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 SampleFormatNotSupportedError,
105 SampleRateNotSupportedError,
106 RequestedInputLatencyNotSupportedError,
107 RequestedOutputLatencyNotSupportedError,
108 PeriodSizeNotSupportedError,
109 PeriodCountNotSupportedError,
110 DeviceConfigurationNotSupportedError,
111 ChannelCountNotSupportedError,
112 InputChannelCountNotSupportedError,
113 OutputChannelCountNotSupportedError,
114 AquireRealtimePermissionError,
115 SettingAudioThreadPriorityError,
116 SettingMIDIThreadPriorityError
119 static std::string get_error_string (ErrorCode);
121 enum StandardDeviceName {
126 static std::string get_standard_device_name (StandardDeviceName);
128 /** Return the AudioBackendInfo object from which this backend
131 AudioBackendInfo& info() const { return _info; }
133 /** Return the name of this backend.
135 * Should use a well-known, unique term. Expected examples
136 * might include "JACK", "CoreAudio", "ASIO" etc.
138 virtual std::string name() const = 0;
140 /** Return true if the callback from the underlying mechanism/API
141 * (CoreAudio, JACK, ASIO etc.) occurs in a thread subject to realtime
142 * constraints. Return false otherwise.
144 virtual bool is_realtime () const = 0;
146 /* Discovering devices and parameters */
148 /** Return true if this backend requires the selection of a "driver"
149 * before any device can be selected. Return false otherwise.
151 * Intended mainly to differentiate between meta-APIs like JACK
152 * which can still expose different backends (such as ALSA or CoreAudio
153 * or FFADO or netjack) and those like ASIO or CoreAudio which
156 virtual bool requires_driver_selection() const { return false; }
158 /** If the return value of requires_driver_selection() is true,
159 * then this function can return the list of known driver names.
161 * If the return value of requires_driver_selection() is false,
162 * then this function should not be called. If it is called
163 * its return value is an empty vector of strings.
165 virtual std::vector<std::string> enumerate_drivers() const { return std::vector<std::string>(); }
167 /** Returns zero if the backend can successfully use @param name as the
168 * driver, non-zero otherwise.
170 * Should not be used unless the backend returns true from
171 * requires_driver_selection()
173 virtual int set_driver (const std::string& /*drivername*/) { return 0; }
175 /** used to list device names along with whether or not they are currently
178 struct DeviceStatus {
182 DeviceStatus (const std::string& s, bool avail) : name (s), available (avail) {}
185 /** An optional alternate interface for backends to provide a facility to
186 * select separate input and output devices.
188 * If a backend returns true then enumerate_input_devices() and
189 * enumerate_output_devices() will be used instead of enumerate_devices()
190 * to enumerate devices. Similarly set_input/output_device_name() should
191 * be used to set devices instead of set_device_name().
193 virtual bool use_separate_input_and_output_devices () const { return false; }
195 /** Returns a collection of DeviceStatuses identifying devices discovered
196 * by this backend since the start of the process.
198 * Any of the names in each DeviceStatus may be used to identify a
199 * device in other calls to the backend, though any of them may become
200 * invalid at any time.
202 virtual std::vector<DeviceStatus> enumerate_devices () const = 0;
204 /** Returns a collection of DeviceStatuses identifying input devices
205 * discovered by this backend since the start of the process.
207 * Any of the names in each DeviceStatus may be used to identify a
208 * device in other calls to the backend, though any of them may become
209 * invalid at any time.
211 virtual std::vector<DeviceStatus> enumerate_input_devices () const
212 { return std::vector<DeviceStatus>(); }
214 /** Returns a collection of DeviceStatuses identifying output devices
215 * discovered by this backend since the start of the process.
217 * Any of the names in each DeviceStatus may be used to identify a
218 * device in other calls to the backend, though any of them may become
219 * invalid at any time.
221 virtual std::vector<DeviceStatus> enumerate_output_devices () const
222 { return std::vector<DeviceStatus>(); }
225 * @return true if backend supports requesting an update to the device list
226 * and any cached properties associated with the devices.
