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,
93 BackendReinitializationError,
95 AudioDeviceCloseError,
96 AudioDeviceInvalidError,
97 AudioDeviceNotAvailableError,
98 AudioDeviceNotConnectedError,
99 AudioDeviceReservationError,
102 MidiDeviceCloseError,
103 MidiDeviceNotAvailableError,
104 MidiDeviceNotConnectedError,
106 SampleFormatNotSupportedError,
107 SampleRateNotSupportedError,
108 RequestedInputLatencyNotSupportedError,
109 RequestedOutputLatencyNotSupportedError,
110 PeriodSizeNotSupportedError,
111 PeriodCountNotSupportedError,
112 DeviceConfigurationNotSupportedError,
113 ChannelCountNotSupportedError,
114 InputChannelCountNotSupportedError,
115 OutputChannelCountNotSupportedError,
116 AquireRealtimePermissionError,
117 SettingAudioThreadPriorityError,
118 SettingMIDIThreadPriorityError,
119 ProcessThreadStartError,
120 FreewheelThreadStartError,
121 PortRegistrationError,
126 static std::string get_error_string (ErrorCode);
128 enum StandardDeviceName {
133 static std::string get_standard_device_name (StandardDeviceName);
135 /** Return the AudioBackendInfo object from which this backend
138 AudioBackendInfo& info() const { return _info; }
140 /** Return the name of this backend.
142 * Should use a well-known, unique term. Expected examples
143 * might include "JACK", "CoreAudio", "ASIO" etc.
145 virtual std::string name() const = 0;
147 /** Return true if the callback from the underlying mechanism/API
148 * (CoreAudio, JACK, ASIO etc.) occurs in a thread subject to realtime
149 * constraints. Return false otherwise.
151 virtual bool is_realtime () const = 0;
153 /* Discovering devices and parameters */
155 /** Return true if this backend requires the selection of a "driver"
156 * before any device can be selected. Return false otherwise.
158 * Intended mainly to differentiate between meta-APIs like JACK
159 * which can still expose different backends (such as ALSA or CoreAudio
160 * or FFADO or netjack) and those like ASIO or CoreAudio which
163 virtual bool requires_driver_selection() const { return false; }
165 /** If the return value of requires_driver_selection() is true,
166 * then this function can return the list of known driver names.
168 * If the return value of requires_driver_selection() is false,
169 * then this function should not be called. If it is called
170 * its return value is an empty vector of strings.
172 virtual std::vector<std::string> enumerate_drivers() const { return std::vector<std::string>(); }
174 /** Returns zero if the backend can successfully use @param name as the
175 * driver, non-zero otherwise.
177 * Should not be used unless the backend returns true from
178 * requires_driver_selection()
180 virtual int set_driver (const std::string& /*drivername*/) { return 0; }
182 /** used to list device names along with whether or not they are currently
185 struct DeviceStatus {
189 DeviceStatus (const std::string& s, bool avail) : name (s), available (avail) {}
192 /** An optional alternate interface for backends to provide a facility to
193 * select separate input and output devices.
195 * If a backend returns true then enumerate_input_devices() and
196 * enumerate_output_devices() will be used instead of enumerate_devices()
197 * to enumerate devices. Similarly set_input/output_device_name() should
198 * be used to set devices instead of set_device_name().
200 virtual bool use_separate_input_and_output_devices () const { return false; }
202 /** Returns a collection of DeviceStatuses identifying devices discovered
203 * 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_devices () const = 0;
211 /** Returns a collection of DeviceStatuses identifying input devices
212 * discovered by this backend since the start of the process.
214 * Any of the names in each DeviceStatus may be used to identify a
215 * device in other calls to the backend, though any of them may become
216 * invalid at any time.
218 virtual std::vector<DeviceStatus> enumerate_input_devices () const
219 { return std::vector<DeviceStatus>(); }
221 /** Returns a collection of DeviceStatuses identifying output devices
222 * discovered by this backend since the start of the process.
224 * Any of the names in each DeviceStatus may be used to identify a
225 * device in other calls to the backend, though any of them may become
226 * invalid at any time.
228 virtual std::vector<DeviceStatus> enumerate_output_devices () const
229 { return std::vector<DeviceStatus>(); }
232 /** An interface to set buffers/period for playback latency.
