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"
42 AudioBackend (AudioEngine& e) : engine (e){}
43 virtual ~AudioBackend () {}
45 /** Return the name of this backend.
47 * Should use a well-known, unique term. Expected examples
48 * might include "JACK", "CoreAudio", "ASIO" etc.
50 virtual std::string name() const = 0;
52 /** Return a private, type-free pointer to any data
53 * that might be useful to a concrete implementation
55 virtual void* private_handle() const = 0;
57 /** Return true if the underlying mechanism/API is still available
58 * for us to utilize. return false if some or all of the AudioBackend
59 * API can no longer be effectively used.
61 virtual bool connected() const = 0;
63 /** Return true if the callback from the underlying mechanism/API
64 * (CoreAudio, JACK, ASIO etc.) occurs in a thread subject to realtime
65 * constraints. Return false otherwise.
67 virtual bool is_realtime () const = 0;
69 /* Discovering devices and parameters */
71 /** Return true if this backend requires the selection of a "driver"
72 * before any device can be selected. Return false otherwise.
74 * Intended mainly to differentiate between meta-APIs like JACK
75 * which can still expose different backends (such as ALSA or CoreAudio
76 * or FFADO or netjack) and those like ASIO or CoreAudio which
79 virtual bool requires_driver_selection() const { return false; }
81 /** If the return value of requires_driver_selection() is true,
82 * then this function can return the list of known driver names.
84 * If the return value of requires_driver_selection() is false,
85 * then this function should not be called. If it is called
86 * its return value is an empty vector of strings.
88 virtual std::vector<std::string> enumerate_drivers() const { return std::vector<std::string>(); }
90 /** Returns zero if the backend can successfully use @param name as the
91 * driver, non-zero otherwise.
93 * Should not be used unless the backend returns true from
94 * requires_driver_selection()
96 virtual int set_driver (const std::string& /*drivername*/) { return 0; }
98 /** used to list device names along with whether or not they are currently
101 struct DeviceStatus {
105 DeviceStatus (const std::string& s, bool avail) : name (s), available (avail) {}
108 /** Returns a collection of DeviceStatuses identifying devices discovered
109 * by this backend since the start of the process.
111 * Any of the names in each DeviceStatus may be used to identify a
112 * device in other calls to the backend, though any of them may become
113 * invalid at any time.
115 virtual std::vector<DeviceStatus> enumerate_devices () const = 0;
117 /** Returns a collection of float identifying sample rates that are
118 * potentially usable with the hardware identified by @param device.
119 * Any of these values may be supplied in other calls to this backend
120 * as the desired sample rate to use with the name device, but the
121 * requested sample rate may turn out to be unavailable, or become invalid
124 virtual std::vector<float> available_sample_rates (const std::string& device) const = 0;
125 /** Returns a collection of uint32 identifying buffer sizes that are
126 * potentially usable with the hardware identified by @param device.
127 * Any of these values may be supplied in other calls to this backend
128 * as the desired buffer size to use with the name device, but the
129 * requested buffer size may turn out to be unavailable, or become invalid
132 virtual std::vector<uint32_t> available_buffer_sizes (const std::string& device) const = 0;
134 /** Returns the maximum number of input channels that are potentially
135 * usable with the hardware identified by @param device. Any number from 1
136 * to the value returned may be supplied in other calls to this backend as
137 * the input channel count to use with the name device, but the requested
138 * count may turn out to be unavailable, or become invalid at any time.
140 virtual uint32_t available_input_channel_count (const std::string& device) const = 0;
142 /** Returns the maximum number of output channels that are potentially
143 * usable with the hardware identified by @param device. Any number from 1
144 * to the value returned may be supplied in other calls to this backend as
145 * the output channel count to use with the name device, but the requested
146 * count may turn out to be unavailable, or become invalid at any time.
148 virtual uint32_t available_output_channel_count (const std::string& device) const = 0;
150 /* Return true if the derived class can change the sample rate of the
151 * device in use while the device is already being used. Return false
152 * otherwise. (example: JACK cannot do this as of September 2013)
154 virtual bool can_change_sample_rate_when_running () const = 0;
155 /* Return true if the derived class can change the buffer size of the
156 * device in use while the device is already being used. Return false
159 virtual bool can_change_buffer_size_when_running () const = 0;
161 /* Set the hardware parameters.
163 * If called when the current state is stopped or paused,
164 * the changes will not take effect until the state changes to running.
