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"
35 #include "ardour/visibility.h"
37 #ifdef ARDOURBACKEND_DLL_EXPORTS // defined if we are building the ARDOUR Panners DLLs (instead of using them)
38 #define ARDOURBACKEND_API LIBARDOUR_HELPER_DLL_EXPORT
40 #define ARDOURBACKEND_API LIBARDOUR_HELPER_DLL_IMPORT
42 #define ARDOURBACKEND_LOCAL LIBARDOUR_HELPER_DLL_LOCAL
46 class LIBARDOUR_API AudioBackend : public PortEngine {
49 AudioBackend (AudioEngine& e) : PortEngine (e), engine (e) {}
50 virtual ~AudioBackend () {}
52 /** Return the name of this backend.
54 * Should use a well-known, unique term. Expected examples
55 * might include "JACK", "CoreAudio", "ASIO" etc.
57 virtual std::string name() const = 0;
59 /** Return true if the callback from the underlying mechanism/API
60 * (CoreAudio, JACK, ASIO etc.) occurs in a thread subject to realtime
61 * constraints. Return false otherwise.
63 virtual bool is_realtime () const = 0;
65 /* Discovering devices and parameters */
67 /** Return true if this backend requires the selection of a "driver"
68 * before any device can be selected. Return false otherwise.
70 * Intended mainly to differentiate between meta-APIs like JACK
71 * which can still expose different backends (such as ALSA or CoreAudio
72 * or FFADO or netjack) and those like ASIO or CoreAudio which
75 virtual bool requires_driver_selection() const { return false; }
77 /** If the return value of requires_driver_selection() is true,
78 * then this function can return the list of known driver names.
80 * If the return value of requires_driver_selection() is false,
81 * then this function should not be called. If it is called
82 * its return value is an empty vector of strings.
84 virtual std::vector<std::string> enumerate_drivers() const { return std::vector<std::string>(); }
86 /** Returns zero if the backend can successfully use @param name as the
87 * driver, non-zero otherwise.
89 * Should not be used unless the backend returns true from
90 * requires_driver_selection()
92 virtual int set_driver (const std::string& /*drivername*/) { return 0; }
94 /** used to list device names along with whether or not they are currently
101 DeviceStatus (const std::string& s, bool avail) : name (s), available (avail) {}
104 /** Returns a collection of DeviceStatuses identifying devices discovered
105 * by this backend since the start of the process.
107 * Any of the names in each DeviceStatus may be used to identify a
108 * device in other calls to the backend, though any of them may become
109 * invalid at any time.
111 virtual std::vector<DeviceStatus> enumerate_devices () const = 0;
113 /** Returns a collection of float identifying sample rates that are
114 * potentially usable with the hardware identified by @param device.
115 * Any of these values may be supplied in other calls to this backend
116 * as the desired sample rate to use with the name device, but the
117 * requested sample rate may turn out to be unavailable, or become invalid
120 virtual std::vector<float> available_sample_rates (const std::string& device) const = 0;
121 /** Returns a collection of uint32 identifying buffer sizes that are
122 * potentially usable with the hardware identified by @param device.
123 * Any of these values may be supplied in other calls to this backend
124 * as the desired buffer size to use with the name device, but the
125 * requested buffer size may turn out to be unavailable, or become invalid
128 virtual std::vector<uint32_t> available_buffer_sizes (const std::string& device) const = 0;
130 /** Returns the maximum number of input channels that are potentially
131 * usable with the hardware identified by @param device. Any number from 1
132 * to the value returned may be supplied in other calls to this backend as
133 * the input channel count to use with the name device, but the requested
134 * count may turn out to be unavailable, or become invalid at any time.
136 virtual uint32_t available_input_channel_count (const std::string& device) const = 0;
138 /** Returns the maximum number of output channels that are potentially
139 * usable with the hardware identified by @param device. Any number from 1
140 * to the value returned may be supplied in other calls to this backend as
141 * the output channel count to use with the name device, but the requested
142 * count may turn out to be unavailable, or become invalid at any time.
