drivers/audio/AudioOutputDevice.h

/***************************************************************************
 *                                                                         *
 *   LinuxSampler - modular, streaming capable sampler                     *
 *                                                                         *
 *   Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck   *
 *   Copyright (C) 2005 - 2013 Christian Schoenebeck                       *
 *                                                                         *
 *   This program is free software; you can redistribute it and/or modify  *
 *   it under the terms of the GNU General Public License as published by  *
 *   the Free Software Foundation; either version 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 *   This program is distributed in the hope that it will be useful,       *
 *   but WITHOUT ANY WARRANTY; without even the implied warranty of        *
 *   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the         *
 *   GNU General Public License for more details.                          *
 *                                                                         *
 *   You should have received a copy of the GNU General Public License     *
 *   along with this program; if not, write to the Free Software           *
 *   Foundation, Inc., 59 Temple Place, Suite 330, Boston,                 *
 *   MA  02111-1307  USA                                                   *
 ***************************************************************************/

#ifndef __LS_AUDIOOUTPUTDEVICE_H__
#define __LS_AUDIOOUTPUTDEVICE_H__

#include <set>
#include <map>
#include <vector>
#include <stdexcept>

#include "../../common/global.h"
#include "../../common/Exception.h"
#include "../Device.h"
#include "../DeviceParameter.h"
#include "../../engines/Engine.h"
#include "AudioChannel.h"
#include "../../common/SynchronizedConfig.h"
#include "../../effects/EffectChain.h"

namespace LinuxSampler {

    // just symbol prototyping
    class Engine;
    class AudioOutputDeviceFactory;
    class IDGenerator;

    /** Abstract base class for audio output drivers in LinuxSampler
     *
     * This class will be derived by specialized classes which implement the
     * connection to a specific audio output system (e.g. Alsa, Jack,
     * CoreAudio).
     */
    class AudioOutputDevice : public Device {
        public:

            /////////////////////////////////////////////////////////////////
            // Device parameters

            /** Device Parameter 'ACTIVE'
             *
             * Used to activate / deactivate the audio output device.
             */
            class ParameterActive : public DeviceCreationParameterBool {
                public:
                    ParameterActive();
                    ParameterActive(String s);
                    virtual String Description() OVERRIDE;
                    virtual bool   Fix() OVERRIDE;
                    virtual bool   Mandatory() OVERRIDE;
                    virtual std::map<String,DeviceCreationParameter*> DependsAsParameters() OVERRIDE;
                    virtual optional<bool> DefaultAsBool(std::map<String,String> Parameters) OVERRIDE;
                    virtual void OnSetValue(bool b) throw (Exception) OVERRIDE;
                    static String Name();
            };

            /** Device Parameter 'SAMPLERATE'
             *
             * Used to set the sample rate of the audio output device.
             */
            class ParameterSampleRate : public DeviceCreationParameterInt {
                public:
                    ParameterSampleRate();
                    ParameterSampleRate(String s);
                    virtual String Description() OVERRIDE;
                    virtual bool   Fix() OVERRIDE;
                    virtual bool   Mandatory() OVERRIDE;
                    virtual std::map<String,DeviceCreationParameter*> DependsAsParameters() OVERRIDE;
                    virtual optional<int>    DefaultAsInt(std::map<String,String> Parameters) OVERRIDE;
                    virtual optional<int>    RangeMinAsInt(std::map<String,String> Parameters) OVERRIDE;
                    virtual optional<int>    RangeMaxAsInt(std::map<String,String> Parameters) OVERRIDE;
                    virtual std::vector<int> PossibilitiesAsInt(std::map<String,String> Parameters) OVERRIDE;
                    virtual int              ValueAsInt() OVERRIDE;
                    virtual void             OnSetValue(int i) throw (Exception) OVERRIDE;
                    static String Name();
            };

