtual framepos_t sample_time () = 0;
593 /** Return the time according to the sample clock in use when the most
594 * recent buffer process cycle began. Can be called from any thread.
596 virtual framepos_t sample_time_at_cycle_start () = 0;
598 /** Return the time since the current buffer process cycle started,
599 * in samples, according to the sample clock in use.
601 * Can ONLY be called from within a process() callback tree (which
602 * implies that it can only be called by a process thread)
604 virtual pframes_t samples_since_cycle_start () = 0;
606 /** Return true if it possible to determine the offset in samples of the
607 * first video frame that starts within the current buffer process cycle,
608 * measured from the first sample of the cycle. If returning true,
609 * set @param offset to that offset.
611 * Eg. if it can be determined that the first video frame within the cycle
612 * starts 28 samples after the first sample of the cycle, then this method
613 * should return true and set @param offset to 28.
615 * May be impossible to support outside of JACK, which has specific support
616 * (in some cases, hardware support) for this feature.
618 * Can ONLY be called from within a process() callback tree (which implies
619 * that it can only be called by a process thread)
621 virtual bool get_sync_offset (pframes_t& /*offset*/) const { return false; }
623 /** Create a new thread suitable for running part of the buffer process
624 * cycle (i.e. Realtime scheduling, memory allocation, etc. etc are all
625 * correctly setup), with a stack size given in bytes by specified @param
626 * stacksize. The thread will begin executing @param func, and will exit
627 * when that function returns.
629 virtual int create_process_thread (boost::function<void()> func) = 0;
631 /** Wait for all processing threads to exit.
633 * Return zero on success, non-zero on failure.
635 virtual int join_process_threads () = 0;
637 /** Return true if execution context is in a backend thread
639 virtual bool in_process_thread () = 0;
641 /** Return the minimum stack size of audio threads in bytes
643 static size_t thread_stack_size () { return 100000; }
645 /** Return number of processing threads
647 virtual uint32_t process_thread_count () = 0;
649 virtual void update_latencies () = 0;
651 /** Set @param speed and @param position to the current speed and position
652 * indicated by some transport sync signal. Return whether the current
653 * transport state is pending, or finalized.
655 * Derived classes only need implement this if they provide some way to
656 * sync to a transport sync signal (e.g. Sony 9 Pin) that is not
657 * handled by Ardour itself (LTC and MTC are both handled by Ardour).
658 * The canonical example is JACK Transport.
660 virtual bool speed_and_position (double& speed, framepos_t& position) {
667 AudioBackendInfo& _info;
670 virtual int _start (bool for_latency_measurement) = 0;
675 #endif /* __libardour_audiobackend_h__ */