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/*************************************************************************** |
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* * |
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* LinuxSampler - modular, streaming capable sampler * |
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* * |
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schoenebeck |
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* Copyright (C) 2003, 2004 by Benno Senoner and Christian Schoenebeck * |
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schoenebeck |
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* * |
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* This program is free software; you can redistribute it and/or modify * |
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* it under the terms of the GNU General Public License as published by * |
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* the Free Software Foundation; either version 2 of the License, or * |
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* (at your option) any later version. * |
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* * |
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* This program is distributed in the hope that it will be useful, * |
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* but WITHOUT ANY WARRANTY; without even the implied warranty of * |
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * |
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* GNU General Public License for more details. * |
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* * |
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* You should have received a copy of the GNU General Public License * |
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* along with this program; if not, write to the Free Software * |
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* Foundation, Inc., 59 Temple Place, Suite 330, Boston, * |
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* MA 02111-1307 USA * |
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***************************************************************************/ |
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#ifndef __LS_AUDIOOUTPUTDEVICE_H__ |
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#define __LS_AUDIOOUTPUTDEVICE_H__ |
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#include <set> |
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#include <vector> |
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#include <stdexcept> |
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#include "../common/global.h" |
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#include "../common/LinuxSamplerException.h" |
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#include "../engines/common/Engine.h" |
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#include "AudioChannel.h" |
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namespace LinuxSampler { |
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// just symbol prototyping |
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class Engine; |
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/** Abstract base class for audio output drivers in LinuxSampler |
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* |
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* This class will be derived by specialized classes which implement the |
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* connection to a specific audio output system (e.g. Alsa, Jack, |
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* CoreAudio). |
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*/ |
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class AudioOutputDevice { |
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public: |
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///////////////////////////////////////////////////////////////// |
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// abstract methods |
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// (these have to be implemented by the descendant) |
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/** |
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* Start playback of audio signal on the audio device. It's the |
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* responsibility of the implementing audio device to call the |
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* RenderAudio(uint Samples) method of all connected engines. |
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* This will cause the engines to continue to render 'Samples' |
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* number of audio sample points and the engines will |
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* automatically add their audio signals to the audio buffers of |
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* the audio channels of this audio device. So the implementing |
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* audio device just has to access the buffers of it's audio |
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* channels. |
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* |
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* @throws AudioOutputException if playback can not be started |
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* @see AudioChannel |
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*/ |
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virtual void Play() = 0; |
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/** |
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* Returns true if the audio device is currently playing back. |
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*/ |
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virtual bool IsPlaying() = 0; |
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/** |
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* Stop playback of audio signal on the audio device. The |
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* implementing audio device will stop calling the RenderAudio() |
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* method of all connected engines and close it's connection to |
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* audio output system. |
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*/ |
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virtual void Stop() = 0; |
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/** |
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* This method will usually be called by the sampler engines that |
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* are connected to this audio device to inform the audio device |
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* how much audio channels the engine(s) need. It's the |
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* responsibility of the audio device to offer that amount of |
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* audio channels - again: this is not an option this is a must! |
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* The engines will assume to be able to access those audio |
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* channels right after. If the audio driver is not able to offer |
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* that much channels, it can simply create mix channels which |
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* are then just mixed to the 'real' audio channels. See |
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* AudioChannel.h for details about channels and mix channels. |
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* |
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* @param Channels - amount of output channels required by |
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* a sampler engine |
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* @throws AudioOutputException if desired amount of channels |
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* cannot be offered |
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* @see AudioChannel |
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*/ |
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virtual void AcquireChannels(uint Channels) = 0; |
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/** |
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* Maximum amount of sample points the implementing audio |
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* device will ever demand the sampler engines to write in one |
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* fragment cycle / period. Simple audio device drivers usually |
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* have a fixed fragment size, so those devices just would return |
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* the fragment size in this method. |
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* |
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* @returns max. amount of sample points ever |
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*/ |
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virtual uint MaxSamplesPerCycle() = 0; |
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/** |
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* Playback samplerate the audio device uses. The sampler engines |
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* currently assume this to be a constant value for the whole |
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* life time of an instance of the implementing audio device. |
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* |
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* @returns sample rate in Hz |
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*/ |
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virtual uint SampleRate() = 0; |
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///////////////////////////////////////////////////////////////// |
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// normal methods |
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// (usually not to be overriden by descendant) |
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/** |
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* Connect given sampler engine to this audio output device. The |
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* engine will be added to the Engines container of this audio |
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* device and the engine will also automatically be informed |
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* about the connection. |
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* |
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* @param pEngine - sampler engine |
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*/ |
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void Connect(Engine* pEngine); |
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/** |
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* Disconnect given sampler engine from this audio output device. |
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* Removes given sampler engine reference from the Engines |
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* container of this audio device. |
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* |
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* @param pEngine - sampler engine |
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*/ |
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void Disconnect(Engine* pEngine); |
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/** |
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* Returns audio channel with index \a ChannelIndex or NULL if |
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* index out of bounds. |
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*/ |
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AudioChannel* Channel(uint ChannelIndex); |
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protected: |
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std::set<Engine*> Engines; ///< All sampler engines that are connected to the audio output device. |
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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. |
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/** |
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* This method should be called by the AudioOutputDevice |
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* descendant to let all connected engines proceed to render the |
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* given amount of sample points. The engines will place their |
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* calculated audio data by themselfes into the buffers of the |
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* respective AudioChannel objects, so the implementing audio |
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* output device just has to copy the AudioChannel buffers to |
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* the output buffer(s) of its audio system. |
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* |
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* @returns 0 on success or the last error return code of one |
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* engine |
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*/ |
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int RenderAudio(uint Samples); |
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/** |
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* This can be called as an alternative to RenderAudio() for |
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* just writing silence to the audio output buffers and not |
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* calling the connected sampler engines for rendering audio, so |
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* to provide a method to stop playback if the used audio output |
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* system doesn't provide a better way. |
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* |
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* @returns 0 on success |
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*/ |
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int RenderSilence(uint Samples); |
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}; |
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/** |
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* Audio output exception that should be thrown by the AudioOutputDevice |
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* descendants in case initialization of the audio output system failed |
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* (which should be done in the constructor of the AudioOutputDevice |
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* descendant). |
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*/ |
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class AudioOutputException : public LinuxSamplerException { |
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public: |
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AudioOutputException(const std::string& msg) : LinuxSamplerException(msg) {} |
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}; |
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} |
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#endif // __LS_AUDIOOUTPUTDEVICE_H__ |