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/types.h"
32 #include "ardour/audioengine.h"
33 #include "ardour/port_engine.h"
34 #include "ardour/visibility.h"
36 #ifdef ARDOURBACKEND_DLL_EXPORTS // defined if we are building the ARDOUR Panners DLLs (instead of using them)
37 #define ARDOURBACKEND_API LIBARDOUR_HELPER_DLL_EXPORT
39 #define ARDOURBACKEND_API LIBARDOUR_HELPER_DLL_IMPORT
41 #define ARDOURBACKEND_LOCAL LIBARDOUR_HELPER_DLL_LOCAL
45 class AudioBackend : public PortEngine {
48 AudioBackend (AudioEngine& e) : PortEngine (e), engine (e) {}
49 virtual ~AudioBackend () {}
51 /** Return the name of this backend.
53 * Should use a well-known, unique term. Expected examples
54 * might include "JACK", "CoreAudio", "ASIO" etc.
56 virtual std::string name() const = 0;
58 /** Return true if the callback from the underlying mechanism/API
59 * (CoreAudio, JACK, ASIO etc.) occurs in a thread subject to realtime
60 * constraints. Return false otherwise.
62 virtual bool is_realtime () const = 0;
64 /* Discovering devices and parameters */
66 /** Return true if this backend requires the selection of a "driver"
67 * before any device can be selected. Return false otherwise.
69 * Intended mainly to differentiate between meta-APIs like JACK
70 * which can still expose different backends (such as ALSA or CoreAudio
71 * or FFADO or netjack) and those like ASIO or CoreAudio which
74 virtual bool requires_driver_selection() const { return false; }
76 /** If the return value of requires_driver_selection() is true,
77 * then this function can return the list of known driver names.
79 * If the return value of requires_driver_selection() is false,
80 * then this function should not be called. If it is called
81 * its return value is an empty vector of strings.
83 virtual std::vector<std::string> enumerate_drivers() const { return std::vector<std::string>(); }
85 /** Returns zero if the backend can successfully use @param name as the
86 * driver, non-zero otherwise.
88 * Should not be used unless the backend returns true from
89 * requires_driver_selection()
91 virtual int set_driver (const std::string& /*drivername*/) { return 0; }
93 /** used to list device names along with whether or not they are currently
100 DeviceStatus (const std::string& s, bool avail) : name (s), available (avail) {}
103 /** Returns a collection of DeviceStatuses identifying devices discovered
104 * by this backend since the start of the process.
106 * Any of the names in each DeviceStatus may be used to identify a
107 * device in other calls to the backend, though any of them may become
108 * invalid at any time.
110 virtual std::vector<DeviceStatus> enumerate_devices () const = 0;
112 /** Returns a collection of float identifying sample rates that are
113 * potentially usable with the hardware identified by @param device.
114 * Any of these values may be supplied in other calls to this backend
115 * as the desired sample rate to use with the name device, but the
116 * requested sample rate may turn out to be unavailable, or become invalid
119 virtual std::vector<float> available_sample_rates (const std::string& device) const = 0;
120 /** Returns a collection of uint32 identifying buffer sizes that are
121 * potentially usable with the hardware identified by @param device.
122 * Any of these values may be supplied in other calls to this backend
123 * as the desired buffer size to use with the name device, but the
124 * requested buffer size may turn out to be unavailable, or become invalid
127 virtual std::vector<uint32_t> available_buffer_sizes (const std::string& device) const = 0;
129 /** Returns the maximum number of input channels that are potentially
130 * usable with the hardware identified by @param device. Any number from 1
131 * to the value returned may be supplied in other calls to this backend as
132 * the input channel count to use with the name device, but the requested
133 * count may turn out to be unavailable, or become invalid at any time.
135 virtual uint32_t available_input_channel_count (const std::string& device) const = 0;
137 /** Returns the maximum number of output channels that are potentially
138 * usable with the hardware identified by @param device. Any number from 1
139 * to the value returned may be supplied in other calls to this backend as
140 * the output channel count to use with the name device, but the requested
141 * count may turn out to be unavailable, or become invalid at any time.
143 virtual uint32_t available_output_channel_count (const std::string& device) const = 0;
145 /* Return true if the derived class can change the sample rate of the
146 * device in use while the device is already being used. Return false
147 * otherwise. (example: JACK cannot do this as of September 2013)
149 virtual bool can_change_sample_rate_when_running () const = 0;
150 /* Return true if the derived class can change the buffer size of the
151 * device in use while the device is already being used. Return false
154 virtual bool can_change_buffer_size_when_running () const = 0;
156 /* Set the hardware parameters.
158 * If called when the current state is stopped or paused,
159 * the changes will not take effect until the state changes to running.
161 * If called while running, the state will change as fast as the
162 * implementation allows.
164 * All set_*() methods return zero on success, non-zero otherwise.
167 /** Set the name of the device to be used
169 virtual int set_device_name (const std::string&) = 0;
170 /** Set the sample rate to be used
172 virtual int set_sample_rate (float) = 0;
173 /** Set the buffer size to be used.