144 virtual uint32_t available_output_channel_count (const std::string& device) const = 0;
146 /* Return true if the derived class can change the sample rate of the
147 * device in use while the device is already being used. Return false
148 * otherwise. (example: JACK cannot do this as of September 2013)
150 virtual bool can_change_sample_rate_when_running () const = 0;
151 /* Return true if the derived class can change the buffer size of the
152 * device in use while the device is already being used. Return false
155 virtual bool can_change_buffer_size_when_running () const = 0;
157 /* Set the hardware parameters.
159 * If called when the current state is stopped or paused,
160 * the changes will not take effect until the state changes to running.
162 * If called while running, the state will change as fast as the
163 * implementation allows.
165 * All set_*() methods return zero on success, non-zero otherwise.
168 /** Set the name of the device to be used
170 virtual int set_device_name (const std::string&) = 0;
171 /** Set the sample rate to be used
173 virtual int set_sample_rate (float) = 0;
174 /** Set the buffer size to be used.
176 * The device is assumed to use a double buffering scheme, so that one
177 * buffer's worth of data can be processed by hardware while software works
178 * on the other buffer. All known suitable audio APIs support this model
179 * (though ALSA allows for alternate numbers of buffers, and CoreAudio
180 * doesn't directly expose the concept).
182 virtual int set_buffer_size (uint32_t) = 0;
183 /** Set the preferred underlying hardware sample format
185 * This does not change the sample format (32 bit float) read and
186 * written to the device via the Port API.
188 virtual int set_sample_format (SampleFormat) = 0;
189 /** Set the preferred underlying hardware data layout.
190 * If @param yn is true, then the hardware will interleave
191 * samples for successive channels; otherwise, the hardware will store
192 * samples for a single channel contiguously.
194 * Setting this does not change the fact that all data streams
195 * to and from Ports are mono (essentially, non-interleaved)
197 virtual int set_interleaved (bool yn) = 0;
198 /** Set the number of input channels that should be used
200 virtual int set_input_channels (uint32_t) = 0;
201 /** Set the number of output channels that should be used
203 virtual int set_output_channels (uint32_t) = 0;
204 /** Set the (additional) input latency that cannot be determined via
205 * the implementation's underlying code (e.g. latency from
206 * external D-A/D-A converters. Units are samples.
208 virtual int set_systemic_input_latency (uint32_t) = 0;
209 /** Set the (additional) output latency that cannot be determined via
210 * the implementation's underlying code (e.g. latency from
211 * external D-A/D-A converters. Units are samples.
213 virtual int set_systemic_output_latency (uint32_t) = 0;
215 /* Retrieving parameters */
217 virtual std::string device_name () const = 0;
218 virtual float sample_rate () const = 0;
219 virtual uint32_t buffer_size () const = 0;
220 virtual SampleFormat sample_format () const = 0;
221 virtual bool interleaved () const = 0;
222 virtual uint32_t input_channels () const = 0;
223 virtual uint32_t output_channels () const = 0;
224 virtual uint32_t systemic_input_latency () const = 0;
225 virtual uint32_t systemic_output_latency () const = 0;
227 /** override this if this implementation returns true from
228 * requires_driver_selection()
230 virtual std::string driver_name() const { return std::string(); }
232 /** Return the name of a control application for the
233 * selected/in-use device. If no such application exists,
234 * or if no device has been selected or is in-use,
235 * return an empty string.
237 virtual std::string control_app_name() const = 0;
238 /** Launch the control app for the currently in-use or
239 * selected device. May do nothing if the control
240 * app is undefined or cannot be launched.
242 virtual void launch_control_app () = 0;
244 /* @return a vector of strings that describe the available
247 * These can be presented to the user to decide which
248 * MIDI drivers, options etc. can be used. The returned strings
249 * should be thought of as the key to a map of possible
250 * approaches to handling MIDI within the backend. Ensure that
251 * the strings will make sense to the user.