228 virtual bool can_request_update_devices () { return false; }
231 * Request an update to the list of devices returned in the enumerations.
232 * The Backend must return true from can_request_update_devices to support
234 * @return true if the devices were updated
236 virtual bool update_devices () { return false; }
238 /** Returns a collection of float identifying sample rates that are
239 * potentially usable with the hardware identified by @param device.
240 * Any of these values may be supplied in other calls to this backend
241 * as the desired sample rate to use with the name device, but the
242 * requested sample rate may turn out to be unavailable, or become invalid
245 virtual std::vector<float> available_sample_rates (const std::string& device) const = 0;
247 /* backends that support separate input and output devices should
248 * implement this function and return an intersection (not union) of available
249 * sample rates valid for the given input + output device combination.
251 virtual std::vector<float> available_sample_rates2 (const std::string& input_device, const std::string& output_device) const {
252 std::vector<float> input_sizes = available_sample_rates (input_device);
253 std::vector<float> output_sizes = available_sample_rates (output_device);
254 std::vector<float> rv;
255 std::set_union (input_sizes.begin (), input_sizes.end (),
256 output_sizes.begin (), output_sizes.end (),
257 std::back_inserter (rv));
261 /* Returns the default sample rate that will be shown to the user when
262 * configuration options are first presented. If the derived class
263 * needs or wants to override this, it can. It also MUST override this
264 * if there is any chance that an SR of 44.1kHz is not in the list
265 * returned by available_sample_rates()
267 virtual float default_sample_rate () const {
271 /** Returns a collection of uint32 identifying buffer sizes that are
272 * potentially usable with the hardware identified by @param device.
273 * Any of these values may be supplied in other calls to this backend
274 * as the desired buffer size to use with the name device, but the
275 * requested buffer size may turn out to be unavailable, or become invalid
278 virtual std::vector<uint32_t> available_buffer_sizes (const std::string& device) const = 0;
280 /* backends that support separate input and output devices should
281 * implement this function and return an intersection (not union) of available
282 * buffer sizes valid for the given input + output device combination.
284 virtual std::vector<uint32_t> available_buffer_sizes2 (const std::string& input_device, const std::string& output_device) const {
285 std::vector<uint32_t> input_rates = available_buffer_sizes (input_device);
286 std::vector<uint32_t> output_rates = available_buffer_sizes (output_device);
287 std::vector<uint32_t> rv;
288 std::set_union (input_rates.begin (), input_rates.end (),
289 output_rates.begin (), output_rates.end (),
290 std::back_inserter (rv));
293 /* Returns the default buffer size that will be shown to the user when
294 * configuration options are first presented. If the derived class
295 * needs or wants to override this, it can. It also MUST override this
296 * if there is any chance that a buffer size of 1024 is not in the list
297 * returned by available_buffer_sizes()
299 virtual uint32_t default_buffer_size (const std::string& device) const {
303 /** Returns the maximum number of input channels that are potentially
304 * usable with the hardware identified by @param device. Any number from 1
305 * to the value returned may be supplied in other calls to this backend as
306 * the input channel count to use with the name device, but the requested
307 * count may turn out to be unavailable, or become invalid at any time.
309 virtual uint32_t available_input_channel_count (const std::string& device) const = 0;
311 /** Returns the maximum number of output channels that are potentially
312 * usable with the hardware identified by @param device. Any number from 1
313 * to the value returned may be supplied in other calls to this backend as
314 * the output channel count to use with the name device, but the requested
315 * count may turn out to be unavailable, or become invalid at any time.
317 virtual uint32_t available_output_channel_count (const std::string& device) const = 0;
319 /* Return true if the derived class can change the sample rate of the
320 * device in use while the device is already being used. Return false
321 * otherwise. (example: JACK cannot do this as of September 2013)
323 virtual bool can_change_sample_rate_when_running () const = 0;
324 /* Return true if the derived class can change the buffer size of the
325 * device in use while the device is already being used. Return false
328 virtual bool can_change_buffer_size_when_running () const = 0;
330 /* Set the hardware parameters.
332 * If called when the current state is stopped or paused,
333 * the changes will not take effect until the state changes to running.
