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"
37 class AudioBackend : public PortEngine {
40 AudioBackend (AudioEngine& e) : PortEngine (e), engine (e) {}
41 virtual ~AudioBackend () {}
43 /** Return the name of this backend.
45 * Should use a well-known, unique term. Expected examples
46 * might include "JACK", "CoreAudio", "ASIO" etc.
48 virtual std::string name() const = 0;
50 /** Return true if the callback from the underlying mechanism/API
51 * (CoreAudio, JACK, ASIO etc.) occurs in a thread subject to realtime
52 * constraints. Return false otherwise.
54 virtual bool is_realtime () const = 0;
56 /* Discovering devices and parameters */
58 /** Return true if this backend requires the selection of a "driver"
59 * before any device can be selected. Return false otherwise.
61 * Intended mainly to differentiate between meta-APIs like JACK
62 * which can still expose different backends (such as ALSA or CoreAudio
63 * or FFADO or netjack) and those like ASIO or CoreAudio which
66 virtual bool requires_driver_selection() const { return false; }
68 /** If the return value of requires_driver_selection() is true,
69 * then this function can return the list of known driver names.
71 * If the return value of requires_driver_selection() is false,
72 * then this function should not be called. If it is called
73 * its return value is an empty vector of strings.
75 virtual std::vector<std::string> enumerate_drivers() const { return std::vector<std::string>(); }
77 /** Returns zero if the backend can successfully use @param name as the
78 * driver, non-zero otherwise.
80 * Should not be used unless the backend returns true from
81 * requires_driver_selection()
83 virtual int set_driver (const std::string& /*drivername*/) { return 0; }
85 /** used to list device names along with whether or not they are currently
92 DeviceStatus (const std::string& s, bool avail) : name (s), available (avail) {}
95 /** Returns a collection of DeviceStatuses identifying devices discovered
96 * by this backend since the start of the process.
98 * Any of the names in each DeviceStatus may be used to identify a
99 * device in other calls to the backend, though any of them may become
100 * invalid at any time.
102 virtual std::vector<DeviceStatus> enumerate_devices () const = 0;
104 /** Returns a collection of float identifying sample rates that are
105 * potentially usable with the hardware identified by @param device.
106 * Any of these values may be supplied in other calls to this backend
107 * as the desired sample rate to use with the name device, but the
108 * requested sample rate may turn out to be unavailable, or become invalid
111 virtual std::vector<float> available_sample_rates (const std::string& device) const = 0;
112 /** Returns a collection of uint32 identifying buffer sizes 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 buffer size to use with the name device, but the
116 * requested buffer size may turn out to be unavailable, or become invalid
119 virtual std::vector<uint32_t> available_buffer_sizes (const std::string& device) const = 0;
121 /** Returns the maximum number of input channels that are potentially
122 * usable with the hardware identified by @param device. Any number from 1
123 * to the value returned may be supplied in other calls to this backend as
124 * the input channel count to use with the name device, but the requested
125 * count may turn out to be unavailable, or become invalid at any time.
127 virtual uint32_t available_input_channel_count (const std::string& device) const = 0;
129 /** Returns the maximum number of output 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 output 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_output_channel_count (const std::string& device) const = 0;
137 /* Return true if the derived class can change the sample rate of the
138 * device in use while the device is already being used. Return false
139 * otherwise. (example: JACK cannot do this as of September 2013)
141 virtual bool can_change_sample_rate_when_running () const = 0;
142 /* Return true if the derived class can change the buffer size of the
143 * device in use while the device is already being used. Return false
146 virtual bool can_change_buffer_size_when_running () const = 0;
148 /* Set the hardware parameters.
150 * If called when the current state is stopped or paused,
151 * the changes will not take effect until the state changes to running.
153 * If called while running, the state will change as fast as the
154 * implementation allows.
156 * All set_*() methods return zero on success, non-zero otherwise.
159 /** Set the name of the device to be used
161 virtual int set_device_name (const std::string&) = 0;
162 /** Set the sample rate to be used
164 virtual int set_sample_rate (float) = 0;
165 /** Set the buffer size to be used.
167 * The device is assumed to use a double buffering scheme, so that one
168 * buffer's worth of data can be processed by hardware while software works
169 * on the other buffer. All known suitable audio APIs support this model
170 * (though ALSA allows for alternate numbers of buffers, and CoreAudio
171 * doesn't directly expose the concept).
173 virtual int set_buffer_size (uint32_t) = 0;
174 /** Set the preferred underlying hardware sample format
176 * This does not change the sample format (32 bit float) read and
177 * written to the device via the Port API.
