src/audiodriver/AudioOutputDevice.h

/***************************************************************************
 *                                                                         *
 *   LinuxSampler - modular, streaming capable sampler                     *
 *                                                                         *
 *   Copyright (C) 2003, 2004 by Benno Senoner and 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 <vector>
#include <stdexcept>

#include "../common/global.h"
#include "../common/LinuxSamplerException.h"
#include "../engines/common/Engine.h"
#include "AudioChannel.h"

namespace LinuxSampler {

    // just symbol prototyping
    class Engine;

    /** 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:

            /////////////////////////////////////////////////////////////////
            // type definitions

            /**
             * List of all currently implemented audio output drivers.
             */
            enum type_t {
                type_alsa,
                type_jack
            };


            /////////////////////////////////////////////////////////////////
            // 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;

            /**
             * 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
             */
            virtual void AcquireChannels(uint Channels) = 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;


            /////////////////////////////////////////////////////////////////
            // 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);

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

            /**
             * Returns the ID that identifies the implementing audio output
             * driver.
             */
            type_t Type();

        protected:
            std::set<Engine*>          Engines;  ///< All sampler engines that are connected to the audio output device.
            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.
            type_t                     AudioOutputType;

            /**
             * Constructor. Has to be called by the implementing audio
             * output driver to define the ID of the driver. When a new
             * audio output driver is implemented, the
             * AudioOutputDevice::type_t enumeration has to be extended with
             * a new ID for the new audio output driver.
             */
            AudioOutputDevice(type_t Type);

            /**
             * 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);
    };