233 * useful for ALSA or JACK/ALSA on Linux.
235 * @return true if the backend supports period-size configuration
237 virtual bool can_set_period_size () const { return false; }
239 /** Returns a vector of supported period-sizes for the given driver */
240 virtual std::vector<uint32_t> available_period_sizes (const std::string& driver) const { return std::vector<uint32_t>(); }
242 /** Set the period size to be used.
243 * must be called before starting the backend.
245 virtual int set_peridod_size (uint32_t) { return -1; }
248 * @return true if backend supports requesting an update to the device list
249 * and any cached properties associated with the devices.
251 virtual bool can_request_update_devices () { return false; }
254 * Request an update to the list of devices returned in the enumerations.
255 * The Backend must return true from can_request_update_devices to support
257 * @return true if the devices were updated
259 virtual bool update_devices () { return false; }
261 /** Returns a collection of float identifying sample rates that are
262 * potentially usable with the hardware identified by @param device.
263 * Any of these values may be supplied in other calls to this backend
264 * as the desired sample rate to use with the name device, but the
265 * requested sample rate may turn out to be unavailable, or become invalid
268 virtual std::vector<float> available_sample_rates (const std::string& device) const = 0;
270 /* backends that support separate input and output devices should
271 * implement this function and return an intersection (not union) of available
272 * sample rates valid for the given input + output device combination.
274 virtual std::vector<float> available_sample_rates2 (const std::string& input_device, const std::string& output_device) const {
275 std::vector<float> input_sizes = available_sample_rates (input_device);
276 std::vector<float> output_sizes = available_sample_rates (output_device);
277 std::vector<float> rv;
278 std::set_union (input_sizes.begin (), input_sizes.end (),
279 output_sizes.begin (), output_sizes.end (),
280 std::back_inserter (rv));
284 /* Returns the default sample rate that will be shown to the user when
285 * configuration options are first presented. If the derived class
286 * needs or wants to override this, it can. It also MUST override this
287 * if there is any chance that an SR of 44.1kHz is not in the list
288 * returned by available_sample_rates()
290 virtual float default_sample_rate () const {
294 /** Returns a collection of uint32 identifying buffer sizes that are
295 * potentially usable with the hardware identified by @param device.
296 * Any of these values may be supplied in other calls to this backend
297 * as the desired buffer size to use with the name device, but the
298 * requested buffer size may turn out to be unavailable, or become invalid
301 virtual std::vector<uint32_t> available_buffer_sizes (const std::string& device) const = 0;
303 /* backends that support separate input and output devices should
304 * implement this function and return an intersection (not union) of available
305 * buffer sizes valid for the given input + output device combination.
307 virtual std::vector<uint32_t> available_buffer_sizes2 (const std::string& input_device, const std::string& output_device) const {
308 std::vector<uint32_t> input_rates = available_buffer_sizes (input_device);
309 std::vector<uint32_t> output_rates = available_buffer_sizes (output_device);
310 std::vector<uint32_t> rv;
311 std::set_union (input_rates.begin (), input_rates.end (),
312 output_rates.begin (), output_rates.end (),
313 std::back_inserter (rv));
316 /* Returns the default buffer size that will be shown to the user when
317 * configuration options are first presented. If the derived class
318 * needs or wants to override this, it can. It also MUST override this
319 * if there is any chance that a buffer size of 1024 is not in the list
320 * returned by available_buffer_sizes()
322 virtual uint32_t default_buffer_size (const std::string& device) const {
326 /** Returns the maximum number of input channels that are potentially
327 * usable with the hardware identified by @param device. Any number from 1
328 * to the value returned may be supplied in other calls to this backend as
329 * the input channel count to use with the name device, but the requested
330 * count may turn out to be unavailable, or become invalid at any time.
332 virtual uint32_t available_input_channel_count (const std::string& device) const = 0;
334 /** Returns the maximum number of output channels that are potentially
335 * usable with the hardware identified by @param device. Any number from 1
336 * to the value returned may be supplied in other calls to this backend as
337 * the output channel count to use with the name device, but the requested
338 * count may turn out to be unavailable, or become invalid at any time.
