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audio/mixer_intern.h

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+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * 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 3 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, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#ifndef AUDIO_MIXER_INTERN_H
+#define AUDIO_MIXER_INTERN_H
+
+#include "common/scummsys.h"
+#include "common/mutex.h"
+#include "audio/mixer.h"
+
+namespace Audio {
+
+/**
+ * @defgroup audio_mixer_intern Mixer implementation
+ * @ingroup audio
+ *
+ * @brief The (default) implementation of the ScummVM audio mixing subsystem.
+ * @{
+ */
+
+/**
+ * The (default) implementation of the ScummVM audio mixing subsystem.
+ *
+ * Backends are responsible for allocating (and later releasing) an instance
+ * of this class, which engines can access via OSystem::getMixer().
+ *
+ * Initialisation of instances of this class usually happens as follows:
+ * 1) Creat a new Audio::MixerImpl instance.
+ * 2) Set the hardware output sample rate via the setSampleRate() method.
+ * 3) Hook up the mixCallback() in a suitable audio processing thread/callback.
+ * 4) Change the mixer into ready mode via setReady(true).
+ * 5) Start audio processing (e.g. by resuming the audio thread, if applicable).
+ *
+ * In the future, we might make it possible for backends to provide
+ * (partial) alternative implementations of the mixer, e.g. to make
+ * better use of native sound mixing support on low-end devices.
+ *
+ * @see OSystem::getMixer()
+ */
+class MixerImpl : public Mixer {
+private:
+	enum {
+		NUM_CHANNELS = 32
+	};
+
+	Common::Mutex _mutex;
+
+	const uint _sampleRate;
+	const bool _stereo;
+	const uint _outBufSize;
+	bool _mixerReady;
+	uint32 _handleSeed;
+
+	struct SoundTypeSettings {
+		SoundTypeSettings() : mute(false), volume(kMaxMixerVolume) {}
+
+		bool mute;
+		int volume;
+	};
+
+	SoundTypeSettings _soundTypeSettings[4];
+	Channel *_channels[NUM_CHANNELS];
+
+
+public:
+
+	MixerImpl(uint sampleRate, bool stereo = true, uint outBufSize = 0);
+	~MixerImpl();
+
+	bool isReady() const override { Common::StackLock lock(_mutex); return _mixerReady; }
+
+	Common::Mutex &mutex() override { return _mutex; }
+
+	void playStream(
+		SoundType type,
+		SoundHandle *handle,
+		AudioStream *input,
+		int id, byte volume, int8 balance,
+		DisposeAfterUse::Flag autofreeStream,
+		bool permanent,
+		bool reverseStereo) override;
+
+	void stopAll() override;
+	void stopID(int id) override;
+	void stopHandle(SoundHandle handle) override;
+
+	void pauseAll(bool paused) override;
+	void pauseID(int id, bool paused) override;
+	void pauseHandle(SoundHandle handle, bool paused) override;
+
+	bool isSoundIDActive(int id) override;
+	int getSoundID(SoundHandle handle) override;
+
+	bool isSoundHandleActive(SoundHandle handle) override;
+
+	void muteSoundType(SoundType type, bool mute) override;
+	bool isSoundTypeMuted(SoundType type) const override;
+
+	void setChannelVolume(SoundHandle handle, byte volume) override;
+	byte getChannelVolume(SoundHandle handle) override;
+	void setChannelBalance(SoundHandle handle, int8 balance) override;
+	int8 getChannelBalance(SoundHandle handle) override;
+	void setChannelFaderL(SoundHandle handle, uint8 scaleL) override;
+	uint8 getChannelFaderL(SoundHandle handle) override;
+	void setChannelFaderR(SoundHandle handle, uint8 scaleR) override;
+	uint8 getChannelFaderR(SoundHandle handle) override;
+	void setChannelRate(SoundHandle handle, uint32 rate) override;
+	uint32 getChannelRate(SoundHandle handle) override;
+	void resetChannelRate(SoundHandle handle) override;
+
+	uint32 getSoundElapsedTime(SoundHandle handle) override;
+	Timestamp getElapsedTime(SoundHandle handle) override;
+
+	void loopChannel(SoundHandle handle) override;
+
+	bool hasActiveChannelOfType(SoundType type) override;
+
+	void setVolumeForSoundType(SoundType type, int volume) override;
+	int getVolumeForSoundType(SoundType type) const override;
+
+	uint getOutputRate() const override;
+	bool getOutputStereo() const override;
+	uint getOutputBufSize() const override;
+
+protected:
+	void insertChannel(SoundHandle *handle, Channel *chan);
+
+public:
+	/**
+	 * The mixer callback function, to be called at regular intervals by
+	 * the backend (e.g. from an audio mixing thread). All the actual mixing
+	 * work is done from here.
+	 *
+	 * @param samples Sample buffer, in which stereo 16-bit samples will be stored.
+	 * @param len Length of the provided buffer to fill (in bytes, should be divisible by 4).
+	 * @return number of sample pairs processed (which can still be silence!)
+	 */
+	int mixCallback(byte *samples, uint len);
+
+	/**
+	 * Set the internal 'is ready' flag of the mixer.
+	 * Backends should invoke Mixer::setReady(true) once initialisation of
+	 * their audio system has been completed.
+	 */
+	void setReady(bool ready);
+};
+
+/** @} */
+} // End of namespace Audio
+
+#endif