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