340 virtual uint32_t available_output_channel_count (const std::string& device) const = 0;
342 /* Return true if the derived class can change the sample rate of the
343 * device in use while the device is already being used. Return false
344 * otherwise. (example: JACK cannot do this as of September 2013)
346 virtual bool can_change_sample_rate_when_running () const = 0;
347 /* Return true if the derived class can change the buffer size of the
348 * device in use while the device is already being used. Return false
351 virtual bool can_change_buffer_size_when_running () const = 0;
353 /** return true if the backend can measure and update
354 * systemic latencies without restart.
356 virtual bool can_change_systemic_latency_when_running () const { return false; }
358 /* Set the hardware parameters.
360 * If called when the current state is stopped or paused,
361 * the changes will not take effect until the state changes to running.
363 * If called while running, the state will change as fast as the
364 * implementation allows.
366 * All set_*() methods return zero on success, non-zero otherwise.
369 /** Set the name of the device to be used
371 virtual int set_device_name (const std::string&) = 0;
373 /** Set the name of the input device to be used if using separate
374 * input/output devices.
376 * @see use_separate_input_and_output_devices()
378 virtual int set_input_device_name (const std::string&) { return 0;}
380 /** Set the name of the output device to be used if using separate
381 * input/output devices.
383 * @see use_separate_input_and_output_devices()
385 virtual int set_output_device_name (const std::string&) { return 0;}
387 /** Deinitialize and destroy current device
389 virtual int drop_device() {return 0;};
390 /** Set the sample rate to be used
392 virtual int set_sample_rate (float) = 0;
393 /** Set the buffer size to be used.
395 * The device is assumed to use a double buffering scheme, so that one
396 * buffer's worth of data can be processed by hardware while software works
397 * on the other buffer. All known suitable audio APIs support this model
398 * (though ALSA allows for alternate numbers of buffers, and CoreAudio
399 * doesn't directly expose the concept).
401 virtual int set_buffer_size (uint32_t) = 0;
402 /** Set the preferred underlying hardware data layout.
403 * If @param yn is true, then the hardware will interleave
404 * samples for successive channels; otherwise, the hardware will store
405 * samples for a single channel contiguously.
407 * Setting this does not change the fact that all data streams
408 * to and from Ports are mono (essentially, non-interleaved)
410 virtual int set_interleaved (bool yn) = 0;
411 /** Set the number of input channels that should be used
413 virtual int set_input_channels (uint32_t) = 0;
414 /** Set the number of output channels that should be used
416 virtual int set_output_channels (uint32_t) = 0;
417 /** Set the (additional) input latency that cannot be determined via
418 * the implementation's underlying code (e.g. latency from
419 * external D-A/D-A converters. Units are samples.
421 virtual int set_systemic_input_latency (uint32_t) = 0;
422 /** Set the (additional) output latency that cannot be determined via
423 * the implementation's underlying code (e.g. latency from
424 * external D-A/D-A converters. Units are samples.
426 virtual int set_systemic_output_latency (uint32_t) = 0;
427 /** Set the (additional) input latency for a specific midi device,
428 * or if the identifier is empty, apply to all midi devices.
430 virtual int set_systemic_midi_input_latency (std::string const, uint32_t) = 0;
431 /** Set the (additional) output latency for a specific midi device,
432 * or if the identifier is empty, apply to all midi devices.
434 virtual int set_systemic_midi_output_latency (std::string const, uint32_t) = 0;
436 /* Retrieving parameters */
438 virtual std::string device_name () const = 0;
439 virtual std::string input_device_name () const { return std::string(); }
440 virtual std::string output_device_name () const { return std::string(); }
441 virtual float sample_rate () const = 0;
442 virtual uint32_t buffer_size () const = 0;
443 virtual bool interleaved () const = 0;
444 virtual uint32_t input_channels () const = 0;
445 virtual uint32_t output_channels () const = 0;
446 virtual uint32_t systemic_input_latency () const = 0;
447 virtual uint32_t systemic_output_latency () const = 0;
448 virtual uint32_t systemic_midi_input_latency (std::string const) const = 0;
449 virtual uint32_t systemic_midi_output_latency (std::string const) const = 0;
450 virtual uint32_t period_size () const { return 0; }
452 /** override this if this implementation returns true from
453 * requires_driver_selection()
455 virtual std::string driver_name() const { return std::string(); }
457 /** Return the name of a control application for the
458 * selected/in-use device. If no such application exists,
459 * or if no device has been selected or is in-use,
460 * return an empty string.