175 * The device is assumed to use a double buffering scheme, so that one
176 * buffer's worth of data can be processed by hardware while software works
177 * on the other buffer. All known suitable audio APIs support this model
178 * (though ALSA allows for alternate numbers of buffers, and CoreAudio
179 * doesn't directly expose the concept).
181 virtual int set_buffer_size (uint32_t) = 0;
182 /** Set the preferred underlying hardware sample format
184 * This does not change the sample format (32 bit float) read and
185 * written to the device via the Port API.
187 virtual int set_sample_format (SampleFormat) = 0;
188 /** Set the preferred underlying hardware data layout.
189 * If @param yn is true, then the hardware will interleave
190 * samples for successive channels; otherwise, the hardware will store
191 * samples for a single channel contiguously.
193 * Setting this does not change the fact that all data streams
194 * to and from Ports are mono (essentially, non-interleaved)
196 virtual int set_interleaved (bool yn) = 0;
197 /** Set the number of input channels that should be used
199 virtual int set_input_channels (uint32_t) = 0;
200 /** Set the number of output channels that should be used
202 virtual int set_output_channels (uint32_t) = 0;
203 /** Set the (additional) input latency that cannot be determined via
204 * the implementation's underlying code (e.g. latency from
205 * external D-A/D-A converters. Units are samples.
207 virtual int set_systemic_input_latency (uint32_t) = 0;
208 /** Set the (additional) output latency that cannot be determined via
209 * the implementation's underlying code (e.g. latency from
210 * external D-A/D-A converters. Units are samples.
212 virtual int set_systemic_output_latency (uint32_t) = 0;
214 /* Retrieving parameters */
216 virtual std::string device_name () const = 0;
217 virtual float sample_rate () const = 0;
218 virtual uint32_t buffer_size () const = 0;
219 virtual SampleFormat sample_format () const = 0;
220 virtual bool interleaved () const = 0;
221 virtual uint32_t input_channels () const = 0;
222 virtual uint32_t output_channels () const = 0;
223 virtual uint32_t systemic_input_latency () const = 0;
224 virtual uint32_t systemic_output_latency () const = 0;
226 /** override this if this implementation returns true from
227 * requires_driver_selection()
229 virtual std::string driver_name() const { return std::string(); }
231 /** Return the name of a control application for the
232 * selected/in-use device. If no such application exists,
233 * or if no device has been selected or is in-use,
234 * return an empty string.
236 virtual std::string control_app_name() const = 0;
237 /** Launch the control app for the currently in-use or
238 * selected device. May do nothing if the control
239 * app is undefined or cannot be launched.
241 virtual void launch_control_app () = 0;
243 /* @return a vector of strings that describe the available
246 * These can be presented to the user to decide which
247 * MIDI drivers, options etc. can be used. The returned strings
248 * should be thought of as the key to a map of possible
249 * approaches to handling MIDI within the backend. Ensure that
250 * the strings will make sense to the user.
252 virtual std::vector<std::string> enumerate_midi_options () const = 0;
254 /* Request the use of the MIDI option named @param option, which
255 * should be one of the strings returned by enumerate_midi_options()
257 * @return zero if successful, non-zero otherwise
259 virtual int set_midi_option (const std::string& option) = 0;
263 /** Start using the device named in the most recent call
264 * to set_device(), with the parameters set by various
265 * the most recent calls to set_sample_rate() etc. etc.
267 * At some undetermined time after this function is successfully called,
268 * the backend will start calling the ::process_callback() method of
269 * the AudioEngine referenced by @param engine. These calls will
270 * occur in a thread created by and/or under the control of the backend.
272 * Return zero if successful, negative values otherwise.
274 virtual int start () = 0;
276 /** Stop using the device currently in use.
278 * If the function is successfully called, no subsequent calls to the
279 * process_callback() of @param engine will be made after the function
280 * returns, until parameters are reset and start() are called again.
282 * The backend is considered to be un-configured after a successful
283 * return, and requires calls to set hardware parameters before it can be
284 * start()-ed again. See pause() for a way to avoid this. stop() should
285 * only be used when reconfiguration is required OR when there are no
286 * plans to use the backend in the future with a reconfiguration.
288 * Return zero if successful, 1 if the device is not in use, negative values on error
290 virtual int stop () = 0;
292 /** Temporarily cease using the device named in the most recent call to set_parameters().
294 * If the function is successfully called, no subsequent calls to the
295 * process_callback() of @param engine will be made after the function
296 * returns, until start() is called again.
298 * The backend will retain its existing parameter configuration after a successful
299 * return, and does NOT require any calls to set hardware parameters before it can be
302 * Return zero if successful, 1 if the device is not in use, negative values on error
304 virtual int pause () = 0;
306 /** While remaining connected to the device, and without changing its
307 * configuration, start (or stop) calling the process_callback() of @param engine
308 * without waiting for the device. Once process_callback() has returned, it
309 * will be called again immediately, thus allowing for faster-than-realtime
312 * All registered ports remain in existence and all connections remain
313 * unaltered. However, any physical ports should NOT be used by the
314 * process_callback() during freewheeling - the data behaviour is undefined.
