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>
38 AudioBackend (AudioEngine& e) : engine (e){}
39 virtual ~AudioBackend () {}
41 /** Return the name of this backend.
43 * Should use a well-known, unique term. Expected examples
44 * might include "JACK", "CoreAudio", "ASIO" etc.
46 virtual std::string name() const = 0;
48 /** return true if the underlying mechanism/API is still available
49 * for us to utilize. return false if some or all of the AudioBackend
50 * API can no longer be effectively used.
52 virtual bool connected() const = 0;
54 /** return true if the callback from the underlying mechanism/API
55 * (CoreAudio, JACK, ASIO etc.) occurs in a thread subject to realtime
56 * constraints. Return false otherwise.
58 virtual bool is_realtime () const = 0;
60 /* Discovering devices and parameters */
62 /** Returns a collection of strings identifying devices known
63 * to this backend. Any of these strings may be used to identify a
64 * device in other calls to the backend, though any of them may become
65 * invalid at any time.
67 virtual std::vector<std::string> enumerate_devices () const = 0;
68 /** Returns a collection of float identifying sample rates that are
69 * potentially usable with the hardware identified by @param device.
70 * Any of these values may be supplied in other calls to this backend
71 * as the desired sample rate to use with the name device, but the
72 * requested sample rate may turn out to be unavailable, or become invalid
75 virtual std::vector<float> available_sample_rates (const std::string& device) const = 0;
76 /** Returns a collection of uint32 identifying buffer sizes that are
77 * potentially usable with the hardware identified by @param device.
78 * Any of these values may be supplied in other calls to this backend
79 * as the desired buffer size to use with the name device, but the
80 * requested buffer size may turn out to be unavailable, or become invalid
83 virtual std::vector<uint32_t> available_buffer_sizes (const std::string& device) const = 0;
85 /** Returns the maximum number of input channels that are potentially
86 * usable with the hardware identified by @param device. Any number from 1
87 * to the value returned may be supplied in other calls to this backend as
88 * the input channel count to use with the name device, but the requested
89 * count may turn out to be unavailable, or become invalid at any time.
91 virtual uint32_t available_input_channel_count (const std::string& device) const = 0;
93 /** Returns the maximum number of output channels that are potentially
94 * usable with the hardware identified by @param device. Any number from 1
95 * to the value returned may be supplied in other calls to this backend as
96 * the output channel count to use with the name device, but the requested
97 * count may turn out to be unavailable, or become invalid at any time.
99 virtual uint32_t available_output_channel_count (const std::string& device) const = 0;
108 /* Set the hardware parameters.
110 * If called when the current state is stopped or paused,
111 * the changes will not take effect until the state changes to running.
113 * If called while running, the state will change as fast as the
114 * implementation allows.
116 * All set_*() methods return zero on success, non-zero otherwise.
119 /** Set the name of the device to be used
121 virtual int set_device_name (const std::string&) = 0;
122 /** Set the sample rate to be used
124 virtual int set_sample_rate (float) = 0;
125 /** Set the buffer size to be used.
127 * The device is assumed to use a double buffering scheme, so that one
128 * buffer's worth of data can be processed by hardware while software works
129 * on the other buffer. All known suitable audio APIs support this model
130 * (though ALSA allows for alternate numbers of buffers, and CoreAudio
131 * doesn't directly expose the concept).
133 virtual int set_buffer_size (uint32_t) = 0;
134 /** Set the preferred underlying hardware sample format
136 * This does not change the sample format (32 bit float) read and
137 * written to the device via the Port API.
139 virtual int set_sample_format (SampleFormat) = 0;
140 /** Set the preferred underlying hardware data layout.
141 * If @param yn is true, then the hardware will interleave
142 * samples for successive channels; otherwise, the hardware will store
143 * samples for a single channel contiguously.
145 * Setting this does not change the fact that all data streams
146 * to and from Ports are mono (essentially, non-interleaved)
148 virtual int set_interleaved (bool yn) = 0;
149 /** Set the number of input channels that should be used
151 virtual int set_input_channels (uint32_t) = 0;
152 /** Set the number of output channels that should be used
154 virtual int set_output_channels (uint32_t) = 0;
155 /** Set the (additional) input latency that cannot be determined via
156 * the implementation's underlying code (e.g. latency from
157 * external D-A/D-A converters. Units are samples.
159 virtual int set_systemic_input_latency (uint32_t) = 0;
160 /** Set the (additional) output latency that cannot be determined via
161 * the implementation's underlying code (e.g. latency from
162 * external D-A/D-A converters. Units are samples.
164 virtual int set_systemic_output_latency (uint32_t) = 0;
166 virtual std::string get_device_name () const = 0;
167 virtual float get_sample_rate () const = 0;
168 virtual uint32_t get_buffer_size () const = 0;
169 virtual SampleFormat get_sample_format () const = 0;
170 virtual bool get_interleaved () const = 0;
171 virtual uint32_t get_input_channels () const = 0;
172 virtual uint32_t get_output_channels () const = 0;
173 virtual uint32_t get_systemic_input_latency () const = 0;
174 virtual uint32_t get_systemic_output_latency () const = 0;
176 /* Basic state control */
178 /** Start using the device named in the most recent call
179 * to set_device(), with the parameters set by various
180 * the most recent calls to set_sample_rate() etc. etc.
182 * At some undetermined time after this function is successfully called,
183 * the backend will start calling the ::process_callback() method of
184 * the AudioEngine referenced by @param engine. These calls will
185 * occur in a thread created by and/or under the control of the backend.