253 virtual std::vector<std::string> enumerate_midi_options () const = 0;
255 /* Request the use of the MIDI option named @param option, which
256 * should be one of the strings returned by enumerate_midi_options()
258 * @return zero if successful, non-zero otherwise
260 virtual int set_midi_option (const std::string& option) = 0;
262 virtual std::string midi_option () const = 0;
266 /* non-virtual method to avoid possible overrides of default
267 * parameters. See Scott Meyers or other books on C++ to
268 * understand this pattern, or possibly just this:
270 * http://stackoverflow.com/questions/12139786/good-pratice-default-arguments-for-pure-virtual-method
272 int start (bool for_latency_measurement=false) {
273 return _start (for_latency_measurement);
276 /** Start using the device named in the most recent call
277 * to set_device(), with the parameters set by various
278 * the most recent calls to set_sample_rate() etc. etc.
280 * At some undetermined time after this function is successfully called,
281 * the backend will start calling the ::process_callback() method of
282 * the AudioEngine referenced by @param engine. These calls will
283 * occur in a thread created by and/or under the control of the backend.
285 * @param for_latency_measurement if true, the device is being started
286 * to carry out latency measurements and the backend should this
287 * take care to return latency numbers that do not reflect
288 * any existing systemic latency settings.
290 * Return zero if successful, negative values otherwise.
292 virtual int _start (bool for_latency_measurement) = 0;
294 /** Stop using the device currently in use.
296 * If the function is successfully called, no subsequent calls to the
297 * process_callback() of @param engine will be made after the function
298 * returns, until parameters are reset and start() are called again.
300 * The backend is considered to be un-configured after a successful
301 * return, and requires calls to set hardware parameters before it can be
302 * start()-ed again. See pause() for a way to avoid this. stop() should
303 * only be used when reconfiguration is required OR when there are no
304 * plans to use the backend in the future with a reconfiguration.
306 * Return zero if successful, 1 if the device is not in use, negative values on error
308 virtual int stop () = 0;
310 /** Temporarily cease using the device named in the most recent call to set_parameters().
312 * If the function is successfully called, no subsequent calls to the
313 * process_callback() of @param engine will be made after the function
314 * returns, until start() is called again.
316 * The backend will retain its existing parameter configuration after a successful
317 * return, and does NOT require any calls to set hardware parameters before it can be
320 * Return zero if successful, 1 if the device is not in use, negative values on error
322 virtual int pause () = 0;
324 /** While remaining connected to the device, and without changing its
325 * configuration, start (or stop) calling the process_callback() of @param engine
326 * without waiting for the device. Once process_callback() has returned, it
327 * will be called again immediately, thus allowing for faster-than-realtime
330 * All registered ports remain in existence and all connections remain
331 * unaltered. However, any physical ports should NOT be used by the
332 * process_callback() during freewheeling - the data behaviour is undefined.
334 * If @param start_stop is true, begin this behaviour; otherwise cease this
335 * behaviour if it currently occuring, and return to calling
336 * process_callback() of @param engine by waiting for the device.
338 * Return zero on success, non-zero otherwise.
340 virtual int freewheel (bool start_stop) = 0;
342 /** return the fraction of the time represented by the current buffer
343 * size that is being used for each buffer process cycle, as a value
346 * E.g. if the buffer size represents 5msec and current processing
347 * takes 1msec, the returned value should be 0.2.
349 * Implementations can feel free to smooth the values returned over
350 * time (e.g. high pass filtering, or its equivalent).
352 virtual float cpu_load() const = 0;
354 /* Transport Control (JACK is the only audio API that currently offers
355 the concept of shared transport control)
358 /** Attempt to change the transport state to TransportRolling.
360 virtual void transport_start () {}
361 /** Attempt to change the transport state to TransportStopped.