462 virtual std::string control_app_name() const = 0;
463 /** Launch the control app for the currently in-use or
464 * selected device. May do nothing if the control
465 * app is undefined or cannot be launched.
467 virtual void launch_control_app () = 0;
469 /* @return a vector of strings that describe the available
472 * These can be presented to the user to decide which
473 * MIDI drivers, options etc. can be used. The returned strings
474 * should be thought of as the key to a map of possible
475 * approaches to handling MIDI within the backend. Ensure that
476 * the strings will make sense to the user.
478 virtual std::vector<std::string> enumerate_midi_options () const = 0;
480 /* Request the use of the MIDI option named @param option, which
481 * should be one of the strings returned by enumerate_midi_options()
483 * @return zero if successful, non-zero otherwise
485 virtual int set_midi_option (const std::string& option) = 0;
487 virtual std::string midi_option () const = 0;
489 /** Detailed MIDI device list - if available */
490 virtual std::vector<DeviceStatus> enumerate_midi_devices () const = 0;
492 /** mark a midi-devices as enabled */
493 virtual int set_midi_device_enabled (std::string const, bool) = 0;
495 /** query if a midi-device is enabled */
496 virtual bool midi_device_enabled (std::string const) const = 0;
498 /** if backend supports systemic_midi_[in|ou]tput_latency() */
499 virtual bool can_set_systemic_midi_latencies () const = 0;
503 /** Start using the device named in the most recent call
504 * to set_device(), with the parameters set by various
505 * the most recent calls to set_sample_rate() etc. etc.
507 * At some undetermined time after this function is successfully called,
508 * the backend will start calling the ::process_callback() method of
509 * the AudioEngine referenced by @param engine. These calls will
510 * occur in a thread created by and/or under the control of the backend.
512 * @param for_latency_measurement if true, the device is being started
513 * to carry out latency measurements and the backend should this
514 * take care to return latency numbers that do not reflect
515 * any existing systemic latency settings.
517 * Return zero if successful, negative values otherwise.
522 * Why is this non-virtual but ::_start() is virtual ?
523 * Virtual methods with default parameters create possible ambiguity
524 * because a derived class may implement the same method with a different
525 * type or value of default parameter.
527 * So we make this non-virtual method to avoid possible overrides of
528 * default parameters. See Scott Meyers or other books on C++ to understand
529 * this pattern, or possibly just this:
531 * http://stackoverflow.com/questions/12139786/good-pratice-default-arguments-for-pure-virtual-method
533 int start (bool for_latency_measurement=false) {
534 return _start (for_latency_measurement);
537 /** Stop using the device currently in use.
539 * If the function is successfully called, no subsequent calls to the
540 * process_callback() of @param engine will be made after the function
541 * returns, until parameters are reset and start() are called again.
543 * The backend is considered to be un-configured after a successful
544 * return, and requires calls to set hardware parameters before it can be
545 * start()-ed again. See pause() for a way to avoid this. stop() should
546 * only be used when reconfiguration is required OR when there are no
547 * plans to use the backend in the future with a reconfiguration.
549 * Return zero if successful, 1 if the device is not in use, negative values on error
551 virtual int stop () = 0;
555 * Return zero if successful, negative values on error
557 virtual int reset_device() = 0;
559 /** While remaining connected to the device, and without changing its
560 * configuration, start (or stop) calling the process_callback() of @param engine
561 * without waiting for the device. Once process_callback() has returned, it
562 * will be called again immediately, thus allowing for faster-than-realtime
565 * All registered ports remain in existence and all connections remain
566 * unaltered. However, any physical ports should NOT be used by the
567 * process_callback() during freewheeling - the data behaviour is undefined.
569 * If @param start_stop is true, begin this behaviour; otherwise cease this
570 * behaviour if it currently occuring, and return to calling
571 * process_callback() of @param engine by waiting for the device.
573 * Return zero on success, non-zero otherwise.
575 virtual int freewheel (bool start_stop) = 0;
577 /** return the fraction of the time represented by the current buffer
578 * size that is being used for each buffer process cycle, as a value
581 * E.g. if the buffer size represents 5msec and current processing
582 * takes 1msec, the returned value should be 0.2.
584 * Implementations can feel free to smooth the values returned over
585 * time (e.g. high pass filtering, or its equivalent).