335 * If called while running, the state will change as fast as the
336 * implementation allows.
338 * All set_*() methods return zero on success, non-zero otherwise.
341 /** Set the name of the device to be used
343 virtual int set_device_name (const std::string&) = 0;
345 /** Set the name of the input device to be used if using separate
346 * input/output devices.
348 * @see use_separate_input_and_output_devices()
350 virtual int set_input_device_name (const std::string&) { return 0;}
352 /** Set the name of the output device to be used if using separate
353 * input/output devices.
355 * @see use_separate_input_and_output_devices()
357 virtual int set_output_device_name (const std::string&) { return 0;}
359 /** Deinitialize and destroy current device
361 virtual int drop_device() {return 0;};
362 /** Set the sample rate to be used
364 virtual int set_sample_rate (float) = 0;
365 /** Set the buffer size to be used.
367 * The device is assumed to use a double buffering scheme, so that one
368 * buffer's worth of data can be processed by hardware while software works
369 * on the other buffer. All known suitable audio APIs support this model
370 * (though ALSA allows for alternate numbers of buffers, and CoreAudio
371 * doesn't directly expose the concept).
373 virtual int set_buffer_size (uint32_t) = 0;
374 /** Set the preferred underlying hardware data layout.
375 * If @param yn is true, then the hardware will interleave
376 * samples for successive channels; otherwise, the hardware will store
377 * samples for a single channel contiguously.
379 * Setting this does not change the fact that all data streams
380 * to and from Ports are mono (essentially, non-interleaved)
382 virtual int set_interleaved (bool yn) = 0;
383 /** Set the number of input channels that should be used
385 virtual int set_input_channels (uint32_t) = 0;
386 /** Set the number of output channels that should be used
388 virtual int set_output_channels (uint32_t) = 0;
389 /** Set the (additional) input latency that cannot be determined via
390 * the implementation's underlying code (e.g. latency from
391 * external D-A/D-A converters. Units are samples.
393 virtual int set_systemic_input_latency (uint32_t) = 0;
394 /** Set the (additional) output latency that cannot be determined via
395 * the implementation's underlying code (e.g. latency from
396 * external D-A/D-A converters. Units are samples.
398 virtual int set_systemic_output_latency (uint32_t) = 0;
399 /** Set the (additional) input latency for a specific midi device,
400 * or if the identifier is empty, apply to all midi devices.
402 virtual int set_systemic_midi_input_latency (std::string const, uint32_t) = 0;
403 /** Set the (additional) output latency for a specific midi device,
404 * or if the identifier is empty, apply to all midi devices.
406 virtual int set_systemic_midi_output_latency (std::string const, uint32_t) = 0;
408 /* Retrieving parameters */
410 virtual std::string device_name () const = 0;
411 virtual std::string input_device_name () const { return std::string(); }
412 virtual std::string output_device_name () const { return std::string(); }
413 virtual float sample_rate () const = 0;
414 virtual uint32_t buffer_size () const = 0;
415 virtual bool interleaved () const = 0;
416 virtual uint32_t input_channels () const = 0;
417 virtual uint32_t output_channels () const = 0;
418 virtual uint32_t systemic_input_latency () const = 0;
419 virtual uint32_t systemic_output_latency () const = 0;
420 virtual uint32_t systemic_midi_input_latency (std::string const) const = 0;
421 virtual uint32_t systemic_midi_output_latency (std::string const) const = 0;
423 /** override this if this implementation returns true from
424 * requires_driver_selection()
426 virtual std::string driver_name() const { return std::string(); }
428 /** Return the name of a control application for the
429 * selected/in-use device. If no such application exists,
430 * or if no device has been selected or is in-use,
431 * return an empty string.
433 virtual std::string control_app_name() const = 0;
434 /** Launch the control app for the currently in-use or
435 * selected device. May do nothing if the control
436 * app is undefined or cannot be launched.
438 virtual void launch_control_app () = 0;
440 /* @return a vector of strings that describe the available
443 * These can be presented to the user to decide which
444 * MIDI drivers, options etc. can be used. The returned strings
445 * should be thought of as the key to a map of possible
446 * approaches to handling MIDI within the backend. Ensure that
447 * the strings will make sense to the user.