            /** Device Parameters 'CHANNELS'
             *
             * Used to increase / decrease the number of audio channels of
             * audio output device.
             */
            class ParameterChannels : public DeviceCreationParameterInt {
                public:
                    ParameterChannels();
                    ParameterChannels(String s);
                    virtual String Description() OVERRIDE;
                    virtual bool   Fix() OVERRIDE;
                    virtual bool   Mandatory() OVERRIDE;
                    virtual std::map<String,DeviceCreationParameter*> DependsAsParameters() OVERRIDE;
                    virtual optional<int>    DefaultAsInt(std::map<String,String> Parameters) OVERRIDE;
                    virtual optional<int>    RangeMinAsInt(std::map<String,String> Parameters) OVERRIDE;
                    virtual optional<int>    RangeMaxAsInt(std::map<String,String> Parameters) OVERRIDE;
                    virtual std::vector<int> PossibilitiesAsInt(std::map<String,String> Parameters) OVERRIDE;
                    virtual void             OnSetValue(int i) throw (Exception) OVERRIDE;
                    static String Name();
            };


            /////////////////////////////////////////////////////////////////
            // abstract methods
            //     (these have to be implemented by the descendant)

            /**
             * Start playback of audio signal on the audio device. It's the
             * responsibility of the implementing audio device to call the
             * RenderAudio(uint Samples) method of all connected engines.
             * This will cause the engines to continue to render 'Samples'
             * number of audio sample points and the engines will
             * automatically add their audio signals to the audio buffers of
             * the audio channels of this audio device. So the implementing
             * audio device just has to access the buffers of it's audio
             * channels.
             *
             * @throws AudioOutputException  if playback can not be started
             * @see AudioChannel
             */
            virtual void Play() = 0;

            /**
             * Returns true if the audio device is currently playing back.
             */
            virtual bool IsPlaying() = 0;

            /**
             * Stop playback of audio signal on the audio device. The
             * implementing audio device will stop calling the RenderAudio()
             * method of all connected engines and close it's connection to
             * audio output system.
             */
            virtual void Stop() = 0;

            /**
             * Maximum amount of sample points the implementing audio
             * device will ever demand the sampler engines to write in one
             * fragment cycle / period. Simple audio device drivers usually
             * have a fixed fragment size, so those devices just would return
             * the fragment size in this method.
             *
             * @returns  max. amount of sample points ever
             */
            virtual uint MaxSamplesPerCycle() = 0;

            /**
             * Playback samplerate the audio device uses. The sampler engines
             * currently assume this to be a constant value for the whole
             * life time of an instance of the implementing audio device.
             *
             * @returns  sample rate in Hz
             */
            virtual uint SampleRate() = 0;

            /**
             * Return the audio output device driver name.
             */
            virtual String Driver() = 0;

            /**
             * Create new audio channel. This will be called by
             * AcquireChannels(). Each driver must implement it.
             */
            virtual AudioChannel* CreateChannel(uint ChannelNr) = 0;
        
            /**
             * Might be optionally implemented by the deriving driver. If
             * implemented, this method will return the current audio
             * latency in seconds. The driver might measure the actual
             * latency with timing functions to return the real latency.
             *
             * If this method is not implemented / overridden by the
             * descending driver, it will simply return the theoretical
             * latency, that is MaxSamplesPerCycle() / SampleRate().
             *
             * Currently this method is not used by the sampler itself.
             * It can be used however for GUIs built on top of the sampler
             * for example, to i.e. display the user the currently
             * effective audio latency in real-time.
             */
            virtual float latency();


            /////////////////////////////////////////////////////////////////
            // normal methods
            //     (usually not to be overriden by descendant)

            /**
             * Connect given sampler engine to this audio output device. The
             * engine will be added to the Engines container of this audio
             * device and the engine will also automatically be informed
             * about the connection.
             *
             * @param pEngine - sampler engine
             */
            void Connect(Engine* pEngine);