166 * If called while running, the state will change as fast as the
167 * implementation allows.
169 * All set_*() methods return zero on success, non-zero otherwise.
172 /** Set the name of the device to be used
174 virtual int set_device_name (const std::string&) = 0;
175 /** Set the sample rate to be used
177 virtual int set_sample_rate (float) = 0;
178 /** Set the buffer size to be used.
180 * The device is assumed to use a double buffering scheme, so that one
181 * buffer's worth of data can be processed by hardware while software works
182 * on the other buffer. All known suitable audio APIs support this model
183 * (though ALSA allows for alternate numbers of buffers, and CoreAudio
184 * doesn't directly expose the concept).
186 virtual int set_buffer_size (uint32_t) = 0;
187 /** Set the preferred underlying hardware sample format
189 * This does not change the sample format (32 bit float) read and
190 * written to the device via the Port API.
192 virtual int set_sample_format (SampleFormat) = 0;
193 /** Set the preferred underlying hardware data layout.
194 * If @param yn is true, then the hardware will interleave
195 * samples for successive channels; otherwise, the hardware will store
196 * samples for a single channel contiguously.
198 * Setting this does not change the fact that all data streams
199 * to and from Ports are mono (essentially, non-interleaved)
201 virtual int set_interleaved (bool yn) = 0;
202 /** Set the number of input channels that should be used
204 virtual int set_input_channels (uint32_t) = 0;
205 /** Set the number of output channels that should be used
207 virtual int set_output_channels (uint32_t) = 0;
208 /** Set the (additional) input 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_input_latency (uint32_t) = 0;
213 /** Set the (additional) output latency that cannot be determined via
214 * the implementation's underlying code (e.g. latency from
215 * external D-A/D-A converters. Units are samples.
217 virtual int set_systemic_output_latency (uint32_t) = 0;
219 /* Retrieving parameters */
221 virtual std::string device_name () const = 0;
222 virtual float sample_rate () const = 0;
223 virtual uint32_t buffer_size () const = 0;
224 virtual SampleFormat sample_format () const = 0;
225 virtual bool interleaved () const = 0;
226 virtual uint32_t input_channels () const = 0;
227 virtual uint32_t output_channels () const = 0;
228 virtual uint32_t systemic_input_latency () const = 0;
229 virtual uint32_t systemic_output_latency () const = 0;
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;
242 /* Basic state control */
244 /** Start using the device named in the most recent call
245 * to set_device(), with the parameters set by various
246 * the most recent calls to set_sample_rate() etc. etc.
248 * At some undetermined time after this function is successfully called,
249 * the backend will start calling the ::process_callback() method of
250 * the AudioEngine referenced by @param engine. These calls will
251 * occur in a thread created by and/or under the control of the backend.
253 * Return zero if successful, negative values otherwise.
255 virtual int start () = 0;
257 /** Stop using the device currently in use.
259 * If the function is successfully called, no subsequent calls to the
260 * process_callback() of @param engine will be made after the function
261 * returns, until parameters are reset and start() are called again.
263 * The backend is considered to be un-configured after a successful
264 * return, and requires calls to set hardware parameters before it can be
265 * start()-ed again. See pause() for a way to avoid this. stop() should
266 * only be used when reconfiguration is required OR when there are no
267 * plans to use the backend in the future with a reconfiguration.
269 * Return zero if successful, 1 if the device is not in use, negative values on error
271 virtual int stop () = 0;
273 /** Temporarily cease using the device named in the most recent call to set_parameters().
275 * If the function is successfully called, no subsequent calls to the
276 * process_callback() of @param engine will be made after the function
277 * returns, until start() is called again.
279 * The backend will retain its existing parameter configuration after a successful
280 * return, and does NOT require any calls to set hardware parameters before it can be
283 * Return zero if successful, 1 if the device is not in use, negative values on error
285 virtual int pause () = 0;
287 /** While remaining connected to the device, and without changing its
288 * configuration, start (or stop) calling the process_callback() of @param engine
289 * without waiting for the device. Once process_callback() has returned, it
290 * will be called again immediately, thus allowing for faster-than-realtime
293 * All registered ports remain in existence and all connections remain
294 * unaltered. However, any physical ports should NOT be used by the
295 * process_callback() during freewheeling - the data behaviour is undefined.
