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      1 /*
      2  * Copyright (C) 2010, Google Inc. All rights reserved.
      3  *
      4  * Redistribution and use in source and binary forms, with or without
      5  * modification, are permitted provided that the following conditions
      6  * are met:
      7  * 1.  Redistributions of source code must retain the above copyright
      8  *    notice, this list of conditions and the following disclaimer.
      9  * 2.  Redistributions in binary form must reproduce the above copyright
     10  *    notice, this list of conditions and the following disclaimer in the
     11  *    documentation and/or other materials provided with the distribution.
     12  *
     13  * THIS SOFTWARE IS PROVIDED BY APPLE INC. AND ITS CONTRIBUTORS ``AS IS'' AND ANY
     14  * EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
     15  * WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
     16  * DISCLAIMED. IN NO EVENT SHALL APPLE INC. OR ITS CONTRIBUTORS BE LIABLE FOR ANY
     17  * DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
     18  * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     19  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
     20  * ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
     21  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
     22  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
     23  */
     24 
     25 #ifndef AudioBufferSourceNode_h
     26 #define AudioBufferSourceNode_h
     27 
     28 #include "AudioBuffer.h"
     29 #include "AudioBus.h"
     30 #include "AudioGain.h"
     31 #include "AudioPannerNode.h"
     32 #include "AudioResampler.h"
     33 #include "AudioSourceNode.h"
     34 #include "AudioSourceProvider.h"
     35 #include <wtf/PassRefPtr.h>
     36 #include <wtf/RefPtr.h>
     37 #include <wtf/Threading.h>
     38 
     39 namespace WebCore {
     40 
     41 class AudioContext;
     42 
     43 // AudioBufferSourceNode is an AudioNode representing an audio source from an in-memory audio asset represented by an AudioBuffer.
     44 // It generally will be used for short sounds which require a high degree of scheduling flexibility (can playback in rhythmically perfect ways).
     45 
     46 class AudioBufferSourceNode : public AudioSourceNode, public AudioSourceProvider {
     47 public:
     48     static PassRefPtr<AudioBufferSourceNode> create(AudioContext*, double sampleRate);
     49 
     50     virtual ~AudioBufferSourceNode();
     51 
     52     // AudioNode
     53     virtual void process(size_t framesToProcess);
     54     virtual void reset();
     55 
     56     // AudioSourceProvider
     57     // When process() is called, the resampler calls provideInput (in the audio thread) to gets its input stream.
     58     virtual void provideInput(AudioBus*, size_t numberOfFrames);
     59 
     60     // setBuffer() is called on the main thread.  This is the buffer we use for playback.
     61     void setBuffer(AudioBuffer*);
     62     AudioBuffer* buffer() { return m_buffer.get(); }
     63 
     64     // numberOfChannels() returns the number of output channels.  This value equals the number of channels from the buffer.
     65     // If a new buffer is set with a different number of channels, then this value will dynamically change.
     66     unsigned numberOfChannels();
     67 
     68     // Play-state
     69     // noteOn(), noteGrainOn(), and noteOff() must all be called from the main thread.
     70     void noteOn(double when);
     71     void noteGrainOn(double when, double grainOffset, double grainDuration);
     72     void noteOff(double when);
     73 
     74     bool looping() const { return m_isLooping; }
     75     void setLooping(bool looping) { m_isLooping = looping; }
     76 
     77     AudioGain* gain() { return m_gain.get(); }
     78     AudioParam* playbackRate() { return m_playbackRate.get(); }
     79 
     80     // If a panner node is set, then we can incorporate doppler shift into the playback pitch rate.
     81     void setPannerNode(PassRefPtr<AudioPannerNode> pannerNode) { m_pannerNode = pannerNode; }
     82 
     83 private:
     84     AudioBufferSourceNode(AudioContext*, double sampleRate);
     85 
     86     // m_buffer holds the sample data which this node outputs.
     87     RefPtr<AudioBuffer> m_buffer;
     88 
     89     // Used for the "gain" and "playbackRate" attributes.
     90     RefPtr<AudioGain> m_gain;
     91     RefPtr<AudioParam> m_playbackRate;
     92 
     93     // m_isPlaying is set to true when noteOn() or noteGrainOn() is called.
     94     bool m_isPlaying;
     95 
     96     // If m_isLooping is false, then this node will be done playing and become inactive after it reaches the end of the sample data in the buffer.
     97     // If true, it will wrap around to the start of the buffer each time it reaches the end.
     98     bool m_isLooping;
     99 
    100     // This node is considered finished when it reaches the end of the buffer's sample data after noteOn() has been called.
    101     // This will only be set to true if m_isLooping == false.
    102     bool m_hasFinished;
    103 
    104     // m_startTime is the time to start playing based on the context's timeline (0.0 or a time less than the context's current time means "now").
    105     double m_startTime; // in seconds
    106 
    107     // m_schedulingFrameDelay is the sample-accurate scheduling offset.
    108     // It's used so that we start rendering audio samples at a very precise point in time.
    109     // It will only be a non-zero value the very first render quantum that we render from the buffer.
    110     int m_schedulingFrameDelay;
    111 
    112     // m_readIndex is a sample-frame index into our buffer representing the current playback position.
    113     unsigned m_readIndex;
    114 
    115     // Granular playback
    116     bool m_isGrain;
    117     double m_grainOffset; // in seconds
    118     double m_grainDuration; // in seconds
    119     int m_grainFrameCount; // keeps track of which frame in the grain we're currently rendering
    120 
    121     // totalPitchRate() returns the instantaneous pitch rate (non-time preserving).
    122     // It incorporates the base pitch rate, any sample-rate conversion factor from the buffer, and any doppler shift from an associated panner node.
    123     double totalPitchRate();
    124 
    125     // m_resampler performs the pitch rate changes to the buffer playback.
    126     AudioResampler m_resampler;
    127 
    128     // m_lastGain provides continuity when we dynamically adjust the gain.
    129     double m_lastGain;
    130 
    131     // We optionally keep track of a panner node which has a doppler shift that is incorporated into the pitch rate.
    132     RefPtr<AudioPannerNode> m_pannerNode;
    133 
    134     // This synchronizes process() with setBuffer() which can cause dynamic channel count changes.
    135     mutable Mutex m_processLock;
    136 
    137     // Reads the next framesToProcess sample-frames from the AudioBuffer into destinationBus.
    138     // A grain envelope will be applied if m_isGrain is set to true.
    139     void readFromBuffer(AudioBus* destinationBus, size_t framesToProcess);
    140 
    141     // readFromBufferWithGrainEnvelope() is a low-level blitter which reads from the AudioBuffer and applies a grain envelope.
    142     void readFromBufferWithGrainEnvelope(float* sourceL, float* sourceR, float* destinationL, float* destinationR, size_t framesToProcess);
    143 };
    144 
    145 } // namespace WebCore
    146 
    147 #endif // AudioBufferSourceNode_h
    148