            /**
             * Disconnect given sampler engine from this audio output device.
             * Removes given sampler engine reference from the Engines
             * container of this audio device.
             *
             * @param pEngine - sampler engine
             */
            void Disconnect(Engine* pEngine);
        
            /**
             * This method can or should be called by the deriving driver in
             * case some fundamental parameter changed, especially if the
             * values returned by MaxSamplesPerCycle() and SamplerRate() have
             * changed, those are values which the sampler engines assume to be
             * constant for the life time of an audio device !
             *
             * By forcing a re-connection with this method, the sampler engines
             * are forced to update those informations metntioned above as well,
             * avoiding crashes or other undesired misbehaviors in such
             * circumstances.
             */
            void ReconnectAll();

            /**
             * Returns audio channel with index \a ChannelIndex or NULL if
             * index out of bounds.
             */
            AudioChannel* Channel(uint ChannelIndex);

            /**
             * This method will usually be called by the sampler engines that
             * are connected to this audio device to inform the audio device
             * how much audio channels the engine(s) need. It's the
             * responsibility of the audio device to offer that amount of
             * audio channels - again: this is not an option this is a must!
             * The engines will assume to be able to access those audio
             * channels right after. If the audio driver is not able to offer
             * that much channels, it can simply create mix channels which
             * are then just mixed to the 'real' audio channels. See
             * AudioChannel.h for details about channels and mix channels.
             *
             * @param Channels - amount of output channels required by
             *                   a sampler engine
             * @throws AudioOutputException  if desired amount of channels
             *                               cannot be offered
             * @see AudioChannel
             */
            void AcquireChannels(uint Channels);

            /**
             * Returns the amount of audio channels (including the so called
             * "mix channels") the device is currently providing.
             */
            uint ChannelCount();

            /**
             * Returns all device parameter settings.
             */
            std::map<String,DeviceCreationParameter*> DeviceParameters();

            /**
             * Add a chain of send effects to this AudioOutputDevice.
             * You actually have to add effects to that chain afterwards.
             */
            EffectChain* AddSendEffectChain();

            /**
             * Remove the send effect chain given by @a iChain .
             *
             * @throws Exception - if given send effect chain doesn't exist
             */
            void RemoveSendEffectChain(uint iChain) throw (Exception);

            /**
             * Returns send effect chain given by @a iChain or @c NULL if
             * there's no such effect chain.
             */
            EffectChain* SendEffectChain(uint iChain) const;

            /**
             * Returns send effect chain with ID @a iChainID or @c NULL if
             * there's no such effect chain.
             */
            EffectChain* SendEffectChainByID(uint iChainID) const;

            /**
             * Returns amount of send effect chains this AudioOutputDevice
             * currently provides.
             */
            uint SendEffectChainCount() const;

            /**
             * @deprecated This method will be removed, use AddSendEffectChain() instead!
             */
            EffectChain* AddMasterEffectChain() DEPRECATED_API;

            /**
             * @deprecated This method will be removed, use RemoveSendEffectChain() instead!
             */
            void RemoveMasterEffectChain(uint iChain) throw (Exception) DEPRECATED_API;

            /**
             * @deprecated This method will be removed, use SendEffectChain() instead!
             */
            EffectChain* MasterEffectChain(uint iChain) const DEPRECATED_API;

            /**
             * @deprecated This method will be removed, use SendEffectChainCount() instead!
             */
            uint MasterEffectChainCount() const DEPRECATED_API;

        protected:
            SynchronizedConfig<std::set<Engine*> >    Engines;     ///< All sampler engines that are connected to the audio output device.
            SynchronizedConfig<std::set<Engine*> >::Reader EnginesReader; ///< Audio thread access to Engines.
            std::vector<AudioChannel*>                Channels;    ///< All audio channels of the audio output device. This is just a container; the descendant has to create channels by himself.
            std::map<String,DeviceCreationParameter*> Parameters;  ///< All device parameters.
            std::vector<EffectChain*>                 vEffectChains;
            IDGenerator*                              EffectChainIDs;