449 virtual std::vector<std::string> enumerate_midi_options () const = 0;
451 /* Request the use of the MIDI option named @param option, which
452 * should be one of the strings returned by enumerate_midi_options()
454 * @return zero if successful, non-zero otherwise
456 virtual int set_midi_option (const std::string& option) = 0;
458 virtual std::string midi_option () const = 0;
460 /** Detailed MIDI device list - if available */
461 virtual std::vector<DeviceStatus> enumerate_midi_devices () const = 0;
463 /** mark a midi-devices as enabled */
464 virtual int set_midi_device_enabled (std::string const, bool) = 0;
466 /** query if a midi-device is enabled */
467 virtual bool midi_device_enabled (std::string const) const = 0;
469 /** if backend supports systemic_midi_[in|ou]tput_latency() */
470 virtual bool can_set_systemic_midi_latencies () const = 0;
474 /** Start using the device named in the most recent call
475 * to set_device(), with the parameters set by various
476 * the most recent calls to set_sample_rate() etc. etc.
478 * At some undetermined time after this function is successfully called,
479 * the backend will start calling the ::process_callback() method of
480 * the AudioEngine referenced by @param engine. These calls will
481 * occur in a thread created by and/or under the control of the backend.
483 * @param for_latency_measurement if true, the device is being started
484 * to carry out latency measurements and the backend should this
485 * take care to return latency numbers that do not reflect
486 * any existing systemic latency settings.
488 * Return zero if successful, negative values otherwise.
493 * Why is this non-virtual but ::_start() is virtual ?
494 * Virtual methods with default parameters create possible ambiguity
495 * because a derived class may implement the same method with a different
496 * type or value of default parameter.
498 * So we make this non-virtual method to avoid possible overrides of
499 * default parameters. See Scott Meyers or other books on C++ to understand
500 * this pattern, or possibly just this:
502 * http://stackoverflow.com/questions/12139786/good-pratice-default-arguments-for-pure-virtual-method
504 int start (bool for_latency_measurement=false) {
505 return _start (for_latency_measurement);
508 /** Stop using the device currently in use.
510 * If the function is successfully called, no subsequent calls to the
511 * process_callback() of @param engine will be made after the function
512 * returns, until parameters are reset and start() are called again.
514 * The backend is considered to be un-configured after a successful
515 * return, and requires calls to set hardware parameters before it can be
516 * start()-ed again. See pause() for a way to avoid this. stop() should
517 * only be used when reconfiguration is required OR when there are no
518 * plans to use the backend in the future with a reconfiguration.
520 * Return zero if successful, 1 if the device is not in use, negative values on error
522 virtual int stop () = 0;
526 * Return zero if successful, negative values on error
528 virtual int reset_device() = 0;
530 /** While remaining connected to the device, and without changing its
531 * configuration, start (or stop) calling the process_callback() of @param engine
532 * without waiting for the device. Once process_callback() has returned, it
533 * will be called again immediately, thus allowing for faster-than-realtime
536 * All registered ports remain in existence and all connections remain
537 * unaltered. However, any physical ports should NOT be used by the
538 * process_callback() during freewheeling - the data behaviour is undefined.
540 * If @param start_stop is true, begin this behaviour; otherwise cease this
541 * behaviour if it currently occuring, and return to calling
542 * process_callback() of @param engine by waiting for the device.
544 * Return zero on success, non-zero otherwise.
546 virtual int freewheel (bool start_stop) = 0;
548 /** return the fraction of the time represented by the current buffer
549 * size that is being used for each buffer process cycle, as a value
552 * E.g. if the buffer size represents 5msec and current processing
553 * takes 1msec, the returned value should be 0.2.
555 * Implementations can feel free to smooth the values returned over
556 * time (e.g. high pass filtering, or its equivalent).
558 virtual float dsp_load() const = 0;
560 /* Transport Control (JACK is the only audio API that currently offers
561 the concept of shared transport control)
564 /** Attempt to change the transport state to TransportRolling.
