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:

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

        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.

            /**
             * 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	schoenebeck	53	/***************************************************************************
2			* *
3			* LinuxSampler - modular, streaming capable sampler *
4			* *
5	schoenebeck	56	* Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck *
6	schoenebeck	53	* *
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			// abstract methods
51			// (these have to be implemented by the descendant)
52
53			/**
54			* Start playback of audio signal on the audio device. It's the
55			* responsibility of the implementing audio device to call the
56			* RenderAudio(uint Samples) method of all connected engines.
57			* This will cause the engines to continue to render 'Samples'
58			* number of audio sample points and the engines will
59			* automatically add their audio signals to the audio buffers of
60			* the audio channels of this audio device. So the implementing
61			* audio device just has to access the buffers of it's audio
62			* channels.
63			*
64			* @throws AudioOutputException if playback can not be started
65			* @see AudioChannel
66			*/
67			virtual void Play() = 0;
68
69			/**
70			* Returns true if the audio device is currently playing back.
71			*/
72			virtual bool IsPlaying() = 0;
73
74			/**
75			* Stop playback of audio signal on the audio device. The
76			* implementing audio device will stop calling the RenderAudio()
77			* method of all connected engines and close it's connection to
78			* audio output system.
79			*/
80			virtual void Stop() = 0;
81
82			/**
83			* This method will usually be called by the sampler engines that
84			* are connected to this audio device to inform the audio device
85			* how much audio channels the engine(s) need. It's the
86			* responsibility of the audio device to offer that amount of
87			* audio channels - again: this is not an option this is a must!
88			* The engines will assume to be able to access those audio
89			* channels right after. If the audio driver is not able to offer
90			* that much channels, it can simply create mix channels which
91			* are then just mixed to the 'real' audio channels. See
92			* AudioChannel.h for details about channels and mix channels.
93			*
94			* @param Channels - amount of output channels required by
95			* a sampler engine
96			* @throws AudioOutputException if desired amount of channels
97			* cannot be offered
98			* @see AudioChannel
99			*/
100			virtual void AcquireChannels(uint Channels) = 0;
101
102			/**
103			* Maximum amount of sample points the implementing audio
104			* device will ever demand the sampler engines to write in one
105			* fragment cycle / period. Simple audio device drivers usually
106			* have a fixed fragment size, so those devices just would return
107			* the fragment size in this method.
108			*
109			* @returns max. amount of sample points ever
110			*/
111			virtual uint MaxSamplesPerCycle() = 0;
112
113			/**
114			* Playback samplerate the audio device uses. The sampler engines
115			* currently assume this to be a constant value for the whole
116			* life time of an instance of the implementing audio device.
117			*
118			* @returns sample rate in Hz
119			*/
120			virtual uint SampleRate() = 0;
121
122
123
124			/////////////////////////////////////////////////////////////////
125			// normal methods
126			// (usually not to be overriden by descendant)
127
128			/**
129			* Connect given sampler engine to this audio output device. The
130			* engine will be added to the Engines container of this audio
131			* device and the engine will also automatically be informed
132			* about the connection.
133			*
134			* @param pEngine - sampler engine
135			*/
136			void Connect(Engine* pEngine);
137
138			/**
139			* Disconnect given sampler engine from this audio output device.
140			* Removes given sampler engine reference from the Engines
141			* container of this audio device.
142			*
143			* @param pEngine - sampler engine
144			*/
145			void Disconnect(Engine* pEngine);
146
147			/**
148			* Returns audio channel with index \a ChannelIndex or NULL if
149			* index out of bounds.
150			*/
151			AudioChannel* Channel(uint ChannelIndex);
152
153			protected:
154			std::set<Engine*> Engines; ///< All sampler engines that are connected to the audio output device.
155			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.
156
157			/**
158			* This method should be called by the AudioOutputDevice
159			* descendant to let all connected engines proceed to render the
160			* given amount of sample points. The engines will place their
161			* calculated audio data by themselfes into the buffers of the
162			* respective AudioChannel objects, so the implementing audio
163			* output device just has to copy the AudioChannel buffers to
164			* the output buffer(s) of its audio system.
165			*
166			* @returns 0 on success or the last error return code of one
167			* engine
168			*/
169			int RenderAudio(uint Samples);
170
171			/**
172			* This can be called as an alternative to RenderAudio() for
173			* just writing silence to the audio output buffers and not
174			* calling the connected sampler engines for rendering audio, so
175			* to provide a method to stop playback if the used audio output
176			* system doesn't provide a better way.
177			*
178			* @returns 0 on success
179			*/
180			int RenderSilence(uint Samples);
181			};
182
183			/**
184			* Audio output exception that should be thrown by the AudioOutputDevice
185			* descendants in case initialization of the audio output system failed
186			* (which should be done in the constructor of the AudioOutputDevice
187			* descendant).
188			*/
189			class AudioOutputException : public LinuxSamplerException {
190			public:
191			AudioOutputException(const std::string& msg) : LinuxSamplerException(msg) {}
192			};
193			}
194
195			#endif // __LS_AUDIOOUTPUTDEVICE_H__