            AudioOutputDevice(std::map<String,DeviceCreationParameter*> DriverParameters);

            virtual ~AudioOutputDevice();

            /**
             * This method should be called by the AudioOutputDevice
             * descendant to let all connected engines proceed to render the
             * given amount of sample points. The engines will place their
             * calculated audio data by themselfes into the buffers of the
             * respective AudioChannel objects, so the implementing audio
             * output device just has to copy the AudioChannel buffers to
             * the output buffer(s) of its audio system.
             *
             * @returns  0 on success or the last error return code of one
             *           engine
             */
            int RenderAudio(uint Samples);

            /**
             * This can be called as an alternative to RenderAudio() for
             * just writing silence to the audio output buffers and not
             * calling the connected sampler engines for rendering audio, so
             * to provide a method to stop playback if the used audio output
             * system doesn't provide a better way.
             *
             * @returns  0 on success
             */
            int RenderSilence(uint Samples);

            friend class AudioOutputDeviceFactory; // allow AudioOutputDeviceFactory class to destroy audio devices

    };

    /**
     * Audio output exception that should be thrown by the AudioOutputDevice
     * descendants in case initialization of the audio output system failed
     * (which should be done in the constructor of the AudioOutputDevice
     * descendant).
     */
    class AudioOutputException : public Exception {
        public:
            AudioOutputException(const std::string& msg) : Exception(msg) {}
    };
}