566 virtual void transport_start () {}
567 /** Attempt to change the transport state to TransportStopped.
569 virtual void transport_stop () {}
570 /** return the current transport state
572 virtual TransportState transport_state () const { return TransportStopped; }
573 /** Attempt to locate the transport to @param pos
575 virtual void transport_locate (framepos_t /*pos*/) {}
576 /** Return the current transport location, in samples measured
577 * from the origin (defined by the transport time master)
579 virtual framepos_t transport_frame() const { return 0; }
581 /** If @param yn is true, become the time master for any inter-application transport
582 * timebase, otherwise cease to be the time master for the same.
584 * Return zero on success, non-zero otherwise
586 * JACK is the only currently known audio API with the concept of a shared
587 * transport timebase.
589 virtual int set_time_master (bool /*yn*/) { return 0; }
591 virtual int usecs_per_cycle () const { return 1000000 * (buffer_size() / sample_rate()); }
592 virtual size_t raw_buffer_size (DataType t) = 0;
596 /** return the time according to the sample clock in use, measured in
597 * samples since an arbitrary zero time in the past. The value should
598 * increase monotonically and linearly, without interruption from any
599 * source (including CPU frequency scaling).
601 * It is extremely likely that any implementation will use a DLL, since
602 * this function can be called from any thread, at any time, and must be
603 * able to accurately determine the correct sample time.
605 * Can be called from any thread.
607 virtual framepos_t sample_time () = 0;
609 /** Return the time according to the sample clock in use when the most
610 * recent buffer process cycle began. Can be called from any thread.
612 virtual framepos_t sample_time_at_cycle_start () = 0;
614 /** Return the time since the current buffer process cycle started,
615 * in samples, according to the sample clock in use.
617 * Can ONLY be called from within a process() callback tree (which
618 * implies that it can only be called by a process thread)
620 virtual pframes_t samples_since_cycle_start () = 0;
622 /** Return true if it possible to determine the offset in samples of the
623 * first video frame that starts within the current buffer process cycle,
624 * measured from the first sample of the cycle. If returning true,
625 * set @param offset to that offset.
627 * Eg. if it can be determined that the first video frame within the cycle
628 * starts 28 samples after the first sample of the cycle, then this method
629 * should return true and set @param offset to 28.
631 * May be impossible to support outside of JACK, which has specific support
632 * (in some cases, hardware support) for this feature.
634 * Can ONLY be called from within a process() callback tree (which implies
635 * that it can only be called by a process thread)
637 virtual bool get_sync_offset (pframes_t& /*offset*/) const { return false; }
639 /** Create a new thread suitable for running part of the buffer process
640 * cycle (i.e. Realtime scheduling, memory allocation, etc. etc are all
641 * correctly setup), with a stack size given in bytes by specified @param
642 * stacksize. The thread will begin executing @param func, and will exit
643 * when that function returns.
645 virtual int create_process_thread (boost::function<void()> func) = 0;
647 /** Wait for all processing threads to exit.
649 * Return zero on success, non-zero on failure.
651 virtual int join_process_threads () = 0;
653 /** Return true if execution context is in a backend thread
655 virtual bool in_process_thread () = 0;
657 /** Return the minimum stack size of audio threads in bytes
659 static size_t thread_stack_size () { return 100000; }
661 /** Return number of processing threads
663 virtual uint32_t process_thread_count () = 0;
665 virtual void update_latencies () = 0;
667 /** Set @param speed and @param position to the current speed and position
668 * indicated by some transport sync signal. Return whether the current
669 * transport state is pending, or finalized.
671 * Derived classes only need implement this if they provide some way to
672 * sync to a transport sync signal (e.g. Sony 9 Pin) that is not
673 * handled by Ardour itself (LTC and MTC are both handled by Ardour).
674 * The canonical example is JACK Transport.
676 virtual bool speed_and_position (double& speed, framepos_t& position) {
683 AudioBackendInfo& _info;
686 virtual int _start (bool for_latency_measurement) = 0;
691 #endif /* __libardour_audiobackend_h__ */