363 virtual void transport_stop () {}
364 /** return the current transport state
366 virtual TransportState transport_state () const { return TransportStopped; }
367 /** Attempt to locate the transport to @param pos
369 virtual void transport_locate (framepos_t /*pos*/) {}
370 /** Return the current transport location, in samples measured
371 * from the origin (defined by the transport time master)
373 virtual framepos_t transport_frame() const { return 0; }
375 /** If @param yn is true, become the time master for any inter-application transport
376 * timebase, otherwise cease to be the time master for the same.
378 * Return zero on success, non-zero otherwise
380 * JACK is the only currently known audio API with the concept of a shared
381 * transport timebase.
383 virtual int set_time_master (bool /*yn*/) { return 0; }
385 virtual int usecs_per_cycle () const { return 1000000 * (buffer_size() / sample_rate()); }
386 virtual size_t raw_buffer_size (DataType t) = 0;
390 /** return the time according to the sample clock in use, measured in
391 * samples since an arbitrary zero time in the past. The value should
392 * increase monotonically and linearly, without interruption from any
393 * source (including CPU frequency scaling).
395 * It is extremely likely that any implementation will use a DLL, since
396 * this function can be called from any thread, at any time, and must be
397 * able to accurately determine the correct sample time.
399 * Can be called from any thread.
401 virtual pframes_t sample_time () = 0;
403 /** Return the time according to the sample clock in use when the most
404 * recent buffer process cycle began. Can be called from any thread.
406 virtual pframes_t sample_time_at_cycle_start () = 0;
408 /** Return the time since the current buffer process cycle started,
409 * in samples, according to the sample clock in use.
411 * Can ONLY be called from within a process() callback tree (which
412 * implies that it can only be called by a process thread)
414 virtual pframes_t samples_since_cycle_start () = 0;
416 /** Return true if it possible to determine the offset in samples of the
417 * first video frame that starts within the current buffer process cycle,
418 * measured from the first sample of the cycle. If returning true,
419 * set @param offset to that offset.
421 * Eg. if it can be determined that the first video frame within the cycle
422 * starts 28 samples after the first sample of the cycle, then this method
423 * should return true and set @param offset to 28.
425 * May be impossible to support outside of JACK, which has specific support
426 * (in some cases, hardware support) for this feature.
428 * Can ONLY be called from within a process() callback tree (which implies
429 * that it can only be called by a process thread)
431 virtual bool get_sync_offset (pframes_t& /*offset*/) const { return false; }
433 /** Create a new thread suitable for running part of the buffer process
434 * cycle (i.e. Realtime scheduling, memory allocation, etc. etc are all
435 * correctly setup), with a stack size given in bytes by specified @param
436 * stacksize. The thread will begin executing @param func, and will exit
437 * when that function returns.
439 virtual int create_process_thread (boost::function<void()> func) = 0;
441 /** Wait for all processing threads to exit.
443 * Return zero on success, non-zero on failure.
445 virtual int join_process_threads () = 0;
447 /** Return true if execution context is in a backend thread
449 virtual bool in_process_thread () = 0;
451 /** Return the minimum stack size of audio threads in bytes
453 static size_t thread_stack_size () { return 100000; }
455 /** Return number of processing threads
457 virtual uint32_t process_thread_count () = 0;
459 virtual void update_latencies () = 0;
465 struct LIBARDOUR_API AudioBackendInfo {
468 /** Using arg1 and arg2, initialize this audiobackend.
470 * Returns zero on success, non-zero otherwise.
472 int (*instantiate) (const std::string& arg1, const std::string& arg2);
474 /** Release all resources associated with this audiobackend
476 int (*deinstantiate) (void);
478 /** Factory method to create an AudioBackend-derived class.
480 * Returns a valid shared_ptr to the object if successfull,
481 * or a "null" shared_ptr otherwise.
483 boost::shared_ptr<AudioBackend> (*factory) (AudioEngine&);
485 /** Return true if the underlying mechanism/API has been
486 * configured and does not need (re)configuration in order
487 * to be usable. Return false otherwise.
489 * Note that this may return true if (re)configuration, even though
490 * not currently required, is still possible.
492 bool (*already_configured)();
497 #endif /* __libardour_audiobackend_h__ */