    /**
     * 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 LinuxSamplerException {
        public:
            AudioOutputException(const std::string& msg) : LinuxSamplerException(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	* *
7	* This program is free software; you can redistribute it and/or modify *
8	* it under the terms of the GNU General Public License as published by *
9	* the Free Software Foundation; either version 2 of the License, or *
10	* (at your option) any later version. *
11	* *
12	* This program is distributed in the hope that it will be useful, *
13	* but WITHOUT ANY WARRANTY; without even the implied warranty of *
14	* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
15	* GNU General Public License for more details. *
16	* *
17	* You should have received a copy of the GNU General Public License *
18	* along with this program; if not, write to the Free Software *
19	* Foundation, Inc., 59 Temple Place, Suite 330, Boston, *
20	* MA 02111-1307 USA *
21	***************************************************************************/
22
23	#ifndef __LS_AUDIOOUTPUTDEVICE_H__
24	#define __LS_AUDIOOUTPUTDEVICE_H__
25
26	#include <set>
27	#include <vector>
28	#include <stdexcept>
29
30	#include "../common/global.h"
31	#include "../common/LinuxSamplerException.h"
32	#include "../engines/common/Engine.h"
33	#include "AudioChannel.h"
34
35	namespace LinuxSampler {
36
37	// just symbol prototyping
38	class Engine;
39
40	/** Abstract base class for audio output drivers in LinuxSampler
41	*
42	* This class will be derived by specialized classes which implement the
43	* connection to a specific audio output system (e.g. Alsa, Jack,
44	* CoreAudio).
45	*/
46	class AudioOutputDevice {
47	public:
48
49	/////////////////////////////////////////////////////////////////
50	// type definitions
51
52	/**
53	* List of all currently implemented audio output drivers.
54	*/
55	enum type_t {
56	type_alsa,
57	type_jack
58	};
59
60
61
62	/////////////////////////////////////////////////////////////////
63	// abstract methods
64	// (these have to be implemented by the descendant)
65
66	/**
67	* Start playback of audio signal on the audio device. It's the
68	* responsibility of the implementing audio device to call the
69	* RenderAudio(uint Samples) method of all connected engines.
70	* This will cause the engines to continue to render 'Samples'
71	* number of audio sample points and the engines will
72	* automatically add their audio signals to the audio buffers of
73	* the audio channels of this audio device. So the implementing
74	* audio device just has to access the buffers of it's audio
75	* channels.
76	*
77	* @throws AudioOutputException if playback can not be started
78	* @see AudioChannel
79	*/
80	virtual void Play() = 0;
81
82	/**
83	* Returns true if the audio device is currently playing back.
84	*/
85	virtual bool IsPlaying() = 0;
86
87	/**
88	* Stop playback of audio signal on the audio device. The
89	* implementing audio device will stop calling the RenderAudio()
90	* method of all connected engines and close it's connection to
91	* audio output system.
92	*/
93	virtual void Stop() = 0;
94
95	/**
96	* This method will usually be called by the sampler engines that
97	* are connected to this audio device to inform the audio device
98	* how much audio channels the engine(s) need. It's the
99	* responsibility of the audio device to offer that amount of
100	* audio channels - again: this is not an option this is a must!
101	* The engines will assume to be able to access those audio
102	* channels right after. If the audio driver is not able to offer
103	* that much channels, it can simply create mix channels which
104	* are then just mixed to the 'real' audio channels. See
105	* AudioChannel.h for details about channels and mix channels.
106	*
107	* @param Channels - amount of output channels required by
108	* a sampler engine
109	* @throws AudioOutputException if desired amount of channels
110	* cannot be offered
111	* @see AudioChannel
112	*/
113	virtual void AcquireChannels(uint Channels) = 0;
114
115	/**
116	* Maximum amount of sample points the implementing audio
117	* device will ever demand the sampler engines to write in one
118	* fragment cycle / period. Simple audio device drivers usually
119	* have a fixed fragment size, so those devices just would return
120	* the fragment size in this method.
121	*
122	* @returns max. amount of sample points ever
123	*/
124	virtual uint MaxSamplesPerCycle() = 0;
125
126	/**
127	* Playback samplerate the audio device uses. The sampler engines
128	* currently assume this to be a constant value for the whole
129	* life time of an instance of the implementing audio device.
130	*
131	* @returns sample rate in Hz
132	*/
133	virtual uint SampleRate() = 0;
134
135
136
137	/////////////////////////////////////////////////////////////////
138	// normal methods
139	// (usually not to be overriden by descendant)
140
141	/**
142	* Connect given sampler engine to this audio output device. The
143	* engine will be added to the Engines container of this audio
144	* device and the engine will also automatically be informed
145	* about the connection.
146	*
147	* @param pEngine - sampler engine
148	*/
149	void Connect(Engine* pEngine);
150
151	/**
152	* Disconnect given sampler engine from this audio output device.
153	* Removes given sampler engine reference from the Engines
154	* container of this audio device.
155	*
156	* @param pEngine - sampler engine
157	*/
158	void Disconnect(Engine* pEngine);
159
160	/**
161	* Returns audio channel with index \a ChannelIndex or NULL if
162	* index out of bounds.
163	*/
164	AudioChannel* Channel(uint ChannelIndex);
165
166	/**
167	* Returns the ID that identifies the implementing audio output
168	* driver.
169	*/
170	type_t Type();
171
172	protected:
173	std::set<Engine*> Engines; ///< All sampler engines that are connected to the audio output device.
174	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.
175	type_t AudioOutputType;
176
177	/**
178	* Constructor. Has to be called by the implementing audio
179	* output driver to define the ID of the driver. When a new
180	* audio output driver is implemented, the
181	* AudioOutputDevice::type_t enumeration has to be extended with
182	* a new ID for the new audio output driver.
183	*/
184	AudioOutputDevice(type_t Type);
185
186	/**
187	* This method should be called by the AudioOutputDevice
188	* descendant to let all connected engines proceed to render the
189	* given amount of sample points. The engines will place their
190	* calculated audio data by themselfes into the buffers of the
191	* respective AudioChannel objects, so the implementing audio
192	* output device just has to copy the AudioChannel buffers to
193	* the output buffer(s) of its audio system.
194	*
195	* @returns 0 on success or the last error return code of one
196	* engine
197	*/
198	int RenderAudio(uint Samples);
199
200	/**
201	* This can be called as an alternative to RenderAudio() for
202	* just writing silence to the audio output buffers and not
203	* calling the connected sampler engines for rendering audio, so
204	* to provide a method to stop playback if the used audio output
205	* system doesn't provide a better way.
206	*
207	* @returns 0 on success
208	*/
209	int RenderSilence(uint Samples);
210	};
211
212	/**
213	* Audio output exception that should be thrown by the AudioOutputDevice
214	* descendants in case initialization of the audio output system failed
215	* (which should be done in the constructor of the AudioOutputDevice
216	* descendant).
217	*/
218	class AudioOutputException : public LinuxSamplerException {
219	public:
220	AudioOutputException(const std::string& msg) : LinuxSamplerException(msg) {}
221	};
222	}
223
224	#endif // __LS_AUDIOOUTPUTDEVICE_H__