587 virtual float dsp_load() const = 0;
589 /* Transport Control (JACK is the only audio API that currently offers
590 the concept of shared transport control)
593 /** Attempt to change the transport state to TransportRolling.
595 virtual void transport_start () {}
596 /** Attempt to change the transport state to TransportStopped.
598 virtual void transport_stop () {}
599 /** return the current transport state
601 virtual TransportState transport_state () const { return TransportStopped; }
602 /** Attempt to locate the transport to @param pos
604 virtual void transport_locate (framepos_t /*pos*/) {}
605 /** Return the current transport location, in samples measured
606 * from the origin (defined by the transport time master)
608 virtual framepos_t transport_frame() const { return 0; }
610 /** If @param yn is true, become the time master for any inter-application transport
611 * timebase, otherwise cease to be the time master for the same.
613 * Return zero on success, non-zero otherwise
615 * JACK is the only currently known audio API with the concept of a shared
616 * transport timebase.
618 virtual int set_time_master (bool /*yn*/) { return 0; }
620 virtual int usecs_per_cycle () const { return 1000000 * (buffer_size() / sample_rate()); }
621 virtual size_t raw_buffer_size (DataType t) = 0;
625 /** return the time according to the sample clock in use, measured in
626 * samples since an arbitrary zero time in the past. The value should
627 * increase monotonically and linearly, without interruption from any
628 * source (including CPU frequency scaling).
630 * It is extremely likely that any implementation will use a DLL, since
631 * this function can be called from any thread, at any time, and must be
632 * able to accurately determine the correct sample time.
634 * Can be called from any thread.
636 virtual framepos_t sample_time () = 0;
638 /** Return the time according to the sample clock in use when the most
639 * recent buffer process cycle began. Can be called from any thread.
641 virtual framepos_t sample_time_at_cycle_start () = 0;
643 /** Return the time since the current buffer process cycle started,
644 * in samples, according to the sample clock in use.
646 * Can ONLY be called from within a process() callback tree (which
647 * implies that it can only be called by a process thread)
649 virtual pframes_t samples_since_cycle_start () = 0;
651 /** Return true if it possible to determine the offset in samples of the
652 * first video frame that starts within the current buffer process cycle,
653 * measured from the first sample of the cycle. If returning true,
654 * set @param offset to that offset.
656 * Eg. if it can be determined that the first video frame within the cycle
657 * starts 28 samples after the first sample of the cycle, then this method
658 * should return true and set @param offset to 28.
660 * May be impossible to support outside of JACK, which has specific support
661 * (in some cases, hardware support) for this feature.
663 * Can ONLY be called from within a process() callback tree (which implies
664 * that it can only be called by a process thread)
666 virtual bool get_sync_offset (pframes_t& /*offset*/) const { return false; }
668 /** Create a new thread suitable for running part of the buffer process
669 * cycle (i.e. Realtime scheduling, memory allocation, etc. etc are all
670 * correctly setup), with a stack size given in bytes by specified @param
671 * stacksize. The thread will begin executing @param func, and will exit
672 * when that function returns.
674 virtual int create_process_thread (boost::function<void()> func) = 0;
676 /** Wait for all processing threads to exit.
678 * Return zero on success, non-zero on failure.
680 virtual int join_process_threads () = 0;
682 /** Return true if execution context is in a backend thread
684 virtual bool in_process_thread () = 0;
686 /** Return the minimum stack size of audio threads in bytes
688 static size_t thread_stack_size () { return 100000; }
690 /** Return number of processing threads
692 virtual uint32_t process_thread_count () = 0;
694 virtual void update_latencies () = 0;
696 /** Set @param speed and @param position to the current speed and position
697 * indicated by some transport sync signal. Return whether the current
698 * transport state is pending, or finalized.
700 * Derived classes only need implement this if they provide some way to
701 * sync to a transport sync signal (e.g. Sony 9 Pin) that is not
702 * handled by Ardour itself (LTC and MTC are both handled by Ardour).
703 * The canonical example is JACK Transport.
705 virtual bool speed_and_position (double& speed, framepos_t& position) {
712 AudioBackendInfo& _info;
715 virtual int _start (bool for_latency_measurement) = 0;
720 #endif /* __libardour_audiobackend_h__ */