#endif // __LS_AUDIOOUTPUTDEVICE_H__
1	/***************************************************************************
2	* *
3	* LinuxSampler - modular, streaming capable sampler *
4	* *
5	* Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck *
6	* Copyright (C) 2005 - 2013 Christian Schoenebeck *
7	* *
8	* This program is free software; you can redistribute it and/or modify *
9	* it under the terms of the GNU General Public License as published by *
10	* the Free Software Foundation; either version 2 of the License, or *
11	* (at your option) any later version. *
12	* *
13	* This program is distributed in the hope that it will be useful, *
14	* but WITHOUT ANY WARRANTY; without even the implied warranty of *
15	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
16	* GNU General Public License for more details. *
17	* *
18	* You should have received a copy of the GNU General Public License *
19	* along with this program; if not, write to the Free Software *
20	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, *
21	* MA 02111-1307 USA *
22	***************************************************************************/
23
24	#ifndef __LS_AUDIOOUTPUTDEVICE_H__
25	#define __LS_AUDIOOUTPUTDEVICE_H__
26
27	#include <set>
28	#include <map>
29	#include <vector>
30	#include <stdexcept>
31
32	#include "../../common/global.h"
33	#include "../../common/Exception.h"
34	#include "../Device.h"
35	#include "../DeviceParameter.h"
36	#include "../../engines/Engine.h"
37	#include "AudioChannel.h"
38	#include "../../common/SynchronizedConfig.h"
39	#include "../../effects/EffectChain.h"
40
41	namespace LinuxSampler {
42
43	// just symbol prototyping
44	class Engine;
45	class AudioOutputDeviceFactory;
46	class IDGenerator;
47
48	/** Abstract base class for audio output drivers in LinuxSampler
49	*
50	* This class will be derived by specialized classes which implement the
51	* connection to a specific audio output system (e.g. Alsa, Jack,
52	* CoreAudio).
53	*/
54	class AudioOutputDevice : public Device {
55	public:
56
57	/////////////////////////////////////////////////////////////////
58	// Device parameters
59
60	/** Device Parameter 'ACTIVE'
61	*
62	* Used to activate / deactivate the audio output device.
63	*/
64	class ParameterActive : public DeviceCreationParameterBool {
65	public:
66	ParameterActive();
67	ParameterActive(String s);
68	virtual String Description() OVERRIDE;
69	virtual bool Fix() OVERRIDE;
70	virtual bool Mandatory() OVERRIDE;
71	virtual std::map<String,DeviceCreationParameter*> DependsAsParameters() OVERRIDE;
72	virtual optional<bool> DefaultAsBool(std::map<String,String> Parameters) OVERRIDE;
73	virtual void OnSetValue(bool b) throw (Exception) OVERRIDE;
74	static String Name();
75	};
76
77	/** Device Parameter 'SAMPLERATE'
78	*
79	* Used to set the sample rate of the audio output device.
80	*/
81	class ParameterSampleRate : public DeviceCreationParameterInt {
82	public:
83	ParameterSampleRate();
84	ParameterSampleRate(String s);
85	virtual String Description() OVERRIDE;
86	virtual bool Fix() OVERRIDE;
87	virtual bool Mandatory() OVERRIDE;
88	virtual std::map<String,DeviceCreationParameter*> DependsAsParameters() OVERRIDE;
89	virtual optional<int> DefaultAsInt(std::map<String,String> Parameters) OVERRIDE;
90	virtual optional<int> RangeMinAsInt(std::map<String,String> Parameters) OVERRIDE;
91	virtual optional<int> RangeMaxAsInt(std::map<String,String> Parameters) OVERRIDE;
92	virtual std::vector<int> PossibilitiesAsInt(std::map<String,String> Parameters) OVERRIDE;
93	virtual int ValueAsInt() OVERRIDE;
94	virtual void OnSetValue(int i) throw (Exception) OVERRIDE;
95	static String Name();
96	};
97
98	/** Device Parameters 'CHANNELS'
99	*
100	* Used to increase / decrease the number of audio channels of
101	* audio output device.
102	*/
103	class ParameterChannels : public DeviceCreationParameterInt {
104	public:
105	ParameterChannels();
106	ParameterChannels(String s);
107	virtual String Description() OVERRIDE;
108	virtual bool Fix() OVERRIDE;
109	virtual bool Mandatory() OVERRIDE;
110	virtual std::map<String,DeviceCreationParameter*> DependsAsParameters() OVERRIDE;
111	virtual optional<int> DefaultAsInt(std::map<String,String> Parameters) OVERRIDE;
112	virtual optional<int> RangeMinAsInt(std::map<String,String> Parameters) OVERRIDE;
113	virtual optional<int> RangeMaxAsInt(std::map<String,String> Parameters) OVERRIDE;
114	virtual std::vector<int> PossibilitiesAsInt(std::map<String,String> Parameters) OVERRIDE;
115	virtual void OnSetValue(int i) throw (Exception) OVERRIDE;
116	static String Name();
117	};
118
119
120
121	/////////////////////////////////////////////////////////////////
122	// abstract methods