179 virtual int set_sample_format (SampleFormat) = 0;
180 /** Set the preferred underlying hardware data layout.
181 * If @param yn is true, then the hardware will interleave
182 * samples for successive channels; otherwise, the hardware will store
183 * samples for a single channel contiguously.
185 * Setting this does not change the fact that all data streams
186 * to and from Ports are mono (essentially, non-interleaved)
188 virtual int set_interleaved (bool yn) = 0;
189 /** Set the number of input channels that should be used
191 virtual int set_input_channels (uint32_t) = 0;
192 /** Set the number of output channels that should be used
194 virtual int set_output_channels (uint32_t) = 0;
195 /** Set the (additional) input latency that cannot be determined via
196 * the implementation's underlying code (e.g. latency from
197 * external D-A/D-A converters. Units are samples.
199 virtual int set_systemic_input_latency (uint32_t) = 0;
200 /** Set the (additional) output latency that cannot be determined via
201 * the implementation's underlying code (e.g. latency from
202 * external D-A/D-A converters. Units are samples.
204 virtual int set_systemic_output_latency (uint32_t) = 0;
206 /* Retrieving parameters */
208 virtual std::string device_name () const = 0;
209 virtual float sample_rate () const = 0;
210 virtual uint32_t buffer_size () const = 0;
211 virtual SampleFormat sample_format () const = 0;
212 virtual bool interleaved () const = 0;
213 virtual uint32_t input_channels () const = 0;
214 virtual uint32_t output_channels () const = 0;
215 virtual uint32_t systemic_input_latency () const = 0;
216 virtual uint32_t systemic_output_latency () const = 0;
218 /** Return the name of a control application for the
219 * selected/in-use device. If no such application exists,
220 * or if no device has been selected or is in-use,
221 * return an empty string.
223 virtual std::string control_app_name() const = 0;
224 /** Launch the control app for the currently in-use or
225 * selected device. May do nothing if the control
226 * app is undefined or cannot be launched.
228 virtual void launch_control_app () = 0;
229 /* Basic state control */
231 /** Start using the device named in the most recent call
232 * to set_device(), with the parameters set by various
233 * the most recent calls to set_sample_rate() etc. etc.
235 * At some undetermined time after this function is successfully called,
236 * the backend will start calling the ::process_callback() method of
237 * the AudioEngine referenced by @param engine. These calls will
238 * occur in a thread created by and/or under the control of the backend.
240 * Return zero if successful, negative values otherwise.
242 virtual int start () = 0;
244 /** Stop using the device currently in use.
246 * If the function is successfully called, no subsequent calls to the
247 * process_callback() of @param engine will be made after the function
248 * returns, until parameters are reset and start() are called again.
250 * The backend is considered to be un-configured after a successful
251 * return, and requires calls to set hardware parameters before it can be
252 * start()-ed again. See pause() for a way to avoid this. stop() should
253 * only be used when reconfiguration is required OR when there are no
254 * plans to use the backend in the future with a reconfiguration.
256 * Return zero if successful, 1 if the device is not in use, negative values on error
258 virtual int stop () = 0;
260 /** Temporarily cease using the device named in the most recent call to set_parameters().
262 * If the function is successfully called, no subsequent calls to the
263 * process_callback() of @param engine will be made after the function
264 * returns, until start() is called again.
266 * The backend will retain its existing parameter configuration after a successful
267 * return, and does NOT require any calls to set hardware parameters before it can be
270 * Return zero if successful, 1 if the device is not in use, negative values on error
272 virtual int pause () = 0;
274 /** While remaining connected to the device, and without changing its
275 * configuration, start (or stop) calling the process_callback() of @param engine
276 * without waiting for the device. Once process_callback() has returned, it
277 * will be called again immediately, thus allowing for faster-than-realtime
280 * All registered ports remain in existence and all connections remain
281 * unaltered. However, any physical ports should NOT be used by the
282 * process_callback() during freewheeling - the data behaviour is undefined.
284 * If @param start_stop is true, begin this behaviour; otherwise cease this
285 * behaviour if it currently occuring, and return to calling
286 * process_callback() of @param engine by waiting for the device.
288 * Return zero on success, non-zero otherwise.
290 virtual int freewheel (bool start_stop) = 0;
292 /** return the fraction of the time represented by the current buffer
293 * size that is being used for each buffer process cycle, as a value
296 * E.g. if the buffer size represents 5msec and current processing
297 * takes 1msec, the returned value should be 0.2.