316 * If @param start_stop is true, begin this behaviour; otherwise cease this
317 * behaviour if it currently occuring, and return to calling
318 * process_callback() of @param engine by waiting for the device.
320 * Return zero on success, non-zero otherwise.
322 virtual int freewheel (bool start_stop) = 0;
324 /** return the fraction of the time represented by the current buffer
325 * size that is being used for each buffer process cycle, as a value
328 * E.g. if the buffer size represents 5msec and current processing
329 * takes 1msec, the returned value should be 0.2.
331 * Implementations can feel free to smooth the values returned over
332 * time (e.g. high pass filtering, or its equivalent).
334 virtual float cpu_load() const = 0;
336 /* Transport Control (JACK is the only audio API that currently offers
337 the concept of shared transport control)
340 /** Attempt to change the transport state to TransportRolling.
342 virtual void transport_start () {}
343 /** Attempt to change the transport state to TransportStopped.
345 virtual void transport_stop () {}
346 /** return the current transport state
348 virtual TransportState transport_state () const { return TransportStopped; }
349 /** Attempt to locate the transport to @param pos
351 virtual void transport_locate (framepos_t /*pos*/) {}
352 /** Return the current transport location, in samples measured
353 * from the origin (defined by the transport time master)
355 virtual framepos_t transport_frame() const { return 0; }
357 /** If @param yn is true, become the time master for any inter-application transport
358 * timebase, otherwise cease to be the time master for the same.
360 * Return zero on success, non-zero otherwise
362 * JACK is the only currently known audio API with the concept of a shared
363 * transport timebase.
365 virtual int set_time_master (bool /*yn*/) { return 0; }
367 virtual int usecs_per_cycle () const { return 1000000 * (buffer_size() / sample_rate()); }
368 virtual size_t raw_buffer_size (DataType t) = 0;
372 /** return the time according to the sample clock in use, measured in
373 * samples since an arbitrary zero time in the past. The value should
374 * increase monotonically and linearly, without interruption from any
375 * source (including CPU frequency scaling).
377 * It is extremely likely that any implementation will use a DLL, since
378 * this function can be called from any thread, at any time, and must be
379 * able to accurately determine the correct sample time.
381 * Can be called from any thread.
383 virtual pframes_t sample_time () = 0;
385 /** Return the time according to the sample clock in use when the most
386 * recent buffer process cycle began. Can be called from any thread.
388 virtual pframes_t sample_time_at_cycle_start () = 0;
390 /** Return the time since the current buffer process cycle started,
391 * in samples, according to the sample clock in use.
393 * Can ONLY be called from within a process() callback tree (which
394 * implies that it can only be called by a process thread)
396 virtual pframes_t samples_since_cycle_start () = 0;
398 /** Return true if it possible to determine the offset in samples of the
399 * first video frame that starts within the current buffer process cycle,
400 * measured from the first sample of the cycle. If returning true,
401 * set @param offset to that offset.
403 * Eg. if it can be determined that the first video frame within the cycle
404 * starts 28 samples after the first sample of the cycle, then this method
405 * should return true and set @param offset to 28.
407 * May be impossible to support outside of JACK, which has specific support
408 * (in some cases, hardware support) for this feature.
410 * Can ONLY be called from within a process() callback tree (which implies
411 * that it can only be called by a process thread)
413 virtual bool get_sync_offset (pframes_t& /*offset*/) const { return false; }
415 /** Create a new thread suitable for running part of the buffer process
416 * cycle (i.e. Realtime scheduling, memory allocation, etc. etc are all
417 * correctly setup), with a stack size given in bytes by specified @param
418 * stacksize. The thread will begin executing @param func, and will exit
419 * when that function returns.
421 virtual int create_process_thread (boost::function<void()> func) = 0;
423 /** Wait for all processing threads to exit.
425 * Return zero on success, non-zero on failure.
427 virtual int join_process_threads () = 0;
429 /** Return true if execution context is in a backend thread
431 virtual bool in_process_thread () = 0;
433 /** Return the minimum stack size of audio threads in bytes
435 static size_t thread_stack_size () { return 100000; }
437 /** Return number of processing threads
439 virtual uint32_t process_thread_count () = 0;
441 virtual void update_latencies () = 0;
447 struct AudioBackendInfo {
450 /** Using arg1 and arg2, initialize this audiobackend.
452 * Returns zero on success, non-zero otherwise.
454 int (*instantiate) (const std::string& arg1, const std::string& arg2);
456 /** Release all resources associated with this audiobackend
458 int (*deinstantiate) (void);
460 /** Factory method to create an AudioBackend-derived class.
462 * Returns a valid shared_ptr to the object if successfull,
463 * or a "null" shared_ptr otherwise.
465 boost::shared_ptr<AudioBackend> (*factory) (AudioEngine&);
467 /** Return true if the underlying mechanism/API has been
468 * configured and does not need (re)configuration in order
469 * to be usable. Return false otherwise.
471 * Note that this may return true if (re)configuration, even though
472 * not currently required, is still possible.
474 bool (*already_configured)();
479 #endif /* __libardour_audiobackend_h__ */