123	// (these have to be implemented by the descendant)
124
125	/**
126	* Start playback of audio signal on the audio device. It's the
127	* responsibility of the implementing audio device to call the
128	* RenderAudio(uint Samples) method of all connected engines.
129	* This will cause the engines to continue to render 'Samples'
130	* number of audio sample points and the engines will
131	* automatically add their audio signals to the audio buffers of
132	* the audio channels of this audio device. So the implementing
133	* audio device just has to access the buffers of it's audio
134	* channels.
135	*
136	* @throws AudioOutputException if playback can not be started
137	* @see AudioChannel
138	*/
139	virtual void Play() = 0;
140
141	/**
142	* Returns true if the audio device is currently playing back.
143	*/
144	virtual bool IsPlaying() = 0;
145
146	/**
147	* Stop playback of audio signal on the audio device. The
148	* implementing audio device will stop calling the RenderAudio()
149	* method of all connected engines and close it's connection to
150	* audio output system.
151	*/
152	virtual void Stop() = 0;
153
154	/**
155	* Maximum amount of sample points the implementing audio
156	* device will ever demand the sampler engines to write in one
157	* fragment cycle / period. Simple audio device drivers usually
158	* have a fixed fragment size, so those devices just would return
159	* the fragment size in this method.
160	*
161	* @returns max. amount of sample points ever
162	*/
163	virtual uint MaxSamplesPerCycle() = 0;
164
165	/**
166	* Playback samplerate the audio device uses. The sampler engines
167	* currently assume this to be a constant value for the whole
168	* life time of an instance of the implementing audio device.
169	*
170	* @returns sample rate in Hz
171	*/
172	virtual uint SampleRate() = 0;
173
174	/**
175	* Return the audio output device driver name.
176	*/
177	virtual String Driver() = 0;
178
179	/**
180	* Create new audio channel. This will be called by
181	* AcquireChannels(). Each driver must implement it.
182	*/
183	virtual AudioChannel* CreateChannel(uint ChannelNr) = 0;
184
185	/**
186	* Might be optionally implemented by the deriving driver. If
187	* implemented, this method will return the current audio
188	* latency in seconds. The driver might measure the actual
189	* latency with timing functions to return the real latency.
190	*
191	* If this method is not implemented / overridden by the
192	* descending driver, it will simply return the theoretical
193	* latency, that is MaxSamplesPerCycle() / SampleRate().
194	*
195	* Currently this method is not used by the sampler itself.
196	* It can be used however for GUIs built on top of the sampler
197	* for example, to i.e. display the user the currently
198	* effective audio latency in real-time.
199	*/
200	virtual float latency();
201
202
203
204	/////////////////////////////////////////////////////////////////
205	// normal methods
206	// (usually not to be overriden by descendant)
207
208	/**
209	* Connect given sampler engine to this audio output device. The
210	* engine will be added to the Engines container of this audio
211	* device and the engine will also automatically be informed
212	* about the connection.
213	*
214	* @param pEngine - sampler engine
215	*/
216	void Connect(Engine* pEngine);
217
218	/**
219	* Disconnect given sampler engine from this audio output device.
220	* Removes given sampler engine reference from the Engines
221	* container of this audio device.
222	*
223	* @param pEngine - sampler engine
224	*/
225	void Disconnect(Engine* pEngine);
226
227	/**
228	* This method can or should be called by the deriving driver in
229	* case some fundamental parameter changed, especially if the
230	* values returned by MaxSamplesPerCycle() and SamplerRate() have
231	* changed, those are values which the sampler engines assume to be
232	* constant for the life time of an audio device !
233	*
234	* By forcing a re-connection with this method, the sampler engines
235	* are forced to update those informations metntioned above as well,
236	* avoiding crashes or other undesired misbehaviors in such
237	* circumstances.
238	*/
239	void ReconnectAll();
240
241	/**
242	* Returns audio channel with index \a ChannelIndex or NULL if
243	* index out of bounds.
244	*/
245	AudioChannel* Channel(uint ChannelIndex);
246
247	/**
248	* This method will usually be called by the sampler engines that
249	* are connected to this audio device to inform the audio device
250	* how much audio channels the engine(s) need. It's the
251	* responsibility of the audio device to offer that amount of
252	* audio channels - again: this is not an option this is a must!