299 * Implementations can feel free to smooth the values returned over
300 * time (e.g. high pass filtering, or its equivalent).
302 virtual float cpu_load() const = 0;
304 /* Transport Control (JACK is the only audio API that currently offers
305 the concept of shared transport control)
308 /** Attempt to change the transport state to TransportRolling.
310 virtual void transport_start () {}
311 /** Attempt to change the transport state to TransportStopped.
313 virtual void transport_stop () {}
314 /** return the current transport state
316 virtual TransportState transport_state () const { return TransportStopped; }
317 /** Attempt to locate the transport to @param pos
319 virtual void transport_locate (framepos_t /*pos*/) {}
320 /** Return the current transport location, in samples measured
321 * from the origin (defined by the transport time master)
323 virtual framepos_t transport_frame() const { return 0; }
325 /** If @param yn is true, become the time master for any inter-application transport
326 * timebase, otherwise cease to be the time master for the same.
328 * Return zero on success, non-zero otherwise
330 * JACK is the only currently known audio API with the concept of a shared
331 * transport timebase.
333 virtual int set_time_master (bool /*yn*/) { return 0; }
335 virtual int usecs_per_cycle () const { return 1000000 * (buffer_size() / sample_rate()); }
336 virtual size_t raw_buffer_size (DataType t) = 0;
340 /** return the time according to the sample clock in use, measured in
341 * samples since an arbitrary zero time in the past. The value should
342 * increase monotonically and linearly, without interruption from any
343 * source (including CPU frequency scaling).
345 * It is extremely likely that any implementation will use a DLL, since
346 * this function can be called from any thread, at any time, and must be
347 * able to accurately determine the correct sample time.
349 * Can be called from any thread.
351 virtual pframes_t sample_time () = 0;
353 /** Return the time according to the sample clock in use when the most
354 * recent buffer process cycle began. Can be called from any thread.
356 virtual pframes_t sample_time_at_cycle_start () = 0;
358 /** Return the time since the current buffer process cycle started,
359 * in samples, according to the sample clock in use.
361 * Can ONLY be called from within a process() callback tree (which
362 * implies that it can only be called by a process thread)
364 virtual pframes_t samples_since_cycle_start () = 0;
366 /** Return true if it possible to determine the offset in samples of the
367 * first video frame that starts within the current buffer process cycle,
368 * measured from the first sample of the cycle. If returning true,
369 * set @param offset to that offset.
371 * Eg. if it can be determined that the first video frame within the cycle
372 * starts 28 samples after the first sample of the cycle, then this method
373 * should return true and set @param offset to 28.
375 * May be impossible to support outside of JACK, which has specific support
376 * (in some cases, hardware support) for this feature.
378 * Can ONLY be called from within a process() callback tree (which implies
379 * that it can only be called by a process thread)
381 virtual bool get_sync_offset (pframes_t& /*offset*/) const { return false; }
383 /** Create a new thread suitable for running part of the buffer process
384 * cycle (i.e. Realtime scheduling, memory allocation, etc. etc are all
385 * correctly setup), with a stack size given in bytes by specified @param
386 * stacksize. The thread will begin executing @param func, and will exit
387 * when that function returns.
389 virtual int create_process_thread (boost::function<void()> func, AudioBackendNativeThread*, size_t stacksize) = 0;
391 /** Wait for the thread specified by @param thread to exit.
393 * Return zero on success, non-zero on failure.
395 virtual int wait_for_process_thread_exit (AudioBackendNativeThread thread) = 0;
397 virtual void update_latencies () = 0;
403 struct AudioBackendInfo {
406 /** Using arg1 and arg2, initialize this audiobackend.
408 * Returns zero on success, non-zero otherwise.
410 int (*instantiate) (const std::string& arg1, const std::string& arg2);
412 /** Release all resources associated with this audiobackend
414 int (*deinstantiate) (void);
416 /** Factory method to create an AudioBackend-derived class.
418 * Returns a valid shared_ptr to the object if successfull,
419 * or a "null" shared_ptr otherwise.
421 boost::shared_ptr<AudioBackend> (*factory) (AudioEngine&);
423 /** Return true if the underlying mechanism/API has been
424 * configured and does not need (re)configuration in order
425 * to be usable. Return false otherwise.
427 * Note that this may return true if (re)configuration, even though
428 * not currently required, is still possible.
430 bool (*already_configured)();
435 #endif /* __libardour_audiobackend_h__ */