187 * Return zero if successful, negative values otherwise.
189 virtual int start () = 0;
191 /** Stop using the device currently in use.
193 * If the function is successfully called, no subsequent calls to the
194 * process_callback() of @param engine will be made after the function
195 * returns, until parameters are reset and start() are called again.
197 * The backend is considered to be un-configured after a successful
198 * return, and requires calls to set hardware parameters before it can be
199 * start()-ed again. See pause() for a way to avoid this. stop() should
200 * only be used when reconfiguration is required OR when there are no
201 * plans to use the backend in the future with a reconfiguration.
203 * Return zero if successful, 1 if the device is not in use, negative values on error
205 virtual int stop () = 0;
207 /** Temporarily cease using the device named in the most recent call to set_parameters().
209 * If the function is successfully called, no subsequent calls to the
210 * process_callback() of @param engine will be made after the function
211 * returns, until start() is called again.
213 * The backend will retain its existing parameter configuration after a successful
214 * return, and does NOT require any calls to set hardware parameters before it can be
217 * Return zero if successful, 1 if the device is not in use, negative values on error
219 virtual int pause () = 0;
221 /** While remaining connected to the device, and without changing its
222 * configuration, start (or stop) calling the process_callback() of @param engine
223 * without waiting for the device. Once process_callback() has returned, it
224 * will be called again immediately, thus allowing for faster-than-realtime
227 * All registered ports remain in existence and all connections remain
228 * unaltered. However, any physical ports should NOT be used by the
229 * process_callback() during freewheeling - the data behaviour is undefined.
231 * If @param start_stop is true, begin this behaviour; otherwise cease this
232 * behaviour if it currently occuring, and return to calling
233 * process_callback() of @param engine by waiting for the device.
235 * Return zero on success, non-zero otherwise.
237 virtual int freewheel (bool start_stop) = 0;
239 /** return the fraction of the time represented by the current buffer
240 * size that is being used for each buffer process cycle, as a value
243 * E.g. if the buffer size represents 5msec and current processing
244 * takes 1msec, the returned value should be 0.2.
246 * Implementations can feel free to smooth the values returned over
247 * time (e.g. high pass filtering, or its equivalent).
249 virtual float get_cpu_load() const = 0;
251 /* Transport Control (JACK is the only audio API that currently offers
252 the concept of shared transport control)
255 /** Attempt to change the transport state to TransportRolling.
257 virtual void transport_start () {}
258 /** Attempt to change the transport state to TransportStopped.
260 virtual void transport_stop () {}
261 /** return the current transport state
263 virtual TransportState transport_state () { return TransportStopped; }
264 /** Attempt to locate the transport to @param pos
266 virtual void transport_locate (framepos_t /*pos*/) {}
267 /** Return the current transport location, in samples measured
268 * from the origin (defined by the transport time master)
270 virtual framepos_t transport_frame() { return 0; }
272 /** If @param yn is true, become the time master for any inter-application transport
273 * timebase, otherwise cease to be the time master for the same.
275 * Return zero on success, non-zero otherwise
277 * JACK is the only currently known audio API with the concept of a shared
278 * transport timebase.
280 virtual int set_time_master (bool /*yn*/) { return 0; }
282 virtual framecnt_t sample_rate () const;
283 virtual pframes_t samples_per_cycle () const;
284 virtual int usecs_per_cycle () const { return 1000000 * (samples_per_cycle() / sample_rate()); }
285 virtual size_t raw_buffer_size (DataType t);
289 /** return the time according to the sample clock in use, measured in
290 * samples since an arbitrary zero time in the past. The value should
291 * increase monotonically and linearly, without interruption from any
292 * source (including CPU frequency scaling).
294 * It is extremely likely that any implementation will use a DLL, since
295 * this function can be called from any thread, at any time, and must be
296 * able to accurately determine the correct sample time.
298 virtual pframes_t sample_time () = 0;
300 /** return the time according to the sample clock in use when the current
301 * buffer process cycle began.
303 * Can ONLY be called from within a process() callback tree (which
304 * implies that it can only be called by a process thread)
306 virtual pframes_t sample_time_at_cycle_start () = 0;
308 /** return the time since the current buffer process cycle started,
309 * in samples, according to the sample clock in use.
311 * Can ONLY be called from within a process() callback tree (which
312 * implies that it can only be called by a process thread)
314 virtual pframes_t samples_since_cycle_start () = 0;
316 /** return true if it possible to determine the offset in samples of the
317 * first video frame that starts within the current buffer process cycle,
318 * measured from the first sample of the cycle. If returning true,
319 * set @param offset to that offset.
321 * Eg. if it can be determined that the first video frame within the cycle
322 * starts 28 samples after the first sample of the cycle, then this method
323 * should return true and set @param offset to 28.
325 * May be impossible to support outside of JACK, which has specific support
326 * (in some cases, hardware support) for this feature.
328 * Can ONLY be called from within a process() callback tree (which implies
329 * that it can only be called by a process thread)
331 virtual bool get_sync_offset (pframes_t& /*offset*/) const { return false; }
333 /** Create a new thread suitable for running part of the buffer process
334 * cycle (i.e. Realtime scheduling, memory allocation, etc. etc are all
335 * correctly setup), with a stack size given in bytes by specified @param
336 * stacksize. The thread will begin executing @param func, and will exit
337 * when that function returns.
339 virtual int create_process_thread (boost::function<void()> func, pthread_t*, size_t stacksize) = 0;
347 #endif /* __libardour_audiobackend_h__ */