297 * If @param start_stop is true, begin this behaviour; otherwise cease this
298 * behaviour if it currently occuring, and return to calling
299 * process_callback() of @param engine by waiting for the device.
301 * Return zero on success, non-zero otherwise.
303 virtual int freewheel (bool start_stop) = 0;
305 /** return the fraction of the time represented by the current buffer
306 * size that is being used for each buffer process cycle, as a value
309 * E.g. if the buffer size represents 5msec and current processing
310 * takes 1msec, the returned value should be 0.2.
312 * Implementations can feel free to smooth the values returned over
313 * time (e.g. high pass filtering, or its equivalent).
315 virtual float cpu_load() const = 0;
317 /* Transport Control (JACK is the only audio API that currently offers
318 the concept of shared transport control)
321 /** Attempt to change the transport state to TransportRolling.
323 virtual void transport_start () {}
324 /** Attempt to change the transport state to TransportStopped.
326 virtual void transport_stop () {}
327 /** return the current transport state
329 virtual TransportState transport_state () const { return TransportStopped; }
330 /** Attempt to locate the transport to @param pos
332 virtual void transport_locate (framepos_t /*pos*/) {}
333 /** Return the current transport location, in samples measured
334 * from the origin (defined by the transport time master)
336 virtual framepos_t transport_frame() const { return 0; }
338 /** If @param yn is true, become the time master for any inter-application transport
339 * timebase, otherwise cease to be the time master for the same.
341 * Return zero on success, non-zero otherwise
343 * JACK is the only currently known audio API with the concept of a shared
344 * transport timebase.
346 virtual int set_time_master (bool /*yn*/) { return 0; }
348 virtual int usecs_per_cycle () const { return 1000000 * (buffer_size() / sample_rate()); }
349 virtual size_t raw_buffer_size (DataType t) = 0;
353 /** return the time according to the sample clock in use, measured in
354 * samples since an arbitrary zero time in the past. The value should
355 * increase monotonically and linearly, without interruption from any
356 * source (including CPU frequency scaling).
358 * It is extremely likely that any implementation will use a DLL, since
359 * this function can be called from any thread, at any time, and must be
360 * able to accurately determine the correct sample time.
362 * Can be called from any thread.
364 virtual pframes_t sample_time () = 0;
366 /** Return the time according to the sample clock in use when the most
367 * recent buffer process cycle began. Can be called from any thread.
369 virtual pframes_t sample_time_at_cycle_start () = 0;
371 /** Return the time since the current buffer process cycle started,
372 * in samples, according to the sample clock in use.
374 * Can ONLY be called from within a process() callback tree (which
375 * implies that it can only be called by a process thread)
377 virtual pframes_t samples_since_cycle_start () = 0;
379 /** Return true if it possible to determine the offset in samples of the
380 * first video frame that starts within the current buffer process cycle,
381 * measured from the first sample of the cycle. If returning true,
382 * set @param offset to that offset.
384 * Eg. if it can be determined that the first video frame within the cycle
385 * starts 28 samples after the first sample of the cycle, then this method
386 * should return true and set @param offset to 28.
388 * May be impossible to support outside of JACK, which has specific support
389 * (in some cases, hardware support) for this feature.
391 * Can ONLY be called from within a process() callback tree (which implies
392 * that it can only be called by a process thread)
394 virtual bool get_sync_offset (pframes_t& /*offset*/) const { return false; }
396 /** Create a new thread suitable for running part of the buffer process
397 * cycle (i.e. Realtime scheduling, memory allocation, etc. etc are all
398 * correctly setup), with a stack size given in bytes by specified @param
399 * stacksize. The thread will begin executing @param func, and will exit
400 * when that function returns.
402 virtual int create_process_thread (boost::function<void()> func, pthread_t*, size_t stacksize) = 0;
404 virtual void update_latencies () = 0;
410 struct AudioBackendInfo {
413 int (*instantiate) (const std::string& arg1, const std::string& arg2);
414 int (*deinstantiate) (void);
416 boost::shared_ptr<AudioBackend> (*backend_factory) (AudioEngine&);
417 boost::shared_ptr<PortEngine> (*portengine_factory) (PortManager&);
419 /** Return true if the underlying mechanism/API has been
420 * configured and does not need (re)configuration in order
421 * to be usable. Return false otherwise.
423 * Note that this may return true if (re)configuration, even though
424 * not currently required, is still possible.
426 bool (*already_configured)();
431 #endif /* __libardour_audiobackend_h__ */