253	* The engines will assume to be able to access those audio
254	* channels right after. If the audio driver is not able to offer
255	* that much channels, it can simply create mix channels which
256	* are then just mixed to the 'real' audio channels. See
257	* AudioChannel.h for details about channels and mix channels.
258	*
259	* @param Channels - amount of output channels required by
260	* a sampler engine
261	* @throws AudioOutputException if desired amount of channels
262	* cannot be offered
263	* @see AudioChannel
264	*/
265	void AcquireChannels(uint Channels);
266
267	/**
268	* Returns the amount of audio channels (including the so called
269	* "mix channels") the device is currently providing.
270	*/
271	uint ChannelCount();
272
273	/**
274	* Returns all device parameter settings.
275	*/
276	std::map<String,DeviceCreationParameter*> DeviceParameters();
277
278	/**
279	* Add a chain of send effects to this AudioOutputDevice.
280	* You actually have to add effects to that chain afterwards.
281	*/
282	EffectChain* AddSendEffectChain();
283
284	/**
285	* Remove the send effect chain given by @a iChain .
286	*
287	* @throws Exception - if given send effect chain doesn't exist
288	*/
289	void RemoveSendEffectChain(uint iChain) throw (Exception);
290
291	/**
292	* Returns send effect chain given by @a iChain or @c NULL if
293	* there's no such effect chain.
294	*/
295	EffectChain* SendEffectChain(uint iChain) const;
296
297	/**
298	* Returns send effect chain with ID @a iChainID or @c NULL if
299	* there's no such effect chain.
300	*/
301	EffectChain* SendEffectChainByID(uint iChainID) const;
302
303	/**
304	* Returns amount of send effect chains this AudioOutputDevice
305	* currently provides.
306	*/
307	uint SendEffectChainCount() const;
308
309	/**
310	* @deprecated This method will be removed, use AddSendEffectChain() instead!
311	*/
312	EffectChain* AddMasterEffectChain() DEPRECATED_API;
313
314	/**
315	* @deprecated This method will be removed, use RemoveSendEffectChain() instead!
316	*/
317	void RemoveMasterEffectChain(uint iChain) throw (Exception) DEPRECATED_API;
318
319	/**
320	* @deprecated This method will be removed, use SendEffectChain() instead!
321	*/
322	EffectChain* MasterEffectChain(uint iChain) const DEPRECATED_API;
323
324	/**
325	* @deprecated This method will be removed, use SendEffectChainCount() instead!
326	*/
327	uint MasterEffectChainCount() const DEPRECATED_API;
328
329	protected:
330	SynchronizedConfig<std::set<Engine*> > Engines; ///< All sampler engines that are connected to the audio output device.
331	SynchronizedConfig<std::set<Engine*> >::Reader EnginesReader; ///< Audio thread access to Engines.
332	std::vector<AudioChannel*> Channels; ///< All audio channels of the audio output device. This is just a container; the descendant has to create channels by himself.
333	std::map<String,DeviceCreationParameter*> Parameters; ///< All device parameters.
334	std::vector<EffectChain*> vEffectChains;
335	IDGenerator* EffectChainIDs;
336
337	AudioOutputDevice(std::map<String,DeviceCreationParameter*> DriverParameters);
338
339	virtual ~AudioOutputDevice();
340
341	/**
342	* This method should be called by the AudioOutputDevice
343	* descendant to let all connected engines proceed to render the
344	* given amount of sample points. The engines will place their
345	* calculated audio data by themselfes into the buffers of the
346	* respective AudioChannel objects, so the implementing audio
347	* output device just has to copy the AudioChannel buffers to
348	* the output buffer(s) of its audio system.
349	*
350	* @returns 0 on success or the last error return code of one
351	* engine
352	*/
353	int RenderAudio(uint Samples);
354
355	/**
356	* This can be called as an alternative to RenderAudio() for
357	* just writing silence to the audio output buffers and not
358	* calling the connected sampler engines for rendering audio, so
359	* to provide a method to stop playback if the used audio output
360	* system doesn't provide a better way.
361	*
362	* @returns 0 on success
363	*/
364	int RenderSilence(uint Samples);
365
366	friend class AudioOutputDeviceFactory; // allow AudioOutputDeviceFactory class to destroy audio devices
367
368	};
369
370	/**
371	* Audio output exception that should be thrown by the AudioOutputDevice
372	* descendants in case initialization of the audio output system failed
373	* (which should be done in the constructor of the AudioOutputDevice
374	* descendant).
375	*/
376	class AudioOutputException : public Exception {
377	public:
378	AudioOutputException(const std::string& msg) : Exception(msg) {}
379	};
380	}
381
382	#endif // __LS_AUDIOOUTPUTDEVICE_H__